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Galinsky R, Dhillon SK, Kelly SB, Wassink G, Davidson JO, Lear CA, van den Heuij LG, Bennet L, Gunn AJ. Magnesium sulphate reduces tertiary gliosis but does not improve EEG recovery or white or grey matter cell survival after asphyxia in preterm fetal sheep. J Physiol 2023; 601:1999-2016. [PMID: 36999348 PMCID: PMC10952359 DOI: 10.1113/jp284381] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Accepted: 03/09/2023] [Indexed: 04/01/2023] Open
Abstract
Maternal magnesium sulphate (MgSO4 ) treatment is widely recommended before preterm birth for neuroprotection. However, this is controversial because there is limited evidence that MgSO4 provides long-term neuroprotection. Preterm fetal sheep (104 days gestation; term is 147 days) were assigned randomly to receive sham occlusion with saline infusion (n = 6) or i.v. infusion with MgSO4 (n = 7) or vehicle (saline, n = 6) from 24 h before hypoxia-ischaemia induced by umbilical cord occlusion until 24 h after occlusion. Sheep were killed after 21 days of recovery, for fetal brain histology. Functionally, MgSO4 did not improve long-term EEG recovery. Histologically, in the premotor cortex and striatum, MgSO4 infusion attenuated post-occlusion astrocytosis (GFAP+ ) and microgliosis but did not affect numbers of amoeboid microglia or improve neuronal survival. In the periventricular and intragyral white matter, MgSO4 was associated with fewer total (Olig-2+ ) oligodendrocytes compared with vehicle + occlusion. Numbers of mature (CC1+ ) oligodendrocytes were reduced to a similar extent in both occlusion groups compared with sham occlusion. In contrast, MgSO4 was associated with an intermediate improvement in myelin density in the intragyral and periventricular white matter tracts. In conclusion, a clinically comparable dose of MgSO4 was associated with moderate improvements in white and grey matter gliosis and myelin density but did not improve EEG maturation or neuronal or oligodendrocyte survival. KEY POINTS: Magnesium sulphate is widely recommended before preterm birth for neuroprotection; however, there is limited evidence that magnesium sulphate provides long-term neuroprotection. In preterm fetal sheep exposed to hypoxia-ischaemia (HI), MgSO4 was associated with attenuated astrocytosis and microgliosis in the premotor cortex and striatum but did not improve neuronal survival after recovery to term-equivalent age, 21 days after HI. Magnesium sulphate was associated with loss of total oligodendrocytes in the periventricular and intragyral white matter tracts, whereas mature, myelinating oligodendrocytes were reduced to a similar extent in both occlusion groups. In the same regions, MgSO4 was associated with an intermediate improvement in myelin density. Functionally, MgSO4 did not improve long-term recovery of EEG power, frequency or sleep stage cycling. A clinically comparable dose of MgSO4 was associated with moderate improvements in white and grey matter gliosis and myelin density but did not improve EEG maturation or neuronal or oligodendrocyte survival.
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Affiliation(s)
- Robert Galinsky
- Department of PhysiologyUniversity of AucklandAucklandNew Zealand
- The Ritchie CentreHudson Institute of Medical ResearchClaytonVictoriaAustralia
- Department of Obstetrics and GynaecologyMonash UniversityVictoriaAustralia
| | | | - Sharmony B. Kelly
- The Ritchie CentreHudson Institute of Medical ResearchClaytonVictoriaAustralia
- Department of Obstetrics and GynaecologyMonash UniversityVictoriaAustralia
| | - Guido Wassink
- Department of PhysiologyUniversity of AucklandAucklandNew Zealand
| | | | | | | | - Laura Bennet
- Department of PhysiologyUniversity of AucklandAucklandNew Zealand
| | - Alistair J. Gunn
- Department of PhysiologyUniversity of AucklandAucklandNew Zealand
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2
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Dhillon SK, Gunn ER, Pedersen MV, Lear CA, Wassink G, Davidson JO, Gunn AJ, Bennet L. Alpha-adrenergic receptor activation after fetal hypoxia-ischaemia suppresses transient epileptiform activity and limits loss of oligodendrocytes and hippocampal neurons. J Cereb Blood Flow Metab 2023; 43:947-961. [PMID: 36703575 DOI: 10.1177/0271678x231153723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Exposure to hypoxic-ischaemia (HI) is consistently followed by a delayed fall in cerebral perfusion. In preterm fetal sheep this is associated with impaired cerebral oxygenation, consistent with mismatch between perfusion and metabolism. In the present study we tested the hypothesis that alpha-adrenergic inhibition after HI would improve cerebral perfusion, and so attenuate mismatch and reduce neural injury. Chronically instrumented preterm (0.7 gestation) fetal sheep received sham-HI (n = 10) or HI induced by complete umbilical cord occlusion for 25 minutes. From 15 minutes to 8 hours after HI, fetuses received either an intravenous infusion of a non-selective alpha-adrenergic antagonist, phentolamine (10 mg bolus, 10 mg/h infusion, n = 10), or saline (n = 10). Fetal brains were processed for histology 72 hours post-HI. Phentolamine infusion was associated with increased epileptiform transient activity and a greater fall in cerebral oxygenation in the early post-HI recovery phase. Histologically, phentolamine was associated with greater loss of oligodendrocytes and hippocampal neurons. In summary, contrary to our hypothesis, alpha-adrenergic inhibition increased epileptiform transient activity with an exaggerated fall in cerebral oxygenation, and increased neural injury, suggesting that alpha-adrenergic receptor activation after HI is an important endogenous neuroprotective mechanism.
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Affiliation(s)
| | - Eleanor R Gunn
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Mette V Pedersen
- Department of Pediatrics, Aarhus University Hospital, Aarhus, Denmark
| | - Christopher A Lear
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Guido Wassink
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Department of Physiology, The University of Auckland, Auckland, New Zealand
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3
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Dhillon SK, Gunn ER, Lear BA, King VJ, Lear CA, Wassink G, Davidson JO, Bennet L, Gunn AJ. Cerebral Oxygenation and Metabolism After Hypoxia-Ischemia. Front Pediatr 2022; 10:925951. [PMID: 35903161 PMCID: PMC9314655 DOI: 10.3389/fped.2022.925951] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 06/15/2022] [Indexed: 11/13/2022] Open
Abstract
Perinatal hypoxia-ischemia (HI) is still a significant contributor to mortality and adverse neurodevelopmental outcomes in term and preterm infants. HI brain injury evolves over hours to days, and involves complex interactions between the endogenous protective and pathological processes. Understanding the timing of evolution of injury is vital to guide treatment. Post-HI recovery is associated with a typical neurophysiological profile, with stereotypic changes in cerebral perfusion and oxygenation. After the initial recovery, there is a delayed, prolonged reduction in cerebral perfusion related to metabolic suppression, followed by secondary deterioration with hyperperfusion and increased cerebral oxygenation, associated with altered neurovascular coupling and impaired cerebral autoregulation. These changes in cerebral perfusion are associated with the stages of evolution of injury and injury severity. Further, iatrogenic factors can also affect cerebral oxygenation during the early period of deranged metabolism, and improving clinical management may improve neuroprotection. We will review recent evidence that changes in cerebral oxygenation and metabolism after HI may be useful biomarkers of prognosis.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Alistair J. Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
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4
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Verma V, Lange F, Bainbridge A, Harvey-Jones K, Robertson NJ, Tachtsidis I, Mitra S. Brain temperature monitoring in newborn infants: Current methodologies and prospects. Front Pediatr 2022; 10:1008539. [PMID: 36268041 PMCID: PMC9577084 DOI: 10.3389/fped.2022.1008539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Accepted: 09/15/2022] [Indexed: 02/02/2023] Open
Abstract
Brain tissue temperature is a dynamic balance between heat generation from metabolism, passive loss of energy to the environment, and thermoregulatory processes such as perfusion. Perinatal brain injuries, particularly neonatal encephalopathy, and seizures, have a significant impact on the metabolic and haemodynamic state of the developing brain, and thereby likely induce changes in brain temperature. In healthy newborn brains, brain temperature is higher than the core temperature. Magnetic resonance spectroscopy (MRS) has been used as a viable, non-invasive tool to measure temperature in the newborn brain with a reported accuracy of up to 0.2 degrees Celcius and a precision of 0.3 degrees Celcius. This measurement is based on the separation of chemical shifts between the temperature-sensitive water peaks and temperature-insensitive singlet metabolite peaks. MRS thermometry requires transport to an MRI scanner and a lengthy single-point measurement. Optical monitoring, using near infrared spectroscopy (NIRS), offers an alternative which overcomes this limitation in its ability to monitor newborn brain tissue temperature continuously at the cot side in real-time. Near infrared spectroscopy uses linear temperature-dependent changes in water absorption spectra in the near infrared range to estimate the tissue temperature. This review focuses on the currently available methodologies and their viability for accurate measurement, the potential benefits of monitoring newborn brain temperature in the neonatal intensive care unit, and the important challenges that still need to be addressed.
