Do Lower Target Temperatures or Prolonged Cooling Provide Improved Outcomes for Comatose Survivors of Cardiac Arrest Treated With Hypothermia?

BACKGROUND Optimal protocols for targeted temperature management are still unclear. This study investigated whether lower target temperatures and/or prolonged cooling could provide improved outcomes in comatose survivors of cardiac arrest. METHODS AND RESULTS This observational study was conducted using the prospectively collected targeted temperature management database in Hiroshima, Japan. Between September 2003 and September 2014, 237 patients treated with TTM after cardiac arrest were enrolled in this study. The target temperatures and durations were assigned by the treating physicians regardless of the patients' conditions. Favorable outcomes were defined as a cerebral performance category scale of 1 or 2 at the 90-day follow-up time point. The rate of favorable outcomes were similar between the patients whose protocols of target temperature were <34°C and ≥34°C (40% versus 35%, P=0.41), cooling durations were <28 and ≥28 hours (33% versus 44%, P=0.11), and rewarming durations were <28 and ≥28 hours (35% versus 41%, P=0.39). However, in patients treated with extracorporeal cardiopulmonary resuscitation, target temperatures <34°C were associated with more favorable outcomes (29% versus 8%, P=0.01). The cooling and rewarming durations >28 hours and target temperatures <34°C were associated with more frequent lethal arrhythmia, pneumonia, and/or bleedings. CONCLUSIONS Prolonged durations of cooling and rewarming ≥28 hours may not improve outcomes and may increase complications. Further studies are necessary to assess the hypothesis that target temperatures <34°C provide improved outcomes in patients treated with extracorporeal cardiopulmonary resuscitation.