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Smolich JJ, Kenna KR, Mynard JP. Extended period of ventilation before delayed cord clamping augments left-to-right shunting and decreases systemic perfusion at birth in preterm lambs. J Physiol 2024; 602:1791-1813. [PMID: 38532618 DOI: 10.1113/jp285799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 02/26/2024] [Indexed: 03/28/2024] Open
Abstract
Previous studies have suggested that an extended period of ventilation before delayed cord clamping (DCC) augments birth-related rises in pulmonary arterial (PA) blood flow. However, it is unknown whether this greater rise in PA flow is accompanied by increases in left ventricular (LV) output and systemic arterial perfusion or whether it reflects enhanced left-to-right shunting across the ductus arteriosus and/or foramen ovale (FO), with decreased systemic arterial perfusion. Using an established preterm lamb birth transition model, this study compared the effect of a short (∼40 s, n = 11), moderate (∼2 min, n = 11) or extended (∼5 min, n = 12) period of initial mechanical lung ventilation before DCC on flow probe-derived perinatal changes in PA flow, LV output, total systemic arterial blood flow, ductal shunting and FO shunting. The LV output was relatively stable during initial ventilation but increased after DCC, with similar responses in all groups. Systemic arterial flow patterns displayed only minor differences during brief and moderate periods of initial ventilation and were similar after DCC. However, an increase in PA flow was augmented with an extended initial ventilation (P < 0.001), owing to an earlier onset of left-to-right ductal and FO shunting (P < 0.001), and was accompanied by a pronounced reduction in total systemic arterial flow (P = 0.005) that persisted for 4 min after DCC (P ≤ 0.039). These findings suggest that, owing to increased left-to-right shunting and a greater reduction in systemic arterial perfusion, an extended period of ventilation before DCC does not result in greater perinatal circulatory benefits than shorter periods of initial ventilation in the birth transition. KEY POINTS: Previous studies suggest that an extended period of initial ventilation before delayed cord clamping (DCC) augments birth-related rises in pulmonary arterial (PA) blood flow. It is unknown whether this greater rise in PA flow is accompanied by an increased left ventricular output and systemic arterial perfusion or whether it reflects enhanced left-to-right shunting across the ductus arteriosus and/or foramen ovale, with decreased systemic arterial perfusion. Anaesthetized preterm fetal lambs instrumented with central arterial flow probes underwent a brief (∼40 s), moderate (∼2 min) or extended (∼5 min) period of ventilation before DCC. Perinatal changes in left ventricular output were similar in all groups, but extended initial ventilation augmented both perinatal increases in PA flow, owing to earlier onset and greater left-to-right ductal and foramen ovale shunting, and perinatal reductions in total systemic arterial perfusion. Extended ventilation before DCC does not confer a greater perinatal circulatory benefit than shorter periods of initial ventilation.
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Affiliation(s)
- Joseph J Smolich
- Heart Research, Murdoch Children's Research Institute, Parkville, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia
| | - Kelly R Kenna
- Heart Research, Murdoch Children's Research Institute, Parkville, Victoria, Australia
| | - Jonathan P Mynard
- Heart Research, Murdoch Children's Research Institute, Parkville, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia
- Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia
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Smolich JJ, Kenna KR, Phillips SE, Mynard JP, Cheung MMM, Lambert GW. Characteristics and physiological basis of falls in ventricular outputs after immediate cord clamping at delivery in preterm fetal lambs. J Physiol 2021; 599:3755-3770. [PMID: 34101823 DOI: 10.1113/jp281693] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 06/07/2021] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Controversy exists about the physiological mechanism(s) underlying decreases in cardiac output after immediate clamping of the umbilical cord at birth. To define these mechanisms, the four major determinants of ventricular output (afterload, preload, heart rate and contractility) were measured concurrently in fetal lambs at 15 s intervals over a 2 min period after cord clamping and before ventilation following delivery. After cord clamping, right (but not left) ventricular output fell by 20% in the initial 30 s, due to increased afterload associated with higher arterial blood pressures, but both outputs then halved over 45 s, due to a falling heart rate and deteriorating ventricular contractility accompanying rapid declines in arterial oxygenation to asphyxial levels. Ventricular outputs subsequently plateaued from 75 to 120 s, associated with rebound rises in ventricular contractility accompanying asphyxia-induced surges in circulating catecholamines. These findings provide a physiological basis for the clinical recommendation that effective ventilation should occur within 60 s after immediate cord clamping. ABSTRACT Controversy exists about the physiological mechanism(s) underlying large decreases in cardiac output after immediate clamping of the umbilical cord at birth. To define these mechanisms, anaesthetized preterm fetal lambs (127(1)d, n = 12) were instrumented with flow probes and catheters in major central arteries, and a left ventricular (LV) micromanometer-conductance catheter. Following immediate cord clamping at delivery, haemodynamics, LV and right ventricular (RV) outputs, and LV contractility were measured at 15 s intervals during a 2 min non-ventilatory period, with aortic blood gases and circulating catecholamine (noradrenaline and adrenaline) concentrations measured at 30 s intervals. After cord clamping, (1) RV (but not LV) output fell by 20% in the initial 30 s, due to a reduced stroke volume associated with increased arterial blood pressures, (2) both outputs then halved over the next 45 s, associated with falls in heart rate, arterial blood pressures and ventricular contractility accompanying a rapid decline in arterial oxygenation to asphyxial levels, (3) reduced outputs subsequently plateaued from 75 to 120 s, associated with rebound rises in blood pressures and ventricular contractility accompanying exponential surges in circulating catecholamines. These findings are consistent with a time-dependent decline of ventricular outputs after immediate cord clamping, which comprised (1) an initial, minor fall in RV output related to altered loading conditions, (2) ensuing large decreases in both LV and RV outputs related to the combination of bradycardia and ventricular dysfunction during emergence of an asphyxial state, and (3) subsequent stabilization of reduced LV and RV outputs during ongoing asphyxia, supported by cardiovascular stimulatory effects of marked sympathoadrenal activation.
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Affiliation(s)
- Joseph J Smolich
- Heart Research, Murdoch Children's Research Institute, Parkville, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia
| | - Kelly R Kenna
- Heart Research, Murdoch Children's Research Institute, Parkville, Victoria, Australia
| | - Sarah E Phillips
- Iverson Health Innovations Research Institute, Swinburne University of Technology, Hawthorn, Victoria, Australia.,Human Neurotransmitters Laboratory, Baker Heart and Diabetes Institute, Prahran, Victoria, Australia
| | - Jonathan P Mynard
- Heart Research, Murdoch Children's Research Institute, Parkville, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia.,Department of Cardiology, Royal Children's Hospital, Parkville, Victoria, Australia.,Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | - Michael M M Cheung
- Heart Research, Murdoch Children's Research Institute, Parkville, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia.,Department of Cardiology, Royal Children's Hospital, Parkville, Victoria, Australia
| | - Gavin W Lambert
- Iverson Health Innovations Research Institute, Swinburne University of Technology, Hawthorn, Victoria, Australia.,Human Neurotransmitters Laboratory, Baker Heart and Diabetes Institute, Prahran, Victoria, Australia
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Baburamani AA, Tran NT, Castillo-Melendez M, Yawno T, Walker DW. Brief hypoxia in late gestation sheep causes prolonged disruption of fetal electrographic, breathing behaviours and can result in early labour. J Physiol 2021; 599:3221-3236. [PMID: 33977538 DOI: 10.1113/jp281266] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 04/21/2021] [Indexed: 01/22/2023] Open
Abstract
KEY POINTS Brief episodes of severe fetal hypoxia can arise in late gestation as a result of interruption of normal umbilical blood flow Systemic parameters and blood chemistry indicate complete recovery within 1-2 hours, although the long-term effects on fetal brain functions are unknown Fetal sheep were subjected to umbilical cord occlusion (UCO) for 10 min at 131 days of gestation, and then monitored intensively until onset of labour or delivery (<145 days of gestation) Normal patterns of fetal behaviour, including breathing movements, episodes of high and low voltage electorcortical activity, eye movements and postural (neck) muscle activity, were disrupted for 3-10 days after the UCO Preterm labour and delivery occurred in a significant number of the pregnancies after UCO compared to the control (sham-UCO) cohort. ABSTRACT Complications arising from antepartum events such as impaired umbilical blood flow can cause significant fetal hypoxia. These complications can be unpredictable, as well as difficult to detect, and thus we lack a detailed understanding of the (patho)physiological changes that occur between the antenatal in utero event and birth. In the present study, we assessed the consequences of brief (∼10 min) umbilical cord occlusion (UCO) in fetal sheep at ∼0.88 gestation on fetal plasma cortisol concentrations and fetal behaviour [electrocortical (EcoG), electo-oculargram (EOG), nuchal muscle electromyography (EMG) and breathing activities] in the days following UCO. UCO caused a rapid onset of fetal hypoxaemia, hypercapnia, and acidosis; however, by 6 h, all blood parameters and cardiovascular status were normalized and not different from the control (Sham-UCO) cohort. Subsequently, the incidence of fetal breathing movements decreased compared to the control group, and abnormal behavioural patterns developed over the days following UCO and leading up to the onset of labour, which included increased high voltage and sub-low voltage ECoG and EOG activities, as well as decreased nuchal EMG activity. Fetuses subjected to UCO went into labour 7.9 ± 3.6 days post-UCO (139.5 ± 3.2 days of gestation) compared to the control group fetuses at 13.6 ± 3.3 days post-sham UCO (144 ± 2.2 days of gestation; P < 0.05), despite comparable increases in fetal plasma cortisol and a similar body weight at birth. Thus, a single transient episode of complete UCO late in gestation in fetal sheep can result in prolonged effects on fetal brain activity and premature labour, suggesting persisting effects on fetal cerebral metabolism.
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Affiliation(s)
- Ana A Baburamani
- Department of Perinatal Imaging and Health, Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
| | - Nhi T Tran
- School of Health and Biomedical Sciences, RMIT University, Melbourne, VIC, Australia.,The Ritchie Centre, Hudson Institute of Medical Research, and Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Margie Castillo-Melendez
- The Ritchie Centre, Hudson Institute of Medical Research, and Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Tamara Yawno
- The Ritchie Centre, Hudson Institute of Medical Research, and Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - David W Walker
- School of Health and Biomedical Sciences, RMIT University, Melbourne, VIC, Australia
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Recher M, Garabedian C, Aubry E, Sharma D, Butruille L, Storme L, De Jonckheere J. Opioid effect on the autonomic nervous system in a fetal sheep model. Arch Gynecol Obstet 2021; 304:73-80. [PMID: 33389095 DOI: 10.1007/s00404-020-05917-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 11/21/2020] [Indexed: 10/22/2022]
Abstract
PURPOSE Opioid use during labour can interfere with cardiotocography patterns. Heart rate variability indirectly reflects a fluctuation in the autonomic nervous system and can be monitored through time and spectral analyses. This experimental study aimed to evaluate the impact of nalbuphine administration on the gasometric, cardiovascular, and autonomic nervous system responses in fetal sheep. METHODS This was an experimental study on chronically instrumented sheep fetuses (surgery at 128 ± 2 days of gestational age, term = 145 days). The model was based on a maternal intravenous bolus injection of nalbuphine, a semisynthetic opioid used as an analgesic during delivery. Fetal gasometric parameters (pH, pO2, pCO2, and lactates), hemodynamic parameters (fetal heart rate and mean arterial pressure), and autonomic nervous system tone (short-term and long-term variation, low-frequency domain, high-frequency domain, and fetal stress index) were recorded. Data obtained at 30-60 min after nalbuphine injection were compared to those recorded at baseline. RESULTS Eleven experiments were performed. Fetal heart rate, mean arterial pressure, and activities at low and high frequencies were stable after injection. Short-term variation decreased at T30 min (P = 0.02), and long-term variation decreased at T60 min (P = 0.02). Fetal stress index gradually increased and reached significance at T60 min (P = 0.02). Fetal gasometric parameters and lactate levels remained stable. CONCLUSION Maternal nalbuphine use during labour may lead to fetal heart changes that are caused by the effect of opioid on the autonomic nervous system; these fluctuations do not reflect acidosis.