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Affiliation(s)
- Vinita Verma
- Institute for Women's Health, University College London, London, United Kingdom
| | - Frederic Lange
- Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Alan Bainbridge
- Medical Physics and Engineering, University College London Hospital, London, United Kingdom
| | - Kelly Harvey-Jones
- Institute for Women's Health, University College London, London, United Kingdom
| | - Nicola J Robertson
- Institute for Women's Health, University College London, London, United Kingdom
| | - Ilias Tachtsidis
- Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Subhabrata Mitra
- Institute for Women's Health, University College London, London, United Kingdom
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5
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Zhou KQ, McDouall A, Drury PP, Lear CA, Cho KHT, Bennet L, Gunn AJ, Davidson JO. Treating Seizures after Hypoxic-Ischemic Encephalopathy-Current Controversies and Future Directions. Int J Mol Sci 2021; 22:ijms22137121. [PMID: 34281174 PMCID: PMC8268683 DOI: 10.3390/ijms22137121] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 06/30/2021] [Accepted: 06/30/2021] [Indexed: 12/20/2022] Open
Abstract
Seizures are common in newborn infants with hypoxic-ischemic encephalopathy and are highly associated with adverse neurodevelopmental outcomes. The impact of seizure activity on the developing brain and the most effective way to manage these seizures remain surprisingly poorly understood, particularly in the era of therapeutic hypothermia. Critically, the extent to which seizures exacerbate brain injury or merely reflect the underlying evolution of injury is unclear. Current anticonvulsants, such as phenobarbital and phenytoin have poor efficacy and preclinical studies suggest that most anticonvulsants are associated with adverse effects on the developing brain. Levetiracetam seems to have less potential neurotoxic effects than other anticonvulsants but may not be more effective. Given that therapeutic hypothermia itself has significant anticonvulsant effects, randomized controlled trials of anticonvulsants combined with therapeutic hypothermia, are required to properly determine the safety and efficacy of these drugs. Small clinical studies suggest that prophylactic phenobarbital administration may improve neurodevelopmental outcomes compared to delayed administration; however, larger high-quality studies are required to confirm this. In conclusion, there is a distinct lack of high-quality evidence for whether and to what extent neonatal seizures exacerbate brain damage after hypoxia-ischemia and how best to manage them in the era of therapeutic hypothermia.
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6
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Lear CA, Bennet L, Lear BA, Westgate JA, Gunn AJ. Lack of evidence for impaired preload or Bezold-Jarisch activation during brief umbilical cord occlusions in fetal sheep. Am J Physiol Regul Integr Comp Physiol 2021; 320:R532-R540. [PMID: 33533313 DOI: 10.1152/ajpregu.00357.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Impaired cardiac preload secondary to umbilical cord occlusion (UCO) has been hypothesized to contribute to intrapartum decelerations, brief falls in fetal heart rate (FHR), through activation of the Bezold-Jarisch reflex. This cardioprotective reflex increases parasympathetic and inhibits sympathetic outflows triggering hypotension, bradycardia, and peripheral vasodilation, but its potential to contribute to intrapartum decelerations has never been systematically examined. In this study, we performed bilateral cervical vagotomy to remove the afferent arm and the efferent parasympathetic arm of the Bezold-Jarisch reflex. Twenty-two chronically instrumented fetal sheep at 0.85 of gestation received vagotomy (n = 7) or sham vagotomy (control, n = 15), followed by three 1-min complete UCOs separated by 4-min reperfusion periods. UCOs in control fetuses were associated with a rapid fall in FHR and reduced femoral blood flow mediated by intense femoral vasoconstriction, leading to hypertension. Vagotomy abolished the rapid fall in FHR (P < 0.001) and, despite reduced diastolic filling time, increased both carotid (P < 0.001) and femoral (P < 0.05) blood flow during UCOs, secondary to carotid vasodilation (P < 0.01) and delayed femoral vasoconstriction (P < 0.05). Finally, vagotomy was associated with an attenuated rise in cortical impedance during UCOs (P < 0.05), consistent with improved cerebral substrate supply. In conclusion, increased carotid and femoral blood flows after vagotomy are consistent with increased left and right ventricular output, which is incompatible with the hypothesis that labor-like UCOs impair ventricular filling. Overall, the cardiovascular responses to vagotomy do not support the hypothesis that the Bezold-Jarisch reflex is activated by UCO. The Bezold-Jarisch reflex is therefore mechanistically unable to contribute 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
| | - Laura Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Benjamin A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Jenny A Westgate
- 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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7
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Min YJ, Ling EA, Li F. Immunomodulatory Mechanism and Potential Therapies for Perinatal Hypoxic-Ischemic Brain Damage. Front Pharmacol 2020; 11:580428. [PMID: 33536907 PMCID: PMC7849181 DOI: 10.3389/fphar.2020.580428] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/13/2020] [Indexed: 12/13/2022] Open
Abstract
Hypoxia-ischemia (HI) is one of the most common causes of death and disability in neonates. Currently, the only available licensed treatment for perinatal HI is hypothermia. However, it alone is not sufficient to prevent the brain injuries and/or neurological dysfunction related to HI. Perinatal HI can activate the immune system and trigger the peripheral and central responses which involve the immune cell activation, increase in production of immune mediators and release of reactive oxygen species. There is mounting evidence indicating that regulation of immune response can effectively rescue the outcomes of brain injury in experimental perinatal HI models such as Rice-Vannucci model of newborn hypoxic-ischemic brain damage (HIBD), local transient cerebral ischemia and reperfusion model, perinatal asphyxia model, and intrauterine hypoxia model. This review summarizes the many studies about immunomodulatory mechanisms and therapies for HI. It highlights the important actions of some widely documented therapeutic agents for effective intervening of HI related brain damage, namely, HIBD, such as EPO, FTY720, Minocycline, Gastrodin, Breviscapine, Milkvetch etc. In this connection, it has been reported that the ameboid microglial cells featured prominently in the perinatal brain represent the key immune cells involved in HIBD. To this end, drugs, chemical agents and herbal compounds which have the properties to suppress microglia activation have recently been extensively explored and identified as potential therapeutic agents or strategies for amelioration of neonatal HIBD.
