Hypothermia did not improve survival for out-of-hospital cardiac arrest

1. Controlled hypothermia was shown not to lower the incidence of death for patients in coma after an out-of-hospital cardiac arrest when compared to normothermia.

2. More patients treated with hypothermia experienced the adverse event of arrhythmia resulting in hemodynamic compromise compared to patients treated with normothermia.

Evidence Rating Level: 1 (Excellent)

Study Rundown: International guidelines indicate targeted hypothermia in the management of patients after an out-of-hospital cardiac arrest to prevent hypoxic-ischemic brain damage. However, the evidence of survival and neurologic benefits to support this approach is of low certainty with a high risk of bias. As such, this study examined the effects of hypothermia, as compared to normothermia, in patients who had had an out-of-hospital cardiac arrest. The study determined there was no significant difference in mortality rates between patients who were treated with either thermoregulation treatment. Similarly, no difference was found in outcomes of disability and adverse events between both groups. A notable exception was the incidence of arrhythmia resulting in hemodynamic instability was higher in the hypothermia treatment group. The study was limited by the open-label design due to the nature of the interventions, and the lack of a control group with no temperature management. Nonetheless, the study provided evidence that hypothermia treatment was unable to lower the incidence of death for the patient subgroup compared to normothermia treatment.

Click here to read the study in NEJM

Relevant Reading: Targeted temperature management at 33oC versus 36oC after cardiac arrest

In-Depth [randomized controlled trial]: This open-label randomized international trial enrolled 1,900 patients. Patients at least 18 years of age, with a coma after an out-of-hospital cardiac arrest, and who had more than 20 consecutive minutes of spontaneous circulation following resuscitation were included in the study. Patients with an unwitnessed cardiac arrest with initial asystole as the initial rhythm were excluded from the study. Patients were randomized in a 1:1 ratio to receive either hypothermia management at 33oC or normothermia management at 37.5oC, respectively. The primary outcome was death from any cause at six months. At the end of the follow-up period, 465 (50%) patients in the hypothermia group and 446 (48%) patients in the normothermia group had died (relative risk with hypothermia [RR], 1.04; 95% confidence interval [CI]. 0.94 to 1.14; P=0.37). Using time-to-event analysis the hazard ratio for the hypothermia group was 1.08 (95% CI, 0.95 to 1.23). Arrhythmias with resultant hemodynamic compromise was more prevalent in the hypothermia group (24%) compared to the normothermia group (16%) (P<0.001). No significant difference was observed in other adverse events. Overall, this study showed no mortality or functional benefits to treating these patients with hypothermia when compared to normothermic management with early treatment of fever.

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