Cerebral effects of circulatory arrest at 20°C in the infant pig
Circulatory arrest at 20°C is used during open heart surgery in infants. It is stated that significant brain damage does not occur. Piglets between 2-6 wk of age were cooled to 20°C using extracorporeal circulation and a membrane oxygenator. After 1 hr of circulatory arrest the perfusion system was used to rewarm the animals and restore normal circulation. Electroencephalogram was monitored throughout perfusion and surgery, and repeated on surviving animals on the 3rd, 5th, 7th and 10th postoperative days. On the 10th day the animals were killed by injection of pentobarbitone. Other groups were subjected to continuous perfusion at 20°C, continuous perfusion at 37°C, thoracotomy and cannulation, ischemia, and hypoxia. The return of E.E.G. activity was delayed after circulatory arrest compared with those continuously perfused. Lesions were found in the cerebral cortex in all the animals which had circulatory arrest and those subjected to ischemia and hypoxia. The brains of animals of the other groups were indistinguishable from those killed without any experimental procedure. Despite apparent recovery, brain damage following hypothermic arrest during open heart surgery remains possible.