Mild therapeutic hypothermia after out-of-hospital cardiac arrest: What does really matter?

Background: Mild therapeutic hypothermia (MTH) is a recommended treatment of comatose patients after out-of-hospital cardiac arrest (OHCA). The aim of the study was to examine determinants of clinical outcome in OHCA survivors treated with MTH and variables associated with MTH induction time.

Methods: Presented herein is an analysis of combined results from a retrospective and a prospective observational study which included 90 OHCA survivors treated with MTH from January 2010 to March 2018. Multivariate regression analysis was performed to determine variables associated with poor neurologic outcome (Cerebral Performance Category 3-5), mortality, and prolonged induction time.

Results: At hospital discharge, 59 (65.6%) patients were alive, of whom 36 (61%) had a good neurologic outcome. Older patients (odds ratio [OR] 1.07, 95% confidence interval [CI] 1.03-1.12) with lower Glasgow Coma Scale (GCS) (OR 0.49, 95% CI 0.30-0.80) were at higher risk of poor neurological outcome. The predictors of in-hospital death included: older age (OR 1.08, 95% CI 1.02-1.13), lower GCS score (OR 0.47, 95% CI 0.25-0.85), presence of cardiogenic shock (OR 3.43, 95% CI 1.11-10.53), and higher doses of adrenaline (OR 1.27, 95% CI 1.04-1.56). Longer induction was associated with shorter cardio-pulmonary resuscitation (CPR) (unstandardized coefficient -3.95, 95% CI -7.09 to -0.81) and lower lactate level (unstandardized coefficient -18.55, 95% CI -36.10 to -1.01).

Conclusions: Unfavorable neurologic outcome in OHCA patients treated with MTH is associated with age and lower GCS score. Risk factors for in-hospital mortality include age, high-dose adrenaline administration, lower GCS score and presence of cardiogenic shock. CPR duration and lactate level were predictive of prolonged MTH induction time.