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Affiliation(s)
- Morgan Recher
- ULR 2694, METRICS, Evaluation des Technologies de Santé et des Pratiques Médicales, University of Lille, 59000, Lille, France. .,Department of Paediatric Intensive Care Unit, CHU Lille, Jeanne de Flandre Hospital, 59000, Lille, France. .,Jeanne de Flandre Hospital, University of Lille Nord de France, 1 rue Eugène Avinée, 59037, Lille Cedex, France.
| | - Charles Garabedian
- ULR 2694, METRICS, Evaluation des Technologies de Santé et des Pratiques Médicales, University of Lille, 59000, Lille, France.,Department of Obstetrics, CHU Lille, Jeanne de Flandre Hospital, 59000, Lille, France
| | - Estelle Aubry
- ULR 2694, METRICS, Evaluation des Technologies de Santé et des Pratiques Médicales, University of Lille, 59000, Lille, France.,Department of Pediatric Surgery, CHU Lille, Jeanne de Flandre Hospital, 59000, Lille, France
| | - Dyuti Sharma
- ULR 2694, METRICS, Evaluation des Technologies de Santé et des Pratiques Médicales, University of Lille, 59000, Lille, France.,Department of Pediatric Surgery, CHU Lille, Jeanne de Flandre Hospital, 59000, Lille, France
| | - Laura Butruille
- ULR 2694, METRICS, Evaluation des Technologies de Santé et des Pratiques Médicales, University of Lille, 59000, Lille, France
| | - Laurent Storme
- ULR 2694, METRICS, Evaluation des Technologies de Santé et des Pratiques Médicales, University of Lille, 59000, Lille, France.,Department of Neonatology, CHU Lille, Jeanne de Flandre Hospital, 59000, Lille, France
| | - Julien De Jonckheere
- ULR 2694, METRICS, Evaluation des Technologies de Santé et des Pratiques Médicales, University of Lille, 59000, Lille, France.,CIC-IT 1403-biosensor and e-health, CHU Lille, 59000, Lille, France
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Wong FY, Gogos A, Hale N, Ingelse SA, Brew N, Shepherd KL, van den Buuse M, Walker DW. Impact of hypoxia-ischemia and dopamine treatment on dopamine receptor binding density in the preterm fetal sheep brain. J Appl Physiol (1985) 2020; 129:1431-1438. [PMID: 33054660 DOI: 10.1152/japplphysiol.00677.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Dopamine is often used to treat hypotension in preterm infants who are at risk of hypoxic-ischemic (HI) brain injury due to cerebral hypoperfusion and impaired autoregulation. There is evidence that systemically administered dopamine crosses the preterm blood-brain barrier. However, the effects of exogenous dopamine and cerebral HI on dopaminergic signaling in the immature brain are unknown. We determined the effect of HI and dopamine on D1 and D2 receptor binding and expressions of dopamine transporter (DAT) and tyrosine hydroxylase (TH) in the striatum of the preterm fetal sheep. Fetal sheep (99 days of gestation, term = 147days) were unoperated controls (n = 6) or exposed to severe HI using umbilical cord occlusion and saline infusion (UCO + saline, n = 8) or to HI with dopamine infusion (UCO + dopamine, 10 µg/kg/min, n = 7) for 74 h. D1 and D2 receptor densities were measured by autoradiography in vitro. DAT, TH, and cell death were measured using immunohistochemistry. HI resulted in cell death in the caudate nucleus and putamen, and dopamine infusion started before HI did not exacerbate or ameliorate these effects. HI led to reduced D1 and D2 receptor densities in the caudate nucleus and reduction in DAT protein expression in the caudate and putamen. Fetal brains exposed to dopamine in addition to HI were not different from those exposed to HI alone in these changes in dopaminergic parameters. We conclude that dopamine infusion does not alter the striatal cell death or the reductions in D1 and D2 receptor densities and DAT protein expression induced by HI in the preterm brain.NEW & NOTEWORTHY This is the first study on the effects of hypoxia-ischemia and dopamine treatment on the dopaminergic pathway in the preterm brain. In the striatum of fetal sheep (equivalent to ∼26-28 wk of human gestation), we demonstrate that hypoxia-ischemia leads to cell death, reduces D1 and D2 receptors, and reduces dopamine transporter. Intravenous dopamine infusion at clinical dosage used in preterm human infants does not alter the striatal cell death, D1 and D2 receptor density levels, and DAT protein expressions after hypoxia-ischemia in the preterm brain.
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Affiliation(s)
- F Y Wong
- The Ritchie Centre, The Hudson Institute of Medical Research, Melbourne, Australia.,Department of Paediatrics, Monash University, Melbourne, Australia.,Monash Newborn, Monash Medical Centre, Melbourne, Australia
| | - A Gogos
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Australia
| | - N Hale
- The Ritchie Centre, The Hudson Institute of Medical Research, Melbourne, Australia
| | - S A Ingelse
- The Ritchie Centre, The Hudson Institute of Medical Research, Melbourne, Australia
| | - N Brew
- The Ritchie Centre, The Hudson Institute of Medical Research, Melbourne, Australia
| | - K L Shepherd
- The Ritchie Centre, The Hudson Institute of Medical Research, Melbourne, Australia.,Department of Paediatrics, Monash University, Melbourne, Australia
| | - M van den Buuse
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Australia.,School of Psychology and Public Health, La Trobe University, Melbourne, Australia
| | - D W Walker
- The Ritchie Centre, The Hudson Institute of Medical Research, Melbourne, Australia.,School of Health & Biomedical Sciences, RMIT University, Melbourne, Australia
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Lear CA, Davidson JO, Dhillon SK, King VJ, Lear BA, Magawa S, Maeda Y, Ikeda T, Gunn AJ, Bennet L. Effects of antenatal dexamethasone and hyperglycemia on cardiovascular adaptation to asphyxia in preterm fetal sheep. Am J Physiol Regul Integr Comp Physiol 2020; 319:R653-R665. [PMID: 33074015 DOI: 10.1152/ajpregu.00216.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Antenatal glucocorticoids improve outcomes among premature infants but are associated with hyperglycemia, which can exacerbate hypoxic-ischemic injury. It is still unclear how antenatal glucocorticoids or hyperglycemia modulate fetal cardiovascular adaptations to severe asphyxia. In this study, preterm fetal sheep received either saline or 12 mg im maternal dexamethasone, followed 4 h later by complete umbilical cord occlusion (UCO) for 25 min. An additional cohort of fetuses received titrated glucose infusions followed 4 h later by UCO to control for the possibility that hyperglycemia contributed to the cardiovascular effects of dexamethasone. Fetuses were studied for 7 days after UCO. Maternal dexamethasone was associated with fetal hyperglycemia (P < 0.001), increased arterial pressure (P < 0.001), and reduced femoral (P < 0.005) and carotid (P < 0.05) vascular conductance before UCO. UCO was associated with bradycardia, femoral vasoconstriction, and transient hypertension. For the first 5 min of UCO, fetal blood pressure in the dexamethasone-asphyxia group was greater than saline-asphyxia (P < 0.001). However, the relative increase in arterial pressure was not different from saline-asphyxia. Fetal heart rate and femoral vascular conductance fell to similar nadirs in both saline and dexamethasone-asphyxia groups. Dexamethasone did not affect the progressive decline in femoral vascular tone or arterial pressure during continuing UCO. By contrast, there were no effects of glucose infusions on the response to UCO. In summary, maternal dexamethasone but not fetal hyperglycemia increased fetal arterial pressure before and for the first 5 min of prolonged UCO but did not augment the cardiovascular adaptations to acute asphyxia.
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Affiliation(s)
- Christopher A Lear
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Simerdeep K Dhillon
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Victoria J King
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Benjamin A Lear
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Shoichi Magawa
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Yoshiki Maeda
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Tomoaki Ikeda
- Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Alistair J Gunn
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
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Lear CA, Kasai M, Booth LC, Drury PP, Davidson JO, Maeda Y, Magawa S, Miyagi E, Ikeda T, Westgate JA, Bennet L, Gunn AJ. Peripheral chemoreflex control of fetal heart rate decelerations overwhelms the baroreflex during brief umbilical cord occlusions in fetal sheep. J Physiol 2020; 598:4523-4536. [PMID: 32705685 DOI: 10.1113/jp279573] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 07/13/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The majority of intrapartum decelerations are widely believed to be mediated by the baroreflex secondary to brief umbilical cord occlusions (UCOs) but this remains unproven. We examined the responses to brief-UCOs in fetal sheep and compared these to a phenylephrine-stimulated baroreflex in a separate cohort. A further cohort was instrumented with near-infrared spectroscopy to measure cerebral oxygenation during UCO. The first 3-4 s of the brief-UCOs were consistent with a baroreflex, and associated with a minor fall in fetal heart rate (FHR). Thereafter, the remainder of the FHR decelerations were highly consistent with the peripheral chemoreflex. The baroreflex is not sufficient to produce deep, rapid decelerations characteristic of variable decelerations and it is therefore likely to be a minor contributor to intrapartum decelerations. ABSTRACT Fetal heart rate (FHR) monitoring is widely used to assess fetal wellbeing during labour, yet the physiology underlying FHR patterns remains incompletely understood. The baroreflex is widely believed to mediate brief intrapartum decelerations, but evidence supporting this theory is lacking. We therefore investigated the physiological changes in near-term fetal sheep during brief repeated umbilical cord occlusions (brief-UCOs, n = 15). We compared this to separate cohorts that underwent a phenylephrine challenge to stimulate the baroreflex (n = 9) or were instrumented with near-infrared spectroscopy and underwent prolonged 15-min complete UCO (prolonged-UCO, n = 9). The first 3-4 s of brief-UCOs were associated with hypertension (P = 0.000), a fall in FHR by 9.7-16.9 bpm (P = 0.002). The FHR/MAP relationship during this time was consistent with that observed during a phenylephrine-induced baroreflex. At 4-5 s, the FHR/MAP relationship began to deviate from the phenylephrine baroreflex curve as FHR fell independently of MAP until its nadir in association with intense peripheral vasoconstriction (P = 0.000). During prolonged-UCO, cerebral oxygenation remained steady until 4 s after the start of prolonged-UCO, and then began to fall (P = 0.000). FHR and cerebral oxygenation then fell in parallel until the FHR nadir. In conclusion, the baroreflex has a minor role in mediating the first 3-4 s of FHR decelerations during complete UCO, but thereafter the peripheral chemoreflex is the dominant mediator. Overall, the baroreflex is neither necessary nor sufficient to produce deep, rapid decelerations characteristic of variable decelerations; it is therefore likely to be a minor contributor to intrapartum decelerations.
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Affiliation(s)
- Christopher A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Michi Kasai
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynecology, Yokohama City University, Yokohama, Japan
| | - Lindsea C Booth
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Paul P Drury
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Yoshiki Maeda
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Shoichi Magawa
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Etsuko Miyagi
- Department of Obstetrics and Gynecology, Yokohama City University, Yokohama, Japan
| | - Tomoaki Ikeda
- Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Jenny A Westgate
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
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Polglase GR, Schmölzer GM, Roberts CT, Blank DA, Badurdeen S, Crossley KJ, Miller SL, Stojanovska V, Galinsky R, Kluckow M, Gill AW, Hooper SB. Cardiopulmonary Resuscitation of Asystolic Newborn Lambs Prior to Umbilical Cord Clamping; the Timing of Cord Clamping Matters! Front Physiol 2020; 11:902. [PMID: 32848852 PMCID: PMC7406709 DOI: 10.3389/fphys.2020.00902] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 07/06/2020] [Indexed: 12/14/2022] Open
Abstract
Background: Current guidelines recommend immediate umbilical cord clamping (UCC) for newborns requiring chest compressions (CCs). Physiological-based cord clamping (PBCC), defined as delaying UCC until after lung aeration, has advantages over immediate UCC in mildly asphyxiated newborns, but its efficacy in asystolic newborns requiring CC is unknown. The aim of this study was to compare the cardiovascular response to CCs given prior to or after UCC in asystolic near-term lambs. Methods: Umbilical, carotid, pulmonary, and femoral arterial flows and pressures as well as systemic and cerebral oxygenation were measured in near-term sheep fetuses [139 ± 2 (SD) days gestation]. Fetal asphyxia was induced until asystole ensued, whereupon lambs received ventilation and CC before (PBCC; n = 16) or after (n = 12) UCC. Epinephrine was administered 1 min after ventilation onset and in 3-min intervals thereafter. The PBCC group was further separated into UCC at either 1 min (PBCC1, n = 8) or 10 min (PBCC10, n = 8) after return of spontaneous circulation (ROSC). Lambs were maintained for a further 30 min after ROSC. Results: The duration of CCs received and number of epinephrine doses required to obtain ROSC were similar between groups. After ROSC, we found no physiological benefits if UCC was delayed for 1 min compared to immediate cord clamping (ICC). However, if UCC was delayed for 10 min after ROSC, we found significant reductions in post-asphyxial rebound hypertension, cerebral blood flow, and cerebral oxygenation. The prevention of the post-asphyxial rebound hypertension in the PBCC10 group occurred due to the contribution of the placental circulation to a low peripheral resistance. As a result, left and right ventricular outputs continued to perfuse the placenta and were evidenced by reduced mean pulmonary blood flow, persistence of right-to-left shunting across the ductus arteriosus, and persistence of umbilical arterial and venous blood flows. Conclusion: It is possible to obtain ROSC after CC while the umbilical cord remains intact. There were no adverse effects of PBCC compared to ICC; however, the physiological changes observed after ROSC in the ICC and early PBCC groups may result in additional cerebral injury. Prolonging UCC after ROSC may provide significant physiological benefits that may reduce the risk of harm to the cerebral circulation.
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Affiliation(s)
- Graeme R Polglase
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Georg M Schmölzer
- Centre for the Studies of Asphyxia and Resuscitation, Neonatal Research Unit, Royal Alexandra Hospital, Edmonton, AB, Canada
| | - Calum T Roberts
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, VIC, Australia.,Department of Paediatrics, Monash University, Melbourne, VIC, Australia
| | - Douglas A Blank
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, VIC, Australia.,Department of Paediatrics, Monash University, Melbourne, VIC, Australia
| | - Shiraz Badurdeen
- Newborn Research Centre, The Royal Women's Hospital, Melbourne, VIC, Australia
| | - Kelly J Crossley
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, VIC, Australia
| | - Suzanne L Miller
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Vanesa Stojanovska
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, VIC, Australia
| | - Robert Galinsky
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, VIC, Australia
| | - Martin Kluckow
- Department of Neonatology, Royal North Shore Hospital, The University of Sydney, Sydney, NSW, Australia
| | - Andrew W Gill
- Centre for Neonatal Research and Education, The University of Western Australia, Subiaco, WA, Australia
| | - Stuart B Hooper
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
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9
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Varcoe TJ, Darby JRT, Holman SL, Bradshaw EL, Kuchel T, Vaughan L, Seed M, Wiese MD, Morrison JL. Fetal cardiovascular response to acute hypoxia during maternal anesthesia. Physiol Rep 2020; 8:e14365. [PMID: 32026576 PMCID: PMC7002532 DOI: 10.14814/phy2.14365] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 01/03/2020] [Indexed: 12/23/2022] Open
Abstract
Preclinical imaging studies of fetal hemodynamics require anesthesia to immobilize the animal. This may induce cardiovascular depression and confound measures under investigation. We compared the impact of four anesthetic regimes upon maternal and fetal blood gas and hemodynamics during baseline periods of normoxia, and in response to an acute hypoxic challenge in pregnant sheep. Merino ewes were surgically prepared with maternal and fetal vascular catheters and a fetal femoral artery flow probe at 105-109 days gestation. At 110-120 days gestation, ewes were anesthetized with either isoflurane (1.6%), isoflurane (0.8%) plus ketamine (3.6 mg·kg-1 ·h-1 ), ketamine (12.6 mg·kg-1 ·h-1 ) plus midazolam (0.78 mg·kg-1 ·h-1 ), propofol (30 mg·kg-1 ·h-1 ), or remained conscious. Following 60 min of baseline recording, nitrogen was administered directly into the maternal trachea to displace oxygen and induce maternal and thus fetal hypoxemia. During normoxia, maternal PaO2 was ~30 mmHg lower in anesthetized ewes compared to conscious controls, regardless of the type of anesthesia (p < .001). There was no effect of anesthesia on fetal mean arterial blood pressure (MAP; p > .05), but heart rate was 32 ± 8 bpm lower in fetuses from ewes administered isoflurane (p = .044). During maternal hypoxia, fetal MAP increased, and peripheral blood flow decreased in all fetuses except those administered propofol (p < .05). Unexpectedly, hypoxemia also induced fetal tachycardia regardless of the anesthetic regime (p < .05). These results indicate that despite maternal anesthesia, the fetus can mount a cardiovascular response to acute hypoxia by increasing blood pressure and reducing peripheral blood flow, although the heart rate response may differ from when no anesthesia is present.
