Alistair J. Gunn

Selective head cooling with mild systemic hypothermia after neonatal encephalopathy: multicentre randomised trial

BACKGROUND Cerebral hypothermia can improve outcome of experimental perinatal hypoxia-ischaemia. We did a multicentre randomised controlled trial to find out if delayed head cooling can improve neurodevelopmental outcome in babies with neonatal encephalopathy. METHODS 234 term infants with moderate to severe neonatal encephalopathy and abnormal amplitude integrated electroencephalography (aEEG) were randomly assigned to either head cooling for 72 h, within 6 h of birth, with rectal temperature maintained at 34-35 degrees C (n=116), or conventional care (n=118). Primary outcome was death or severe disability at 18 months. Analysis was by intention to treat. We examined in two predefined subgroup analyses the effect of hypothermia in babies with the most severe aEEG changes before randomisation--ie, severe loss of background amplitude, and seizures--and those with less severe changes. FINDINGS In 16 babies, follow-up data were not available. Thus in 218 infants (93%), 73/110 (66%) allocated conventional care and 59/108 (55%) assigned head cooling died or had severe disability at 18 months (odds ratio 0.61; 95% CI 0.34-1.09, p=0.1). After adjustment for the severity of aEEG changes with a logistic regression model, the odds ratio for hypothermia treatment was 0.57 (0.32-1.01, p=0.05). No difference was noted in the frequency of clinically important complications. Predefined subgroup analysis suggested that head cooling had no effect in infants with the most severe aEEG changes (n=46, 1.8; 0.49-6.4, p=0.51), but was beneficial in infants with less severe aEEG changes (n=172, 0.42; 0.22-0.80, p=0.009). INTERPRETATION These data suggest that although induced head cooling is not protective in a mixed population of infants with neonatal encephalopathy, it could safely improve survival without severe neurodevelopmental disability in infants with less severe aEEG changes.

Neurological outcomes at 18 months of age after moderate hypothermia for perinatal hypoxic ischaemic encephalopathy: synthesis and meta-analysis of trial data

Objective To determine whether moderate hypothermia after hypoxic-ischaemic encephalopathy in neonates improves survival and neurological outcome at 18 months of age. Design A meta-analysis was performed using a fixed effect model. Risk ratios, risk difference, and number needed to treat, plus 95% confidence intervals, were measured. Data sources Studies were identified from the Cochrane central register of controlled trials, the Oxford database of perinatal trials, PubMed, previous reviews, and abstracts. Review methods Reports that compared whole body cooling or selective head cooling with normal care in neonates with hypoxic-ischaemic encephalopathy and that included data on death or disability and on specific neurological outcomes of interest to patients and clinicians were selected. Results We found three trials, encompassing 767 infants, that included information on death and major neurodevelopmental disability after at least 18 months’ follow-up. We also identified seven other trials with mortality information but no appropriate neurodevelopmental data. Therapeutic hypothermia significantly reduced the combined rate of death and severe disability in the three trials with 18 month outcomes (risk ratio 0.81, 95% confidence interval 0.71 to 0.93, P=0.002; risk difference −0.11, 95% CI −0.18 to −0.04), with a number needed to treat of nine (95% CI 5 to 25). Hypothermia increased survival with normal neurological function (risk ratio 1.53, 95% CI 1.22 to 1.93, P<0.001; risk difference 0.12, 95% CI 0.06 to 0.18), with a number needed to treat of eight (95% CI 5 to 17), and in survivors reduced the rates of severe disability (P=0.006), cerebral palsy (P=0.004), and mental and the psychomotor developmental index of less than 70 (P=0.01 and P=0.02, respectively). No significant interaction between severity of encephalopathy and treatment effect was detected. Mortality was significantly reduced when we assessed all 10 trials (1320 infants; relative risk 0.78, 95% CI 0.66 to 0.93, P=0.005; risk difference −0.07, 95% CI −0.12 to −0.02), with a number needed to treat of 14 (95% CI 8 to 47). Conclusions In infants with hypoxic-ischaemic encephalopathy, moderate hypothermia is associated with a consistent reduction in death and neurological impairment at 18 months.

