AUDITORY-EVOKED RESPONSES IN CHILDREN DURING HYPOTHERMIC CARDIOPULMONARY BYPASS - REPORT OF CASES

Variations in core temperature and cerebral blood flow during open hea rt surgery may affect auditory brainstem responses (ABRs) and middle l atency responses (MLRs) in both adults and children. We documented the changes in ABRs of two infants (ages 3 and 11 weeks, respectively) wi th variations in core temperature during hypothermic cardiopulmonary b ypass and total circulatory arrest and compared them with those of a 1 9-year-old adult. Changes in MLRs that occurred in association with re ductions in cerebral blood flow as monitored by transcranial Doppler a re also reported in a 6-year-old child. With the reductions in tempera ture in both infants and the young adult, ABR latencies increased and amplitudes decreased. Effects of hypothermia on ABR latencies were com pletely reversed by rewarming. MLR amplitudes were transiently reduced during periods of normothermic hypoperfusion. Hypothermia partially p revented these changes, and normoperfusion after rewarming recovered M LRs. Monitoring ABRs and MLRs may be a useful technique for assessment of brain function during hypothermic cardiopulmonary bypass in childr en and infants.