The comparison of the Effect of Mild Therapeutic Hypothermia on Good Neurological Recovery of Out-of-hospital Cardiac Arrest victims according to the locations of ROSC: Pre-hospital vs. Emergency department

Abstract

Introduction: 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). It is unclear whether MTH has an interaction with location of ROSC (Prehospital vs. ED) for good neurological recovery. The study aims to examine the association between MTH by 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. Study variables included age, gender, place of OHCA occurrence, witness, bystander cardiopulmonary resuscitation (CPR), metropolitan, emergency medical services (EMS) response time, prehospital defibrillation, levels of ED, reperfusion therapy, primary ECG, and P-ROSC versus ED-ROSC. 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 measured by hospital medical record review. 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: Of 138,410 adult OHCAs with cardiac etiology, 11,158(8.1%) patients survived to admission. Among such cases, good neurological recovery was 23.6% (399/1,691) in MTH vs. 15.0% (1,400/9,316) in non-MTH (p<0.001), and 58.2% (1,074/1,864) in P-ROSC vs. 7.9% (725/9,161) in ED-ROSC (p<0.001). MTH was performed in 15.4% of total patients, 16.1% in P-ROSC (n=1,846), and 13.2% in ED-ROSC (n=9,161), respectively. 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.

Conclusions: MTH was significantly associated with good neurological recovery among OHCA survivors, but the effect was different in P-ROSC and ED-ROSC. Prehospital ROSC group showed substantially higher good neurological recovery. However, MTH showed significant benefits in patient group with ROSC at ED, not in P-ROSC group, in a nationwide observational study.

Keywords: Cardiac Arrest, Hypothermia, Return of Spontaneous Circulation, Outcomes