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Tran NT, Kowalski GM, Muccini AM, Nitsos I, Hale N, Snow RJ, Walker DW, Ellery SJ. Creatine supplementation reduces the cerebral oxidative and metabolic stress responses to acute in utero hypoxia in the late-gestation fetal sheep. J Physiol 2022; 600:3193-3210. [PMID: 35587817 PMCID: PMC9542404 DOI: 10.1113/jp282840] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 04/22/2022] [Indexed: 11/24/2022] Open
Abstract
Abstract Prophylactic creatine treatment may reduce hypoxic brain injury due to its ability to sustain intracellular ATP levels thereby reducing oxidative and metabolic stress responses during oxygen deprivation. Using microdialysis, we investigated the real‐time in vivo effects of fetal creatine supplementation on cerebral metabolism following acute in utero hypoxia caused by umbilical cord occlusion (UCO). Fetal sheep (118 days’ gestational age (dGA)) were implanted with an inflatable Silastic cuff around the umbilical cord and a microdialysis probe inserted into the right cerebral hemisphere for interstitial fluid sampling. Creatine (6 mg kg−1 h−1) or saline was continuously infused intravenously from 122 dGA. At 131 dGA, a 10 min UCO was induced. Hourly microdialysis samples were obtained from −24 to 72 h post‐UCO and analysed for percentage change of hydroxyl radicals (•OH) and interstitial metabolites (lactate, pyruvate, glutamate, glycerol, glycine). Histochemical markers of protein and lipid oxidation were assessed at post‐mortem 72 h post‐UCO. Prior to UCO, creatine treatment reduced pyruvate and glycerol concentrations in the microdialysate outflow. Creatine treatment reduced interstitial cerebral •OH outflow 0 to 24 h post‐UCO. Fetuses with higher arterial creatine concentrations before UCO presented with reduced levels of hypoxaemia (PO2 and SO2) during UCO which associated with reduced interstitial cerebral pyruvate, lactate and •OH accumulation. No effects of creatine treatment on immunohistochemical markers of oxidative stress were found. In conclusion, fetal creatine treatment decreased cerebral outflow of •OH and was associated with an improvement in cerebral bioenergetics following acute hypoxia.
![]() Key points Fetal hypoxia can cause persistent metabolic and oxidative stress responses that disturb energy homeostasis in the brain. Creatine in its phosphorylated form is an endogenous phosphagen; therefore, supplementation is a proposed prophylactic treatment for fetal hypoxia. Fetal sheep instrumented with a cerebral microdialysis probe were continuously infused with or without creatine‐monohydrate for 10 days before induction of 10 min umbilical cord occlusion (UCO; 131 days’ gestation). Cerebral interstitial fluid was collected up to 72 h following UCO. Prior to UCO, fetal creatine supplementation reduced interstitial cerebral pyruvate and glycerol concentrations. Fetal creatine supplementation reduced cerebral hydroxyl radical efflux up to 24 h post‐UCO. Fetuses with higher arterial creatine concentrations before UCO and reduced levels of systemic hypoxaemia during UCO were associated with reduced cerebral interstitial pyruvate, lactate and •OH following UCO. Creatine supplementation leads to some improvements in cerebral bioenergetics following in utero acute hypoxia.
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Affiliation(s)
- Nhi Thao Tran
- School of Health & Biomedical Sciences, RMIT University, Bundoora, Melbourne, Victoria, Australia.,The Ritchie Centre, Hudson Institute of Medical Research, Monash Medical Centre, Clayton, Melbourne, Victoria, Australia
| | - Greg M Kowalski
- Institute for Physical Activity & Nutrition, Deakin University, Burwood, School of Exercise & Nutrition Sciences, Deakin University, Geelong Melbourne, Victoria, Australia.,Metabolic Research Unit, School of Medicine, Deakin University, Geelong, Victoria, Australia
| | - Anna M Muccini
- The Ritchie Centre, Hudson Institute of Medical Research, Monash Medical Centre, Clayton, Melbourne, Victoria, Australia.,Genetic Research Services, University of Queensland, Queensland, Australia
| | - Ilias Nitsos
- The Ritchie Centre, Hudson Institute of Medical Research, Monash Medical Centre, Clayton, Melbourne, Victoria, Australia.,Department of Obstetrics & Gynecology, Monash University, Clayton, Melbourne, Victoria, Australia
| | - Nadia Hale
- School of Health & Biomedical Sciences, RMIT University, Bundoora, Melbourne, Victoria, Australia.,The Ritchie Centre, Hudson Institute of Medical Research, Monash Medical Centre, Clayton, Melbourne, Victoria, Australia
| | - Rod J Snow
- Institute for Physical Activity & Nutrition, Deakin University, Burwood, School of Exercise & Nutrition Sciences, Deakin University, Geelong Melbourne, Victoria, Australia
| | - David W Walker
- School of Health & Biomedical Sciences, RMIT University, Bundoora, Melbourne, Victoria, Australia
| | - Stacey J Ellery
- The Ritchie Centre, Hudson Institute of Medical Research, Monash Medical Centre, Clayton, Melbourne, Victoria, Australia.,Department of Obstetrics & Gynecology, Monash University, Clayton, Melbourne, Victoria, Australia
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Gunn AJ, Thoresen M. Neonatal encephalopathy and hypoxic-ischemic encephalopathy. HANDBOOK OF CLINICAL NEUROLOGY 2019; 162:217-237. [PMID: 31324312 DOI: 10.1016/b978-0-444-64029-1.00010-2] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Acute hypoxic-ischemic encephalopathy around the time of birth remains a major cause of death and life-long disability. The key insight that led to the modern revival of studies of neuroprotection was that, after profound asphyxia, many brain cells show initial recovery from the insult during a short "latent" phase, typically lasting approximately 6h, only to die hours to days later after a "secondary" deterioration characterized by seizures, cytotoxic edema, and progressive failure of cerebral oxidative metabolism. Studies designed around this framework showed that mild hypothermia initiated as early as possible before the onset of secondary deterioration and continued for a sufficient duration to allow the secondary deterioration to resolve is associated with potent, long-lasting neuroprotection. There is now compelling evidence from randomized controlled trials that mild to moderate induced hypothermia significantly improves survival and neurodevelopmental outcomes in infancy and mid-childhood.
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Affiliation(s)
- Alistair J Gunn
- Departments of Physiology and Paediatrics, University of Auckland, Auckland, New Zealand.
| | - Marianne Thoresen
- Department of Physiology University of Oslo, Oslo, Norway; Neonatal Neuroscience, Translational Health Sciences, University of Bristol, Bristol, United Kingdom
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Garabedian C, Aubry E, Sharma D, Bleu G, Clermont-Hama Y, Ghesquière L, Hubert T, Deruelle P, Storme L, De Jonckheere J, Houfflin-Debarge V. Exploring fetal response to acidosis in ewes: Choosing an adequate experimental model. J Gynecol Obstet Hum Reprod 2018; 47:397-403. [PMID: 29654942 DOI: 10.1016/j.jogoh.2018.04.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Accepted: 04/10/2018] [Indexed: 01/02/2023]
Abstract
INTRODUCTION Knowledge of fetal physiology during labor has been largely generated from animal models. Our team recently developed a new index to assess parasympathetic activity using different experimental protocols to obtain acidosis. The objective of the present study was to discuss the different protocols and to review other models proposed in the literature. MATERIAL AND METHODS Pregnant ewes underwent a surgical procedure at the 123±2 days gestational age (term=145 days). Three experimental protocols were used: protocol A consisted of 25%, 50% and 75% umbilical cord occlusion (UCO) for 20min. Protocol B consisted of partial 75% UCO until reaching a pH<7.10. Protocol C consisted of brief, repetitive complete occlusion until severe acidosis occurred. Hemodynamic and blood gas parameters were compared to those of the stability period before UCO. RESULTS Protocol A led to a progressive response depending on the degree of occlusion (decrease in fetal heart rate, arterial hypertension and pH). Protocol B led to severe acidosis, although the duration of UCO varied per animal. Protocol C also progressively led to acidosis. We observed high inter individual variability in the acidosis response. CONCLUSION Pregnant ewes are a relevant model for exploring fetal response to acidosis. The frequency of UCO and partial or complete occlusion should be adapted to the expected effects. Knowledge of these protocols is important to respect ethical guidelines and to reduce the required number of animals. Moreover, it is important to consider the high individual variability of the acidosis response in the interpretation of the results.