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Affiliation(s)
- Tamara J. Varcoe
- Early Origins of Adult Health Research GroupUniversity of South AustraliaAdelaideAustralia
- School of Pharmacy and Medical SciencesUniversity of South AustraliaAdelaideAustralia
| | - Jack R. T. Darby
- Early Origins of Adult Health Research GroupUniversity of South AustraliaAdelaideAustralia
- School of Pharmacy and Medical SciencesUniversity of South AustraliaAdelaideAustralia
| | - Stacey L. Holman
- Early Origins of Adult Health Research GroupUniversity of South AustraliaAdelaideAustralia
- School of Pharmacy and Medical SciencesUniversity of South AustraliaAdelaideAustralia
| | - Emma L. Bradshaw
- Early Origins of Adult Health Research GroupUniversity of South AustraliaAdelaideAustralia
- School of Pharmacy and Medical SciencesUniversity of South AustraliaAdelaideAustralia
| | - Tim Kuchel
- South Australian Health and Medical Research InstituteAdelaideAustralia
| | - Lewis Vaughan
- South Australian Health and Medical Research InstituteAdelaideAustralia
| | | | - Michael D. Wiese
- School of Pharmacy and Medical SciencesUniversity of South AustraliaAdelaideAustralia
| | - Janna L. Morrison
- Early Origins of Adult Health Research GroupUniversity of South AustraliaAdelaideAustralia
- School of Pharmacy and Medical SciencesUniversity of South AustraliaAdelaideAustralia
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10
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Smolich JJ, Kenna KR, Cheung MMH, Mynard JP. Brief asphyxial state following immediate cord clamping accelerates onset of left-to-right shunting across the ductus arteriosus after birth in preterm lambs. J Appl Physiol (1985) 2020; 128:429-439. [PMID: 31971471 DOI: 10.1152/japplphysiol.00559.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Reversal of shunting across the ductus arteriosus from right-to-left to left-to-right is a characteristic feature of the birth transition. Given that immediate cord clamping (ICC) followed by an asphyxial cord clamp-to-ventilation (CC-V) interval may augment left ventricular (LV) output and central blood flows after birth, we tested the hypothesis that an asphyxial CC-V interval accelerates the onset of postnatal left-to-right ductal shunting. High-fidelity central blood flow signals were obtained in anesthetized preterm lambs (gestation 128 ± 2 days) after ICC followed by a nonasphyxial (∼40 s, n = 9) or asphyxial (∼90 s, n = 9) CC-V interval before mechanical ventilation for 30 min after birth. Left-to-right ductal flow segments were related to aortic isthmus and descending aortic flow profiles to quantify sources of ductal shunting. In the nonasphyxial group, phasic left-to-right ductal shunting was initially minor after birth, but then rose progressively to 437 ± 164 ml/min by 15 min (P < 0.001). However, in the asphyxial group, this shunting increased from 24 ± 21 to 199 ± 93 ml/min by 15 s after birth (P < 0.001) and rose further to 471 ± 190 ml/min by 2 min (P < 0.001). This earlier onset of left-to-right ductal shunting was supported by larger contributions (P < 0.001) from direct systolic LV flow and retrograde diastolic discharge from an arterial reservoir/windkessel located in the descending aorta and its major branches, and associated with increased pulmonary arterial blood flow having a larger ductal component. These findings suggest that the duration of the CC-V interval after ICC is an important modulator of left-to-right ductal shunting, LV output and pulmonary perfusion at birth.NEW & NOTEWORTHY This birth transition study in preterm lambs demonstrated that a brief (∼90 s) asphyxial interval between umbilical cord clamping and ventilation onset resulted in earlier and greater left-to-right shunting across the ductus arteriosus after birth. This greater shunting 1) resulted from an increased left ventricular output associated with a higher systolic left-to-right ductal flow and increased retrograde diastolic discharge from a lower body arterial reservoir/windkessel, and 2) was accompanied by greater lung perfusion after birth.
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Affiliation(s)
- Joseph J Smolich
- Heart Research, Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia
| | - Kelly R Kenna
- Heart Research, Murdoch Children's Research Institute, Melbourne, Australia
| | - Michael M H Cheung
- Heart Research, Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia.,Department of Cardiology, Royal Children's Hospital, Parkville, Victoria, Australia
| | - Jonathan P Mynard
- Heart Research, Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia.,Department of Biomedical Engineering, University of Melbourne, Melbourne, Australia.,Department of Cardiology, Royal Children's Hospital, Parkville, Victoria, Australia
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11
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Pacora P, Romero R, Jaiman S, Erez O, Bhatti G, Panaitescu B, Benshalom-Tirosh N, Jung Jung E, Hsu CD, Hassan SS, Yeo L, Kadar N. Mechanisms of death in structurally normal stillbirths. J Perinat Med 2019; 47:222-240. [PMID: 30231013 PMCID: PMC6349478 DOI: 10.1515/jpm-2018-0216] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 07/20/2018] [Indexed: 01/05/2023]
Abstract
Objectives To investigate mechanisms of in utero death in normally formed fetuses by measuring amniotic fluid (AF) biomarkers for hypoxia (erythropoietin [EPO]), myocardial damage (cardiac troponin I [cTnI]) and brain injury (glial fibrillary acidic protein [GFAP]), correlated with risk factors for fetal death and placental histopathology. Methods This retrospective, observational cohort study included intrauterine deaths with transabdominal amniocentesis prior to induction of labor. Women with a normal pregnancy and an indicated amniocentesis at term were randomly selected as controls. AF was assayed for EPO, cTnI and GFAP using commercial immunoassays. Placental histopathology was reviewed, and CD15-immunohistochemistry was used. Analyte concentrations >90th centile for controls were considered "raised". Raised AF EPO, AF cTnI and AF GFAP concentrations were considered evidence of hypoxia, myocardial and brain injury, respectively. Results There were 60 cases and 60 controls. Hypoxia was present in 88% (53/60), myocardial damage in 70% (42/60) and brain injury in 45% (27/60) of fetal deaths. Hypoxic fetuses had evidence of myocardial injury, brain injury or both in 77% (41/53), 49% (26/53) and 13% (7/53) of cases, respectively. Histopathological evidence for placental dysfunction was found in 74% (43/58) of these cases. Conclusion Hypoxia, secondary to placental dysfunction, was found to be the mechanism of death in the majority of fetal deaths among structurally normal fetuses. Ninety-one percent of hypoxic fetal deaths sustained brain, myocardial or both brain and myocardial injuries in utero. Hypoxic myocardial injury was an attributable mechanism of death in 70% of the cases. Non-hypoxic cases may be caused by cardiac arrhythmia secondary to a cardiac conduction defect.
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Affiliation(s)
- Percy Pacora
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan
| | - Roberto Romero
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, Michigan,Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, Michigan,Center for Molecular Medicine and Genetics, Wayne State University, Detroit, Michigan
| | - Sunil Jaiman
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan
| | - Offer Erez
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan,Department of Obstetrics and Gynecology, Soroka University Medical Center, School of Medicine, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beersheba, Israel
| | - Gaurav Bhatti
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan
| | - Bogdan Panaitescu
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan
| | - Neta Benshalom-Tirosh
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan,Department of Obstetrics and Gynecology, Soroka University Medical Center, School of Medicine, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beersheba, Israel
| | - Eun Jung Jung
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan
| | - Chaur-Dong Hsu
- Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan
| | - Sonia S. Hassan
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan,Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Lami Yeo
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan
| | - Nicholas Kadar
- Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, Maryland, and Detroit, Michigan,Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan
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12
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Lear CA, Westgate JA, Ugwumadu A, Nijhuis JG, Stone PR, Georgieva A, Ikeda T, Wassink G, Bennet L, Gunn AJ. Understanding Fetal Heart Rate Patterns That May Predict Antenatal and Intrapartum Neural Injury. Semin Pediatr Neurol 2018; 28:3-16. [PMID: 30522726 DOI: 10.1016/j.spen.2018.05.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Electronic fetal heart rate (FHR) monitoring is widely used to assess fetal well-being throughout pregnancy and labor. Both antenatal and intrapartum FHR monitoring are associated with a high negative predictive value and a very poor positive predictive value. This in part reflects the physiological resilience of the healthy fetus and the remarkable effectiveness of fetal adaptations to even severe challenges. In this way, the majority of "abnormal" FHR patterns in fact reflect a fetus' appropriate adaptive responses to adverse in utero conditions. Understanding the physiology of these adaptations, how they are reflected in the FHR trace and in what conditions they can fail is therefore critical to appreciating both the potential uses and limitations of electronic FHR monitoring.
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Affiliation(s)
- Christopher A Lear
- Department of Physiology, The Fetal Physiology and Neuroscience Group, The University of Auckland, Auckland, New Zealand
| | - Jenny A Westgate
- Department of Physiology, The Fetal Physiology and Neuroscience Group, The University of Auckland, Auckland, New Zealand; Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - Austin Ugwumadu
- Department of Obstetrics and Gynaecology, St George's, University of London, London, United Kingdom
| | - Jan G Nijhuis
- Department of Obstetrics and Gynaecology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, Netherlands
| | - Peter R Stone
- Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - Antoniya Georgieva
- Nuffield Department of Obstetrics and Gynaecology, The John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - Tomoaki Ikeda
- Department of Obstetrics and Gynaecology, Mie University Graduate School of Medicine, Mie, Japan
| | - Guido Wassink
- Department of Physiology, The Fetal Physiology and Neuroscience Group, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Department of Physiology, The Fetal Physiology and Neuroscience Group, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- Department of Physiology, The Fetal Physiology and Neuroscience Group, The University of Auckland, Auckland, New Zealand; Department of Paediatrics, Starship Children's Hospital, Auckland, New Zealand.
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13
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Lingwood BE, Eiby YA, Bjorkman ST, Miller SM, Wright IMR. Supporting preterm cardiovascular function. Clin Exp Pharmacol Physiol 2018; 46:274-279. [PMID: 30347457 DOI: 10.1111/1440-1681.13044] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 09/04/2018] [Accepted: 10/15/2018] [Indexed: 11/30/2022]
Abstract
Preterm infants are at higher risk of adverse neurodevelopmental outcomes. Inadequate cerebral oxygen delivery resulting from poor cardiovascular function is likely to be a significant contributor to preterm brain injury. In this context, improved support of cardiovascular function is integral to improving preterm outcomes. Many of the treatments used to support preterm cardiovascular function are based on adult physiology and may not be appropriate for the unique physiology of the preterm infant. The preterm heart is structurally immature with reduced contractility and low cardiac output. However, there is limited evidence that inotropic support with dopamine and/or dobutamine is effective in preterm babies. Hypovolemia may also contribute to poor preterm cardiovascular function; there is evidence that capillary leakage results in considerable loss of plasma from the circulation of newborn preterm babies. In addition, the vasoconstrictor response to acute stimuli does not develop until quite late in gestation and is limited in the preterm infant. This may lead to inappropriate vasodilatation adding to functional hypovolemia. The first line treatment for hypotension in preterm infants is volume expansion with crystalloid solutions, but this has limited efficacy in the preterm infant. More effective methods of volume expansion are required. Effective support of preterm cardiovascular function requires better understanding of preterm cardiovascular physiology so that treatments can target mechanisms that are sufficiently mature to respond.
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Affiliation(s)
- Barbara E Lingwood
- UQ Centre for Clinical Research and Perinatal Research Centre, The University of Queensland, Brisbane, Australia
| | - Yvonne A Eiby
- UQ Centre for Clinical Research and Perinatal Research Centre, The University of Queensland, Brisbane, Australia
| | - Stella T Bjorkman
- UQ Centre for Clinical Research and Perinatal Research Centre, The University of Queensland, Brisbane, Australia
| | - Stephanie M Miller
- UQ Centre for Clinical Research and Perinatal Research Centre, The University of Queensland, Brisbane, Australia
| | - Ian M R Wright
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, Australia
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14
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Eiby YA, Shrimpton NY, Wright IMR, Lumbers ER, Colditz PB, Duncombe GJ, Lingwood BE. Reduced blood volume decreases cerebral blood flow in preterm piglets. J Physiol 2018; 596:6033-6041. [PMID: 29917228 DOI: 10.1113/jp275583] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 06/11/2018] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS Preterm infants often have poor cardiovascular function that is associated with adverse neurodevelopmental outcomes. Preterm infants may be vulnerable to hypovolaemia due to excessive vasodilatation and leaky capillaries. Following reduction in blood volume, cardiac output and mean arterial pressure were reduced to the same extent in term and preterm piglets. Cerebral blood flow was maintained following blood volume reduction in term but not in preterm piglets. Effective detection and treatment of functional hypovolaemia may reduce the risk of brain injury in preterm infants. ABSTRACT Preterm infants often have impaired cardiovascular function that may contribute to poor neurodevelopmental outcomes. The study aimed to determine the effects of reduced blood volume on cardiovascular function, including cerebral blood flow, in preterm and term piglets. In preterm (97/115 days) and term piglets, up to 10% of the estimated blood volume was removed. Removal of blood was stopped if MAP dropped below 20 mmHg. Heart rate, cardiac contractility and relaxation, cardiac output, mean arterial pressure (MAP), and cerebral blood flow were measured at baseline and again after blood volume reduction. The volume of blood removed was less in preterm piglets than in term piglets (5.1 ± 1.8 vs. 7.7 ± 0.9 mL kg-1 , mean ± SD, P < 0.001). Cardiac output and MAP decreased to the same extent in term and preterm piglets. Cerebral blood flow decreased in preterm but not term piglets and cerebral vascular conductance increased in term piglets only. Compensatory responses to maintain cerebral blood flow after blood volume reduction are active in term piglets but not in preterm piglets. As a result, even a small reduction in blood volume, or an increase in the capacity of the circulatory system leading to functional hypovolaemia, may lead to a significant reduction in cerebral blood flow and contribute to brain injury in preterm neonates.
