Effect of hypothermia on brain cell membrane function and energy metabolism after transient global hypoxia-ischemia in the newborn piglet

This study was done to determine the effects of hypothermia on brain cell m embrane function and energy metabolism after transient hypoxia-ischemia (HI ) in the newborn piglet. Cerebral HI was induced by temporarily complete oc clusion of bilateral common carotid arteries with surgical dips and simulta neous breathing with 8% oxygen for 30 min, followed by release of carotid o cclusion and normoxic ventilation for 4 hr. Rectal temperature was maintain ed between 38.0 and 39.0 degreesC in normothermic groups, and between 34.0 and 35.0 degreesC in hypothermic groups for 4 hr after HI. During HI, heart rate, glucose and lactate level in the blood and cerebrospinal fluid incre ased, and base excess, pH and blood pressure decreased significantly in bot h normothermic and hypothermic groups. After HI, these abnormalities return ed to normal in normothermic group, but lactic acidosis persisted in hypoth ermic group. Decreased cerebral Na+,K(+)ATPase activity and increased lipid peroxidation products, indicative of HI-induced brain injury, were more pr ofound in hypothermic group than in normothermic group. Brain ATP and phosp hocreatine levels were not different between normothermic and hypothermic g roups. In summary, hypothermia applied immediately after HI for 4 hr did no t improve the recovery of brain cell membrane function and energy metabolis m in the newborn piglet.