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Affiliation(s)
- C Garabedian
- University Lille, EA 4489 - Perinatal Environment and Health, F-59000 Lille, France; CHU Lille, Department of Obstetrics, F-59000 Lille, France.
| | - E Aubry
- University Lille, EA 4489 - Perinatal Environment and Health, F-59000 Lille, France; CHU Lille, Department of Pediatric Surgery, F-59000 Lille, France
| | - D Sharma
- University Lille, EA 4489 - Perinatal Environment and Health, F-59000 Lille, France; CHU Lille, Department of Pediatric Surgery, F-59000 Lille, France
| | - G Bleu
- University Lille, EA 4489 - Perinatal Environment and Health, F-59000 Lille, France; CHU Lille, Department of Obstetrics, F-59000 Lille, France
| | - Y Clermont-Hama
- University Lille, EA 4489 - Perinatal Environment and Health, F-59000 Lille, France; CHU Lille, Department of Obstetrics, F-59000 Lille, France
| | - L Ghesquière
- University Lille, EA 4489 - Perinatal Environment and Health, F-59000 Lille, France; CHU Lille, Department of Obstetrics, F-59000 Lille, France
| | - T Hubert
- University Lille, CHU Lille, Experimental Resources Platform, F-59000 Lille, France
| | - P Deruelle
- University Lille, EA 4489 - Perinatal Environment and Health, F-59000 Lille, France; CHU Lille, Department of Obstetrics, F-59000 Lille, France
| | - L Storme
- University Lille, EA 4489 - Perinatal Environment and Health, F-59000 Lille, France; CHU Lille, Department of Neonatology, F-59000 Lille, France
| | - J De Jonckheere
- University Lille, EA 4489 - Perinatal Environment and Health, F-59000 Lille, France; CHU Lille, CIC-IT 1403, MRRC, F-59000 Lille, France
| | - V Houfflin-Debarge
- University Lille, EA 4489 - Perinatal Environment and Health, F-59000 Lille, France; CHU Lille, Department of Obstetrics, F-59000 Lille, France
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Garabedian C, Clermont-Hama Y, Sharma D, Aubry E, Butruille L, Deruelle P, Storme L, De Jonckheere J, Houfflin-Debarge V. Correlation of a new index reflecting the fluctuation of parasympathetic tone and fetal acidosis in an experimental study in a sheep model. PLoS One 2018; 13:e0190463. [PMID: 29320537 PMCID: PMC5761865 DOI: 10.1371/journal.pone.0190463] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Accepted: 11/20/2017] [Indexed: 12/21/2022] Open
Abstract
The autonomic nervous system plays a leading role in the control of fetal homeostasis. Fetal heart rate variability (HRV) analysis is a reflection of its activity. We developed a new index (the Fetal Stress Index, FSI) reflecting parasympathetic tone. The objective of this study was to evaluate this index as a predictor of fetal acid-base status. This was an experimental study on chronically instrumented fetal lambs (n = 11, surgery at 128 +/- 2 days gestational age, term = 145 days). The model was based on 75% occlusion of the umbilical cord for a maximum of 120 minutes or until an arterial pH ≤ 7.20 was reached. Hemodynamic, gasometric and FSI parameters were recorded throughout the experimentation. We studied the FSI during the 10 minutes prior to pH samplings and compared values for pH>7.20 and pH≤ 7.20. In order to analyze the FSI evolution during the 10 minutes periods, we analyzed the minimum, maximum and mean values of the FSI (respectively FSImin, FSImax and FSImean) over the periods. 11 experimentations were performed. During occlusion, the heart rate dropped with an increase in blood pressure (respectively 160(155-182) vs 106(101-120) bpm and 42(41-45) vs 58(55-62) mmHg after occlusion). The FSImin was 38.6 (35.2-43.3) in the group pH>7.20 and was higher in the group pH less than 7.20 (46.5 (43.3-52.0), p = 0.012). The correlation of FSImin was significant for arterial pH (coefficient of -0.671; p = 0.004) and for base excess (coefficient of -0.632; p = 0.009). The correlations were not significant for the other parameters. In conclusion, our new index seems well correlated with the fetal acid-base status. Other studies must be carried out in a situation close to the physiology of labor by sequential occlusion of the cord.
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Affiliation(s)
- C. Garabedian
- Univ. Lille, EA 4489 –Perinatal Environment and Health, Lille, France
- CHU Lille, Department of Obstetrics, Lille, France
- * E-mail:
| | - Y. Clermont-Hama
- Univ. Lille, EA 4489 –Perinatal Environment and Health, Lille, France
- CHU Lille, Department of Obstetrics, Lille, France
| | - D. Sharma
- Univ. Lille, EA 4489 –Perinatal Environment and Health, Lille, France
- CHU Lille, Department of Pediatric Surgery, Lille, France
| | - E. Aubry
- Univ. Lille, EA 4489 –Perinatal Environment and Health, Lille, France
- CHU Lille, Department of Pediatric Surgery, Lille, France
| | - L. Butruille
- Univ. Lille, EA 4489 –Perinatal Environment and Health, Lille, France
| | - P. Deruelle
- Univ. Lille, EA 4489 –Perinatal Environment and Health, Lille, France
- CHU Lille, Department of Obstetrics, Lille, France
| | - L. Storme
- Univ. Lille, EA 4489 –Perinatal Environment and Health, Lille, France
- CHU Lille, Department of Neonatology, Lille, France
| | - J. De Jonckheere
- Univ. Lille, EA 4489 –Perinatal Environment and Health, Lille, France
- CHU Lille, CIC-IT 1403, Lille, France
| | - V. Houfflin-Debarge
- Univ. Lille, EA 4489 –Perinatal Environment and Health, Lille, France
- CHU Lille, Department of Obstetrics, Lille, France
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Millar LJ, Shi L, Hoerder-Suabedissen A, Molnár Z. Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges. Front Cell Neurosci 2017; 11:78. [PMID: 28533743 PMCID: PMC5420571 DOI: 10.3389/fncel.2017.00078] [Citation(s) in RCA: 213] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 03/07/2017] [Indexed: 12/11/2022] Open
Abstract
Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.