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Affiliation(s)
- Yvonne A Eiby
- UQ Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia.,Perinatal Research Centre, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Nicole Y Shrimpton
- UQ Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia.,Perinatal Research Centre, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Ian M R Wright
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales, Australia.,Graduate Medicine and The Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
| | - Eugenie R Lumbers
- UQ Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia.,School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales, Australia
| | - Paul B Colditz
- UQ Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia.,Perinatal Research Centre, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia.,Royal Brisbane and Women's Hospital, Department of Obstetrics and Gynaecology, Brisbane, Queensland, Australia
| | - Greg J Duncombe
- UQ Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia.,Royal Brisbane and Women's Hospital, Department of Obstetrics and Gynaecology, Brisbane, Queensland, Australia
| | - Barbara E Lingwood
- UQ Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia.,Perinatal Research Centre, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia.,Royal Brisbane and Women's Hospital, Department of Obstetrics and Gynaecology, Brisbane, Queensland, Australia
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15
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Dhillon SK, Lear CA, Galinsky R, Wassink G, Davidson JO, Juul S, Robertson NJ, Gunn AJ, Bennet L. The fetus at the tipping point: modifying the outcome of fetal asphyxia. J Physiol 2018; 596:5571-5592. [PMID: 29774532 DOI: 10.1113/jp274949] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 04/13/2018] [Indexed: 12/13/2022] Open
Abstract
Brain injury around birth is associated with nearly half of all cases of cerebral palsy. Although brain injury is multifactorial, particularly after preterm birth, acute hypoxia-ischaemia is a major contributor to injury. It is now well established that the severity of injury after hypoxia-ischaemia is determined by a dynamic balance between injurious and protective processes. In addition, mothers who are at risk of premature delivery have high rates of diabetes and antepartum infection/inflammation and are almost universally given treatments such as antenatal glucocorticoids and magnesium sulphate to reduce the risk of death and complications after preterm birth. We review evidence that these common factors affect responses to fetal asphyxia, often in unexpected ways. For example, glucocorticoid exposure dramatically increases delayed cell loss after acute hypoxia-ischaemia, largely through secondary hyperglycaemia. This critical new information is important to understand the effects of clinical treatments of women whose fetuses are at risk of perinatal asphyxia.
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Affiliation(s)
| | - Christopher A Lear
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Robert Galinsky
- The Department of Physiology, University of Auckland, Auckland, New Zealand.,The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Victoria, Australia
| | - Guido Wassink
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Sandra Juul
- Department of Pediatrics, University of Washington, Seattle, WA, USA
| | | | - Alistair J Gunn
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- The Department of Physiology, University of Auckland, Auckland, New Zealand
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16
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Galinsky R, Dhillon SK, Lear CA, Yamaguchi K, Wassink G, Gunn AJ, Bennet L. Magnesium sulfate and sex differences in cardiovascular and neural adaptations during normoxia and asphyxia in preterm fetal sheep. Am J Physiol Regul Integr Comp Physiol 2018; 315:R205-R217. [PMID: 29561649 DOI: 10.1152/ajpregu.00390.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Magnesium sulfate (MgSO4) is recommended for preterm neuroprotection, preeclampsia, and preterm labor prophylaxis. There is an important, unmet need to carefully test clinical interventions in both sexes. Therefore, we aimed to investigate cardiovascular and neurophysiological adaptations to MgSO4 during normoxia and asphyxia in preterm male and female fetal sheep. Fetuses were instrumented at 98 ± 1 days of gestation (term = 147 days). At 104 days, unanesthetized fetuses were randomly assigned to intravenous MgSO4 ( n = 12 female, 10 male) or saline ( n = 13 female, 10 male). At 105 days fetuses underwent umbilical cord occlusion for up to 25 min. Occlusions were stopped early if mean arterial blood pressure (MAP) fell below 8 mmHg or asystole occurred for >20 s. During normoxia, MgSO4 was associated with similar reductions in fetal heart rate (FHR), EEG power, and movement in both sexes ( P < 0.05 vs. saline controls) and suppression of α- and β-spectral band power in males ( P < 0.05 vs. saline controls). During occlusion, similar FHR and MAP responses occurred in MgSO4-treated males and females compared with saline controls. Recovery of FHR and MAP after release of occlusion was more prolonged in MgSO4-treated males ( P < 0.05 vs. saline controls). During and after occlusion, EEG power was lower in MgSO4-treated females ( P < 0.05 vs. saline controls). In conclusion, MgSO4 infusion was associated with subtle sex-specific effects on EEG spectral power and cardiac responses to asphyxia in utero, possibly reflecting sex-specific differences in interneuronal connectivity and regulation of cardiac output.
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Affiliation(s)
- Robert Galinsky
- Department of Physiology, University of Auckland , Auckland , New Zealand.,The Ritchie Centre, Hudson Institute of Medical Research , Clayton, VIC , Australia
| | | | - Christopher A Lear
- Department of Physiology, University of Auckland , Auckland , New Zealand
| | - Kyohei Yamaguchi
- Department of Physiology, University of Auckland , Auckland , New Zealand
| | - Guido Wassink
- Department of Physiology, University of Auckland , Auckland , New Zealand
| | - Alistair J Gunn
- Department of Physiology, University of Auckland , Auckland , New Zealand
| | - Laura Bennet
- Department of Physiology, University of Auckland , Auckland , New Zealand
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17
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Gilles F, Gressens P, Dammann O, Leviton A. Hypoxia-ischemia is not an antecedent of most preterm brain damage: the illusion of validity. Dev Med Child Neurol 2018; 60:120-125. [PMID: 28656697 PMCID: PMC5745320 DOI: 10.1111/dmcn.13483] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/06/2017] [Indexed: 01/05/2023]
Abstract
UNLABELLED Brain injury in preterm newborn infants is often attributed to hypoxia-ischemia even when neither hypoxia nor ischemia is documented, and many causative speculations are based on the same assumption. We review human and animal study contributions with their strengths and limitations, and conclude that - despite all the work done in human fetal neuropathology and developmental models in animals - the evidence remains unconvincing that hypoxemia, in the fetus or newborn infant, contributes appreciably to any encephalopathy of prematurity. Giving an inappropriate causal name to a disorder potentially limits the options for change, should our understanding of the etiologies advance. The only observationally-based title we think appropriate is 'encephalopathy of prematurity'. Future pathophysiological research should probably include appropriately designed epidemiology studies, highly active developmental processes, infection and other inflammatory stimuli, the immature immune system, long chain fatty acids and their transporters, and growth (neurotrophic) factors. WHAT THIS PAPER ADDS Fetal hypoxemia is rarely documented in brain injury studies. Animal studies fail to consider human-animal fetal anatomical differences. Putative treatments from animal models have not found clinical use. Observational studies constitute the only approach to etiological understanding. No convincing evidence yet that hypoxemia injures preterm brain. Encephalopathy of prematurity is preferable to hypoxia-ischemia as a term for this disorder. Encephalopathy of prematurity is preferable to hypoxia-ischemia as a term for this disorder.
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Affiliation(s)
| | - Pierre Gressens
- InsermU1141Hôpital Robert DebréParisFrance,Univ Paris DiderotSorbonne Paris CitéUMRS 1141ParisFrance,Centre for the Developing BrainDivision of Imaging Sciences and Biomedical EngineeringKCLSt. Thomas' HospitalLondonUK
| | - Olaf Dammann
- Tufts University School of MedicineBostonMAUSA,Hannover Medical SchoolHannoverGermany
| | - Alan Leviton
- Boston Children's Hospital and Harvard Medical SchoolBostonMAUSA
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18
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Dreiling M, Schiffner R, Bischoff S, Rupprecht S, Kroegel N, Schubert H, Witte OW, Schwab M, Rakers F. Impact of chronic maternal stress during early gestation on maternal-fetal stress transfer and fetal stress sensitivity in sheep. Stress 2018; 21:1-10. [PMID: 29041862 DOI: 10.1080/10253890.2017.1387534] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Acute stress-induced reduction of uterine blood flow (UBF) is an indirect mechanism of maternal-fetal stress transfer during late gestation. Effects of chronic psychosocial maternal stress (CMS) during early gestation, as may be experienced by many working women, on this stress signaling mechanism are unclear. We hypothesized that CMS in sheep during early gestation augments later acute stress-induced decreases of UBF, and aggravates the fetal hormonal, cardiovascular, and metabolic stress responses during later development. Six pregnant ewes underwent repeated isolation stress (CMS) between 30 and 100 days of gestation (dGA, term: 150 dGA) and seven pregnant ewes served as controls. At 110 dGA, ewes were chronically instrumented and underwent acute isolation stress. The acute stress decreased UBF by 19% in both the CMS and control groups (p < .05), but this was prolonged in CMS versus control ewes (74 vs. 30 min, p < .05). CMS increased fetal circulating baseline and stress-induced cortisol and norepinephrine concentrations indicating a hyperactive hypothalamus-pituitary-adrenal (HPA)-axis and sympathetic-adrenal-medullary system. Increased fetal norepinephrine is endogenous as maternal catecholamines do not cross the placenta. Cortisol in the control but not in the CMS fetuses was correlated with maternal cortisol blood concentrations; these findings indicate: (1) no increased maternal-fetal cortisol transfer with CMS, (2) cortisol production in CMS fetuses when the HPA-axis is normally inactive, due to early maturation of the fetal HPA-axis. CMS fetuses were better oxygenated, without shift towards acidosis compared to the controls, potentially reflecting adaptation to repeated stress. Hence, CMS enhances maternal-fetal stress transfer by prolonged reduction in UBF and increased fetal HPA responsiveness.
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Affiliation(s)
- Michelle Dreiling
- a Hans Berger Department of Neurology , Jena University Hospital , Jena , Germany
| | - Rene Schiffner
- a Hans Berger Department of Neurology , Jena University Hospital , Jena , Germany
| | - Sabine Bischoff
- b Institute of Lab Animal Sciences and Welfare , Jena University Hospital , Jena , Germany
| | - Sven Rupprecht
- a Hans Berger Department of Neurology , Jena University Hospital , Jena , Germany
| | - Nasim Kroegel
- a Hans Berger Department of Neurology , Jena University Hospital , Jena , Germany
| | - Harald Schubert
- b Institute of Lab Animal Sciences and Welfare , Jena University Hospital , Jena , Germany
| | - Otto W Witte
- a Hans Berger Department of Neurology , Jena University Hospital , Jena , Germany
| | - Matthias Schwab
- a Hans Berger Department of Neurology , Jena University Hospital , Jena , Germany
| | - Florian Rakers
- a Hans Berger Department of Neurology , Jena University Hospital , Jena , Germany
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19
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Antolic A, Wood CE, Keller-Wood M. Use of radiotelemetry to assess perinatal cardiac function in the ovine fetus and newborn. Am J Physiol Regul Integr Comp Physiol 2017; 313:R660-R668. [PMID: 28855176 PMCID: PMC5814690 DOI: 10.1152/ajpregu.00078.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 07/26/2017] [Accepted: 08/23/2017] [Indexed: 12/11/2022]
Abstract
The late gestation fetal ECG (fECG) has traditionally been difficult to characterize due to the low fECG signal relative to high maternal noise. Although new technologies have improved the feasibility of its acquisition and separation, little is known about its development in late gestation, a period in which the fetal heart undergoes extensive maturational changes. Here, we describe a method for the chronic implantation of radiotelemetry devices into late gestation ovine fetuses to characterize parameters of the fECG following surgery, throughout late gestation, and in the perinatal period. We found no significant changes in mean aortic pressure (MAP), heart rate (HR), or ECG in the 5 days following implantation; however, HR decreased in the first 24 h following the end of surgery, with associated increases in RR, PR, and QRS intervals. Over the last 14 days of fetal life, fetal MAP significantly increased, and HR significantly decreased, as expected. MAP and HR increased as labor progressed. Although there were no significant changes over time in the ECG during late gestation, the duration of the PR interval initially decreased and then increased as birth approached. These results indicate that although critical maturational changes occur in the late gestation fetal myocardium, the mechanisms that control the cardiac conduction are relatively mature in late gestation. The study demonstrates that radiotelemetry can be successfully used to assess fetal cardiac function, in particular conduction, through the process of labor and delivery, and may therefore be a useful tool for study of peripartum cardiac events.