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Affiliation(s)
- Ying-Jun Min
- Department of Pathology and Pathophysiology, School of Basic Medical Sciences, Kunming Medical University, Kunming, China
| | - Eng-Ang Ling
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Fan Li
- Department of Pathology and Pathophysiology, School of Basic Medical Sciences, Kunming Medical University, Kunming, China
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8
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Davidson JO, van den Heuij LG, Fraser M, Wassink G, Miller SL, Lim R, Wallace EM, Jenkin G, Gunn AJ, Bennet L. Window of opportunity for human amnion epithelial stem cells to attenuate astrogliosis after umbilical cord occlusion in preterm fetal sheep. Stem Cells Transl Med 2020; 10:427-440. [PMID: 33103374 PMCID: PMC7900589 DOI: 10.1002/sctm.20-0314] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 09/22/2020] [Accepted: 10/09/2020] [Indexed: 12/19/2022] Open
Abstract
There is increasing evidence that administration of many types of stem cells, including human amnion epithelial cells (hAECs), can reduce hypoxic-ischemic injury, including in the perinatal brain. However, the therapeutic window for single dose treatment is not known. We compared the effects of early and delayed intracerebroventricular administration of hAECs in fetal sheep at 0.7 gestation on brain injury induced by 25 minutes of complete umbilical cord occlusion (UCO) or sham occlusion. Fetuses received either 1 × 106 hAECs or vehicle alone, as an infusion over 1 hour, either 2 or 24 hours after UCO. Fetuses were killed for brain histology at 7 days post-UCO. hAEC infusion at both 2 and 24 hours had dramatic anti-inflammatory and anti-gliotic effects, including significantly attenuating the increase in microglia after UCO in the white and gray matter and the number of astrocytes in the white matter. Both protocols partially improved myelination, but had no effect on total or immature/mature numbers of oligodendrocytes. Neuronal survival in the hippocampus was increased by hAEC infusion at either 2 or 24 hours, whereas only hAECs at 24 hours were associated with improved neuronal survival in the striatum and thalamus. Neither protocol improved recovery of electroencephalographic (EEG) power. These data suggest that a single infusion of hAECs is anti-inflammatory, anti-gliotic, and neuroprotective in preterm fetal sheep when given up to 24 hours after hypoxia-ischemia, but was associated with limited white matter protection after 7 days recovery and no improvement in the recovery of EEG power.
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Affiliation(s)
- Joanne O Davidson
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Lotte G van den Heuij
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Mhoyra Fraser
- 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
| | - Suzanne L Miller
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, Victoria, Australia.,Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia
| | - Rebecca Lim
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, Victoria, Australia.,Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia
| | - Euan M Wallace
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, Victoria, Australia.,Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia
| | - Graham Jenkin
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, Victoria, Australia.,Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia
| | - Alistair J Gunn
- 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
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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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10
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Witsch J, Frey HP, Schmidt JM, Velazquez A, Falo CM, Reznik M, Roh D, Agarwal S, Park S, Connolly ES, Claassen J. Electroencephalographic Periodic Discharges and Frequency-Dependent Brain Tissue Hypoxia in Acute Brain Injury. JAMA Neurol 2017; 74:301-309. [PMID: 28097330 DOI: 10.1001/jamaneurol.2016.5325] [Citation(s) in RCA: 120] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Importance Periodic discharges (PDs) that do not meet seizure criteria, also termed the ictal interictal continuum, are pervasive on electroencephalographic (EEG) recordings after acute brain injury. However, their association with brain homeostasis and the need for clinical intervention remain unknown. Objective To determine whether distinct PD patterns can be identified that, similar to electrographic seizures, cause brain tissue hypoxia, a measure of ongoing brain injury. Design, Setting, and Participants This prospective cohort study included 90 comatose patients with high-grade spontaneous subarachnoid hemorrhage who underwent continuous surface (scalp) EEG (sEEG) recording and multimodality monitoring, including invasive measurements of intracortical (depth) EEG (dEEG), partial pressure of oxygen in interstitial brain tissue (Pbto2), and regional cerebral blood flow (CBF). Patient data were collected from June 1, 2006, to September 1, 2014, at a single tertiary care center. The retrospective analysis was performed from September 1, 2014, to May 1, 2016, with a hypothesis that the effect on brain tissue oxygenation was primarily dependent on the discharge frequency. Main Outcomes and Measures Electroencephalographic recordings were visually classified based on PD frequency and spatial distribution of discharges. Correlations between mean multimodality monitoring data and change-point analyses were performed to characterize electrophysiological changes by applying bootstrapping. Results Of the 90 patients included in the study (26 men and 64 women; mean [SD] age, 55 [15] years), 32 (36%) had PDs on sEEG and dEEG recordings and 21 (23%) on dEEG recordings only. Frequencies of PDs ranged from 0.5 to 2.5 Hz. Median Pbto2 was 23 mm Hg without PDs compared with 16 mm Hg at 2.0 Hz and 14 mm Hg at 2.5 Hz (differences were significant for 0 vs 2.5 Hz based on bootstrapping). Change-point analysis confirmed a temporal association of high-frequency PD onset (≥2.0 Hz) and Pbto2 reduction (median normalized Pbto2 decreased by 25% 5-10 minutes after onset). Increased regional CBF of 21.0 mL/100 g/min for 0 Hz, 25.9 mL/100 g/min for 1.0 Hz, 27.5 mL/100 g/min for 1.5 Hz, and 34.7 mL/100 g/min for 2.0 Hz and increased global cerebral perfusion pressure of 91 mm Hg for 0 Hz, 100.5 mm Hg for 0.5 Hz, 95.5 mm Hg for 1.0 Hz, 97.0 mm Hg for 2.0 Hz, 98.0 mm Hg for 2.5 Hz, 95.0 mm Hg for 2.5 Hz, and 67.8 mm Hg for 3.0 Hz were seen for higher PD frequencies. Conclusions and Relevance These data give some support to consider redefining the continuum between seizures and PDs, suggesting that additional damage after acute brain injury may be reflected by frequency changes in electrocerebral recordings. Similar to seizures, cerebral blood flow increases in patients with PDs to compensate for the increased metabolic demand but higher-frequency PDs (>2 per second) may be inadequately compensated without an additional rise in CBF and associated with brain tissue hypoxia, or higher-frequency PDs may reflect inadequacies in brain compensatory mechanisms.
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Affiliation(s)
- Jens Witsch
- Department of Neurology, Columbia University, New York, New York
| | - Hans-Peter Frey
- Department of Neurology, Columbia University, New York, New York
| | | | - Angela Velazquez
- Department of Neurology, Columbia University, New York, New York
| | - Cristina M Falo
- Department of Neurology, Columbia University, New York, New York
| | - Michael Reznik
- Department of Neurology, Columbia University, New York, New York
| | - David Roh
- Department of Neurology, Columbia University, New York, New York
| | - Sachin Agarwal
- Department of Neurology, Columbia University, New York, New York
| | - Soojin Park
- Department of Neurology, Columbia University, New York, New York
| | | | - Jan Claassen
- Department of Neurology, Columbia University, New York, New York
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11
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Galinsky R, Draghi V, Wassink G, Davidson JO, Drury PP, Lear CA, Gunn AJ, Bennet L. Magnesium sulfate reduces EEG activity but is not neuroprotective after asphyxia in preterm fetal sheep. J Cereb Blood Flow Metab 2017; 37:1362-1373. [PMID: 27317658 PMCID: PMC5453457 DOI: 10.1177/0271678x16655548] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 04/21/2016] [Accepted: 05/17/2016] [Indexed: 12/29/2022]
Abstract
Magnesium sulfate is now widely recommended for neuroprotection for preterm birth; however, this has been controversial because there is little evidence that magnesium sulfate is neuroprotective. Preterm fetal sheep (104 days gestation; term is 147 days) were randomly assigned to receive sham occlusion (n = 7), i.v. magnesium sulfate (n = 10) or saline (n = 8) starting 24 h before asphyxia until 24 h after asphyxia. Sheep were killed 72 h after asphyxia. Magnesium sulfate infusion reduced electroencephalograph power and fetal movements before asphyxia. Magnesium sulfate infusion did not affect electroencephalograph power during recovery, but was associated with marked reduction of the post-asphyxial seizure burden (mean ± SD: 34 ± 18 min vs. 107 ± 74 min, P < 0.05). Magnesium sulfate infusion did not affect subcortical neuronal loss. In the intragyral and periventricular white matter, magnesium sulfate was associated with reduced numbers of all (Olig-2+ve) oligodendrocytes in the intragyral (125 ± 23 vs. 163 ± 38 cells/field) and periventricular white matter (162 ± 39 vs. 209 ± 44 cells/field) compared to saline-treated controls ( P < 0.05), but no effect on microglial induction or astrogliosis. In conclusion, a clinically comparable dose of magnesium sulfate showed significant anticonvulsant effects after asphyxia in preterm fetal sheep, but did not reduce asphyxia-induced brain injury and exacerbated loss of oligodendrocytes.
