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 ϭ 9) or sham cooling ( n ϭ 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 Њ C, and a fall in esophageal temperature of 1.5-3 Њ 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 Ͻ 0.001).
Mild selective head cooling combined with mild systemic hypothermia in term newborn infants after perinatal asphyxia is a safe and convenient method of quickly reducing cerebral temperature with an increased gradient between the surface of the scalp and core temperature. The safety of mild hypothermia with selective head cooling is in contrast with the historical evidence of adverse effects with greater depths of whole-body hypothermia. This safety study and the strong experimental evidence for improved cerebral outcome justify a multicenter trial of selective head cooling for neonatal encephalopathy in term infants.
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.
Somatomedin concentrations in human umbilical sera (n = 206) were measured using a specific radioimmunoassay for insulin-like growth factor (IGF)-I and a specific radioreceptor assay for IGF-II following acid-ethanol extraction of the sera to remove the somatomedin binding proteins. IGF-I concentrations were lower (P less than 0.001) than adult values and correlated with gestational age (P less than 0.001) and birth weight (P less than 0.0001). Multiple regression analysis demonstrated that both birth weight expressed independently of gestational age as the standard deviate score (P less than 0.0001) and gestational age (P less than 0.002) had effects on umbilical cord IGF-I concentrations. IGF-II concentrations were similar to adult values and did not correlate with gestational age, birth size or IGF-I values. IGF-II concentrations were higher (P less than 0.005) in male than female fetuses. These data support a role for IGF-I in influencing fetal growth and suggest the independent regulation of the secretion of IGF-I and II in the perinatal period. These was no evidence to suggest a distinct perinatal form of somatomedin.
This study suggests that selective head cooling combined with mild systemic hypothermia of 34.4 degrees C or 35.0 degrees C is a stable, well-tolerated method of reducing cerebral temperature in term newborn infants after perinatal asphyxia.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.