Effects of hypothermia on brainstem auditory evoked potentials in humans

Abstract

Ten adult patients who underwent open heart surgery under induced hypothermia had brainstem auditory evoked potentials (BAEPs) recorded at 1°‐ to 2°C‐steps as body temperature was lowered from 36°C to 20°C to determine temperature‐dependent changes. Hypothermia produced increased latencies of BAEP waves I, III, and V; the prolongation was more severe for the later components with the result that interpeak latencies I–III, III–V, and I–V were also prolonged. The temperature‐latency relationship was nonlinear and best expressed by exponential curve. The latencies of waves I, III, V and the interpeak latency I–V increased roughly 7% for each 1°C drop; they doubled at a temperature around 26°C. The amplitude of the BAEP components had a quasiparabolic relationship to temperature; the amplitude rose with hypothermia to 28° or 27°C, but Decemberreased lineraly with further cooling. All BAEP components were present at temperatures above 23°C and absent below 20°C. With rewarming, the changes reversed and BAEPs returned to initial prehypothermia status.