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Affiliation(s)
- Robert Galinsky
- Department of Physiology, University of Auckland, Auckland, New Zealand
- The Ritchie Centre, the Hudson Institute of Medical Research, Clayton, Victoria, Australia
| | - Vittoria Draghi
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Guido Wassink
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Paul P Drury
- 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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12
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Yao D, Zhang W, He X, Wang J, Jiang K, Zhao Z. Establishment and identification of a hypoxia-ischemia brain damage model in neonatal rats. Biomed Rep 2016; 4:437-443. [PMID: 27073628 DOI: 10.3892/br.2016.610] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 01/25/2016] [Indexed: 11/06/2022] Open
Abstract
The present study was designed to set up a reliable model of severe hypoxia-ischemia brain damage (HIBD) in neonatal rats and several methods were used to identify whether the model was successful. A total of 40 healthy 7-day-old Sprague-Dawley rats were randomly divided into 2 groups: The sham-surgery group (n=18) and the HIBD model group (n=22). The HIBD model was produced according to the traditional Rice method. The rats were anesthetized with ethyl ether. The left common carotid artery (CCA) was exposed, ligated and cut. Following this, the rats were exposed to hypoxia in a normobaric chamber filled with 8% oxygen and 92% nitrogen for 2 h. In the sham-surgery group, the left CCA was exposed but was not ligated, cut or exposed to hypoxia. The neurobehavioral changes of the rats were observed in the 24 h after HIBD. The brains were collected after 72 h to observe the pathological morphological changes of the brain tissue. The behavioral ability and neurobehavioral changes were studied in each group. The water maze test was used for evaluating the learning-memory ability when the rats were 28 days old. Compared with the sham-surgery group, all the HIBD model rats had a lag of motor development. The rats had evident changes in anatomy and Nissl staining, and cognitive impairment was shown through the result of the water maze. Therefore, the model of HIBD in neonatal rats is feasible and provides a reliable model for subsequent studies.
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Affiliation(s)
- Dan Yao
- Department of Pediatric Health Care, The Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
| | - Weiran Zhang
- Department of Pediatric Health Care, The Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
| | - Xue He
- Department of Pediatric Health Care, The Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
| | - Jinhu Wang
- Department of Pediatric Surgery, The Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
| | - Kewen Jiang
- Department of Neurology, The Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
| | - Zhengyan Zhao
- Department of Pediatric Health Care, The Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
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13
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Mitra S, Bale G, Mathieson S, Uria-Avellanal C, Meek J, Tachtsidis I, Robertson NJ. Changes in Cerebral Oxidative Metabolism during Neonatal Seizures Following Hypoxic-Ischemic Brain Injury. Front Pediatr 2016; 4:83. [PMID: 27559538 PMCID: PMC4978952 DOI: 10.3389/fped.2016.00083] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 07/27/2016] [Indexed: 01/01/2023] Open
Abstract
Seizures are common following hypoxic-ischemic brain injury in newborn infants. Prolonged or recurrent seizures have been shown to exacerbate neuronal damage in the developing brain; however, the precise mechanism is not fully understood. Cytochrome-c-oxidase is responsible for more than 90% of ATP production inside mitochondria. Using a novel broadband near-infrared spectroscopy system, we measured the concentration changes in the oxidation state of cerebral cytochrome-c-oxidase (Δ[oxCCO]) and hemodynamics during recurrent neonatal seizures following hypoxic-ischemic encephalopathy in a newborn infant. A rapid increase in Δ[oxCCO] was noted at the onset of seizures along with a rise in the baseline of amplitude-integrated electroencephalogram. Cerebral oxygenation and cerebral blood volume fell just prior to the seizure onset but recovered rapidly during seizures. Δ[oxCCO] during seizures correlated with changes in mean electroencephalogram voltage indicating an increase in neuronal activation and energy demand. The progressive decline in the Δ[oxCCO] baseline during seizures suggests a progressive decrease of mitochondrial oxidative metabolism.
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Affiliation(s)
- Subhabrata Mitra
- Department of Neonatology, Institute for Women's Health, University College London , London , UK
| | - Gemma Bale
- Department of Medical Physics and Biomedical Engineering, University College London , London , UK
| | - Sean Mathieson
- Department of Neonatology, Institute for Women's Health, University College London , London , UK
| | - Cristina Uria-Avellanal
- Department of Neonatology, Institute for Women's Health, University College London , London , UK
| | - Judith Meek
- Department of Neonatology, Institute for Women's Health, University College London , London , UK
| | - Ilias Tachtsidis
- Department of Medical Physics and Biomedical Engineering, University College London , London , UK
| | - Nicola J Robertson
- Department of Neonatology, Institute for Women's Health, University College London , London , UK
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14
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Non-additive effects of delayed connexin hemichannel blockade and hypothermia after cerebral ischemia in near-term fetal sheep. J Cereb Blood Flow Metab 2015; 35:2052-61. [PMID: 26174327 PMCID: PMC4671127 DOI: 10.1038/jcbfm.2015.171] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 06/07/2015] [Accepted: 06/09/2015] [Indexed: 12/31/2022]
Abstract
Hypothermia is partially neuroprotective after neonatal hypoxic-ischemic encephalopathy. Blockade of connexin hemichannels can improve recovery of brain activity and cell survival after ischemia in near-term fetal sheep. In this study, we investigated whether combining delayed hypothermia with connexin hemichannel blockade with intracerebroventricular infusion of a mimetic peptide can further improve outcomes after cerebral ischemia. Fetal sheep (0.85 gestation) received 30 minutes of cerebral ischemia followed by a 3-hour recovery period before treatment was started. Fetuses were randomized to one of the following treatment groups: normothermia (n=8), hypothermia for 3 days (n=8), connexin hemichannel blockade (50 μmol/L intracerebroventricular over 1 hour followed by 50 μmol/L over 24 hours, n=8) or hypothermia plus hemichannel blockade (n=7). After 7 days recovery, hypothermia was associated with reduced seizure burden, improved electroencephalographic (EEG) power, and a significant increase in neuronal and oligodendrocyte survival and reduced induction of Iba1-positive microglia. In contrast, although hemichannel blockade reduced seizure burden, there was no effect on EEG power or histology (P<0.05). There was no further improvement in outcomes with combined hypothermia plus hemichannel blockade. In conclusion, these data show that there is no additive neuroprotection with combined hypothermia and hemichannel blockade after cerebral ischemia in near-term fetal sheep.
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15
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Lear CA, Koome ME, Davidson JO, Drury PP, Quaedackers JS, Galinsky R, Gunn AJ, Bennet L. The effects of dexamethasone on post-asphyxial cerebral oxygenation in the preterm fetal sheep. J Physiol 2014; 592:5493-505. [PMID: 25384775 DOI: 10.1113/jphysiol.2014.281253] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Exposure to clinical doses of the glucocorticoid dexamethasone increases brain activity and causes seizures in normoxic preterm fetal sheep without causing brain injury. In contrast, the same treatment after asphyxia increased brain injury. We hypothesised that increased injury was in part mediated by a mismatch between oxygen demand and oxygen supply. In preterm fetal sheep at 0.7 gestation we measured cerebral oxygenation using near-infrared spectroscopy, electroencephalographic (EEG) activity, and carotid blood flow (CaBF) from 24 h before until 72 h after asphyxia induced by 25 min of umbilical cord occlusion. Ewes received dexamethasone intramuscularly (12 mg 3 ml(-1)) or saline 15 min after the end of asphyxia. Fetuses were studied for 3 days after occlusion. During the first 6 h of recovery after asphyxia, dexamethasone treatment was associated with a significantly greater fall in CaBF (P < 0.05), increased carotid vascular resistance (P < 0.001) and a greater fall in cerebral oxygenation as measured by the difference between oxygenated and deoxygenated haemoglobin (delta haemoglobin; P < 0.05). EEG activity was similarly suppressed in both groups. From 6 to 10 h onward, dexamethasone treatment was associated with a return of CaBF to saline control levels, increased EEG power (P < 0.005), greater epileptiform transient activity (P < 0.001), increased oxidised cytochrome oxidase (P < 0.05) and an attenuated increase in [delta haemoglobin] (P < 0.05). In conclusion, dexamethasone treatment after asphyxia is associated with greater hypoperfusion in the critical latent phase, leading to impaired intracerebral oxygenation that may exacerbate neural injury after asphyxia.