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Affiliation(s)
- A Antolic
- Department of Pharmacodynamics, University of Florida, Gainesville, Florida;
| | - C E Wood
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida; and
| | - M Keller-Wood
- Department of Pharmacodynamics, University of Florida, Gainesville, Florida
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20
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Zarate MA, Chang EI, Antolic A, Wood CE. Ketamine modulates fetal hemodynamic and endocrine responses to umbilical cord occlusion. Physiol Rep 2017; 4:4/17/e12962. [PMID: 27597770 PMCID: PMC5027363 DOI: 10.14814/phy2.12962] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 08/06/2016] [Indexed: 12/13/2022] Open
Abstract
Umbilical cord occlusion (UCO) is a hypoxic insult that has been used to model birth asphyxia and umbilical cord compression in utero. UCO triggers vigorous neural and endocrine responses that include increased plasma ACTH and cortisol concentrations, increased blood pressure (BP), and decreased heart rate (HR). We have previously reported that ketamine, a noncompetitive N‐methyl‐D‐aspartate receptor antagonist, can modify the fetal hemodynamic and ACTH responses to ventilatory hypoxia and cerebral ischemia‐reperfusion. We performed the present experiments to test the hypothesis that ketamine has similar effects on the neuroendocrine and cardiovascular responses to UCO. Fetal sheep were chronically catheterized at gestational day 125. Ketamine (3 mg/kg) was administered intravenously to the fetus 10 min prior to the insult. UCO was induced for 30 min by reducing the umbilical vein blood flow until fetal PaO2 levels were reduced from 17 ± 1 to 11 ± 1 mm Hg. UCO produced an initial increase on fetal BP in both control and ketamine groups (P = 0.018 time), followed by a decrease in the control group, but values remained higher with ketamine. HR decreased after UCO (P = 0.041 stimulus*time) in both groups, but the reduction was greater initially in control compared to ketamine groups. Fetal PaCO2 levels increased after UCO (P < 0.01 stimulus*time), but values were higher in the control versus ketamine groups. UCO significantly decreased fetal pH values (P < 0.01 stimulus*time) with a greater effect on the control versus ketamine group. Ketamine delayed the cortisol responses to UCO (P < 0.001 stimulus*time), and UCO produced a robust increase in ACTH levels from 19 ± 2 to 280 ± 27 pg/mL (P < 0.001 stimulus*time), but there were no differences in ACTH levels between UCO groups. We conclude that ketamine augmented the cardiovascular response to UCO, but did not alter the ACTH response to UCO.
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Affiliation(s)
- Miguel A Zarate
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, Florida
| | - Eileen I Chang
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, Florida
| | - Andrew Antolic
- Department of Pharmacodynamics, University of Florida College of Pharmacy, Gainesville, Florida
| | - Charles E Wood
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, Florida
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21
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Duan AQ, Lock MC, Perumal SR, Darby JR, Soo JY, Selvanayagam JB, Macgowan CK, Seed M, Morrison JL. Feasibility of detecting myocardial infarction in the sheep fetus using late gadolinium enhancement CMR imaging. J Cardiovasc Magn Reson 2017; 19:69. [PMID: 28903760 PMCID: PMC5598048 DOI: 10.1186/s12968-017-0383-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 08/29/2017] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) imaging has enabled the accurate assessment of myocardial infarction (MI). However, LGE CMR has not been performed successfully in the fetus, where it could be useful for animal studies of interventions to promote cardiac regeneration. We believe that LGE imaging could allow us to document the presence, extent and effect of MI in utero and would thereby expand our capacity for conducting fetal sheep MI research. We therefore aimed to investigate the feasibility of using LGE to detect MI in sheep fetuses. METHODS Six sheep fetuses underwent a thoracotomy and ligation of a left anterior descending (LAD) coronary artery branch; while two fetuses underwent a sham surgery. LGE CMR was performed in a subset of fetuses immediately after the surgery and three days later. Early gadolinium enhancement (EGE) CMR was also performed in a subset of fetuses on both days. Cine imaging of the heart was performed to measure ventricular function. RESULTS The imaging performed immediately after LAD ligation revealed no evidence of infarct on LGE (n=3). Two of four infarcted fetuses (50%) showed hypoenhancement at the infarct site on the EGE images. Three days after the ligation, LGE images revealed a clear, hyper-enhanced infarct zone in four of the five infarcted fetuses (80%). No hyper-enhanced infarct zone was seen on the one sham fetus that underwent LGE CMR. No hypoenhancement could be seen in the EGE images in either the sham (n=1) or the infarcted fetus (n=1). No regional wall motion abnormalities were apparent in two of the five infarcted fetuses. CONCLUSION LGE CMR detected the MI three days after LAD ligation, but not immediately after. Using available methods, EGE imaging was less useful for detecting deficits in perfusion. Our study provides evidence for the ability of a non-invasive tool to monitor the progression of cardiac repair and damage in fetuses with MI. However, further investigation into the optimal timing of LGE and EGE scans and improvement of the sequences should be pursued with the aim of expanding our capacity to monitor cardiac regeneration after MI in fetal sheep.
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Affiliation(s)
- An Qi Duan
- Institute of Medical Science, Faculty of Medicine, University of Toronto, 1 King’s College Circle, Room 2374, Toronto, ON M5S 1A8 Canada
| | - Mitchell C. Lock
- Early Origins of Adult Health Research Group, Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Frome Road, Adelaide, South Australia 5000 Australia
| | - Sunthara Rajan Perumal
- Preclinical, Imaging and Research Laboratories, South Australian Health and Medical Research Institute, 101 Blacks Road, Gilles Plains, Adelaide, South Australia 5086 Australia
| | - Jack R. Darby
- Early Origins of Adult Health Research Group, Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Frome Road, Adelaide, South Australia 5000 Australia
| | - Jia Yin Soo
- Early Origins of Adult Health Research Group, Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Frome Road, Adelaide, South Australia 5000 Australia
| | - Joseph B. Selvanayagam
- Cardiac Imaging Research Group, Department of Heart Health, South Australian Health & Medical Research Institute, and Flinders University, GPO Box 2100, Adelaide, South Australia 5001 Australia
| | - Christopher K. Macgowan
- Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Room 08.9714, 686 Bay Street, Toronto, ON M5G 0A4 Canada
| | - Mike Seed
- Division of Cardiology, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8 Canada
| | - Janna L. Morrison
- Early Origins of Adult Health Research Group, Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Frome Road, Adelaide, South Australia 5000 Australia
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22
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More S, Bicout D, Botner A, Butterworth A, Calistri P, Depner K, Edwards S, Garin-Bastuji B, Good M, Gortazar Schmidt C, Michel V, Miranda MA, Saxmose Nielsen S, Velarde A, Thulke HH, Sihvonen L, Spoolder H, Stegeman JA, Raj M, Willeberg P, Candiani D, Winckler C. Animal welfare aspects in respect of the slaughter or killing of pregnant livestock animals (cattle, pigs, sheep, goats, horses). EFSA J 2017; 15:e04782. [PMID: 32625488 PMCID: PMC7009911 DOI: 10.2903/j.efsa.2017.4782] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
This scientific opinion addresses animal welfare aspects of slaughtering of livestock pregnant animals. Term of Reference (ToR) 1 requested assessment of the prevalence of animals slaughtered in a critical developmental stage of gestation when the livestock fetuses might experience negative affect. Limited data on European prevalence and related uncertainties necessitated a structured expert knowledge elicitation (EKE) exercise. Estimated median percentages of animals slaughtered in the last third of gestation are 3%, 1.5%, 0.5%, 0.8% and 0.2% (dairy cows, beef cattle, pigs, sheep and goats, respectively). Pregnant animals may be sent for slaughter for health, welfare, management and economic reasons (ToR2); there are also reasons for farmers not knowing that animals sent for slaughter are pregnant. Measures to reduce the incidence are listed. ToR3 asked whether livestock fetuses can experience pain and other negative affect. The available literature was reviewed and, at a second multidisciplinary EKE meeting, judgements and uncertainty were elicited. It is concluded that livestock fetuses in the last third of gestation have the anatomical and neurophysiological structures required to experience negative affect (with 90-100% likelihood). However, there are two different possibilities whether they perceive negative affect. It is more probable that the neurophysiological situation does not allow for conscious perception (with 66-99% likelihood) because of brain inhibitory mechanisms. There is also a less probable situation that livestock fetuses can experience negative affect (with 1-33% likelihood) arising from differences in the interpretation of the fetal electroencephalogram, observed responses to external stimuli and the possibility of fetal learning. Regarding methods to stun and kill livestock fetuses at slaughter (ToR4), sets of scenarios and respective actions take account of both the probable and less probable situation regarding fetal ability for conscious perception. Finally, information was collated on methods to establish the dam's gestational stage based on physical features of livestock fetuses (ToR5).
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23
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Bennet L. Sex, drugs and rock and roll: tales from preterm fetal life. J Physiol 2017; 595:1865-1881. [PMID: 28094441 DOI: 10.1113/jp272999] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Accepted: 12/22/2016] [Indexed: 12/14/2022] Open
Abstract
Premature fetuses and babies are at greater risk of mortality and morbidity than their term counterparts. The underlying causes are multifactorial, but include exposure to hypoxia. Immaturity of organs and their functional control may impair the physiological defence responses to hypoxia and the preterm fetal responses, or lack thereof, to moderate hypoxia appear to support this concept. However, as this review demonstrates, despite immaturity, the preterm fetus responds to asphyxia in a qualitatively similar manner to that seen at term. This highlights the importance in understanding metabolism versus homeostatic threat when assessing fetal responses to adverse challenges such as hypoxia. Data are presented to show that the preterm fetal adaptation to asphyxia is triphasic in nature. Phase one represents the rapid institution of maximal defences, designed to maintain blood pressure and central perfusion at the expense of peripheral organs. Phase two is one of adaptive compensation. Controlled reperfusion partially offsets peripheral tissue oxygen debt, while maintaining sufficient vasoconstriction to limit the fall in perfusion. Phase three is about decompensation. Strikingly, the preterm fetus generally performs better during phases two and three, and can survive for longer without injury. Paradoxically, however, the ability to survive can lead to longer exposure to hypotension and hypoperfusion and thus potentially greater injury. The effects of fetal sex, inflammation and drugs on the triphasic adaptations are reviewed. Finally, the review highlights the need for more comprehensive studies to understand the complexity of perinatal physiology if we are to develop effective strategies to improve preterm outcomes.
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Affiliation(s)
- Laura Bennet
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, 85 Park Road, Grafton, Auckland, 1023, New Zealand
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24
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Garabedian C, De Jonckheere J, Butruille L, Deruelle P, Storme L, Houfflin-Debarge V. Understanding fetal physiology and second line monitoring during labor. J Gynecol Obstet Hum Reprod 2017; 46:113-117. [PMID: 28403965 DOI: 10.1016/j.jogoh.2016.11.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 11/04/2016] [Accepted: 11/10/2016] [Indexed: 12/31/2022]
Abstract
Cardiotocography (CTG) is a technique used to monitor intrapartum fetal condition and is one of the most common obstetric procedures. Second line methods of fetal monitoring have been developed in an attempt to reduce unnecessary interventions due to continuous cardiotocography and to better identify fetuses at risk of intrapartum asphyxia. The acid-base balance of the fetus is evaluated by fetal blood scalp samples, the modification of the myocardial oxygenation by the fetal ECG ST-segment analysis (STAN) and the autonomic nervous system by the power spectral analysis of the fetal heart variability. To correctly interpret the features observed on CTG traces or second line methods, it seems important to understand normal physiology during labor and the compensatory mechanisms of the fetus in case of hypoxemia. Therefore, the aim of this review is first to describe fetal physiology during labor and then to explain the modification of the second line monitoring during labor.
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Affiliation(s)
- C Garabedian
- EA 4489, perinatal growth and environment, university Lille, 59000 Lille, France; Department of obstetrics, Jeanne-de-Flandre hospital, CHU Lille, 59000 Lille, France.
| | - J De Jonckheere
- EA 4489, perinatal growth and environment, university Lille, 59000 Lille, France; CIC-IT 1403, Maison Régionale de la Recherche Clinique, CHU Lille, 59000 Lille, France
| | - L Butruille
- EA 4489, perinatal growth and environment, university Lille, 59000 Lille, France
| | - P Deruelle
- EA 4489, perinatal growth and environment, university Lille, 59000 Lille, France; Department of obstetrics, Jeanne-de-Flandre hospital, CHU Lille, 59000 Lille, France
| | - L Storme
- EA 4489, perinatal growth and environment, university Lille, 59000 Lille, France; Department of neonatology, Jeanne-de-Flandre hospital, CHU Lille, 59000 Lille, France
| | - V Houfflin-Debarge
- EA 4489, perinatal growth and environment, university Lille, 59000 Lille, France; Department of obstetrics, Jeanne-de-Flandre hospital, CHU Lille, 59000 Lille, France
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25
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Brinks L, Moonen RMJ, Moral-Sanz J, Barreira B, Kessels L, Perez-Vizcaino F, Cogolludo A, Villamor E. Hypoxia-induced contraction of chicken embryo mesenteric arteries: mechanisms and developmental changes. Am J Physiol Regul Integr Comp Physiol 2016; 311:R858-R869. [DOI: 10.1152/ajpregu.00461.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 08/10/2016] [Indexed: 11/22/2022]
Abstract
The fetal cardiovascular responses to acute hypoxia include a redistribution of the cardiac output toward the heart and the brain at the expense of other organs, such as the intestine. We hypothesized that hypoxia exerts a direct effect on the mesenteric artery (MA) that may contribute to this response. Using wire myography, we investigated the response to hypoxia (Po2 ~2.5 kPa for 20 min) of isolated MAs from 15- to 21-day chicken embryos (E15, E19, E21), and 1- to 45-day-old chickens (P1, P3, P14, P45). Agonist-induced pretone or an intact endothelium were not required to obtain a consistent and reproducible response to hypoxia, which showed a pattern of initial rapid phasic contraction followed by a sustained tonic contraction. Phasic contraction was reduced by elimination of extracellular Ca2+ or by presence of the neurotoxin tetrodotoxin, the α1-adrenoceptor antagonist prazosin, or inhibitors of L-type voltage-gated Ca2+ channels (nifedipine), mitochondrial electron transport chain (rotenone and antimycin A), and NADPH oxidase (VAS2870). The Rho-kinase inhibitor Y27632 impaired both phasic and tonic contraction and, when combined with elimination of extracellular Ca2+, hypoxia-induced contraction was virtually abolished. Hypoxic MA contraction was absent at E15 but present from E19 and increased toward the first days posthatching. It then decreased during the first weeks of life and P45 MAs were unable to sustain hypoxia-induced contraction over time. In conclusion, the results of the present study demonstrate that hypoxic vasoconstriction is an intrinsic feature of chicken MA vascular smooth muscle cells during late embryogenesis and the perinatal period.