Dramatic neuronal rescue with prolonged selective head cooling after ischemia in fetal lambs.

Hypothermia has been proposed as a neuroprotective strategy. However, short-term cooling after hypoxia-ischemia is effective only if started immediately during resuscitation. The aim of this study was to determine whether prolonged head cooling, delayed into the late postinsult period, improves outcome from severe ischemia. Unanesthetized near term fetal sheep were subject to 30 min of cerebral ischemia. 90 min later they were randomized to either cooling (n = 9) or sham cooling (n = 7) for 72 h. Intrauterine cooling was induced by a coil around the fetal head, leading initially to a fall in extradural temperature of 5-10 degrees C, and a fall in esophageal temperature of 1.5-3 degrees C. Cooling was associated with mild transient systemic metabolic effects, but not with hypotension or altered fetal heart rate. Cerebral cooling reduced secondary cortical cytotoxic edema (P < 0.001). After 5 d of recovery there was greater residual electroencephalogram activity (-5.2+/-1.6 vs. -15.5+/-1.5 dB, P < 0.001) and a dramatic reduction in the extent of cortical infarction and neuronal loss in all regions assessed (e.g., 40 vs. 99% in the parasagittal cortex, P < 0.001). Selective head cooling, maintained throughout the secondary phase of injury, is noninvasive and safe and shows potential for improving neonatal outcome after perinatal asphyxia.

Neuroprotection with prolonged head cooling started before postischemic seizures in fetal sheep

Objective. Cerebral hypothermia has been shown to reduce damage from experimental hy-poxia-ischemia if started shortly after reperfusion. However, in the newborn infant it may not be feasible to determine prognosis so soon after exposure to asphyxia. The aim of this study was to determine whether head cooling, delayed until shortly before the onset of postasphyxial seizure activity, is neuroprotective. Methods. Unanesthetized near-term fetal sheep in utero were subjected to 30 minutes of cerebral ischemia. Later, at 5.5 hours, they were randomized to either cooling (n = 7) or sham cooling (n = 10) for 72 hours. Intrauterine cooling was induced by circulating cold water through a coil around the fetal head. The water temperature was titrated to reduce fetal extradural temperature from 39.1 ± 0.1°C to between 30°C and 33°C, while maintaining esophageal temperature >37°C. Results. Cerebral cooling suppressed the secondary rise in cortical impedance (a measure of cytotoxic edema), but did not prevent delayed seizures, 8 to 30 hours after ischemia. Transient metabolic changes including increased plasma lactate and glucose levels were seen with a moderate sustained rise in blood pressure. This severe cerebral insult resulted in depressed residual parietal electroencephalographic activity after 5 days recovery (−14.2 ± 1.5 decibels), associated with a watershed distribution of neuronal loss (eg, 94 ± 4% in parasagittal cortex and 77 ± 4% in the lateral cortex). Hypothermia was associated with better recovery of electroencephalographic activity (−8.9% ± 1.8 decibels) and substantially reduced neuronal loss in the parasagittal cortex (46 ± 13%), the lateral cortex (9 ± 4%), and other regions except the cornu ammonis sectors 1 and 2 of the hippocampus. Conclusions. Delayed selective head cooling begun before the onset of postischemic seizures and continued for 3 days may have potential to significantly improve the outcome of moderate to severe hypoxic-ischemic encephalopathy.