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Affiliation(s)
- Christopher A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Miriam E Koome
- 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
| | - Paul P Drury
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Josine S Quaedackers
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Robert Galinsky
- 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
| | - Laura Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
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16
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Status epilepticus after prolonged umbilical cord occlusion is associated with greater neural injury in [corrected] fetal sheep at term-equivalent. PLoS One 2014; 9:e96530. [PMID: 24797081 PMCID: PMC4010475 DOI: 10.1371/journal.pone.0096530] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Accepted: 04/08/2014] [Indexed: 12/24/2022] Open
Abstract
The majority of pre-clinical studies of hypoxic-ischemic encephalopathy at term-equivalent have focused on either relatively mild insults, or on functional paradigms of cerebral ischemia or hypoxia-ischemia/hypotension. There is surprisingly little information on the responses to single, severe ‘physiological’ insults. In this study we examined the evolution and pattern of neural injury after prolonged umbilical cord occlusion (UCO). 36 chronically instrumented fetal sheep at 125–129 days gestational age (term = 147 days) were subjected to either UCO until mean arterial pressure was < = 8 mmHg (n = 29), or sham occlusion (n = 7). Surviving fetuses were killed after 72 hours for histopathologic assessment with acid-fuchsin thionine. After UCO, 11 fetuses died with intractable hypotension and 5 ewes entered labor and were euthanized. The remaining 13 fetuses showed marked EEG suppression followed by evolving seizures starting at 5.8 (6.8) hours (median (interquartile range)). 6 of 13 developed status epilepticus, which was associated with a transient secondary increase in cortical impedance (a measure of cytotoxic edema, p<0.05). All fetuses showed moderate to severe neuronal loss in the hippocampus and the basal ganglia but mild cortical cell loss (p<0.05 vs sham occlusion). Status epilepticus was associated with more severe terminal hypotension (p<0.05) and subsequently, greater neuronal loss (p<0.05). In conclusion, profound UCO in term-equivalent fetal sheep was associated with delayed seizures, secondary cytotoxic edema, and subcortical injury, consistent with the predominant pattern after peripartum sentinel events at term. It is unclear whether status epilepticus exacerbated cortical injury or was simply a reflection of a longer duration of asphyxia.
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17
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Barrett RD, Bennet L, Blood AB, Wassink G, Gunn AJ. Asphyxia and therapeutic hypothermia modulate plasma nitrite concentrations and carotid vascular resistance in preterm fetal sheep. Reprod Sci 2014; 21:1483-91. [PMID: 24740991 DOI: 10.1177/1933719114530187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In this study, we tested the hypothesis that cerebral hypoperfusion after asphyxia and induced hypothermia is associated with reduced circulating nitrite levels as an index of nitric oxide synthase (NOS) activity. The preterm fetal sheep at 0.7 gestation (103-104 days, term = 147 days) received 25-minute umbilical cord occlusion, followed by mild whole-body cooling from 30 minutes to 72 hours after occlusion. Occlusion and induced hypothermia were independently associated with reduced carotid vascular conductance (CaVC) from 2 to 72 hours, and with transiently suppressed plasma nitrite levels at 6 hours. There was a significant within-subjects correlation (r(2) = 0.33, P = .002) between CaVC and plasma nitrite values in the first 24 hours after occlusion but not after sham occlusion. These findings suggest that in preterm fetal sheep, changes in NOS activity are an important mediator of changes in carotid vascular tone in the early recovery phase after asphyxia and may help mediate some of the vascular effects of induced hypothermia.
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Affiliation(s)
- Robert D Barrett
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Arlin B Blood
- Department of Pediatrics and Center for Perinatal Biology, Division of Neonatology, Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Guido Wassink
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- Department of Physiology, University of Auckland, Auckland, New Zealand
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18
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Drury PP, Davidson JO, Mathai S, van den Heuij LG, Ji H, Bennet L, Tan S, Silverman RB, Gunn AJ. nNOS inhibition during profound asphyxia reduces seizure burden and improves survival of striatal phenotypic neurons in preterm fetal sheep. Neuropharmacology 2014; 83:62-70. [PMID: 24726307 DOI: 10.1016/j.neuropharm.2014.03.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 03/17/2014] [Accepted: 03/31/2014] [Indexed: 12/01/2022]
Abstract
Basal ganglia injury after hypoxia-ischemia remains common in preterm infants, and is closely associated with later cerebral palsy. In the present study we tested the hypothesis that a highly selective neuronal nitric oxide synthase (nNOS) inhibitor, JI-10, would improve survival of striatal phenotypic neurons after profound asphyxia, and that the subsequent seizure burden and recovery of EEG are associated with neural outcome. 24 chronically instrumented preterm fetal sheep were randomized to either JI-10 (3 ml of 0.022 mg/ml, n = 8) or saline (n = 8) infusion 15 min before 25 min complete umbilical cord occlusion, or saline plus sham-occlusion (n = 8). Umbilical cord occlusion was associated with reduced numbers of calbindin-28k-, GAD-, NPY-, PV-, Calretinin- and nNOS-positive striatal neurons (p < 0.05 vs. sham occlusion) but not ChAT-positive neurons. JI-10 was associated with increased numbers of calbindin-28k-, GAD-, nNOS-, NPY-, PV-, Calretinin- and ChAT-positive striatal neurons (p < 0.05 vs. saline + occlusion). Seizure burden was strongly associated with loss of calbindin-positive cells (p < 0.05), greater seizure amplitude was associated with loss of GAD-positive cells (p < 0.05), and with more activated microglia in the white matter tracts (p < 0.05). There was no relationship between EEG power after 7 days recovery and total striatal cell loss, but better survival of NPY-positive neurons was associated with lower EEG power. In summary, these findings suggest that selective nNOS inhibition during asphyxia is associated with protection of phenotypic striatal projection neurons and has potential to help reduce basal ganglia injury in some premature babies.
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Affiliation(s)
- Paul P Drury
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Sam Mathai
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | | | - Haitao Ji
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, IL 60208-3113, USA; Department of Chemistry, University of Utah, Salt Lake City, UT, USA
| | - Laura Bennet
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Sidhartha Tan
- Department of Pediatrics, NorthShore University HealthSystem, Evanston, IL, USA
| | - Richard B Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, IL 60208-3113, USA
| | - Alistair J Gunn
- Department of Physiology, University of Auckland, Auckland, New Zealand.