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Affiliation(s)
- Lancelot J. Millar
- Molnár Group, Department of Physiology, Anatomy and Genetics, University of OxfordOxford, UK
| | - Lei Shi
- Molnár Group, Department of Physiology, Anatomy and Genetics, University of OxfordOxford, UK
- JNU-HKUST Joint Laboratory for Neuroscience and Innovative Drug Research, College of Pharmacy, Jinan UniversityGuangzhou, China
| | | | - Zoltán Molnár
- Molnár Group, Department of Physiology, Anatomy and Genetics, University of OxfordOxford, UK
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Bhide A, Rasanen J, Huhta H, Junno J, Erkinaro T, Ohtonen P, Haapsamo M, Acharya G. Effect of Hypoxemia on Fetal Ventricular Deformation in a Chronically Instrumented Sheep Model. ULTRASOUND IN MEDICINE & BIOLOGY 2017; 43:967-973. [PMID: 28268036 DOI: 10.1016/j.ultrasmedbio.2017.01.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 12/01/2016] [Accepted: 01/19/2017] [Indexed: 06/06/2023]
Abstract
We hypothesized that in near-term sheep fetuses, hypoxemia changes myocardial function as reflected in altered ventricular deformation on speckle-tracking echocardiography. Fetuses in 21 pregnant sheep were instrumented. After 4 d of recovery, fetal cardiac function was assessed by echocardiography at baseline, after 30 and 120 min of induced fetal hypoxemia and after its reversal. Left (LV) and right (RV) ventricular cardiac output and myocardial strain were measured. Baseline mean (standard deviation [SD]) LV and RV global longitudinal strains were -18.7% (3.8) and -14.3% (5.3). Baseline RV global longitudinal and circumferential deformations were less compared with those of the left ventricle (p = 0.016 and p < 0.005). LV, but not RV, global longitudinal strain was decreased (p = 0.003) compared with baseline with hypoxemia. Circumferential and radial strains did not exhibit significant changes. In the near-term sheep fetus, LV global longitudinal and circumferential strains are more negative than RV strains. Acute hypoxemia leads to LV rather than RV dysfunction as reflected by decreased deformation.
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Affiliation(s)
- Amarnath Bhide
- Women's Health & Perinatal Research Group, Department of Clinical Medicine, UiT-The Arctic University of Norway, Tromsø, Norway.
| | - Juha Rasanen
- Department of Obstetrics and Gynecology, Kuopio University Hospital and University of Eastern Finland, Kuopio, Finland; Department of Obstetrics and Gynecology, Helsinki University Hospital, Helsinki, Finland; Department of Obstetrics and Gynecology, Oulu University Hospital, Oulu, Finland
| | - Heikki Huhta
- Department of Obstetrics and Gynecology, Oulu University Hospital, Oulu, Finland
| | - Juulia Junno
- Department of Obstetrics and Gynecology, Oulu University Hospital, Oulu, Finland
| | - Tiina Erkinaro
- Department of Anaesthesiology, Oulu University Hospital, Oulu, Finland
| | - Pasi Ohtonen
- Department of Statistics, Oulu University Hospital, Oulu, Finland
| | - Mervi Haapsamo
- Department of Obstetrics and Gynecology, Lapland Central Hospital, Rovaniemi, Finland
| | - Ganesh Acharya
- Women's Health & Perinatal Research Group, Department of Clinical Medicine, UiT-The Arctic University of Norway, Tromsø, Norway; Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden
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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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Te Pas AB, Sobotka K, Hooper SB. Novel Approaches to Neonatal Resuscitation and the Impact on Birth Asphyxia. Clin Perinatol 2016; 43:455-67. [PMID: 27524447 DOI: 10.1016/j.clp.2016.04.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Historically, recommendations for neonatal resuscitation were largely based on dogma, but there is renewed interest in performing resuscitation studies at birth. The emphasis for resuscitation following birth asphyxia is administering effective ventilation, as adequate lung aeration leads not only to an increase in oxygenation but also increased pulmonary blood flow and heart rate. To aerate the lung, an initial sustained inflation can increase heart rate, oxygenation, and blood pressure recovery much faster when compared with standard ventilation. Hyperoxia should be avoided, and extra oxygen given to restore cardiac function and spontaneous breathing should be titrated based on oxygen saturations.
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Affiliation(s)
- Arjan B Te Pas
- Division of Neonatology, Department of Pediatrics, Leiden University Medical Centre, J6-S, PO Box 9600, Leiden 2300 RC, The Netherlands.
| | - Kristina Sobotka
- Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Box 432, Göteborg 405 30, Sweden
| | - Stuart B Hooper
- The Ritchie Centre, MIMR-PHI Institute of Medical Research, Monash Institute of Medical Research, Monash University, 27-31 Wright Street, Clayton, Melbourne, Victoria 3168, Australia
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Rumajogee P, Bregman T, Miller SP, Yager JY, Fehlings MG. Rodent Hypoxia-Ischemia Models for Cerebral Palsy Research: A Systematic Review. Front Neurol 2016; 7:57. [PMID: 27199883 PMCID: PMC4843764 DOI: 10.3389/fneur.2016.00057] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 04/03/2016] [Indexed: 12/28/2022] Open
Abstract
Cerebral palsy (CP) is a complex multifactorial disorder, affecting approximately 2.5-3/1000 live term births, and up to 22/1000 prematurely born babies. CP results from injury to the developing brain incurred before, during, or after birth. The most common form of this condition, spastic CP, is primarily associated with injury to the cerebral cortex and subcortical white matter as well as the deep gray matter. The major etiological factors of spastic CP are hypoxia/ischemia (HI), occurring during the last third of pregnancy and around birth age. In addition, inflammation has been found to be an important factor contributing to brain injury, especially in term infants. Other factors, including genetics, are gaining importance. The classic Rice-Vannucci HI model (in which 7-day-old rat pups undergo unilateral ligation of the common carotid artery followed by exposure to 8% oxygen hypoxic air) is a model of neonatal stroke that has greatly contributed to CP research. In this model, brain damage resembles that observed in severe CP cases. This model, and its numerous adaptations, allows one to finely tune the injury parameters to mimic, and therefore study, many of the pathophysiological processes and conditions observed in human patients. Investigators can recreate the HI and inflammation, which cause brain damage and subsequent motor and cognitive deficits. This model further enables the examination of potential approaches to achieve neural repair and regeneration. In the present review, we compare and discuss the advantages, limitations, and the translational value for CP research of HI models of perinatal brain injury.
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Affiliation(s)
- Prakasham Rumajogee
- Division of Genetics and Development, Krembil Research Institute, Toronto Western Hospital, University Health Network , Toronto, ON , Canada
| | - Tatiana Bregman
- Division of Genetics and Development, Krembil Research Institute, Toronto Western Hospital, University Health Network , Toronto, ON , Canada
| | - Steven P Miller
- Department of Pediatrics, Hospital for Sick Children , Toronto, ON , Canada
| | - Jerome Y Yager
- Division of Pediatric Neurosciences, Stollery Children's Hospital, University of Alberta , Edmonton, AB , Canada
| | - Michael G Fehlings
- Division of Genetics and Development, Krembil Research Institute, Toronto Western Hospital, University Health Network, Toronto, ON, Canada; Division of Neurosurgery, Institute of Medical Science, University of Toronto, Toronto, ON, Canada
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Sobotka KS, Hooper SB, Crossley KJ, Ong T, Schmölzer GM, Barton SK, McDougall ARA, Miller SL, Tolcos M, Klingenberg C, Polglase GR. Single Sustained Inflation followed by Ventilation Leads to Rapid Cardiorespiratory Recovery but Causes Cerebral Vascular Leakage in Asphyxiated Near-Term Lambs. PLoS One 2016; 11:e0146574. [PMID: 26765258 PMCID: PMC4713062 DOI: 10.1371/journal.pone.0146574] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 12/18/2015] [Indexed: 11/19/2022] Open
Abstract
Background A sustained inflation (SI) rapidly restores cardiac function in asphyxic, bradycardic newborns but its effects on cerebral haemodynamics and brain injury are unknown. We determined the effect of different SI strategies on carotid blood flow (CaBF) and cerebral vascular integrity in asphyxiated near-term lambs. Methods Lambs were instrumented and delivered at 139 ± 2 d gestation and asphyxia was induced by delaying ventilation onset. Lambs were randomised to receive 5 consecutive 3 s SI (multiple SI; n = 6), a single 30 s SI (single SI; n = 6) or conventional ventilation (no SI; n = 6). Ventilation continued for 30 min in all lambs while CaBF and respiratory function parameters were recorded. Brains were assessed for gross histopathology and vascular leakage. Results CaBF increased more rapidly and to a greater extent during a single SI (p = 0.01), which then decreased below both other groups by 10 min, due to a higher cerebral oxygen delivery (p = 0.01). Blood brain barrier disruption was increased in single SI lambs as indicated by increased numbers of blood vessel profiles with plasma protein extravasation (p = 0.001) in the cerebral cortex. There were no differences in CaBF or cerebral oxygen delivery between the multiple SI and no SI lambs. Conclusions Ventilation with an initial single 30 s SI improves circulatory recovery, but is associated with greater disruption of blood brain barrier function, which may exacerbate brain injury suffered by asphyxiated newborns. This injury may occur as a direct result of the initial SI or to the higher tidal volumes delivered during subsequent ventilation.
