Effects of deep hypothermia and circulatory arrest on the auditory brain stem responses

The effects of hypothermia on auditory brain stem response (ABR) in both children with congenital heart disease undergoing cardiac surgery and cats as an animal model were investigated. The latency of the ABR waves were prolonged with decreased body temperature. The latency of the later response components were prolonged more than that of the earlier response components; all waves disappeared below 25 degrees C and during artificial cardiac arrest. When the body temperature was raised, the later component began to reappear above 25 degrees C; the latency of all components shortened with temperature until normal responses were obtained at 34 degrees C. The data from both humans and cats were comparable. The ABR seems to be a useful monitor for evaluating brain stem function during deep hypothermia.