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19
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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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20
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Drury PP, Davidson JO, Bennet L, Booth LC, Tan S, Fraser M, van den Heuij LG, Gunn AJ. Partial neural protection with prophylactic low-dose melatonin after asphyxia in preterm fetal sheep. J Cereb Blood Flow Metab 2014; 34:126-35. [PMID: 24103904 PMCID: PMC3887352 DOI: 10.1038/jcbfm.2013.174] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 08/13/2013] [Accepted: 09/09/2013] [Indexed: 12/11/2022]
Abstract
Melatonin is a naturally occurring indolamine with mild antioxidant properties that is neuroprotective in perinatal animals. There is limited information on its effects on preterm brain injury. In this study, 23 chronically instrumented fetal sheep received 25 minutes of complete umbilical cord occlusion at 101 to 104 days gestation (term is 147 days). Melatonin was administered to the ewe 15 minutes before occlusion (0.1 mg/kg bolus followed by 0.1 mg/kg per hour for 6 hours, n=8), or the equivalent volume of vehicle (2% ethanol, n=7), or saline (n=8), or maternal saline plus sham occlusion (n=8). Sheep were killed after 7 days recovery in utero. Fetal blood pressure, heart rate, nuchal activity, and temperature were similar between groups. Vehicle infusion was associated with improved neuronal survival in the caudate nucleus, but greater neuronal loss in the regions of the hippocampus, with reduced proliferation and increased ameboid microglia in the white matter (P<0.05). Maternal melatonin infusion was associated with faster recovery of fetal EEG, prolonged reduction in carotid blood flow, similar neuronal survival to vehicle, improved numbers of mature oligodendrocytes, and reduced microglial activation in the white matter (P<0.05). Prophylactic maternal melatonin treatment is partially protective but its effects may be partly confounded by ethanol used to dissolve melatonin.
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Affiliation(s)
- Paul P Drury
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Lindsea C Booth
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Sidhartha Tan
- Department of Pediatrics, NorthShore University HealthSystem, Evanston, Illinois, USA
| | - Mhoyra Fraser
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | | | - Alistair J Gunn
- Department of Physiology, University of Auckland, Auckland, New Zealand
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21
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Drury PP, Davidson JO, van den Heuij LG, Tan S, Silverman RB, Ji H, Blood AB, Fraser M, Bennet L, Gunn AJ. Partial neuroprotection by nNOS inhibition during profound asphyxia in preterm fetal sheep. Exp Neurol 2013; 250:282-92. [PMID: 24120436 DOI: 10.1016/j.expneurol.2013.10.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2013] [Revised: 09/30/2013] [Accepted: 10/02/2013] [Indexed: 11/19/2022]
Abstract
Preterm brain injury is partly associated with hypoxia-ischemia starting before birth. Excessive nitric oxide production during HI may cause nitrosative stress, leading to cell membrane and mitochondrial damage. We therefore tested the hypothesis that therapy with a new, selective neuronal nitric oxide synthase (nNOS) inhibitor, JI-10 (0.022mg/kg bolus, n=8), given 30min before 25min of complete umbilical cord occlusion was protective in preterm fetal sheep at 101-104day gestation (term is 147days), compared to saline (n=8). JI-10 had no effect on fetal blood pressure, heart rate, carotid and femoral blood flow, total EEG power, nuchal activity, temperature or intracerebral oxygenation on near-infrared spectroscopy during or after occlusion. JI-10 was associated with later onset of post-asphyxial seizures compared with saline (p<0.05), and attenuation of the subsequent progressive loss of cytochrome oxidase (p<0.05). After 7days recovery, JI-10 was associated with improved neuronal survival in the caudate nucleus (p<0.05), but not the putamen or hippocampus, and more CNPase positive oligodendrocytes in the periventricular white matter (p<0.05). In conclusion, prophylactic nNOS inhibition before profound asphyxia was associated with delayed onset of seizures, slower decline of cytochrome oxidase and partial white and gray matter protection, consistent with protection of mitochondrial function.
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Affiliation(s)
- Paul P Drury
- Department of Physiology, University of Auckland, Auckland, New Zealand.
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22
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Mathai S, Booth LC, Davidson JO, Drury PP, Fraser M, Jensen EC, George S, Naylor A, Gunn AJ, Bennet L. Acute on chronic exposure to endotoxin in preterm fetal sheep. Am J Physiol Regul Integr Comp Physiol 2012; 304:R189-97. [PMID: 23235324 DOI: 10.1152/ajpregu.00388.2012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Acute, high-dose exposure to endotoxin lipopolysaccharide (LPS) in preterm fetal sheep can trigger periventricular white matter lesions (PVL), in association with severe hypotension/hypoxemia and significant mortality. Intriguingly, however, chronic or repeated exposure to LPS can induce tachyphylaxis. We therefore tested the hypothesis that progressive, acute on chronic fetal infection would be associated with white matter injury with little fetal mortality. Chronically instrumented preterm (0.7 gestational age) fetal sheep were exposed to a continuous low-dose LPS infusion (100 ng over 24 h, followed by 250 ng/24 h for 96 h) or saline. Boluses of 1 μg LPS or saline were given at 48, 72, and 96 h; sheep were killed at day 10. Six of 11 fetal sheep exposed to saline infusion + LPS boluses died 4-7 h after the first bolus. In contrast, there was no fetal mortality after saline infusions alone (n = 9), low-dose LPS infusion + saline boluses (n = 5), or low-dose LPS + LPS boluses (n = 9). Low-dose LPS infusion + LPS boluses was associated with greater microglial induction than low-dose LPS + saline boluses but a similar area of periventricular white matter inflammation. One fetus developed severe focal white matter necrosis after LPS infusion + boluses. The acute cardiovascular compromise associated with high-dose, acute exposure to LPS is markedly attenuated by previous low-dose infusions, with limited apparent exacerbation of periventricular white matter injury compared with low-dose infusion alone.
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Affiliation(s)
- Sam Mathai
- Department of Physiology, the University of 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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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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Silas R, Sehgal A, Walker AM, Wong FY. Cerebral oxygenation during subclinical seizures in neonatal hypoxic-ischaemic encephalopathy. Eur J Paediatr Neurol 2012; 16:304-7. [PMID: 21978628 DOI: 10.1016/j.ejpn.2011.09.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 07/23/2011] [Accepted: 09/18/2011] [Indexed: 11/25/2022]
Abstract
Treatment of subclinical seizures in newborn HIE remains a contentious issue, especially in light of potential adverse effects of aggressive use of anticonvulsants. We report on the association of subclinical seizures with changes in cerebral oxygenation in an infant with HIE. Our results show that subclinical seizures of longer durations and with associated autonomic disturbance (increased blood pressure) are more likely to be associated with fluctuation in cerebral oxygenation, with some seizures resulting in cerebral hypoxia. Future studies should aim to delineate the effects of subclinical seizure and anticonvulsant treatment on cerebral oxygenation, and their relationships to developmental outcome. Level of cerebral oxygenation may play a role in refining anti-convulsant treatment and management of subclinical seizures in newborns.
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Affiliation(s)
- Reshma Silas
- The Ritchie Centre, Monash University, Level 5, Monash Medical Centre, 246 Clayton Road, Clayton, Melbourne, VIC 3168, Australia
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Keogh MJ, Drury PP, Bennet L, Davidson JO, Mathai S, Gunn ER, Booth LC, Gunn AJ. Limited predictive value of early changes in EEG spectral power for neural injury after asphyxia in preterm fetal sheep. Pediatr Res 2012; 71:345-53. [PMID: 22391634 DOI: 10.1038/pr.2011.80] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
INTRODUCTION This study examined whether spectral analysis of the electroencephalogram (EEG) can discriminate between mild and severe hypoxic-ischemic injury in the immature brain. RESULTS Total EEG power was profoundly suppressed after umbilical cord occlusion and recovered to baseline by 5 h after 15-min of occlusion, in contrast with transient recovery in the 25-min (P < 0.05). Power spectra were not different between groups in the first 3 h; α and β power were significantly higher in the 15-min group from 4 h, and Δ and θ power from 5 h (P < 0.05). The 25-min group showed severe neuronal loss in hippocampal regions and basal ganglia at 3 days, in contrast with no/minimal injury in the 15-min group. DISCUSSION EEG power after asphyxia did not discriminate between mild and severe injury in the first 3 h in preterm fetal sheep. Severe subcortical neural injury was associated with persistent loss of high-frequency activity. METHODS Chronically instrumented fetal sheep at 0.7 gestation (101-104 days; term is 147 days) received either 15-min (n = 13) or 25-min (n = 13) of complete umbilical cord occlusion. The Δ (0-3.9 Hz), θ (4-7.9 Hz), α (8-12.9 Hz), and β (13-22 Hz) components of the EEG were determined by power spectral analysis. Brains were taken at 3 days for histopathology.