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Affiliation(s)
- Kristina S. Sobotka
- The Ritchie Centre, Monash University, Melbourne, Australia
- Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- * E-mail:
| | - Stuart B. Hooper
- The Ritchie Centre, Monash University, Melbourne, Australia
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia
| | - Kelly J. Crossley
- The Ritchie Centre, Monash University, Melbourne, Australia
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia
| | - Tracey Ong
- The Ritchie Centre, Monash University, Melbourne, Australia
| | - Georg M. Schmölzer
- Department of Pediatrics, Medical University, Graz, Austria
- Centre for the Studies of Asphyxia and Resuscitation, Neonatal Research Unit, Royal Alexandra Hospital, Edmonton, Canada
- Department of Pediatrics, University of Alberta, Edmonton, Canada
| | | | | | - Suzie L. Miller
- The Ritchie Centre, Monash University, Melbourne, Australia
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia
| | - Mary Tolcos
- The Ritchie Centre, Monash University, Melbourne, Australia
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia
| | - Claus Klingenberg
- Department of Paediatrics, University Hospital of North Norway, Tromsø, Norway
- Paediatric Research Group, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway
| | - Graeme R. Polglase
- The Ritchie Centre, Monash University, Melbourne, Australia
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, 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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12
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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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13
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Baburamani AA, Ek CJ, Walker DW, Castillo-Melendez M. Vulnerability of the developing brain to hypoxic-ischemic damage: contribution of the cerebral vasculature to injury and repair? Front Physiol 2012; 3:424. [PMID: 23162470 PMCID: PMC3493883 DOI: 10.3389/fphys.2012.00424] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 10/17/2012] [Indexed: 11/13/2022] Open
Abstract
As clinicians attempt to understand the underlying reasons for the vulnerability of different regions of the developing brain to injury, it is apparent that little is known as to how hypoxia-ischemia may affect the cerebrovasculature in the developing infant. Most of the research investigating the pathogenesis of perinatal brain injury following hypoxia-ischemia has focused on excitotoxicity, oxidative stress and an inflammatory response, with the response of the developing cerebrovasculature receiving less attention. This is surprising as the presentation of devastating and permanent injury such as germinal matrix-intraventricular haemorrhage (GM-IVH) and perinatal stroke are of vascular origin, and the origin of periventricular leukomalacia (PVL) may also arise from poor perfusion of the white matter. This highlights that cerebrovasculature injury following hypoxia could primarily be responsible for the injury seen in the brain of many infants diagnosed with hypoxic-ischemic encephalopathy (HIE). Interestingly the highly dynamic nature of the cerebral blood vessels in the fetus, and the fluctuations of cerebral blood flow and metabolic demand that occur following hypoxia suggest that the response of blood vessels could explain both regional protection and vulnerability in the developing brain. However, research into how blood vessels respond following hypoxia-ischemia have mostly been conducted in adult models of ischemia or stroke, further highlighting the need to investigate how the developing cerebrovasculature responds and the possible contribution to perinatal brain injury following hypoxia. This review discusses the current concepts on the pathogenesis of perinatal brain injury, the development of the fetal cerebrovasculature and the blood brain barrier (BBB), and key mediators involved with the response of cerebral blood vessels to hypoxia.
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Affiliation(s)
- Ana A Baburamani
- The Ritchie Centre, Monash Medical Centre, Monash Institute of Medical Research, Clayton Melbourne, VIC, Australia ; Sahlgrenska Academy, Gothenburg University Göteborg, Sweden
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Sobotka KS, Hooper SB, Allison BJ, Te Pas AB, Davis PG, Morley CJ, Moss TJM. An initial sustained inflation improves the respiratory and cardiovascular transition at birth in preterm lambs. Pediatr Res 2011; 70:56-60. [PMID: 21659961 DOI: 10.1203/pdr.0b013e31821d06a1] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A sustained inflation (SI) facilitates lung aeration after birth but may impair the neonatal cardiovascular transition. We aimed to determine the effect of an initial SI on pulmonary arterial and carotid blood flow (PBF and CBF) after preterm birth. Fetal sheep were instrumented at ∼ 122 d of gestation (d). Lambs were delivered at ∼ 127 d and received either an initial SI (40 cm H2O for 1 min or until a volume of 20 mL/kg was administered) followed by ventilation for 30 min (SI; n = 7) or ventilation for 30 min (non-SI; n = 6). At 10 min after ventilation onset, inspired O2 content increased from 21 to 100% for 10 min. PBF, CBF, pulmonary arterial and carotid pressures, tidal volume, and inspiratory pressures were recorded. PBF was greater during the SI (p < 0.05) but thereafter was similar between groups. Non-SI lambs were hypoxemic and had higher CBF than SI lambs (p < 0.05). Cerebral oxygen delivery was constant in SI lambs but increased ∼ 4-fold in non-SI lambs during ventilation with 100% O2 (p < 0.05). Lung compliance and respiratory status were better in SI than non-SI lambs (p < 0.05). A SI improved lung function without adverse circulatory effects, seemed to stabilize neonatal cerebral O2 delivery, and may protect against cerebral hyperoxia.
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Affiliation(s)
- Kristina S Sobotka
- The Ritchie Centre, Monash Institute of Medical Research, PO Box 5481, Clayton, VIC 3168, Australia
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15
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Gunn AJ, Bennet L. Fetal hypoxia insults and patterns of brain injury: insights from animal models. Clin Perinatol 2009; 36:579-93. [PMID: 19732615 PMCID: PMC2767254 DOI: 10.1016/j.clp.2009.06.007] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The outcome of perinatal hypoxiaischemia is highly variable, with only a very broad relationship to the 'severity' of oxygen debt as shown by peripheral base deficit and the risk of damage. The present article examines the pathophysiology of asphyxial injury. We dissect the multiple factors that modify the risk of injury, including the depth ('severity'), duration, and repetition of the insult, the maturity, and condition of the fetus, pre-existing hypoxia, and exposure to pyrexia and infection/inflammation.
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Affiliation(s)
- Alistair Jan Gunn
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, 85 Park Road, Grafton, Auckland 1023, New Zealand.
| | - Laura Bennet
- Professor, Dept of Physiology, University of Auckland, Auckland, New Zealand
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16
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Abstract
This article examines recent studies that have systematically dissected features of fetal heart rate responses to labor that may help identify developing fetal compromise, such as the slope of the deceleration, overshoot, and variability. Although repeated deep decelerations are never necessarily benign, fetuses with normal placental reserve can fully compensate even for frequent deep but brief decelerations for surprisingly prolonged intervals before developing profound acidosis and hypotension.