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Affiliation(s)
- Leonie Brinks
- Department of Pediatrics, Maastricht University Medical Center (MUMC+), School for Oncology and Developmental Biology (GROW), Maastricht, The Netherlands
| | - Rob M. J. Moonen
- Department of Pediatrics, Maastricht University Medical Center (MUMC+), School for Oncology and Developmental Biology (GROW), Maastricht, The Netherlands
- Department of Pediatrics, Zuyderland Medical Center, Heerlen, The Netherlands; and
| | - Javier Moral-Sanz
- Department of Pharmacology, School of Medicine, Universidad Complutense de Madrid, Centro de Investigaciones Biomédicas en Red de Enfermedades Respiratorias (CIBERES), Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain
| | - Bianca Barreira
- Department of Pharmacology, School of Medicine, Universidad Complutense de Madrid, Centro de Investigaciones Biomédicas en Red de Enfermedades Respiratorias (CIBERES), Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain
| | - Lilian Kessels
- Department of Pediatrics, Maastricht University Medical Center (MUMC+), School for Oncology and Developmental Biology (GROW), Maastricht, The Netherlands
| | - Francisco Perez-Vizcaino
- Department of Pharmacology, School of Medicine, Universidad Complutense de Madrid, Centro de Investigaciones Biomédicas en Red de Enfermedades Respiratorias (CIBERES), Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain
| | - Angel Cogolludo
- Department of Pharmacology, School of Medicine, Universidad Complutense de Madrid, Centro de Investigaciones Biomédicas en Red de Enfermedades Respiratorias (CIBERES), Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain
| | - Eduardo Villamor
- Department of Pediatrics, Maastricht University Medical Center (MUMC+), School for Oncology and Developmental Biology (GROW), Maastricht, The Netherlands
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26
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Galinsky R, Lear CA, Yamaguchi K, Wassink G, Westgate JA, Bennet L, Gunn AJ. Cholinergic and β-adrenergic control of cardiovascular reflex responses to brief repeated asphyxia in term-equivalent fetal sheep. Am J Physiol Regul Integr Comp Physiol 2016; 311:R949-R956. [PMID: 27654399 DOI: 10.1152/ajpregu.00340.2016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 09/12/2016] [Indexed: 11/22/2022]
Abstract
The role of cholinergic and β-adrenergic activity in mediating fetal cardiovascular recovery from brief repeated episodes of asphyxia consistent with established labor, remains unclear. In this study, we tested the effect of cholinergic and β-adrenergic blockade on the fetal chemoreflex and fetal heart rate (FHR) overshoot responses during brief repeated asphyxia at rates consistent with early or active labor. Chronically instrumented fetal sheep at 0.85 of gestation received either i.v. atropine sulfate (cholinergic blockade, n=8) or vehicle (n=7) followed by 3 x 1-minute umbilical cord occlusions repeated every 5 minutes (1:5; consistent with early labor), or i.v. propranolol hydrochloride (β-adrenergic blockade, n=6) or vehicle (n=6) followed by 3 x 2-minute occlusions repeated every 5 minutes (2:5; consistent with active labor). In vehicle-controls, 1:5 occlusions were associated with rapid and sustained FHR decelerations followed by rapid return of FHR to baseline values after release of the occlusion. Cholinergic blockade abolished FHR decelerations during occlusions and caused FHR overshoot after release of the occlusion (P<0.05 vs. control 1:5). In vehicle-controls, 2:5 occlusions caused rapid and sustained FHR decelerations followed by FHR overshoot after release of the occlusion. β-adrenergic blockade was associated with greater reduction in FHR during occlusions and attenuated FHR overshoot (P<0.05 vs. control 2:5). These data demonstrate that the FHR overshoot pattern after asphyxia is mediated by a combination of attenuated parasympathetic activity and increased β-adrenergic stimulation of the fetal heart.
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27
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Nikiforou M, Willburger C, de Jong AE, Kloosterboer N, Jellema RK, Ophelders DRMG, Steinbusch HWM, Kramer BW, Wolfs TGAM. Global hypoxia-ischemia induced inflammation and structural changes in the preterm ovine gut which were not ameliorated by mesenchymal stem cell treatment. Mol Med 2016; 22:244-257. [PMID: 27257938 PMCID: PMC5023518 DOI: 10.2119/molmed.2015.00252] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 04/11/2016] [Indexed: 12/13/2022] Open
Abstract
Perinatal asphyxia, a condition of impaired gas exchange during birth, leads to fetal hypoxia-ischemia (HI) and is associated with postnatal adverse outcomes including intestinal dysmotility and necrotizing enterocolitis (NEC). Evidence from adult animal models of transient, locally-induced intestinal HI has shown that inflammation is essential in HI-induced injury of the gut. Importantly, mesenchymal stem cell (MSC) treatment prevented this HI-induced intestinal damage. We therefore assessed whether fetal global HI induced inflammation, injury and developmental changes in the gut and whether intravenous MSC administration ameliorated these HI-induced adverse intestinal effects. In a preclinical ovine model, fetuses were subjected to umbilical cord occlusion (UCO), with or without MSC treatment, and sacrificed 7 days after UCO. Global HI increased the number of myeloperoxidase positive cells in the mucosa, upregulated mRNA levels of interleukin (IL)-1β and IL-17 in gut tissue and caused T-cell invasion in the intestinal muscle layer. Intestinal inflammation following global HI was associated with increased Ki67+ cells in the muscularis and subsequent muscle hyperplasia. Global HI caused distortion of glial fibrillary acidic protein immunoreactivity in the enteric glial cells and increased synaptophysin and serotonin expression in the myenteric ganglia. Intravenous MSC treatment did not ameliorate these HI-induced adverse intestinal events. Global HI resulted in intestinal inflammation and enteric nervous system abnormalities which are clinically associated with postnatal complications including feeding intolerance, altered gastrointestinal transit and NEC. The intestinal histopathological changes were not prevented by intravenous MSC treatment directly after HI, indicating that alternative treatment regimens for cell-based therapies should be explored.
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Affiliation(s)
- Maria Nikiforou
- Department of Pediatrics, Maastricht University Medical Center, Maastricht, The Netherlands
- School for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Carolin Willburger
- Department of Pediatrics, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Anja E de Jong
- Department of Pediatrics, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Nico Kloosterboer
- Department of Pediatrics, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Reint K Jellema
- Department of Pediatrics, Maastricht University Medical Center, Maastricht, The Netherlands
- School for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Daan RMG Ophelders
- Department of Pediatrics, Maastricht University Medical Center, Maastricht, The Netherlands
- School for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Harry WM Steinbusch
- School for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Boris W Kramer
- Department of Pediatrics, Maastricht University Medical Center, Maastricht, The Netherlands
- School for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
- School of Oncology and Developmental Biology, Maastricht University, Maastricht, The Netherlands
| | - Tim GAM Wolfs
- Department of Pediatrics, Maastricht University Medical Center, Maastricht, The Netherlands
- School of Oncology and Developmental Biology, Maastricht University, Maastricht, The Netherlands
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28
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Lear CA, Galinsky R, Wassink G, Yamaguchi K, Davidson JO, Westgate JA, Bennet L, Gunn AJ. The myths and physiology surrounding intrapartum decelerations: the critical role of the peripheral chemoreflex. J Physiol 2016; 594:4711-25. [PMID: 27328617 DOI: 10.1113/jp271205] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Accepted: 02/17/2016] [Indexed: 11/08/2022] Open
Abstract
A distinctive pattern of recurrent rapid falls in fetal heart rate, called decelerations, are commonly associated with uterine contractions during labour. These brief decelerations are mediated by vagal activation. The reflex triggering this vagal response has been variably attributed to a mechanoreceptor response to fetal head compression, to baroreflex activation following increased blood pressure during umbilical cord compression, and/or a Bezold-Jarisch reflex response to reduced venous return from the placenta. Although these complex explanations are still widespread today, there is no consistent evidence that they are common during labour. Instead, the only mechanism that has been systematically investigated, proven to be reliably active during labour and, crucially, capable of producing rapid decelerations is the peripheral chemoreflex. The peripheral chemoreflex is triggered by transient periods of asphyxia that are a normal phenomenon associated with all uterine contractions. This should not cause concern as the healthy fetus has a remarkable ability to adapt to these repeated but short periods of asphyxia. This means that the healthy fetus is typically not at risk of hypotension and injury during uncomplicated labour even during repeated brief decelerations. The physiologically incorrect theories surrounding decelerations that ignore the natural occurrence of repeated asphyxia probably gained widespread support to help explain why many babies are born healthy despite repeated decelerations during labour. We propose that a unified and physiological understanding of intrapartum decelerations that accepts the true nature of labour is critical to improve interpretation of intrapartum fetal heart rate patterns.
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Affiliation(s)
- Christopher A Lear
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Robert Galinsky
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Guido Wassink
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Kyohei Yamaguchi
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynaecology, Mie University Graduate School of Medicine, Mie, Japan
| | - Joanne O Davidson
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Jenny A Westgate
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Starship Children's Hospital, Auckland, New Zealand
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Brew N, Azhan A, den Heijer I, Boomgardt M, Davies G, Nitsos I, Miller S, Walker A, Walker D, Wong F. Dopamine treatment during acute hypoxia is neuroprotective in the developing sheep brain. Neuroscience 2016; 316:82-93. [DOI: 10.1016/j.neuroscience.2015.12.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 12/04/2015] [Accepted: 12/14/2015] [Indexed: 11/15/2022]
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van den Heuij LG, Wassink G, Gunn AJ, Bennet L. Using Pregnant Sheep to Model Developmental Brain Damage. NEUROMETHODS 2016. [DOI: 10.1007/978-1-4939-3014-2_16] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Effects of chest compressions on cardiovascular and cerebral hemodynamics in asphyxiated near-term lambs. Pediatr Res 2015; 78:395-400. [PMID: 26086644 DOI: 10.1038/pr.2015.117] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 03/16/2015] [Indexed: 11/08/2022]
Abstract
BACKGROUND Chest compressions (CC) and adrenaline administration are recommended in asphyxiated newborns with persistent bradycardia despite effective ventilation. The effects of CC on cerebral blood flow in newborns at birth are unknown. Our aim was to determine the effects of CC, with or without adrenaline administration, on the return of spontaneous circulation, carotid blood flow (CBF), and carotid arterial pressure (CAP) in asphyxiated near-term lambs. METHODS Asphyxia was induced in near-term lambs by clamping the umbilical cord and delaying ventilation onset until spontaneous circulation ceased. Lambs were then resuscitated by positive pressure ventilation along with CC followed by adrenaline administration. CAP and CBF were continuously recorded. RESULTS Mean CAP did not increase significantly during CC and only increased following adrenaline administration. CC did not increase mean CBF but increased CBF amplitude due to increased peak flow and the onset of retrograde flow during diastole. Adrenaline increased mean CBF from 1 ± 2 to 15 ± 5 ml/kg/min and abolished retrograde diastolic CBF, leading to the return in spontaneous circulation. CONCLUSION We conclude that CC with adrenaline administration was required to increase CBF and restore spontaneous circulation in asphyxiated lambs. Low CBF and retrograde diastolic CBF during CC indicate hypoperfusion to the brain.
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Galinsky R, Davidson JO, Drury PP, Wassink G, Lear CA, van den Heuij LG, Gunn AJ, Bennet L. Magnesium sulphate and cardiovascular and cerebrovascular adaptations to asphyxia in preterm fetal sheep. J Physiol 2015; 594:1281-93. [PMID: 26077461 DOI: 10.1113/jp270614] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 06/08/2015] [Indexed: 11/08/2022] Open
Abstract
Magnesium sulphate is a standard therapy for eclampsia in pregnancy and is widely recommended for perinatal neuroprotection during threatened preterm labour. MgSO4 is a vasodilator and negative inotrope. Therefore the aim of this study was to investigate the effect of MgSO4 on the cardiovascular and cerebrovascular responses of the preterm fetus to asphyxia. Fetal sheep were instrumented at 98 ± 1 days of gestation (term = 147 days). At 104 days, unanaesthetised fetuses were randomly assigned to receive an intravenous infusion of MgSO4 (n = 6) or saline (n = 9). At 105 days all fetuses underwent umbilical cord occlusion for 25 min. Before occlusion, MgSO4 treatment reduced heart rate and increased femoral blood flow (FBF) and vascular conductance compared to controls. During occlusion, carotid and femoral arterial conductance and blood flows were higher in MgSO4-treated fetuses than controls. After occlusion, fetal heart rate was lower and carotid and femoral arterial conductance and blood flows were higher in MgSO4-treated fetuses than controls. Femoral arterial waveform height and width were increased during MgSO4 infusion, consistent with increased stroke volume. MgSO4 did not alter the fetal neurophysiological or nuchal electromyographic responses to asphyxia. These data demonstrate that a clinically comparable dose of MgSO4 increased FBF and stroke volume without impairing mean arterial pressure (MAP) or carotid blood flow (CaBF) during and immediately after profound asphyxia. Thus, MgSO4 may increase perfusion of peripheral vascular beds during adverse perinatal events.
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Affiliation(s)
- Robert Galinsky
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Paul P Drury
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Guido Wassink
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Christopher A Lear
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | | | - Alistair J Gunn
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- The Department of Physiology, University of Auckland, Auckland, New Zealand
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Sandgren J, Scholz TD, Segar JL. ANG II modulation of cardiac growth and remodeling in immature fetal sheep. Am J Physiol Regul Integr Comp Physiol 2015; 308:R965-72. [PMID: 25810382 DOI: 10.1152/ajpregu.00034.2015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 03/20/2015] [Indexed: 01/09/2023]
Abstract
ANG II increases fetal blood pressure and stimulates fetal heart growth; however, little is known regarding its direct effects on cardiomyocytes in vivo. We sought to determine whether ANG II stimulates heart growth and cardiomyocyte hypertrophy and/or hyperplasia in utero in the immature fetal heart independent of the effects on cardiac afterload. In twin gestation, fetal sheep at ∼100 days gestation (term 145 days), one fetus received a chronic (6 days) infusion of ANG II alone (50 μg·kg(-1)·min(-1)) or ANG II plus nitroprusside (NTP) to attenuate the increase in blood pressure; noninstrumented twins served as controls. ANG II alone, but not ANG II + NTP resulted in a significant increase in heart mass (left and right ventricle + septum, corrected for body weight) compared with controls. ANG II, but not ANG II+NTP, also significantly increased cardiomyocyte area compared with control and increased the percentage of binucleated myocytes. ANG II with or without concomitant infusion of NTP increased cardiac PCNA expression, a marker of proliferation. Steady-state protein expression of terminal mitogen-activated protein kinases, cyclin B1, cyclin E1, and p21 were similar among groups. We conclude that in vivo, ANG II increases fetal cardiac mass via cardiomyocyte hypertrophy, differentiation, and to a lesser extent hyperplasia. The effects of ANG II on hypertrophy appear dependent upon the increase in blood pressure (mechanical load), whereas effects on proliferation are load-independent.
