Electroencephalogram for prognosis after cardiac arrest

In assessing neurologic prognosis after cardiac arrest (CA), electroencephalogram (EEG) reactivity has not been specifically included with EEG classifications. Most studies have divided recordings into benign and malignant; however, some patterns within these groups may have greater prognostic significance than such broad classifications. We sought to explore reactivity, with broad classifications and subclassifications for their prognostic significance.

All consecutive adults in coma who had an EEG recording performed at least 1 day after CA or during normothermia after a 24-hour mild hypothermia protocol. Outcomes were dichotomous: recovery of awareness or no recovery of awareness during hospitalization.

Twenty-nine patients met the inclusion criteria. Of the 18 patients with no reactivity, only 1 recovered awareness; of the 11 patients who demonstrated reactivity, 10 recovered awareness (sensitivity of 90% [95% confidence interval, or CI, 0.57-1] and specificity of 94% [95% CI, 0.7-1]). Of those with benign patterns, 7 recovered awareness and 1 did not; however, those patients demonstrating malignant patterns, 4 recovered and 17 did not (sensitivity of 94% [95% CI, 0.7-1] and a specificity of 63% [95% CI, 0.32-0.88]). None of the 15 patients with suppression or generalized spikes recovered consciousness, and none of these patients demonstrated reactivity.

Electroencephalogram reactivity after CA is a relatively favorable EEG feature; generalized suppression or generalized epileptiform activity, without reactivity, is associated with lack of recovery of awareness.