The effect of mild therapeutic hypothermia on good neurological recovery after out-of-hospital cardiac arrest according to location of return of spontaneous circulation: a nationwide observational study

Abstract

Background: Mild therapeutic hypothermia (MTH) has been known to be associated with good neurological recovery after out-of-hospital cardiac arrest (OHCA). Prehospital return of spontaneous circulation (P-ROSC) is associated with better hospital outcomes than ROSC at emergency department (ED-ROSC). The study aims to examine the association between MTH by location of ROSC and good neurological recovery after OHCA.

Methods: Adult OHCA cases with presumed cardiac etiology who survived to hospital admission were collected from a nationwide cardiac registry between 2008 and 2013. MTH was defined as a case receiving hypothermia procedure regardless of procedure method. Primary outcome was good neurological recovery with cerebral performance category score of 1 and 2. Multivariable logistic regression analysis was performed adjusting for potential confounders with an interaction term between MTH and location of ROSC to calculate adjusted odds ratios (AORs) and 95% confidence intervals (CIs).

Results: Among 11,158 patients survived to admission, good neurological recovery was 23.6% (399/1691) in MTH vs. 15.0% (1400/9316) in non-MTH (p<0.001), and 58.2% (1074/1864) in P-ROSC vs. 7.9% (725/9161) in ED-ROSC (p<0.001). There was a significant association between MTH and good neurological recovery (AOR=1.32, 95% CI=1.11-1.57). In the interaction model, AOR of MTH and interaction effect with P-ROSC and ED-ROSC was 0.78 (0.58-2.70) and 1.68 (1.34-1.98), respectively.

Conclusion: MTH was significantly associated with good neurological recovery among OHCA survivors. In the interaction model, MTH showed significant benefits in patient group with ROSC at ED, not in P-ROSC group.

Keywords: Cardiac arrest; Hypothermia; Outcomes; Return of spontaneous circulation.