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Affiliation(s)
- Jeremy Sandgren
- Stead Family Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa
| | - Thomas D Scholz
- Stead Family Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa
| | - Jeffrey L Segar
- Stead Family Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa
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Smolich JJ, Kenna KR, Cheung MM. Onset of asphyxial state in nonrespiring interval between cord clamping and ventilation increases hemodynamic lability of birth transition in preterm lambs. J Appl Physiol (1985) 2015; 118:675-83. [PMID: 25614604 DOI: 10.1152/japplphysiol.01147.2014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Experimentally, a typical ∼2-min cord clamp-to-ventilation interval in preterm lambs is accompanied by increased hemodynamic lability of the birth transition. However, whether this lability is related to development of asphyxia after cord clamping, or can be avoided with a shorter clamp-to-ventilation interval, is unknown. To address these questions, anesthetized preterm fetal lambs (gestation 127 ± 2 days) were instrumented with ductus arteriosus and left pulmonary artery flow probes to obtain right ventricular (RV) output, brachiocephalic trunk and aortic isthmus flow probes to measure left ventricular (LV) output, and aortic trunk catheters for pressure measurement and blood gas analysis. With hemodynamics recorded continuously, fetuses were delivered onto the ewe's abdomen and the cord clamped for 1.5 min before ventilation (n = 8), with aortic sampling at 15, 30, 45, and 60 s, or for 0.5 min, with sampling at 15 s (n = 4). With 1.5-min cord clamping, an asphyxial state (Po2 < 10 mmHg) was evident at ≥45 s, with bradycardia and marked falls in LV and RV outputs (by 60% and 50%, P < 0.001), followed after ventilation onset by tachycardia and LV and RV output surges (4- and 3-fold, P < 0.001). By contrast, heart rate and outputs remained stable after 0.5-min cord clamping, with no postventilation change in heart rate or RV output, and a lesser rise in LV output (22%, P < 0.005). In preterm lambs, rapid development of an asphyxial state within 45 s in the cord clamp-to-ventilation interval increased hemodynamic lability of the birth transition, which was reduced with a shorter (∼0.5 min) cord clamp-to-ventilation interval.
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Affiliation(s)
- Joseph J Smolich
- Heart Research Group, Murdoch Childrens Research Institute, Parkville, Australia; Department of Paediatrics, University of Melbourne, Parkville, Australia
| | - Kelly R Kenna
- Heart Research Group, Murdoch Childrens Research Institute, Parkville, Australia
| | - Michael M Cheung
- Heart Research Group, Murdoch Childrens Research Institute, Parkville, Australia; Department of Cardiology, Royal Children's Hospital, Parkville, Australia; and Department of Paediatrics, University of Melbourne, Parkville, Australia
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Eiby YA, Lumbers ER, Staunton MP, Wright LL, Colditz PB, Wright IMR, Lingwood BE. Endogenous angiotensins and catecholamines do not reduce skin blood flow or prevent hypotension in preterm piglets. Physiol Rep 2014; 2:2/12/e12245. [PMID: 25538149 PMCID: PMC4332223 DOI: 10.14814/phy2.12245] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Endocrine control of cardiovascular function is probably immature in the preterm infant; thus, it may contribute to the relative ineffectiveness of current adrenergic treatments for preterm cardiovascular compromise. This study aimed to determine the cardiovascular and hormonal responses to stress in the preterm piglet. Piglets were delivered by cesarean section either preterm (97 of 115 days) or at term (113 days). An additional group of preterm piglets received maternal glucocorticoids as used clinically. Piglets were sedated and underwent hypoxia (4% FiO2 for 20 min) to stimulate a cardiovascular response. Arterial blood pressure, skin blood flow, heart rate and plasma levels of epinephrine, norepinephrine, angiotensin II (Ang II), angiotensin‐(1–7) (Ang‐(1‐7)), and cortisol were measured. Term piglets responded to hypoxia with vasoconstriction; preterm piglets had a lesser response. Preterm piglets had lower blood pressures throughout, with a delayed blood pressure response to the hypoxic stress compared with term piglets. This immature response occurred despite similar high levels of circulating catecholamines, and higher levels of Ang II compared with term animals. Prenatal exposure to glucocorticoids increased the ratio of Ang‐(1‐7):Ang II. Preterm piglets, in contrast to term piglets, had no increase in cortisol levels in response to hypoxia. Preterm piglets have immature physiological responses to a hypoxic stress but no deficit of circulating catecholamines. Reduced vasoconstriction in preterm piglets could result from vasodilator actions of Ang II. In glucocorticoid exposed preterm piglets, further inhibition of vasoconstriction may occur because of an increased conversion of Ang II to Ang‐(1‐7). This study aimed to determine if immature hormonal control of the cardiovascular system contributes to preterm cardiovascular compromise. Physiological and hormonal responses of preterm piglets to hypoxia are immature compared with term piglets. This is not due to a lack of endogenous catecholamines or angiotensin II, but may be due to the differences in cardiovascular actions of the renin–angiotensin system.
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Affiliation(s)
- Yvonne A Eiby
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Eugenie R Lumbers
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales, Australia
| | - Michael P Staunton
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Layne L Wright
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Paul B Colditz
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Ian M R Wright
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales, Australia Graduate School of Medicine and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
| | - Barbara E Lingwood
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
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Urakova NA, Urakov AL. Diagnosis of Intrauterine Brain Hypoxia Using Thermal Imaging Video Monitoring of the Fetus. BIOMEDICAL ENGINEERING 2014; 48:111-115. [DOI: 10.1007/s10527-014-9432-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/26/2024]
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van den Heuij LG, Mathai S, Davidson JO, Lear CA, Booth LC, Fraser M, Gunn AJ, Bennet L. Synergistic white matter protection with acute-on-chronic endotoxin and subsequent asphyxia in preterm fetal sheep. J Neuroinflammation 2014; 11:89. [PMID: 24886663 PMCID: PMC4039331 DOI: 10.1186/1742-2094-11-89] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2014] [Accepted: 05/01/2014] [Indexed: 12/16/2022] Open
Abstract
Background Perinatal asphyxia and exposure to intrauterine infection are associated with impaired neurodevelopment in preterm infants. Acute exposure to non-injurious infection and/or inflammation can either protect or sensitize the brain to subsequent hypoxia-ischemia. However, the effects of subacute infection and/or inflammation are unclear. In this study we tested the hypothesis that acute-on-chronic exposure to lipopolysaccharide (LPS) would exacerbate white matter injury after subsequent asphyxia in preterm fetal sheep. Methods Fetal sheep at 0.7 gestational age received a continuous LPS infusion at 100 ng/kg for 24 hours, then 250 ng/kg/24 hours for 96 hours, plus 1 μg boluses of LPS at 48, 72, and 96 hours or the same volume of saline. Four hours after the last bolus, complete umbilical cord occlusion or sham occlusion was induced for 15 minutes. Sheep were sacrificed 10 days after the start of infusions. Results LPS exposure was associated with induction of microglia and astrocytes and loss of total and immature and mature oligodendrocytes (n = 9) compared to sham controls (n = 9). Umbilical cord occlusion with saline infusions was associated with induction of microglia, astrogliosis, and loss of immature and mature oligodendrocytes (n = 9). LPS exposure before asphyxia (n = 8) was associated with significantly reduced microglial activation and astrogliosis and improved numbers of immature and mature oligodendrocytes compared to either LPS exposure or asphyxia alone. Conclusions Contrary to our initial hypothesis, the combination of acute-on-chronic LPS with subsequent asphyxia reduced neuroinflammation and white matter injury compared with either intervention alone.
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Affiliation(s)
| | | | | | | | | | | | - Alistair J Gunn
- Department of Physiology, University of Auckland, Park Road, Grafton, Auckland 1023, New Zealand.
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Galinsky R, Jensen EC, Bennet L, Mitchell CJ, Gunn ER, Wassink G, Fraser M, Westgate JA, Gunn AJ. Sustained sympathetic nervous system support of arterial blood pressure during repeated brief umbilical cord occlusions in near-term fetal sheep. Am J Physiol Regul Integr Comp Physiol 2014; 306:R787-95. [PMID: 24647590 DOI: 10.1152/ajpregu.00001.2014] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sympathetic nervous system (SNS)-mediated peripheral vasoconstriction plays a key role in initial maintenance of blood pressure during rapid-onset asphyxia in the mammalian fetus, but it is attenuated after the first few minutes. It is unclear whether the SNS response is sustained during the brief, but frequently repeated, episodes of asphyxia characteristic of labor. In the present study, 14 fetal sheep at 0.85 of gestation received either chemical sympathectomy with 6-hydroxydopamine (6-OHDA; n = 7) or sham injection (control; n = 7), followed 4-5 days later by repeated 2-min episodes of complete umbilical cord occlusion every 5 min for up to 4 h or until mean arterial blood pressure (MAP) fell to <20 mmHg for two successive occlusions. In controls, umbilical cord occlusions were associated with a rapid initial fall in fetal heart rate (FHR) and femoral blood flow (FBF), with initial hypertension, followed by progressive development of hypotension during ongoing occlusions. Sympathectomy was associated with attenuation of the initial rise in MAP during umbilical cord occlusion, and after the onset of hypotension, a markedly more rapid fall of MAP to the nadir, with a correspondingly slower fall in FBF (P < 0.05). In contrast, MAP and FHR between successive occlusions were higher after sympathectomy (P < 0.05). There was no significant difference in the number of occlusions before terminal hypotension (6-OHDA; 16.1 ± 2.2 vs. control; 18.7 ± 2.3). These data show that SNS activity provides ongoing support for fetal MAP during prolonged exposure to brief repeated asphyxia.
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Affiliation(s)
- Robert Galinsky
- Department of Physiology, University of Auckland, Auckland, New Zealand; and
| | - Ellen C Jensen
- Department of Physiology, University of Auckland, Auckland, New Zealand; and
| | - Laura Bennet
- Department of Physiology, University of Auckland, Auckland, New Zealand; and
| | - Clinton J Mitchell
- Department of Physiology, University of Auckland, Auckland, New Zealand; and
| | - Eleanor R Gunn
- Department of Physiology, University of Auckland, Auckland, New Zealand; and
| | - Guido Wassink
- Department of Physiology, University of Auckland, Auckland, New Zealand; and
| | - Mhoyra Fraser
- Department of Physiology, University of Auckland, Auckland, New Zealand; and The Liggins Institute, University of Auckland, Auckland, New Zealand
| | - Jennifer A Westgate
- Department of Physiology, University of Auckland, Auckland, New Zealand; and
| | - Alistair J Gunn
- Department of Physiology, University of Auckland, Auckland, New Zealand; and
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Olhager E, Nold-Petry CA, Joshi MS, Doery JCG, Samarasinghe T, Walker AM, Wong FY. Preterm lambs given intravenous dopamine show increased dopamine in their cerebrospinal fluid. Acta Paediatr 2014; 103:337-42. [PMID: 24267481 DOI: 10.1111/apa.12520] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 10/07/2013] [Accepted: 11/20/2013] [Indexed: 11/26/2022]
Abstract
AIM Dopamine is used as an inotropic medication in preterm infants. The preterm human blood brain barrier (BBB) is permeable to intravascular dopamine, and the impact of exogenous dopamine on the preterm brain remains unknown. The preterm lamb model may be suitable for studying the cerebral impact of dopamine therapy whether its BBB permeability is similar to preterm human infants. We aimed to examine BBB permeability to exogenous dopamine in the preterm lamb, by measuring dopamine levels in the cerebrospinal fluid (CSF). METHODS Nine preterm foetal lambs (125-130 days, term = 147 days) were given either dopamine at 10 μg/kg/min (dopamine, n = 4) or saline (control, n = 5). CSF, and plasma samples were taken for dopamine assay. RESULTS The median (range) baseline CSF dopamine level for the combined control and dopamine groups (n = 9) was 0.10(0.03-0.16) ng/mL, and baseline plasma dopamine was 0.30(0.13-0.84) ng/mL. The dopamine lambs showed increase in CSF dopamine to 3.91(1.87-11.35) ng/mL with plasma dopamine increased to 14.2 (9.1-57.9) ng/mL. No change was found in the control lambs. CONCLUSION In the preterm lamb, the BBB permeability and pharmacokinetics to dopamine infusion are similar to findings in the preterm human infant, supporting applicability of the preterm lamb model for studying effects of dopamine infusion in the preterm human brain.
