Somatosensory and brainstem auditory evoked potentials in cardiac arrest patients treated with hypothermia.

OBJECTIVE

To evaluate the prognostic value of short-latency median nerve somatosensory evoked potentials and brainstem auditory evoked potentials in outcome prediction for comatose cardiac arrest patients treated with hypothermia.

DESIGN

Prospective, randomized, controlled trial of mild hypothermia after out-of-hospital cardiac arrest; a substudy of the European Hypothermia After Cardiac Arrest study.

SETTING

Intensive care unit of a tertiary referral hospital (Helsinki University Central Hospital).

PATIENTS

Sixty consecutive patients (aged 18-75 yrs) resuscitated from out-of-hospital ventricular fibrillation and comatose at 24 hrs after cardiac arrest; all patients were randomly assigned either to therapeutic hypothermia of 33 degrees C or normothermia.

INTERVENTIONS

All patients received standard intensive care for at least 2 days. Patients randomized to hypothermia were cooled with an external cooling device for 24 hrs and then allowed to rewarm slowly for 12 hrs. In the normothermia group, the core temperature was kept below 38 degrees C with antipyretics and by physical means. The clinical outcome was assessed 6 months after cardiac arrest.

MEASUREMENTS AND MAIN RESULTS

Somatosensory evoked potentials and brainstem auditory evoked potentials were recorded 24-28 hrs after cardiac arrest. All wave latencies were significantly prolonged in the hypothermia group. Bilaterally absent N20 waves predicted permanent coma with a specificity of 100% in both treatment groups. Brainstem auditory evoked potential recordings did not correlate with the outcome in either treatment group.

CONCLUSIONS

The prognostic ability of median nerve short-latency somatosensory evoked potentials does not seem to be affected by therapeutic hypothermia. Brainstem auditory evoked potentials had no additional value in outcome prediction.