[Relationship between body temperature, neuron-specific enolase, and clinical course in patients after out-of-hospital cardiac arrest]

Abstract

Background: According to ILCOR (International Liaison Committee on Resuscitation) recommendations (released in 2003), use of therapeutic hypothermia is recommended for unconscious adult patients who have survived a cardiac arrest regardless of the initial monitored cardiac rhythm. Thereby, the treatment goal is to achieve and maintain a body temperature of 32-34 °C for a period of 12-24 h. According to the October 2015 recommendations of the European Resuscitation Council (ERC), targeted temperature management (TTM) remains part of treatment, but, as an option, it is advised that the targeted body temperature be 36 °C rather than 32-34 °C.

Patient population and methods: For a non-randomized retrospective observational study, a total of 149 patients were treated with cardiopulmonary resuscitation (CPR) between May 1999 and September 2009. For the first 4 days after CPR, data associated with demography, resuscitation, therapy (temperature course, neuron-specific enolase [NSE]) and clinical-neurological development (Glasgow Outcome Scale [GOS]) were collected. In the study, patients receiving mild hyperthermia were compared with those who did not receive hypothermia.

Results: Of the 149 patients included, 90 were treated with mild hypothermia (as decided by the attending physician), while 59 received no hypothermia therapy. Assessment reveals that mild hypothermia positively influences clinical-neurological progression, but not survival. On day three and four, patients with an unfavorable neurological progression exhibited significantly increased serum levels of NSE (day 4: 108.7 ± 137.3 ng/ml versus 25.5 ± 15.4 ng/ml). Patients receiving hypothermia showed lower average NSE levels compared with persons not receiving hypothermia. Furthermore, during the first 4 days, their NSE values tended to increase slower (NSE value at day 4: 55.9 ± 64.9 ng/ml versus 129.9 ± 174.9 ng/ml). The best cut-off-value for an unfavorable neurological result was 74.2 ng/ml at day four (specificity 100%, sensitivity 48.6%). For the group of patients who received hypothermia, the best cut-off-value was 74.2 ng/ml at day four (specificity 100%, sensitivity 40.9%), and, for the comparison group, best cut-off-value was 25.5 ng/ml at day three (specificity 100%, sensitivity 88.2%).

Conclusion: After out-of-hospital resuscitation, there is a trend for improved clinical-neurological progression with mild hypothermia but it does not influence the prognostic significance of serum NSE. After assessment of available data, it is not possible to recommend uniform cut-off values for patients who received mild therapeutic hypothermia and for those who did not receive hypothermia treatment.

Keywords: Mild hypothermia; Neuron-specific enolase; Out-of-hospital resuscitation.