What is the role of somatosensory evoked potentials (SEPs) in the workup of hypothermia?

Updated: Oct 25, 2019
  • Author: Andrew B Evans, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Guerit et al studied the use of the SEP to determine the optimal degree of hypothermia during circulatory arrest and found that the delay of SEP reappearance after restoration of blood flow correlated significantly with cardiac arrest duration. [77] They concluded that neurophysiologic monitoring of brainstem activity, as provided by SEPs, enables determination of the optimal temperature for hypothermic circulatory arrest.

The investigators sequentially recorded subcortical (P14) and cortical (N20) SEPs in 32 patients undergoing deep hypothermic circulatory arrest. [77] Under normal hemodynamic conditions, hypothermia initially produced N20 disappearance at a mean nasopharyngeal temperature of 20.4 ± 2.6° C (range, 14.5-26.1°C) and P14 disappearance at a mean of 16.9 ± 2.0°C (range, 12.4-20.2°C). On rewarming, P14 reappeared at mean temperatures of 19.3 ± 4.0°C (range, 13.5-29.2°C) and N20 at a mean of 21.1 ± 4.1°C (range, 14.3-29.6°C). [77]

Neurologic recovery was uneventful in 23 patients; 5 patients presented with neurologic sequelae (minor or transient in 4; no recovery from anesthesia and death after 48 hours in 1), and 4 patients died during the operation. [77] Of the 24 surviving patients in whom P14 disappeared when the hypothermia was deep enough to cause cardiac arrest (duration, 17-94 min), 23 had a normal neurologic outcome. By contrast, all surviving patients in whom cortical SEPs disappeared at higher temperatures presented neurological sequelae.


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