Auditory evoked responses in children during hypothermic cardiopulmonary bypass: report of cases.

Variations in core temperature and cerebral blood flow during open heart surgery may affect auditory brainstem responses (ABRs) and middle latency responses (MLRs) in both adults and children. We documented the changes in ABRs of two infants (ages 3 and 11 weeks, respectively) with variations in core temperature during hypothermic cardiopulmonary bypass and total circulatory arrest and compared them with those of a 19-year-old adult. Changes in MLRs that occurred in association with reductions in cerebral blood flow as monitored by transcranial Doppler are also reported in a 6-year-old child. With the reductions in temperature in both infants and the young adult, ABR latencies increased and amplitudes decreased. Effects of hypothermia on ABR latencies were completely reversed by rewarming. MLR amplitudes were transiently reduced during periods of normothermic hypoperfusion. Hypothermia partially prevented these changes, and normoperfusion after rewarming recovered MLRs. Monitoring ABRs and MLRs may be a useful technique for assessment of brain function during hypothermic cardiopulmonary bypass in children and infants.