Abstract 286: Hypothermic Out-of-hospital Cardiac Arrest: Favorable Outcomes, But With Limited Defibrillation Or Adrenaline Administration Effectiveness In The Prehospital Setting

Introduction: Hypothermic out-of-hospital cardiac arrest (OHCA) is assumed to be associated with favorable neurological outcomes compared with OHCA from other etiologies. However, supporting evidence is limited. In addition, inconsistencies for number of defibrillation and adrenaline administration attempts in prehospital management guidelines can be identified. Hypothesis: We evaluated whether hypothermic OHCA is associated with favorable outcomes compared with OHCA from other etiologies. Further, the effectiveness of defibrillation or adrenaline administration was evaluated. Methods: Using data from a nationwide, population-based retrospective study conducted in Japan from 2013 to 2016, we compared two OHCA patient groups: patients with hypothermic etiology and those with non-hypothermic etiology. The primary outcome measure was one-month favorable neurological outcomes, defined as Cerebral Performance Category score ≤ 2. Multivariable logistic regression was used to calculate odds ratios (ORs) and their confidence intervals (CIs) to evaluate the impact of hypothermic OHCA. We further looked for an association between prehospital management and neurological outcomes among patients with hypothermic etiology. Results: We divided the cohort of 477,606 OHCA patients into the hypothermic group (n=842) and the non-hypothermic group (n=476,763). The hypothermic group had significantly higher odds of favorable neurological outcomes (64/842 (7.6%) vs. 13,052/476,763 (1.4 %), adjusted OR 3.12, 95%, CI 1.96-4.96) compared with the non-hypothermic group. In the hypothermic group, prehospital defibrillation (OR 1.52, 95%, CI 0.86-2.68) and adrenaline administration (OR 1.32, 95%, CI 0.67-2.62) did not contribute to favorable neurological outcomes overall. However, when the data was stratified by age and number of shocks, three or less defibrillation attempts in patients under 65 years old (OR 3.37, 95%, CI 1.31-8.67) was associated with favorable neurological outcomes. Conclusion: We found that hypothermic OHCA was associated with a higher chance of a favorable neurological outcome. Even prehospital defibrillation seems to have limited efficacy for hypothermic OHCA.