Effects of moderate hypothermia versus normothermia on survival outcomes according to the initial body temperature in out-of-hospital cardiac patients: A nationwide observational study

Abstract

AimWe aimed to investigate whether the effect of moderate hypothermia compared to normothermia on survival outcomes after out-of-hospital cardiac arrest (OHCA) patients who underwent targeted temperature management (TTM) differed between patients with and without initial spontaneous hypothermia. MethodsWe used data from a nationwide OHCA database collected between 2016 and 2017. Adult patients with OHCA of presumed cardiac aetiology who underwent TTM were included. Moderate hypothermia was defined as a target temperature of TTM < 35.5 °C. Initial hypothermia was defined as the measured temperature before starting TTM < 35.5 °C. Endpoints were survival to discharge and good neurological recovery (CPC 1 or 2). We compared outcomes between moderate hypothermia vs. normothermia using multivariable logistic regression with an interaction term between target temperature of TTM and initial spontaneous hypothermia. ResultsOf the 744 patients, 628 (84.4%) underwent moderate hypothermia. Initial spontaneous hypothermia was observed in 28.5% and 25.0% in the moderate hypothermia and normothermia groups, respectively. There was no significant difference in survival to discharge between moderate hypothermia and normothermia (57.2% vs 62.9%, p = 0.248). The initial spontaneous hypothermia group showed poorer survival than the initial non-hypothermia group (41.8% vs 64.4%, p < 0.001). In the interaction model, AOR (95% CI) for survival to discharge of moderate hypothermia was 3.51 (1.33–9.25) in patients with initial spontaneous hypothermia and 0.49 (0.27–0.89) in patients without initial spontaneous hypothermia. ConclusionThe effect of moderate hypothermia was modified by the initial temperature of OHCA survivors who underwent TTM. The positive effect of moderate hypothermia was increased in patients with initial spontaneous hypothermia.