Effects of hypothermia with cardiopulmonary bypass on posterior tibial nerve somatosensory evoked potentials in man]

Somatosensory evoked potential after posterior tibial nerve stimulation (PTN-SEP), as well as nasopharyngeal, bladder and plantar temperature were recorded in ten patients during cardiac surgery with hypothermic cardiopulmonary bypass. There was a best negative correlation between latencies (P27, P40 and the interpeak latency between P40 and P27 (P40-P27)) and nasopharyngeal temperature, but no correlation was found between latencies and plantar temperature during cooling and rewarming (27-37 degrees C) with cardiopulmonary bypass. No correlation was found between changes in amplitude and temperature. The slope of linear regression line of latencies versus nasopharyngeal temperature was -1.05 msec.degrees C-1 for P27 (r = -0.93), -1.47 msec.degrees C-1 for P40 (r = -0.95) and -0.43 msec.degrees C-1 for P40-P27 (r = -0.78). This study suggests that nasopharyngeal temperature measurement is required to aid the interpretation of PTN-SEP changes during hypothermia.