Earlier Hypothermia Attainment is Associated with Improved Outcomes after Cardiac Arrest

Introduction: Therapeutic hypothermia (TH, 32-34ºC) reduces mortality and improves neurologic outcomes after ventricular fibrillation cardiac arrest (CA). The relationship between time to achieve TH and outcomes remains undefined. We hypothesized that a shorter interval from CA to achieve TH would be associated with improved neurologic outcome.

Methods: We retrospectively reviewed subjects within or out-of-hospital CA treated with TH between November 2006 and April 2009 at our institution. The time to target temperature was defined as the interval between witnessed CA and first measurement of hypothermia (≤ 34 ºC) and further categorized as early (< 6 hours) or delayed (> 6 hours). Outcomes were assessed at the time of death or discharge using Cerebral Performance Category Score (CPC); good outcome was defined as CPC ≤ 2. Fisher's Exact test was used to assess the univariate relationship between time to TH and outcome.

Results: 26 patients achieved TH after in-hospital (39%) and out-of-hospital (61%) CA. Five patients (5/26) reached early target temperature; 80% (4/5) of those had a good neurological outcome. 24% (5/21) of subjects with delayed target temperature achieved a good neurological outcome. The univariate relationship between time to target temperature and neurological outcome was statistically significant (p=0.034).

Conclusion: Attaining TH within 6 hours of in or out-of-hospital CA was associated with a greater likelihood of a good neurological outcome at discharge. Time from CA to achieved TH should be included as a clinically important covariate in future studies of predictors of outcome after CA.