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Auditory evoked responses in children during hypothermic cardiopulmonary bypass: report of cases
R A Rodriguez1, S M Audenaert, E H Austin
1Department of Surgery (Neurological and Cardiothoracic), University of Louisville, Kentucky 40202, USA.
Insights
Monitoring auditory brainstem responses (ABRs) and middle latency responses (MLRs) can assess brain function during pediatric open-heart surgery. Changes in ABRs and MLRs correlate with temperature and blood flow variations.
Area of Science:
- Neuroscience
- Cardiovascular Surgery
- Pediatric Anesthesiology
Background:
- Core temperature and cerebral blood flow fluctuations during open-heart surgery can impact neurological function.
- Auditory brainstem responses (ABRs) and middle latency responses (MLRs) are electrophysiological measures sensitive to brain activity.
Purpose of the Study:
- To investigate the effects of hypothermia and altered cerebral blood flow on ABRs and MLRs in infants and children during cardiopulmonary bypass.
- To compare these effects with those observed in a young adult.
Main Methods:
- Documented changes in ABRs in two infants undergoing hypothermic cardiopulmonary bypass and total circulatory arrest.
- Compared infant ABRs with those of a 19-year-old adult.
- Monitored MLRs using transcranial Doppler in a 6-year-old child during periods of reduced cerebral blood flow.
Main Results:
- Decreased core temperature led to increased ABR latencies and decreased amplitudes in both infants and the adult, with complete reversal upon rewarming.
- MLR amplitudes were transiently reduced during normothermic hypoperfusion, with partial prevention by hypothermia and recovery after rewarming.
Conclusions:
- ABRs and MLRs reflect changes in brain function related to core temperature and cerebral blood flow during pediatric open-heart surgery.
- Monitoring these auditory evoked potentials may provide a valuable tool for assessing brain status in infants and children undergoing hypothermic cardiopulmonary bypass.
Abstract:
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.