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Affiliation(s)
- Laura Bennet
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
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17
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Yan EB, Baburamani AA, Walker AM, Walker DW. Changes in cerebral blood flow, cerebral metabolites, and breathing movements in the sheep fetus following asphyxia produced by occlusion of the umbilical cord. Am J Physiol Regul Integr Comp Physiol 2009; 297:R60-9. [PMID: 19403864 DOI: 10.1152/ajpregu.00047.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Severe global fetal asphyxia, if caused by a brief occlusion of the umbilical cord, results in prolonged cerebral hypoperfusion in fetal sheep. In this study, we sought evidence to support the hypothesis that cerebral hypoperfusion is a consequence of suppressed cerebral metabolism. In the 24 h following complete occlusion of the umbilical cord for 10 min, sagittal sinus blood flow velocity was significantly decreased for up to 12 h. Capillary blood flow, measured using microspheres, decreased at 1 and 5 h after cord occlusion in many brain regions, including cortical gray and white matter. Microdialysis probes implanted in the cerebral cortex revealed an increase in extracellular glucose concentrations in gray matter for 7-8 h postasphyxia, while lactate increased only briefly, suggesting decreased cerebral glucose utilization over this time. Although these data, as well as the concurrent suppression of breathing movements and electrocortical activity, support the concept of hypometabolic hypoperfusion, the significant increase of pyruvate and glycerol concentrations in dialysate fluid obtained from the cerebral cortex at 3-8 h after cord occlusion suggests an eventual loss of membrane integrity. The prolonged increase of breathing movements for many hours suggests loss of the pontine/thalamic control that produces the distinct pattern of fetal breathing movements.
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Affiliation(s)
- Edwin B Yan
- National Trauma Research Institute, The Alfred Hospital, Melbourne, Victoria, Australia
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18
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Thakor AS, Giussani DA. Effects of acute acidemia on the fetal cardiovascular defense to acute hypoxemia. Am J Physiol Regul Integr Comp Physiol 2008; 296:R90-9. [PMID: 18922958 DOI: 10.1152/ajpregu.90689.2008] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In complicated pregnancy, fetal hypoxemia rarely occurs in isolation but is often accompanied by fetal acidemia. There is growing clinical concern about the combined effects of fetal hypoxemia and fetal acidemia on neonatal outcome. However, the effects on the fetal defense responses to acute hypoxemia during fetal acidemia are not well understood. This study tested the hypothesis that fetal acidemia affects the fetal defense responses to acute hypoxemia. The hypothesis was tested by investigating, in the late-gestation sheep fetus surgically prepared for long-term recording, the in vivo effects of acute fetal acidemia on 1) the fetal cardiovascular responses to acute hypoxemia and 2) the neural and endocrine mechanisms mediating these responses. Under general anesthesia, five sheep fetuses at 0.8 gestation were instrumented with catheters and Transonic flow probes around the femoral and umbilical arteries. After 5 days, animals were subjected to an acute hypoxemia protocol during intravenous infusion of saline or treatment with acidified saline. Treatment with acidified saline reduced fetal basal pH from 7.35 +/- 0.01 to 7.29 +/- 0.01 but did not alter basal cardiovascular variables, blood glucose, or plasma concentrations of catecholamines, ACTH, and cortisol. During hypoxemia, treatment with acidified saline increased the magnitude of the fetal bradycardia and femoral vasoconstriction and concomitantly increased chemoreflex function and enhanced the increments in plasma concentrations of catecholamines, ACTH, and cortisol. Acidemia also reversed the increase in umbilical vascular conductance during hypoxemia to vasoconstriction. In conclusion, the data support our hypothesis and show that acute acidemia markedly alters fetal hemodynamic, metabolic, and endocrine responses to acute hypoxemia.
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Affiliation(s)
- A S Thakor
- Dept. of Physiology, Development & Neuroscience, Univ. of Cambridge, Cambridge CB2 3EG, UK
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19
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Wong FY, Barfield CP, Campbell L, Brodecky VA, Walker AM. Validation of cerebral venous oxygenation measured using near-infrared spectroscopy and partial jugular venous occlusion in the newborn lamb. J Cereb Blood Flow Metab 2008; 28:74-80. [PMID: 17519977 DOI: 10.1038/sj.jcbfm.9600507] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Near-infrared spectroscopy combined with partial jugular venous occlusion (JVO) offers promise for determining cerebral venous saturation (CSvO(2)) in sick preterm infants, but has not been validated in the newborn brain or under conditions of hypoxaemia. We assessed the accuracy of the CSvO(2) estimate using cerebral venous oxygen saturation in superior sagittal sinus blood (SSSO(2)) as the 'gold standard'. Comparisons were made in seven newborn lambs over a wide range of arterial oxygen saturations (SaO(2)) of 20% to 100%. Overall, median (range) CSvO(2) was 49.8% (10.6% to 88.5%), whereas SSSO(2) was 45.5% (4.3% to 76.6%); Bland-Altman analysis revealed a mean difference (CSvO(2)-SSSO(2)) of 5.1% and limits of agreement of +/-27.4%. The change in cerebral blood volume (DeltaCBV) induced by JVO increased with SaO(2) (P<0.05). In addition, the strength of the correlation of CSvO(2) with SSSO(2) progressively improved with increasing change in total haemoglobin concentration (DeltaHbT) induced by JVO. With Bland-Altman analysis repeated for data with DeltaHbT >30 micromol cm, the mean difference (CSvO(2)-SSSO(2)) decreased to 2.4% with limits of agreement of +/-18.8%. We conclude that the accuracy of estimating CSvO(2) varies with the DeltaCBV induced by JVO. Potential differences of optical properties between the head of the lamb and the human infant suggest that caution be exercised in directly applying these data to the human newborn. Nevertheless, this critical aspect of the JVO technique needs to be taken into consideration in developing an accurate measurement for sick preterm human infants.
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Affiliation(s)
- Flora Y Wong
- Ritchie Centre for Baby Health Research, Monash University, Clayton, Victoria, Australia
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20
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Westgate JA, Wibbens B, Bennet L, Wassink G, Parer JT, Gunn AJ. The intrapartum deceleration in center stage: a physiologic approach to the interpretation of fetal heart rate changes in labor. Am J Obstet Gynecol 2007; 197:236.e1-11. [PMID: 17826402 DOI: 10.1016/j.ajog.2007.03.063] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Revised: 02/15/2007] [Accepted: 03/14/2007] [Indexed: 11/21/2022]
Abstract
One of the most distinctive features of fetal heart rate recordings in labor is the deceleration. In clinical practice, there has been much confusion about the types of decelerations and their significance. In the present review, we examined uteroplacental perfusion in labor, describe the pathophysiologic condition of decelerations, and explain some of the reasons behind the confusion about the terminology. We summarize recent studies that systematically have dissected the features of variable decelerations that may help to identify developing fetal compromise, such as the slope of the deceleration, overshoot, and variability changes. Although no pattern of repeated deep decelerations is necessarily benign, fetuses with normal placental reserve can compensate fully, even for frequent deep but brief decelerations, for surprisingly prolonged intervals before the development of profound acidosis and hypotension. This tolerance reflects the remarkable ability of the fetus to adapt to repeated hypoxia. We propose that, rather than focus on descriptive labels, clinicians should be trained to understand the physiologic mechanisms of fetal heart rate decelerations and the patterns of fetal heart rate change that indicate progressive loss of fetal compensation.
