Effects of systemic or spinal cord cooling on conductive spinal evoked potentials.

To elucidate the mechanism of alterations of spinal evoked potentials after hypothermia, the effects of systemic and local cooling on conductive spinal evoked potentials were studied in cats. Conductive spinal evoked potentials were recorded from the L1 epidural space after epidural stimulation at the T4 level and during concomitant reduction of body temperature followed by rewarming. On local cooling and rewarming of the stimulating area or the recording area, conductive spinal evoked potentials changes were also analyzed. Systemic cooling provoked an increase in latency, duration, and amplitude as the body temperature decreased. Evoked potentials were not changed by the local cooling of the stimulating area. Thus, the evoked potentials changes of the spinal cord suggest that spinal cord cooling does not influence the stimulus threshold, but may affect the interaction between the amplitude change and the duration in individual spike potentials, and produces changes in temporal dispersion.