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Affiliation(s)
- Elisabeth Olhager
- The Ritchie Centre; Monash University; Melbourne VIC Australia
- Department of clinical and experimental medicine; Linkoping University; Linkoping Sweden
| | | | - Mandar S Joshi
- The Ritchie Centre; Monash University; Melbourne VIC Australia
| | - James CG Doery
- Department of Biochemistry; Monash Medical Centre; Melbourne VIC Australia
- Department of Medicine; Monash University; Melbourne VIC Australia
| | | | - Adrian M Walker
- The Ritchie Centre; Monash University; Melbourne VIC Australia
| | - Flora Y Wong
- The Ritchie Centre; Monash University; Melbourne VIC Australia
- Monash Newborn, Monash Medical Centre; Melbourne VIC Australia
- Department of Paediatrics; Monash University; Melbourne VIC Australia
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Does Maturity Affect Cephalic Perfusion and T/QRS Ratio during Prolonged Umbilical Cord Occlusion in Fetal Sheep? Obstet Gynecol Int 2014; 2014:314159. [PMID: 24693290 PMCID: PMC3945773 DOI: 10.1155/2014/314159] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 12/18/2013] [Accepted: 12/31/2013] [Indexed: 11/17/2022] Open
Abstract
T/QRS ratio monitoring is used to help identify fetal asphyxia. However, immature animals have greater capacity to maintain blood pressure during severe asphyxia, raising the possibility that they may show an attenuated T/QRS increase during asphyxia. Chronically instrumented fetal sheep at 0.6 of gestation (0.6 GA; n = 12), 0.7 GA (n = 12), and 0.8 GA (n = 8) underwent complete umbilical cord occlusion for 30 min, 25 min, or 15 min, respectively. Cord occlusion was associated with progressive metabolic acidosis and initial hypertension followed by severe hypotension, with a more rapid fall in mean arterial blood pressure (MAP) and carotid blood flow (CaBF) with advancing gestation. T/QRS ratio rose after occlusion more rapidly at 0.8 GA than in immature fetuses, to a similar final peak at all ages, followed by a progressive fall that was slower at 0.8 GA than in the immature fetuses. The increase in T/QRS ratio correlated with initial hypertension at 0.8 GA (P < 0.05, R2 = 0.38), and conversely, its fall correlated closely with falling MAP in all gestational groups (P < 0.01, R2 = 0.67). In conclusion, elevation of the T/QRS ratio is an index of onset of severe asphyxia in the last third of gestation, but not of fetal compromise.
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Koome ME, Bennet L, Booth LC, Davidson JO, Wassink G, Gunn AJ. Ontogeny and control of the heart rate power spectrum in the last third of gestation in fetal sheep. Exp Physiol 2013; 99:80-8. [DOI: 10.1113/expphysiol.2013.074567] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Wassink G, Bennet L, Davidson JO, Westgate JA, Gunn AJ. Pre-existing hypoxia is associated with greater EEG suppression and early onset of evolving seizure activity during brief repeated asphyxia in near-term fetal sheep. PLoS One 2013; 8:e73895. [PMID: 23991209 PMCID: PMC3749175 DOI: 10.1371/journal.pone.0073895] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 07/23/2013] [Indexed: 11/19/2022] Open
Abstract
Spontaneous antenatal hypoxia is associated with high risk of adverse outcomes, however, there is little information on neural adaptation to labor-like insults. Chronically instrumented near-term sheep fetuses (125 ± 3 days, mean ± SEM) with baseline PaO2 < 17 mmHg (hypoxic group: n = 8) or > 17 mmHg (normoxic group: n = 8) received 1-minute umbilical cord occlusions repeated every 5 minutes for a total of 4 hours, or until mean arterial blood pressure (MAP) fell below 20 mmHg for two successive occlusions. 5/8 fetuses with pre-existing hypoxia were unable to complete the full series of occlusions (vs. 0/8 normoxic fetuses). Pre-existing hypoxia was associated with progressive metabolic acidosis (nadir: pH 7.08 ± 0.04 vs. 7.33 ± 0.02, p<0.01), hypotension during occlusions (nadir: 24.7 ± 1.8 vs. 51.4 ± 3.2 mmHg, p<0.01), lower carotid blood flow during occlusions (23.6 ± 6.1 vs. 63.0 ± 4.8 mL/min, p<0.01), greater suppression of EEG activity during, between, and after occlusions (p<0.01) and slower resolution of cortical impedance, an index of cytotoxic edema. No normoxic fetuses, but 4/8 hypoxic fetuses developed seizures 148 ± 45 minutes after the start of occlusions, with a seizure burden of 26 ± 6 sec during the inter-occlusion period, and 15.1 ± 3.4 min/h in the first 6 hours of recovery. In conclusion, in fetuses with pre-existing hypoxia, repeated brief asphyxia at a rate consistent with early labor is associated with hypotension, cephalic hypoperfusion, greater EEG suppression, inter-occlusion seizures, and more sustained cytotoxic edema, consistent with early onset of neural injury.
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Affiliation(s)
- Guido Wassink
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | | | | | - Alistair J. Gunn
- Department of Physiology, University of Auckland, Auckland, New Zealand
- * E-mail:
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Booth LC, Drury PP, Muir C, Jensen EC, Gunn AJ, Bennet L. Acute on chronic exposure to endotoxin is associated with enhanced chemoreflex responses in preterm fetal sheep. Am J Physiol Regul Integr Comp Physiol 2013; 304:R799-803. [DOI: 10.1152/ajpregu.00005.2013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is increasing evidence that exposure to infection can sensitize the fetus to subsequent hypoxic injury. However, it is unclear whether this involves compromise of the fetal cardiovascular adaptation to acute asphyxia. Chronically instrumented 103-day-old (0.7 gestational age, term is 147 days) fetal sheep in utero were randomized to receive either gram-negative lipopolysaccharide (LPS) as a continuous low-dose infusion for 120 h plus boluses of 1 μg LPS at 48, 72, and 96 h with asphyxia at 102 h (i.e., 6 h after the final LPS bolus) induced by umbilical cord occlusion for 15 min (LPS treated, n = 8), or the same volume of saline plus occlusion (saline treated, n = 7). Fetuses were killed 5 days after occlusion. LPS was associated with a more rapid fall in fetal heart rate at the onset of occlusion ( P < 0.05) and with minimally lower values during occlusion ( P < 0.05). The LPS-treated fetuses had lower fetal mean arterial blood pressure (BP) and greater carotid artery blood flow (CaBF) before occlusion ( P < 0.05) but showed an increase in BP and fall in CaBF to similar values as saline controls during occlusion. There were no differences between the groups in femoral blood flow before or during occlusion. Contrary to our initial hypothesis, acute on chronic exposure to LPS was associated with more rapid cardiovascular adaptation to umbilical cord occlusion.
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Affiliation(s)
- Lindsea C. Booth
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Paul P. Drury
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Cameron Muir
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Ellen C. Jensen
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Alistair J. Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, Auckland, New Zealand
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Drury PP, Booth LC, Bennet L, Davidson JO, Wibbens B, Gunn AJ. Dopamine infusion for postresuscitation blood pressure support after profound asphyxia in near-term fetal sheep. Exp Physiol 2012; 98:699-709. [DOI: 10.1113/expphysiol.2012.069989] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Bennet L, Booth LC, Drury PP, Quaedackers JSL, Gunn AJ. Preterm neonatal cardiovascular instability: Does understanding the fetus help evaluate the newborn? Clin Exp Pharmacol Physiol 2012; 39:965-72. [DOI: 10.1111/j.1440-1681.2012.05744.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Laura Bennet
- Fetal Physiology and Neuroscience Group; Department of Physiology; Faculty of Medical and Health; The University of Auckland; Auckland; New Zealand
| | - Lindsea C Booth
- Neurobiology Division; Florey Neuroscience Institutes; University of Melbourne; Melbourne; Victoria; Australia
| | - Paul P Drury
- Fetal Physiology and Neuroscience Group; Department of Physiology; Faculty of Medical and Health; The University of Auckland; Auckland; New Zealand
| | - Josine SL Quaedackers
- Fetal Physiology and Neuroscience Group; Department of Physiology; Faculty of Medical and Health; The University of Auckland; Auckland; New Zealand
| | - Alistair J Gunn
- Fetal Physiology and Neuroscience Group; Department of Physiology; Faculty of Medical and Health; The University of Auckland; Auckland; New Zealand
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Drury PP, Bennet L, Booth LC, Davidson JO, Wassink G, Gunn AJ. Maturation of the mitochondrial redox response to profound asphyxia in fetal sheep. PLoS One 2012; 7:e39273. [PMID: 22720088 PMCID: PMC3376132 DOI: 10.1371/journal.pone.0039273] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 05/22/2012] [Indexed: 12/04/2022] Open
Abstract
Fetal susceptibility to hypoxic brain injury increases over the last third of gestation. This study examined the hypothesis that this is associated with impaired mitochondrial adaptation, as measured by more rapid oxidation of cytochrome oxidase (CytOx) during profound asphyxia. Methods: Chronically instrumented fetal sheep at 0.6, 0.7, and 0.85 gestation were subjected to either 30 min (0.6 gestational age (ga), n = 6), 25 min (0.7 ga, n = 27) or 15 min (0.85 ga, n = 17) of complete umbilical cord occlusion. Fetal EEG, cerebral impedance (to measure brain swelling) and near-infrared spectroscopy-derived intra-cerebral oxygenation (ΔHb = HbO2 – Hb), total hemoglobin (THb) and CytOx redox state were monitored continuously. Occlusion was associated with profound, rapid fall in ΔHb in all groups to a plateau from 6 min, greatest at 0.85 ga compared to 0.6 and 0.7 ga (p<0.05). THb initially increased at all ages, with the greatest rise at 0.85 ga (p<0.05), followed by a progressive fall from 7 min in all groups. CytOx initially increased in all groups with the greatest rise at 0.85 ga (p<0.05), followed by a further, delayed increase in preterm fetuses, but a striking fall in the 0.85 group after 6 min of occlusion. Cerebral impedance (a measure of cytotoxic edema) increased earlier and more rapidly with greater gestation. In conclusion, the more rapid rise in CytOx and cortical impedance during profound asphyxia with greater maturation is consistent with increasing dependence on oxidative metabolism leading to earlier onset of neural energy failure before the onset of systemic hypotension.
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Affiliation(s)
- Paul P. Drury
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Lindsea C. Booth
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
- Howard Florey Institute, University of Melbourne, Melbourne, Victoria, Australia
| | - Joanne O. Davidson
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Guido Wassink
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alistair J. Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
- Starship Children's Hospital, Auckland, New Zealand
- * E-mail:
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Booth LC, Malpas SC, Barrett CJ, Guild SJ, Gunn AJ, Bennet L. Renal sympathetic nerve activity during asphyxia in fetal sheep. Am J Physiol Regul Integr Comp Physiol 2012; 303:R30-8. [PMID: 22552793 DOI: 10.1152/ajpregu.00063.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The sympathetic nervous system (SNS) is an important mediator of fetal adaptation to life-threatening in utero challenges, such as asphyxia. Although the SNS is active well before term, SNS responses mature significantly over the last third of gestation, and its functional contribution to adaptation to asphyxia over this critical period of life remains unclear. Therefore, we examined the hypotheses that increased renal sympathetic nerve activity (RSNA) is the primary mediator of decreased renal vascular conductance (RVC) during complete umbilical cord occlusion in preterm fetal sheep (101 ± 1 days; term 147 days) and that near-term fetuses (119 ± 0 days) would have a more rapid initial vasomotor response, with a greater increase in RSNA. Causality of the relationship of RSNA and RVC was investigated using surgical (preterm) and chemical (near-term) denervation. All fetal sheep showed a significant increase in RSNA with occlusion, which was more sustained but not significantly greater near-term. The initial fall in RVC was more rapid in near-term than preterm fetal sheep and preceded the large increase in RSNA. These data suggest that although RSNA can increase as early as 0.7 gestation, it is not the primary determinant of RVC. This finding was supported by denervation studies. Interestingly, chemical denervation in near-term fetal sheep was associated with an initial fall in blood pressure, suggesting that by 0.8 gestation sympathetic innervation of nonrenal vascular beds is critical to maintain arterial blood pressure during the rapid initial adaptation to asphyxia.
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Affiliation(s)
- Lindsea C Booth
- Department of Physiology, The University of Auckland, Auckland, New Zealand
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Thompson JA, Gimbel SA, Richardson BS, Gagnon R, Regnault TRH. The Effect of Intermittent Umbilical Cord Occlusion on Elastin Composition in the Ovine Fetus. Reprod Sci 2011; 18:990-7. [DOI: 10.1177/1933719111401655] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Jennifer A. Thompson
- Department of Physiology, The University of Western Ontario, London, Ontario, Canada
| | - Sarah A. Gimbel
- Department of Obstetrics and Gynecology, The University of Western Ontario, London, Ontario, Canada
| | - Bryan S. Richardson
- Department of Physiology, The University of Western Ontario, London, Ontario, Canada
- Department of Obstetrics and Gynecology, The University of Western Ontario, London, Ontario, Canada
| | - Robert Gagnon
- Department of Obstetrics and Gynecology, McGill University, Montreal, Quebec, Canada
| | - Timothy R. H. Regnault
- Department of Physiology, The University of Western Ontario, London, Ontario, Canada
- Department of Obstetrics and Gynecology, The University of Western Ontario, London, Ontario, Canada
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Booth LC, Bennet L, Guild SJ, Barrett CJ, May CN, Gunn AJ, Malpas SC. Maturation-related changes in the pattern of renal sympathetic nerve activity from fetal life to adulthood. Exp Physiol 2010; 96:85-93. [DOI: 10.1113/expphysiol.2010.055236] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
Cerebral hypothermia reduces brain injury and improves behavioral recovery after hypoxia-ischemia (HI) at birth. However, using current enrolment criteria many infants are not helped, and conversely, a significant proportion of control infants survive without disability. In order to further improve treatment we need better biomarkers of injury. A 'true' biomarker for the phase of evolving, 'treatable' injury would allow us to identify not only whether infants are at risk of damage, but also whether they are still able to benefit from intervention. Even a less specific measure that allowed either more precise early identification of infants at risk of adverse neurodevelopmental outcome would reduce the variance of outcome of trials, improving trial power while reducing the number of infants unnecessarily treated. Finally, valid short-term surrogates for long term outcome after treatment would allow more rapid completion of preliminary evaluation and thus allow new strategies to be tested more rapidly. Experimental studies have demonstrated that there is a relatively limited 'window of opportunity' for effective treatment (up to about 6-8h after HI, the 'latent phase'), before secondary cell death begins. We critically evaluate the utility of proposed biochemical, electronic monitoring, and imaging biomarkers against this framework. This review highlights the two central limitations of most presently available biomarkers: that they are most precise for infants with severe injury who are already easily identified, and that their correlation is strongest at times well after the latent phase, when injury is no longer 'treatable'. This is an important area for further research.
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Affiliation(s)
- L. Bennet
- Corresponding author. Dr Laura Bennet, Professor, Fetal Physiology and Neuroscience Group Department of Physiology, The University of Auckland, Private Bag 92019 Auckland, New Zealand Tel.: +64 9 373 7599 ext. 84890; fax: +64 9 373 7499. (L. Bennet)
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