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Affiliation(s)
- Jenny A Westgate
- Department of Obstetrics and Gynaecology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, NZ
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21
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Wassink G, Bennet L, Booth LC, Jensen EC, Wibbens B, Dean JM, Gunn AJ. The ontogeny of hemodynamic responses to prolonged umbilical cord occlusion in fetal sheep. J Appl Physiol (1985) 2007; 103:1311-7. [PMID: 17656627 DOI: 10.1152/japplphysiol.00396.2007] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There is evidence that preterm fetuses have blunted chemoreflex-mediated responses to hypoxia. However, the preterm fetus has much lower aerobic requirements than at term, and so moderate hypoxia may not be sufficient to elicit maximal chemoreflex responses; there are only limited quantitative data on the ontogeny of chemoreflex and hemodynamic responses to severe asphyxia. Chronically instrumented fetal sheep at 0.6 (n = 12), 0.7 (n = 12), and 0.85 (n = 8) of gestational age (GA; term = 147 days) were exposed to 30, 25, or 15 min of complete umbilical cord occlusion, respectively. At all ages, occlusion was associated with early onset of bradycardia, profoundly reduced femoral blood flow and conductance, and hypertension. The 0.6-GA fetuses showed a significantly slower and lesser fall in femoral blood flow and conductance compared with the 0.85-GA group, with a correspondingly reduced relative rise in mean arterial blood pressure. As occlusion continued, the initial adaptation was followed by loss of peripheral vasoconstriction and progressive development of hypotension in all groups. The 0.85-GA fetuses showed significantly more sustained reduction in femoral conductance but also more rapid onset of hypotension than either of the younger groups. Electroencephalographic (EEG) activity was suppressed during occlusion in all groups, but the degree of suppression was less at 0.6 GA than at term. In conclusion, the near-midgestation fetus shows attenuated initial (chemoreflex) peripheral vasomotor responses to severe asphyxia compared with more mature fetuses but more sustained hemodynamic adaptation and reduced suppression of EEG activity during continued occlusion of the umbilical cord.
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Affiliation(s)
- Guido Wassink
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand
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22
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Bennet L, Booth L, Malpas SC, Quaedackers JS, Jensen E, Dean J, Gunn AJ. Acute systemic complications in the preterm fetus after asphyxia: role of cardiovascular and blood flow responses. Clin Exp Pharmacol Physiol 2006; 33:291-9. [PMID: 16620290 DOI: 10.1111/j.1440-1681.2006.04364.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. Poor perfusion of the kidneys and gut, and associated functional impairment, are major problems in the first days of life in very preterm infants. These complications can be associated with a substantial mortality and further problems such as reduced kidney growth and chronic renal problems in later childhood. 2. There is very little information, and consequently considerable debate, about how or even whether to improve perfusion of the vital organs of this most vulnerable group of babies. Current treatments simply do not consistently improve babies' perfusion generally or kidney and gut perfusion and function in particular. 3. In this review we critically examine clinical and experimental evidence that suggests that exposure to low oxygen levels before and during birth may be a significant contributor to impaired systemic perfusion, and highlight areas requiring further research. 4. This knowledge is essential to develop and refine ways of improving perfusion of the kidneys and other vital organs in premature babies.
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Affiliation(s)
- L Bennet
- Department of Physiology, Faculty of Medicine and Health Sciences, The University of Auckland, Auckland, New Zealand.
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Baserga MC, Bertolotto C, Sola A. Different Doses of Dopamine Have Heterogeneous Effects on Cerebral Hemodynamics and Dopamine Receptors in Young Rabbits as Measured with Near Infrared Spectroscopy. Neonatology 2005; 87:229-35. [PMID: 15655313 DOI: 10.1159/000083372] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2004] [Accepted: 10/12/2004] [Indexed: 11/19/2022]
Abstract
BACKGROUND Fluctuations in cerebral blood volume and cerebral oxygenation may be important in the pathogenesis of intraventricular hemorrhage and hypoxic-ischemic brain injury in the neonate. The cerebral hemodynamic response to dopamine infusion in premature infants is not well established. The newborn rabbit, a rather immature species at birth, is a suitable model for monitoring the physiological changes of the cerebral circulation. METHODS The effect of dopamine upon cerebral hemodynamics and basal ganglia dopaminergic receptors were studied using four different dopamine doses. RESULTS No significant changes in near infrared spectroscopy (NIRS) parameters were observed in the animals that received 0.5 (n = 5) and 1 microg/kg/min (n = 4) of dopamine intravenously. In contrast, in those animals that received dopamine at 5 microg/kg/min (n = 7) and 50 microg/kg/min (n = 7), there was a significant decrease in oxygenated hemoglobin. Moreover, this was accompanied by a significant increase in deoxygenated hemoglobin soon after drug infusion. Cerebral blood volume was increased in the group that received 5 microg/kg/min, but significantly decreased in the group that received 50 microg/kg/min. In both groups NIRS parameters returned to baseline values soon after stopping dopamine infusion. CONCLUSION Despite evidence of a physiological response, we found no difference in the distribution of dopamine receptors between experimental and control animals. We therefore speculate that dopamine has an effect on the cerebrovasculature that could be mediated by factors other than changes in the basal ganglia dopamine receptors.
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Affiliation(s)
- Mariana C Baserga
- Department of Pediatrics, Children's Hospital of Orange County, Orange, CA, USA
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Fujii EY, Kozuki M, Mu J, Ino Y, Ushioda N, Tomimatsu T, Fukuda H, Kanzaki T, Nakayama M, Murata Y. Correlation of neuron-specific enolase and S100B with histological cerebral damage in fetal sheep after severe asphyxia. Brain Res 2004; 1018:136-40. [PMID: 15262215 DOI: 10.1016/j.brainres.2004.05.061] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/25/2004] [Indexed: 10/26/2022]
Abstract
Experimental brain damage was induced in 16 fetal sheep by umbilical cord occlusion, and the correlation of neuron-specific enolase (NSE) or S100B with the damage grade was investigated in seven fetuses. Significant correlations of damage degree with NSE (p = 0.016) and S100B (p = 0.018) in serum 2 h after insult were shown by Spearman's test. These findings suggest that they represent potentially useful markers for detecting brain damage at early stage after ischemic insult.
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Affiliation(s)
- Eriko Y Fujii
- Department of Obstetrics and Gynecology, Osaka University Graduate School of Medicine, Japan.
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25
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Ley D, Oskarsson G, Bellander M, Hernandez-Andrade E, Lingman G, Marsal K, Olsson T, Pesonen E, Thorngren-Jerneck K, Werner O, Hellström-Westas L. Different responses of myocardial and cerebral blood flow to cord occlusion in exteriorized fetal sheep. Pediatr Res 2004; 55:568-75. [PMID: 14739362 DOI: 10.1203/01.pdr.0000113785.66455.e7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Type and duration of fetal asphyxial insult affect the distribution of blood flow to the heart and brain. The purpose of this study was to describe dynamic and quantitative changes in regional myocardial and cerebral blood flow (CBF) during fetal asphyxia induced by total occlusion of the umbilical cord. Eleven exteriorized fetal sheep were subjected to total umbilical cord occlusion and five fetal sheep served as sham controls. Regional blood flow (BF) to the brain and heart was quantified using radioactive microspheres before and after 5 min of occlusion and finally when fetal mean arterial blood pressure had decreased below 25 mm Hg, 9.8 (0.8) [mean (SD)] min after occlusion. Right coronary arterial (RCA) blood flow velocity and carotid BF were registered continuously. Mean values of arterial pH and oxygen content (mL O(2)/100 mL) were 7.08 (0.11) and 4.4 (2.9) before cord occlusion and decreased to 6.83 (0.05) and 1.4 (0.9) at 5 min after occlusion (p < 0.01, respectively). Carotid BF was significantly below preocclusion values by 2.5 min (p < 0.05), whereas RCA velocity time integral per minute remained above preocclusion values for 9 min. CBF decreased from 316 (24) before cord occlusion to 156 (30) mL/min/100 g at 5 min (p < 0.01), whereas right myocardial BF was maintained at 792 (125) and 751 (183) mL/min/100 g, respectively. CBF decreased rapidly after total cord occlusion whereas myocardial BF increased and was maintained until shortly before cardiac arrest, suggesting the myocardium to be better preserved during this type of insult in already partially asphyxiated fetuses.
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Affiliation(s)
- David Ley
- Department of Pediatrics, Lunds University Hospital, 221 85 Lund, Sweden.
