Introduction: Recent studies have brought to question the efficacy of the use of prehospital therapeutic hypothermia for victims of out-of-hospital cardiac arrest (OHCA). Though guidelines recommend therapeutic hypothermia as a critical link in the chain of survival, the safety of this intervention, with the possibility of minimal treatment benefit, becomes important. Hypothesis/Problem This study examined prehospital therapeutic hypothermia for OHCA, its association with survival, and its complication profile in a large, metropolitan, fire-based Emergency Medical Services (EMS) system, where bystander cardiopulmonary resuscitation (CPR) and post-arrest care are in the process of being optimized.
Methods: This evaluation was a retrospective chart review of all OHCA patients with return of spontaneous circulation (ROSC) treated with therapeutic hypothermia, from January 1, 2013 through November 30, 2013. The primary outcomes were the proportion of patients with initiation of prehospital therapeutic hypothermia with survival to hospital admission, the proportion of patients with initiation of prehospital therapeutic hypothermia with survival to hospital discharge, and the complication profile of therapeutic hypothermia in this population. The complication profile included several clinical, radiographic, and laboratory parameters. Exclusion criteria included: no prehospital therapeutic hypothermia initiation; no ROSC; and age of 17 year old or younger.
Results: Fifty-one post-cardiac arrest patients were identified that met inclusion criteria. The mean age was 61 years (SD=14.7 years), and 33 (72%) were male. The initial rhythm was ventricular fibrillation or pulseless ventricular tachycardia in 17 (37%) patients, and bystander CPR was performed in 28 (61%) patients with ROSC. Thirty-nine (85%) patients survived to hospital admission. Twenty-one patients (48%; 95% CI, 33-64) were administered vasopressors, 10 patients (24%; 95% CI, 10-37) were administered diuretics, and 19 patients (44%; 95% CI, 29-60) were administered antibiotics. Initial chest radiograph (CXR) findings were normal in 12 (29%) patients. Overall, 13 (28%; 95% CI, 15-42) study patients survived to hospital discharge.
Conclusion: Recent reports have questioned the efficacy and safety of prehospital therapeutic hypothermia. In this evaluation, in the setting of unstandardized post-arrest care, 85% of the patients survived to hospital admission and 28% survived to hospital discharge, with a complication profile which was similar to that noted in other studies. This suggests that further evidence may be needed before EMS systems stop administering therapeutic hypothermia to appropriately selected patients. In less-optimized systems, therapeutic hypothermia may still be an essential link in the chain of survival.
Keywords: AED automated external defibrillator; AHA American Heart Association; ALS Advanced Life Support; CPR cardiopulmonary resuscitation; CXR chest radiograph/x-ray; EMS Emergency Medical Services; EMT emergency medical technician; Emergency Medical Services; OHCA out-of-hospital cardiac arrest; ROSC return of spontaneous circulation; hypothermia; induced; out-of-hospital cardiac arrest.