Effect of therapeutic hypothermia on survival to hospital discharge in out-of-hospital cardiac arrest secondary to nonshockable rhythms

Abstract

Objectives Therapeutic hypothermia has been shown to improve neurologic outcome and survival in out-of-hospital cardiac arrest (OHCA) following return of spontaneous circulation (ROSC), and current guidelines recommend therapeutic hypothermia for all comatose survivors of OHCA. However, recommendations for nonshockable rhythms are not as strongly supported. Our study aims to provide further evidence on the use of therapeutic hypothermia in nonshockable rhythms. Methods A multivariate analysis with propensity score matching was performed using a cardiac arrest registry maintained by the Houston Fire Department. The analysis was limited to adult patients achieving ROSC following OHCA secondary to nonshockable rhythm in Houston from 2007 to 2012 with definitive information regarding the implementation of therapeutic hypothermia. The primary outcome was survival to hospital discharge. Results Of 9,479 records identified for analysis, 7,839 had an initial nonshockable rhythm. Of these, 2,609 (33.3%) had sustained ROSC and 1,768 (22.6%) were admitted to the hospital. Data on therapeutic hypothermia use were available for 696 patients, with 335 (48.1%) receiving therapeutic hypothermia. Propensity score matching yielded 260 case/control pairs. The odds of survival to hospital discharge was an odds ratio of 1.07 (95% confidence interval = 0.71 to 1.60) for those in the therapeutic hypothermia group versus the nontherapeutic hypothermia group (p = 0.79). Conclusions Based on this retrospective study, therapeutic hypothermia is not associated with improved survival in patients with OHCA secondary to nonshockable rhythms. Given the limitations of our study, further prospective trials to assess the effect of therapeutic hypothermia for OHCA with nonshockable rhythms are warranted.