The influence of rewarming after therapeutic hypothermia on outcome after cardiac arrest.

INTRODUCTION Treatment with hypothermia has been shown to improve outcome after cardiac arrest (CA). Current consensus is to rewarm at 0.25-0.5 °C/h and avoid fever. The aim of this study was to investigate whether active rewarming, the rate of rewarming or development of fever after treatment with hypothermia after CA was correlated with poor outcome. METHODS This retrospective cohort study included adult patients treated with hypothermia after CA and admitted to the intensive care unit between January 2006 and January 2009. The average rewarming rate from end of hypothermia treatment (passive rewarming) or start active rewarming until 36 °C was dichotomized in a high (≥ 0.5 °C/h) or normal rate (<0.5 °C/h). Fever was defined as >38 °C within 72 h after admission. Poor outcome was defined as death, vegetative state, or severe disability after 6 months. RESULTS From 128 included patients, 56% had a poor outcome. Actively rewarmed patients (38%) had a higher risk for poor outcome, OR 2.14 (1.01-4.57), p<0.05. However, this effect disappeared after adjustment for the confounders age and initial rhythm, OR 1.51 (0.64-3.58). A poor outcome was found in 15/21 patients (71%) with a high rewarming rate, compared to 54/103 patients (52%) with a normal rewarming rate, OR 2.61 (0.88-7.73), p = 0.08. Fever was not associated with outcome, OR 0.64 (0.31-1.30), p = 0.22. CONCLUSIONS This study showed that patients who needed active rewarming after therapeutic hypothermia after CA did not have a higher risk for a poor outcome. In addition, neither speed of rewarming, nor development of fever had an effect on outcome.