Predictors of neurologic outcome in hypothermia after cardiac arrest

Abstract

Objective: To evaluate the predictive value of neurologic prognostic indicators for patients treated with hypothermia after surviving cardiopulmonary arrest.

Methods: Patients who survived cardiopulmonary arrest were prospectively collected from June 2006 to October 2009. Detailed neurologic examinations were performed. Serum neuron specific enolase (NSE) measurements, brain imaging findings, somatosensory evoked potentials, and electroencephalogram (EEG) results were recorded. EEG patterns were blindly dichotomized with malignant patterns consisting of burst-suppression, generalized suppression, status epilepticus, and nonreactivity. Outcome measure of in-hospital mortality was assessed.

Results: A total of 192 patients (103 hypothermic, 89 nonhypothermic) were studied. The absence of pupillary light responses, corneal reflexes, and an extensor or absent motor response at Day 3 after cardiac arrest remained accurate predictors of poor outcome after therapeutic hypothermia (p < 0.0001 for all). Myoclonic status epilepticus was invariably associated with death (p = 0.0002). Malignant EEG patterns and global cerebral edema on head computed tomography (CT) were associated with death in both populations (p < 0.001). NSE > 33 ng/ml levels measured 1-3 days after cardiac arrest remained associated with poor outcome (p = 0.017), but had a false-positive rate of 29.3% (95% confidence interval [CI] 0.164-0.361).

Interpretation: Clinical examination (brainstem reflexes, motor response, and presence of myoclonus) at Day 3 after cardiac arrest remains an accurate predictor of outcome after therapeutic hypothermia. Sedative medications in both hypothermic and nonhypothermic patients may confound the clinical exam. NSE > 33 ng/ml has a high false-positive rate in patients treated with hypothermia and should be interpreted with caution.