Abstract 2054: Neuron-specific Enolase as a Prognostic Parameter in Patients Treated with Mild Hypothermia After Cardiopulmonary Resuscitation for Out-of-hospital Cardiac Arrest

Abstract

Background: Overall prognosis in comatose survivors of Cardiopulmonary resuscitation is poor and the degree of hypoxic brain damage is usually the most important prognostic factor. Elevation of the neuron-specific enolase (NSE) as measured with 72 hours after admission has been identified as a predictor of neurologic outcome, and a threshold level of 33 ng/ml has been proposed as a highly specific cut-off value, above which neurologic outcome will be unfavourable. Therapeutic hypothermia is a new concept to improve neurologic outcome in patients after resuscitation, and the prognostic relevance of elevated NSE levels in patients treated by hypothermia has not yet been assessed. Methods: Mild therapeutic hypothermia (33–34°C) was applied via an intravenous cooling catheter for 24 hours in 38 consecutive patients admitted after successful on-site resuscitation following out-of-hospital cardiac arrest (28 male, 10 female, age 38 – 83 years, mean age 64.4±12.7 years). 72 hours after admission, NSE level was measured. Clinical and neurologic outcome was assessed at 1 and 4 weeks. Results: Out of 38 patients, 4 patients died within the first 72 hours. In 2 additional patients, NSE measurement was impossible because of haemolytic serum. NSE levels displayed a wide range (9.8 ng/ml − 720 ng/ml). Of the 32 patients available for analysis, 17 patients suffered severe ischemic brain damage or died during the further course (NSE 11.0 –720 ng/ml, mean 150.4±185.9 ng/ml). 15 patients recovered and had favourable neurologic outcome (NSE 9.8 – 47.9 ng/ml, mean 21.1±11.9 ng/ml). Using the recommended threshold value of 33 ng/ml, the sensitivity for ischemic brain damage was 76.5%, specificity was 80.0%, and the positive predictive value was 81.3%. Conclusions: Based on prior experience in patients without therapeutic hypothermia, a cut-off level of 33 ng/ml has been recommended as a highly specific threshold above which neurologic outcome in patients resuscitated for out-of-hospital cardiac arrest will be poor. Our data demonstrate, however, that favourable outcome can be achieved even for higher NSE levels in patients who are treated with therapeutic hypothermia. Thus, the prognostic value of NSE in these patients must be reconsidered.