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26
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Hunter CJ, Blood AB, Power GG. Cerebral metabolism during cord occlusion and hypoxia in the fetal sheep: a novel method of continuous measurement based on heat production. J Physiol 2003; 552:241-51. [PMID: 12878759 PMCID: PMC2343310 DOI: 10.1113/jphysiol.2003.048082] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
This study was undertaken to validate a new method of measuring cerebral metabolic rate in the fetal sheep based on heat production in a local region of the brain. Heat production was compared to oxygen use in 20 near-term fetuses during basal conditions, moderate hypoxia and cord occlusion. Thermocouples were placed to measure core and brain temperature and a composite probe placed in the parietal cortex to measure changes in cortical blood flow (CBF) using laser Doppler flowmetry and tissue PO2 using fluorescent decay. Catheters were inserted in a brachiocephalic artery and sagittal sinus for blood sampling. With moderate hypoxia, induced by administering 10-12 % oxygen to the ewes, fetal arterial PO2 declined from 23 +/- 1 to 11 +/- 1 Torr and brain tissue PO2 fell from 7.6+/- 0.7 to a nadir of 0.8 +/- 0.4 Torr, while CBF increased to 139 +/- 5 % of baseline. Cortical heat production, calculated as the product of CBF, the temperature gain from artery to brain tissue, and the specific heat of blood, decreased by 45 +/- 11 % in parallel to similar declines in oxygen uptake. With severe asphyxia induced by complete cord occlusion for 10 min, fetal arterial PO2 declined from 23 +/- 1 to 9 +/- 2 Torr and brain tissue PO2 fell from 7.0 +/- 0.7 to essentially 0 Torr while CBF decreased 40 +/- 5 %. Cortical heat production decreased by 78 +/- 6 % while oxygen use declined by 90 +/- 3 %. Glucose uptake increased significantly relative to oxygen use and lactate concentration increased in sagittal sinus blood. We conclude that local measurements of heat production in the brain provide a useful index of overall metabolic rate, closely reflecting oxygen use in moderate hypoxia and indicating a significant contribution from anaerobic metabolism during severe asphyxia.
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Affiliation(s)
- Christian J Hunter
- Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA
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Chipchase J, Kirkby D, Peebles D, Cope M, Rodeck C. Cerebral hemoglobin concentration and oxygen saturation measured by intensity modulated optical spectroscopy in the human fetus during labor. J Perinat Med 2003; 30:502-9. [PMID: 12530107 DOI: 10.1515/jpm.2002.078] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AIMS To quantify hemoglobin concentration and oxygen saturation in the human fetal brain using intensity modulated optical spectroscopy during labor. METHODS A specially designed probe was applied to the fetal scalp in 20 women during uncomplicated labor at term. Optical fibres transmitted near infra-red light to and from an intensity modulated optical spectrometer (IMOS), which detected changes in the optical parameters of the infra-red light source. Using novel off-line analytic techniques, these changes were converted into absolute measurements of oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb). Summing Hb and HbO2 gives total hemoglobin concentration (HbT) and HbO2/HbT x 100% provided measurements of cerebral saturation (SmcO2). RESULTS Of 20 fetuses studied, data from 10 fetuses were suitable for analysis. Over three consecutive uterine contractions, the mean (+/- SD) absolute cerebral concentrations of Hb and HbO2 were 30 +/- 18 and 46 +/- 21 mumol/l, respectively. This gave a mean cerebral HbT of 77 +/- 29 mumol/l and a mean SmcO2 of 59 +/- 12%. In the other ten fetuses insufficient light was detected to allow chromophore quantification. CONCLUSION These are the first absolute measurements of cerebral Hb and HbO2 in human fetuses during labor. The values of total hemoglobin are similar to those obtained in neonates with hypoxia-ischemia and the measurements of fetal cerebral oxygen saturation are similar to previously published values.
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Affiliation(s)
- Jeremy Chipchase
- Department of Obstetrics and Gynecology, University College London, London, U.K
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Fujii EY, Takahashi N, Kodama Y, Roman C, Ferriero DM, Parer JT. Hemodynamic changes during complete umbilical cord occlusion in fetal sheep related to hippocampal neuronal damage. Am J Obstet Gynecol 2003; 188:413-8. [PMID: 12592249 DOI: 10.1067/mob.2003.40] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVES The purpose of our study was to examine the physiologic changes caused by 10 minutes of umbilical cord occlusion in fetal sheep and to determine the correlation between fetal acidemia or cerebral ischemia and hippocampal neuronal damage. STUDY DESIGN Thirteen fetal sheep were instrumented and catheterized. Carotid artery blood flow (CaF), fetal mean arterial blood pressure (FMABP), pH, PCO (2), base excess, oxygen saturation (SatO(2)), and PO (2) were monitored throughout the occlusion study. Brain sections were examined for the hippocampal neuronal damage. RESULTS Our data showed severe ischemia (CaF: 10 +/- 7 mL/min; FMABP: 29 +/- 8 mm Hg) and acidemia (pH: 7.0 +/- 0.05; base excess: -9.9 +/- 2.4 mEq/L) at the end of occlusion. The neuronal damage score had significant correlations with ischemia and also with reperfusion, but not with the acidemic or hypoxic parameters. CONCLUSION We demonstrated that the degree of hippocampal damage was correlated with the degree of ischemia and reperfusion.
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Affiliation(s)
- Eriko Y Fujii
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, USA.
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Dimmitt RA, Beckman SA, Halamek LP, Moss RL, Mickas NA, Falco DA, Chubb C, Skarsgard ED. Effects of partial liquid ventilation on cerebral blood flow and cerebral metabolism in neonatal lambs. J Pediatr Surg 2002; 37:840-4. [PMID: 12037746 DOI: 10.1053/jpsu.2002.32884] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND/PURPOSE Liquid ventilation is a promising therapy for respiratory failure. The effects of perfluorochemical on cardiac output have not been well described. The purpose of this study was to compare cerebral blood flow (Q(CAROTID)) and cerebral metabolic rates (CMR) during conventional ventilation (CV) and partial liquid ventilation (PLV). METHODS Five 2-week-old lambs underwent tracheostomy and central venous, aortic, and postcerebral venous catheter placement. Doppler flow probes were placed around the common ovine trunk, and the lambs underwent CV for 1 hour. Ventilation was adjusted to maintain physiologic blood gases. Pre- and postcerebral blood gas, glucose, and lactate samples were obtained every 15 minutes. Perfluorodecalin then was instilled endotracheally. The lambs underwent 1 hour of PLV with similar sampling. Data were analyzed using the Wilcoxon matched pairs test, significance at P </=.05. RESULTS The authors observed no difference in mean Q(CAROTID) or carotid vascular resistance between CV and PLV (P =.35 and.34, respectively). The CMR of oxygen, glucose, and lactate were calculated using the Fick principle. CMR was unchanged between modes (P =.5). CONCLUSIONS PLV did not adversely alter Q(CAROTID) or CMR in lambs, implying that this mode of ventilation should be safe in neonatal patients at risk for neurologic injury.
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Affiliation(s)
- Reed A Dimmitt
- Division of Neonatal and Developmental Medicine, Department of Pediatrics; Stanford University School of Medicine, Stanford, California, USA
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Abstract
This study determined the effect of in utero hypoxia on fetal heart and brain pro- and antioxidant trace metals. Dunkin-Hartley guinea pigs (50-60 days gestation) were exposed to 1 h hypoxia (7% O2/93% N2) followed by 4 h reoxygenation in room air. Fetal hearts and brains were harvested and analyzed for copper, iron, magnesium and zinc. Fetal brain iron was significantly increased 28% after hypoxia and 35% by 1 h posthypoxia. Fetal brain magnesium demonstrated progressive decreases of 18% by 4 h posthypoxia. No significant effects of hypoxia were observed on heart trace metals. These results indicate that prooxidant metals may be increased and antioxidant metals may be decreased in posthypoxic fetal brain during a time when these tissues may be vulnerable to oxidative injury.
