THE EFFECT OF FOCAL CEREBRAL COOLING ON PERINATAL HYPOXIC-ISCHEMIC BRAIN-DAMAGE

We describe a method of focal cooling of the head and its effects on h ypoxic-ischemic cerebral damage in neonatal rat. Focal cooling of the head was obtained by positioning a catheter under the scalp ipsilatera l to the ligated common carotid artery and by running cold water throu gh the catheter during 2 h of systemic hypoxia. Hypoxia was produced i n neonatal rats by breathing 8% oxygen for 2 h in a 37 degrees C chamb er. Animals underwent focal cooling with ipsilateral scalp temperature s ranging from 22 degrees C to 35 degrees C. Temperature recordings fr om the ipsilateral scalp, cerebral hemisphere (dorsal hippocampus) and core (rectal) were obtained. The results suggest that the method is e ffective in cooling of brain and also to a lesser extent in lowering o f the core temperature. At a mean scalp temperature of 28 degrees C, m ean hippocampal temperature in hypoxic rat was 29.5 degrees C and mean core temperature in hypoxic rat was 32.8 degrees C. At a lower scalp temperature of 22 degrees C, mean hippocampal temperature in hypoxic r at was 24.7 degrees C and mean core temperature was 31.3 degrees C. Ne uropathologic examination 3-4 days following hypoxia-ischemia showed t hat focal cooling with a scalp temperature of lower than 28 degrees C completely protected from brain damage, and that there was a trend tow ards greater damage with higher scalp temperatures.