Determinants of outcomes after head cooling for neonatal encephalopathy

OBJECTIVE. The goal of this study was to evaluate the role of factors that may determine the efficacy of treatment with delayed head cooling and mild systemic hypothermia for neonatal encephalopathy. METHODS. A total of 218 term infants with moderate to severe neonatal encephalopathy plus abnormal amplitude-integrated electroencephalographic recordings, assigned randomly to head cooling for 72 hours, starting within 6 hours after birth (with the rectal temperature maintained at 34.5 ± 0.5°C), or conventional care, were studied. Death or severe disability at 18 months of age was assessed in a multicenter, randomized, controlled study (the CoolCap trial). RESULTS. Treatment, lower encephalopathy grade, lower birth weight, greater amplitude-integrated electroencephalographic amplitude, absence of seizures, and higher Apgar score, but not gender or gestational age, were associated significantly with better outcomes. In a multivariate analysis, each of the individually predictive factors except for Apgar score remained predictive. There was a significant interaction between treatment and birth weight, categorized as ≥25th or <25th percentile for term, such that larger infants showed a lower frequency of favorable outcomes in the control group but greater improvement with cooling. For larger infants, the number needed to treat was 3.8. Pyrexia (≥38°C) in control infants was associated with adverse outcomes. Although there was a small correlation with birth weight, the adverse effect of greater birth weight in control infants remained significant after adjustment for pyrexia and severity of encephalopathy. CONCLUSIONS. Outcomes after hypothermic treatment were strongly influenced by the severity of neonatal encephalopathy. The protective effect of hypothermia was greater in larger infants.

Hypoxia-ischemia induces transforming growth factor β1 mRNA in the infant rat brain

Transforming growth factor beta 1 (TGF beta 1) mRNA expression was examined after hypoxia-ischemia in rat brains using in situ hybridization. Twenty-one-day-old Wistar rats had unilateral ligation of the right carotid artery followed by either 15 or 90 min inhalational hypoxia. Fifteen min of hypoxia resulted in moderate damage with selective neuronal loss in cortical layer 3 and in the hippocampus of the ligated hemisphere. Seventy-two hours after hypoxia TGF beta 1 expression was markedly increased above control levels in those sites. Levels were normal after 120 h. Ninety min of hypoxia led to an infarction of the lateral cerebral cortex and hippocampus of the ligated hemisphere. One hour after hypoxia TGF beta 1 mRNA was expressed in the hippocampus of the damaged side. Seventy-two and 120 h after hypoxia, expressing cells were found throughout the cerebral cortex, piriform cortex, striatum, thalamus and hippocampus of the infarcted side. These data show that TGF beta 1 mRNA expression is induced after a hypoxic-ischemic insult in the brain. TGF beta 1 may be involved in post-asphyxial repair mechanisms.

Congenital idiopathic growth hormone deficiency associated with prenatal and early postnatal growth failure

To assess the role of growth hormone in fetal and infant growth, we analyzed the pretreatment data on 52 patients with a diagnosis of congenital growth hormone deficiency before 2 years of age, obtained from the Kabi Pharmacia International Growth Study. These infants had reduced birth-length standard deviation scores, an excess of birth weight relative to length, and progressive growth failure. We conclude that congenital growth hormone deficiency may cause impaired growth in utero and early infancy, and that growth hormone plays an important role in perinatal and infantile growth.

Time course of intracellular edema and epileptiform activity following prenatal cerebral ischemia in sheep.

The role of edema in the pathogenesis of hypoxic-ischemic injury in the immature brain is controversial. We studied 15 chronically instrumented fetal sheep following transient cerebral ischemia, to estimate changes in extracellular space using an impedance technique, to quantify the electroencephalogram with real-time spectral analysis, and to assess histologic outcome 3 days after the insult. These measurements were made in the parasagittal cortex. There was a rapid loss of extracellular space from 5 +/- 2 minutes after the onset of ischemia. Following 10 minutes of ischemia (n = 7) the intracellular edema peaked but then quickly resolved (6 +/- 4 minutes), and mild selective neuronal loss was seen. In contrast, the swelling was biphasic after 30-40 minutes of ischemia (n = 8). The early edema resolved slowly (28 +/- 12 minutes) but incompletely, and secondary swelling began at 7 +/- 2 hours and peaked at 28 +/- 6 hours. The early swelling was the more severe. Postinsult epileptiform activity began at 8 +/- 2 hours and peaked at 10 +/- 3 hours; later there was laminar necrosis of the underlying cortex. The secondary decrease of extracellular space indicates that a progressive loss of membrane function started with the onset of postischemic epileptiform activity. The increased metabolic load of the epileptiform activity may have worsened this delayed deterioration.