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Affiliation(s)
- Saul R Powell
- Department of Obstetrics and Gynecology, Winthrop University Hospital, Mineola, USA.
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Thorngren-Jerneck K, Ley D, Hellström-Westas L, Hernandez-Andrade E, Lingman G, Ohlsson T, Oskarsson G, Pesonen E, Sandell A, Strand SE, Werner O, Marsal K. Reduced postnatal cerebral glucose metabolism measured by PET after asphyxia in near term fetal lambs. J Neurosci Res 2001; 66:844-50. [PMID: 11746410 DOI: 10.1002/jnr.10051] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The effects of fetal asphyxia on cerebral function and development, involve the transition from fetal to neonatal life. Changes in cerebral glucose metabolism may be an early postnatal indicator of fetal asphyxia. The objective is to develop an experimental lamb model involving the transition from fetal to neonatal life and to examine the effect of fetal asphyxia with cerebral hypoxic ischemia on early postnatal cerebral glucose metabolism. Fetal asphyxia was induced by total umbilical cord occlusion in eight near-term fetal lambs (134-138 days) with the ewe under isoflurane-opiate anesthesia. The mean occlusion time until cardiac arrest was 14.5 (4.2) min (SD). Lambs were immediately delivered and standardized resuscitation was instituted after 2 min asystole. At 4 hr postnatal age, [18-F]Fluoro-2-deoxy-glucose (18-FDG) was injected intravenously in eight asphyxiated lambs and in eight controls. Cerebral glucose metabolism was examined by positron emission tomography (PET). As a result the mean arterial blood pressure, acid-base values, blood glucose and serum lactate at 4 hr postnatal age did not differ significantly between lambs subjected to umbilical cord occlusion and controls. EEG was abnormal in all lambs subjected to cord occlusion and normal in the controls at 4 hr postnatal age. Global cerebral metabolic rate (CMRgl) as determined by PET was significantly lower in lambs subjected to cord occlusion mean/median (SD) 22.2/19.6 (8.4) micromol/min/100 g) than in controls mean/median (SD) 37.8/35.9 (6.1); P < 0.01). Global CMRgl is significantly reduced in newborn lambs 4 hr after fetal asphyxia induced by umbilical cord occlusion. A reduction in CMRgl is an early indicator of global hypoxic cerebral ischemia.
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Affiliation(s)
- K Thorngren-Jerneck
- Department of Pediatrics, University Hospital, Lund University, SE-221 85 Lund, Sweden.
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Bennet L, Quaedackers JS, Gunn AJ, Rossenrode S, Heineman E. The effect of asphyxia on superior mesenteric artery blood flow in the premature sheep fetus. J Pediatr Surg 2000; 35:34-40. [PMID: 10646770 DOI: 10.1016/s0022-3468(00)80009-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND/PURPOSE The aim of this study was to determine superior mesenteric artery blood flow changes during and after an asphyxial insult in utero in chronically instrumented unanaesthetised premature fetal sheep. METHODS Fetal sheep at 0.7 gestation (103 to 104 days) underwent 25 minutes of complete umbilical cord occlusion (n = 6) or sham occlusion (n = 6). Fetal heart rate, blood pressure, superior mesenteric artery (SMA) blood flow and vascular resistance, electroencephalographic activity, and nuchal electromyographic activity were measured from 6 hours before occlusion until 3 days after occlusion. Fetal gastrointestinal tissue was taken for histological assessment. RESULTS During occlusion, cardiovascular response was characterised by 3 phases: initial redistribution of blood flow away from the gut to maintain vital organ function, subsequently partial failure of this redistribution, and finally near terminal cardiovascular collapse with profound hypotension and gastrointestinal hypoperfusion. Postasphyxia there was a secondary period of hypoperfusion that was mediated by increased vascular resistance, not hypotension. There was no evidence of injury on standard histological assessment after 3 days of recovery. CONCLUSIONS SMA blood flow is not only significantly reduced during asphyxia, but also for several hours after an asphyxial insult. The authors speculate that these perturbations of gastrointestinal blood flow could compromise gut wall integrity potentially leading to increased vulnerability to necrotising enterocolitis.
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Affiliation(s)
- L Bennet
- Research Centre for Developmental Medicine and Biology, Department of Paediatrics, The University of Auckland, New Zealand
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Newman JP, Peebles DM, Harding SR, Springett R, Hanson MA. Hemodynamic and metabolic responses to moderate asphyxia in brain and skeletal muscle of late-gestation fetal sheep. J Appl Physiol (1985) 2000; 88:82-90. [PMID: 10642366 DOI: 10.1152/jappl.2000.88.1.82] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to investigate metabolic and hemodynamic responses in two fetal tissues, hindlimb muscle and brain, to an episode of acute moderate asphyxia. Near-infrared spectroscopy was used to measure changes in total hemoglobin concentration ([tHb]) and the redox state of cytochrome oxidase (COX) simultaneously in the brain and hindlimb of near-term unanesthetized fetal sheep in utero. Oxygen delivery (DO(2)) to, and consumption (VO(2)) by, each tissue was derived from the arteriovenous difference in oxygen content and blood flow, measured by implanted flow probes. One hour of moderate asphyxia (n = 11), caused by occlusion of the maternal common internal iliac artery, led to a significant fall in DO(2) to both tissues and to a significant drop in VO(2) by the head. This was associated with an initial fall in redox state COX in the leg but an increase in the brain. [tHb], and therefore blood volume, fell in the leg and increased in the brain. These data suggest the presence of a fetal metabolic response to hypoxia, which, in the brain, occurs rapidly and could be neuroprotective.
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Affiliation(s)
- J P Newman
- Department of Obstetrics and Gynaecology, University College London, London WC1E 6HX, United Kingdom.
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Bennet L, Rossenrode S, Gunning MI, Gluckman PD, Gunn AJ. The cardiovascular and cerebrovascular responses of the immature fetal sheep to acute umbilical cord occlusion. J Physiol 1999; 517 ( Pt 1):247-57. [PMID: 10226163 PMCID: PMC2269318 DOI: 10.1111/j.1469-7793.1999.0247z.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
1. In premature fetal sheep (89-93 days gestation) we examined the fetal response to asphyxia induced by 30 min of complete umbilical cord occlusion. Fetuses were also studied during the first 3 days after asphyxia. We measured heart rate, blood pressure, carotid and femoral blood flows, vascular resistance, electroencephalographic activity and cerebral changes in haemoglobin concentration by near infrared spectroscopy (NIRS). 2. Fetuses tolerated 30 min of asphyxia and the cardiovascular response was characterized by three phases: initial redistribution of blood flow away from the periphery to maintain vital organ function, partial failure of this redistribution and near terminal cardiovascular collapse, with profound hypotension and cerebral and peripheral hypoperfusion. 3. Post-asphyxia carotid blood flow and NIRS data demonstrated that between 3-5 h there was a significant secondary reduction in cerebral blood flow, blood volume and oxygenation despite normal perfusion pressure and heart rate. There was also a secondary fall in femoral blood flow which persisted throughout recovery. 4. These data demonstrate that the immature fetus can survive a prolonged period of asphyxia, but paradoxically the capacity to survive exposes the fetus to profound hypotension and hypoperfusion. A secondary period of significant cerebral hypoperfusion and reduced oxygen delivery also occurred post-asphyxia. These cardiovascular and cerebrovascular responses may contribute to the patterns of cerebral injury seen in the human preterm fetus.
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Affiliation(s)
- L Bennet
- Research Centre for Developmental Medicine and Biology, Department of Paediatrics, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
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