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Affiliation(s)
- Michael J Keogh
- Fetal Physiology and Neuroscience Group, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
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Sex differences in mechanisms and outcome of neonatal hypoxia-ischemia in rodent models: implications for sex-specific neuroprotection in clinical neonatal practice. Neurol Res Int 2012; 2012:867531. [PMID: 22474588 PMCID: PMC3306914 DOI: 10.1155/2012/867531] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 11/03/2011] [Accepted: 11/16/2011] [Indexed: 11/20/2022] Open
Abstract
Clinical findings show that male infants with hypoxic-ischemic injury (HI) fare more poorly than matched females on cognitive outcomes. Rodent models of neonatal hypoxia-ischemia support this difference, with data showing that perinatal brain injury leads to long-term behavioral deficits primarily in male rodents and in female rodents treated with early androgens. Results support the idea that sex-specific gonadal hormones may modulate developmental response to injury and dovetail with overwhelming evidence of developmental androgen effects on typical brain morphology and behavior. However, mechanisms underlying sex differences in response to early brain injury may be more complicated. Specifically, activation of cell death pathways in response to HI may also differ by sex. In females, the preferential activation of the caspase-dependent apoptotic pathway may actually afford greater protection, potentially due to the actions of X-linked inhibitor of apoptosis (XIAP) within this pathway. This contrasts the pattern of preferential activation of the caspase-independent pathway in males. While an integrated model of sex-specific hormonal and genetic modulation of response to early injury remains to be fully elucidated, these findings suggest that infants might benefit from sex-specific neuroprotection following HI injury.
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Jensen EC, Bennet L, Fraser M, Power GG, Hunter CJ, Gunn AJ. Adenosine A1 receptor mediated suppression of adrenal activity in near-term fetal sheep. Am J Physiol Regul Integr Comp Physiol 2010; 298:R700-6. [DOI: 10.1152/ajpregu.00474.2009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Activation of the hypothalamic-pituitary-adrenal (HPA) axis is a critical response to perinatal hypoxia. Recent data show that adenosine appears to inhibit baseline levels of fetal cortisol and to restrict the increase in ACTH and cortisol during moderate hypoxia. Because adenosine increases substantially during profound asphyxia, it is possible, but untested, that counterintuitively it might restrict the HPA response to more severe insults. It is unclear which receptors mediate the effects of adenosine on the HPA axis; however, adenosine A1 receptor activation is important for adaptation to hypoxia. We therefore investigated whether adenosine A1 receptor blockade modulates ACTH and cortisol levels in fetal sheep at 118 to 126 days gestation, randomly allocated to receive an intravenous infusion of either vehicle (vehicle-occlusion, n = 7) or 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, an A1 receptor antagonist, DPCPX-occlusion, n = 7) infused 60 min before and during 10 min of umbilical cord occlusion, or infusion of DPCPX for 70 min without occlusion (DPCPX-sham, n = 6). Experiments were terminated after 72 h. Fetal ACTH levels increased significantly ( P < 0.01) during occlusion, but not sham occlusion, and returned to baseline values by 60 min after occlusion. In the vehicle-occlusion group, fetal cortisol and cortisone plasma levels increased significantly ( P < 0.05) 60 min after the occlusion and returned to baseline values by 24 h. In contrast, there was a marked increase in both fetal cortisol and cortisone during DPCPX infusion before occlusion to a level greater even than the maximum rise seen after occlusion alone. This increase was sustained after occlusion, with increased cortisol levels compared with occlusion alone up to 72 h. In conclusion, fetal cortisol concentrations are suppressed by adenosine A1 receptor activity, largely though a direct adrenal mechanism. This suppression can be partially overcome by supraphysiological stimuli such as asphyxia.
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Affiliation(s)
- E. C. Jensen
- Faculty of Medical and Health Sciences, Department of Physiology, The University of Auckland, Auckland, New Zealand; and
| | - L. Bennet
- Faculty of Medical and Health Sciences, Department of Physiology, The University of Auckland, Auckland, New Zealand; and
| | - M. Fraser
- Faculty of Medical and Health Sciences, Department of Physiology, The University of Auckland, Auckland, New Zealand; and
| | - G. G. Power
- The Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, California
| | - C. J. Hunter
- The Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, California
| | - A. J. Gunn
- Faculty of Medical and Health Sciences, Department of Physiology, The University of Auckland, Auckland, New Zealand; and
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Lang EW, Mulvey JM, Mudaliar Y, Dorsch NWC. Direct cerebral oxygenation monitoring--a systematic review of recent publications. Neurosurg Rev 2007; 30:99-106; discussion 106-7. [PMID: 17221264 DOI: 10.1007/s10143-006-0062-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2006] [Revised: 08/15/2006] [Accepted: 10/03/2006] [Indexed: 10/23/2022]
Abstract
This review has been compiled to assess publications related to the clinical application of direct cerebral tissue oxygenation (PtiO2) monitoring published in international, peer-reviewed scientific journals. Its goal was to extract relevant, i.e. positive and negative information on indications, clinical application, safety issues and impact on clinical situations as well as treatment strategies in neurosurgery, neurosurgical anaesthesiology, neurosurgical intensive care, neurology and related specialties. For completeness' sake it also presents some related basic science research. PtiO2 monitoring technology is a safe and valuable cerebral monitoring device in neurocritical care. Although a randomized outcome study is not available its clinical utility has repeatedly been clearly confirmed because it adds a monitoring parameter, independent from established cerebral monitoring devices. It offers new insights into cerebral physiology and pathophysiology. Pathologic values have been established in peer-reviewed research, which are not only relevant to outcome but are treatable. The benefits clearly outweigh the risks, which remains unchallenged in all publications retrieved. It is particularly attractive because it offers continuous, real-time data and is available at the bedside.
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Affiliation(s)
- Erhard W Lang
- Neurosurgical Associates, Red Cross Hospital, Bergmannstrasse 32, 34121 Kassel, Germany
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Bennet L, Roelfsema V, Dean JM, Wassink G, Power GG, Jensen EC, Gunn AJ. Regulation of cytochrome oxidase redox state during umbilical cord occlusion in preterm fetal sheep. Am J Physiol Regul Integr Comp Physiol 2006; 292:R1569-76. [PMID: 17170231 DOI: 10.1152/ajpregu.00743.2006] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The preterm fetus is capable of surviving prolonged periods of severe hypoxia without neural injury for much longer than at term. To evaluate the hypothesis that regulated suppression of brain metabolism contributes to this remarkable tolerance, we assessed changes in the redox state of cytochrome oxidase (CytOx) relative to cerebral heat production, and cytotoxic edema measured using cerebral impedance, during 25 min of complete umbilical cord occlusion or sham occlusion in fetal sheep at 0.7 gestation. Occlusion was followed by rapid, profound reduction in relative cerebral oxygenation and EEG intensity and an immediate increase in oxidized CytOx, indicating a reduction in electron flow down the mitochondrial electron transfer chain. Confirming rapid suppression of cerebral metabolism there was a loss of the temperature difference between parietal cortex and body at a time when carotid blood flow was maintained at control values. As occlusion continued, severe hypotension/hypoperfusion developed, with a further increase in CytOx levels to a plateau between 8 and 13 min and a progressive rise in cerebral impedance. In conclusion, these data strongly suggest active regulation of cerebral metabolism during the initial response to severe hypoxia, which may help to protect the immature brain from injury.