Cerebral Histologic and Electrocorticographic Changes after Asphyxia in Fetal Sheep

ABSTRACT: Asphyxia can cause neurologic damage in the fetus, hot there are few data relating severity or duration of asphyxia to the degree of cerebral damage. We report cerebral histologic and electrophysiologic changes after asphyxia in chronically instrumented late-gestation fetal sheep. We reduced uterine blood flow to produce an ascending aortic blood oxygen content < 1.5 mM for either 30 or 60 min (n = 13). In a subsequent protocol (n = 6), if full occlusion of the common uterine artery for 15 min did not reduce the EEC voltage to less than 20% of baseline, supplementary maternal hypoxia was added for a maximum of 120 min. Histologic outcome was assessed 3 d postinsnlt. Uterine artery occlusion resulted in severe hy-poxemia, hypercarbia, acidosis, and an initial hypertension and bradycardia. Eight of 14 surviving fetuses showed neuronal damage, with greatest loss in the parasagHtal cortex, striatum, and the CA1/2 region of the hippocampus. Neuronal damage was strongly associated with the percentage of decrease in blood pressure during the insult (r = 0.75, p < 0.005) but not with the degree of hypoxia. No other factor was independently predictive, but, when considered separately, pH (r = 054; p < 0.05) and loss of intensity of the EEC (r = 0.61, p < 0.02) at the end of asphyxia were also correlated with outcome. The pH fell to < 7.0 in six of eight fetuses with damage, whereas it remained >7.0 in five of six without damage (p < 0.05). We conclude that severe intrauterine asphyxia for periods of 30 to 120 min can cause predominant parasagittal neuronal death and that this is associated with hypotension, severe metabolic acidosis, and suppression of EEC during the insolt. These data are consistent with the suggestion that impairment of cerebral perfusion is a critical event in localizing cerebral damage during perinatal asphyxia.

Accumulation of cytotoxins during the development of seizures and edema after hypoxic-ischemic injury in late gestation fetal sheep

Several hours after an hypoxic-ischemic injury to the developing brain, hyperemia, then seizures, edema, and infarction can develop. The roles of nitric oxide (NO) synthesis and excitotoxin accumulation during these later phases of injury are not known. The time course of extracellular levels of amino acids within the parasagittal parietal cortex were measured with microdialysis during and for 3 d after 30 min of cerebral ischemia in nine chronically instrumented near-term fetal sheep (119-133 d). Cortical electroencephalographic (EEG) activity and extracellular space (ECS) were quantified simultaneously with real-time spectral analysis and cortical impedance measurements, respectively. Amino acid concentrations were measured using HPLC. During ischemia, citrulline (by-product of NO synthesis), glutamate, glycine, and γ-aminobutyric acid (GABA) concentrations rose to 147 ± 18%, 180 ± 20%, 290 ± 50% and 4800 ± 1300% of baseline respectively (p < 0.05). The excitotoxic index([glutamate] × [glycine]/[GABA]) decreased to 15 ± 8%. Upon reperfusion, the cytotoxic edema and amino acid accumulation largely resolved within 1 h, and the EEG was depressed. Citrulline began to rise again by 4 h(p < 0.05), reaching a maximum (273 ± 21%) at 32 ± 2 h. Seizure activity developed at 7 ± 2 h, and impedance plus the excitotoxic index then rose progressively and peaked at 32 ± 2 h (480± 170%). At 72 h, there was severe neuronal loss and laminar necrosis within the parasagittal cortex. These data suggest that, several hours after a severe hypoxic-ischemic injury, NO synthesis increased, then seizures arose, and edema developed concomitantly with the accumulation of excitotoxins.