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Affiliation(s)
- Laura Bennet
- Department of Physiology, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
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31
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Dean JM, Gunn AJ, Wassink G, George S, Bennet L. Endogenous alpha2-adrenergic receptor-mediated neuroprotection after severe hypoxia in preterm fetal sheep. Neuroscience 2006; 142:615-28. [PMID: 16952424 DOI: 10.1016/j.neuroscience.2006.06.066] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Revised: 06/20/2006] [Accepted: 06/21/2006] [Indexed: 11/28/2022]
Abstract
Central alpha-adrenergic receptor activity is important for fetal adaptation to hypoxia before birth. It is unclear whether it is also important during recovery. We therefore tested the hypothesis that an infusion of the specific alpha(2)-adrenergic receptor antagonist idazoxan (1 mg/kg/h i.v.) from 15 min to 4 h after profound hypoxia induced by 25 min umbilical cord occlusion in fetal sheep at 70% of gestation (equivalent to the 28-32 weeks in humans) would increase neural injury. After 3 days' recovery, idazoxan infusion was associated with a significant increase in neuronal loss in the hippocampus (P<0.05), expression of cleaved caspase-3 (P<0.05), and numbers of activated microglia (P<0.05). There was no significant effect on other neuronal regions or on loss of O4-positive premyelinating oligodendrocytes in the subcortical white matter. Idazoxan was associated with an increase in evolving epileptiform electroencephalographic (EEG) transient activity after occlusion (difference at peak 2.5+/-1.0 vs. 11.7+/-4.7 counts/min, P<0.05) and significantly reduced average spectral edge frequency, but not EEG intensity, from 54 until 72 h after occlusion (P<0.05). Hippocampal neuronal loss was correlated with total numbers of epileptiform transients during idazoxan infusion (P<0.01; r(2)=0.7). In conclusion, endogenous inhibitory alpha(2)-adrenergic receptor activation after severe hypoxia appears to significantly limit evolving hippocampal damage in the immature brain.
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Affiliation(s)
- J M Dean
- Department of Physiology, Faculty of Medicine and Health Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
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Jensen EC, Bennet L, Hunter CJ, Power GC, Gunn AJ. Post-hypoxic hypoperfusion is associated with suppression of cerebral metabolism and increased tissue oxygenation in near-term fetal sheep. J Physiol 2006; 572:131-9. [PMID: 16484307 PMCID: PMC1779646 DOI: 10.1113/jphysiol.2005.100768] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Secondary cerebral hypoperfusion is common following perinatal hypoxia-ischaemia. However, it remains unclear whether this represents a true failure to provide sufficient oxygen and nutrients to tissues, or whether it is simply a consequence of reduced cerebral metabolic demand. We therefore examined the hypothesis that cerebral oxygenation would be reduced during hypoperfusion after severe asphyxia, and further, that the greater neural injury associated with blockade of the adenosine A(1) receptor during the insult would be associated with greater hypoperfusion and deoxygenation. Sixteen near-term fetal sheep received either vehicle or 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) for 1 h, followed by 10 min of severe asphyxia induced by complete occlusion of the umbilical cord. Infusions were discontinued at the end of the occlusion and data were analysed for the following 8 h. A transient, secondary fall in carotid artery blood flow and laser Doppler flow was seen from approximately 1-4 h after occlusion (P < 0.001), with no significant differences between vehicle and DPCPX. Changes in laser Doppler blood flow were highly correlated with carotid blood flow (r(2)= 0.81, P < 0.001). Cortical metabolism was suppressed, reaching a nadir 1 h after occlusion and then resolving. Cortical tissue P(O(2)) was significantly increased at 1, 2 and 3 h after occlusion compared to baseline, and inversely correlated with carotid blood flow (r(2)= 0.69, P < 0.001). In conclusion, contrary to our initial hypothesis, delayed posthypoxic hypoperfusion was associated with suppression of cerebral metabolism and increased tissue P(O(2)), and was not significantly affected by preceding adenosine A1 blockade. These data suggest that posthypoxic hypoperfusion is actively mediated and reflects suppressed cerebral metabolism.
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Affiliation(s)
- E C Jensen
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
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Bennet L, Roelfsema V, Pathipati P, Quaedackers JS, Gunn AJ. Relationship between evolving epileptiform activity and delayed loss of mitochondrial activity after asphyxia measured by near-infrared spectroscopy in preterm fetal sheep. J Physiol 2006; 572:141-54. [PMID: 16484298 PMCID: PMC1779651 DOI: 10.1113/jphysiol.2006.105197] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Early onset cerebral hypoperfusion after birth is highly correlated with neurological injury in premature infants, but the relationship with the evolution of injury remains unclear. We studied changes in cerebral oxygenation, and cytochrome oxidase (CytOx) using near-infrared spectroscopy in preterm fetal sheep (103-104 days of gestation, term is 147 days) during recovery from a profound asphyxial insult (n= 7) that we have shown produces severe subcortical injury, or sham asphyxia (n= 7). From 1 h after asphyxia there was a significant secondary fall in carotid blood flow (P < 0.001), and total cerebral blood volume, as reflected by total haemoglobin (P < 0.005), which only partially recovered after 72 h. Intracerebral oxygenation (difference between oxygenated and deoxygenated haemoglobin concentrations) fell transiently at 3 and 4 h after asphyxia (P < 0.01), followed by a substantial increase to well over sham control levels (P < 0.001). CytOx levels were normal in the first hour after occlusion, was greater than sham control values at 2-3 h (P < 0.05), but then progressively fell, and became significantly suppressed from 10 h onward (P < 0.01). In the early hours after reperfusion the fetal EEG was highly suppressed, with a superimposed mixture of fast and slow epileptiform transients; overt seizures developed from 8 +/- 0.5 h. These data strongly indicate that severe asphyxia leads to delayed, evolving loss of mitochondrial oxidative metabolism, accompanied by late seizures and relative luxury perfusion. In contrast, the combination of relative cerebral deoxygenation with evolving epileptiform transients in the early recovery phase raises the possibility that these early events accelerate or worsen the subsequent mitochondrial failure.
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Affiliation(s)
- L Bennet
- Department of Physiology, University of Auckland, Private Bag 92019, Auckland, New Zealand.
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Dean JM, Gunn AJ, Wassink G, Bennet L. Transient NMDA receptor-mediated hypoperfusion following umbilical cord occlusion in preterm fetal sheep. Exp Physiol 2005; 91:423-33. [PMID: 16317084 DOI: 10.1113/expphysiol.2005.032375] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Exposure to severe hypoxia leads to delayed cerebral and peripheral hypoperfusion. There is evidence in the very immature brain that transient abnormal glutaminergic receptor activity can occur during this phase of recovery. We therefore examined the role of N-methyl-D-aspartate (NMDA) receptor activity in mediating secondary hypoperfusion in preterm fetal sheep at 70% of gestation. Fetuses received either sham asphyxia or asphyxia and were studied for 12 h recovery. The specific, non-competitive NMDA receptor antagonist dizocilpine maleate (2 mg kg-1 bolus plus 0.07 mg kg h-1i.v.) or saline (vehicle) was infused from 15 min after asphyxia until 4 h. In the asphyxia-vehicle group abnormal epileptiform EEG transients were observed during the first 4 h of reperfusion, the peak of which corresponded approximately to the nadir in peripheral and cerebral hypoperfusion. Dizocilpine significantly suppressed this activity (2.7+/-1.3 versus 11.2+/-2.7 counts min-1 at peak frequency, P<0.05) and markedly delayed and attenuated the rise in vascular resistance in both peripheral and cerebral vascular beds observed after asphyxia, effectively preventing the initial deep period of hypoperfusion in carotid blood flow and femoral blood flow (P<0.01). However, while continued infusion did attenuate subsequent transient tachycardia, it did not prevent the development of a secondary phase of persistent but less profound hypoperfusion. In conclusion, the present studies suggest that in the immature brain the initial phase of delayed cerebral and peripheral hypoperfusion following exposure to severe hypoxia is mediated by NMDA receptor activity. The timing of this effect in the cerebral circulation corresponds closely to abnormal EEG activity, suggesting a pathological glutaminergic activation that we speculate is related to evolving brain injury.
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Affiliation(s)
- Justin M Dean
- Department of Physiology, Faculty of Medicine and Health Science, The University of Auckland, Private Bag 92019, Auckland, New Zealand
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