Moderate hypothermia improved neurologic outcomes after cardiac arrest with nonshockable rhythm

Mortality was similar whether patients were randomized to a target temperature of 33 °C or 37 °C, but those in the former group were more likely to have a favorable Cerebral Performance Category score at 90 days.

Patients who underwent moderate therapeutic hypothermia after resuscitation from cardiac arrest with nonshockable rhythm were more likely to have a favorable neurologic outcome, a recent trial found.

The trial included 584 patients with coma who had been admitted to 25 French ICUs after resuscitation from cardiac arrest with nonshockable rhythm (asystole or pulseless electrical activity) from January 2014 through January 2018. They were randomized to either moderate therapeutic hypothermia (33 °C during the first 24 hours) or targeted normothermia (37 °C). The primary outcome was survival with a favorable neurologic outcome at 90 days, defined as a 1 or 2 on the Cerebral Performance Category (CPC) scale. Results were published by the New England Journal of Medicine on Oct. 2.

Three patients (all in the hypothermia group) withdrew consent, so 581 were included in the analysis. On day 90, 29 of 284 patients (10.2%) in the hypothermia group and 17 of 297 (5.7%) in the normothermia group met the primary outcome (difference, 4.5 percentage points; 95% CI, 0.1 to 8.9; P=0.04). Mortality at 90 days did not differ significantly between groups (81.3% and 83.2%, respectively; difference, −1.9 percentage points [95% CI, −8.0 to 4.3]), nor did incidence of prespecified adverse events.

The authors concluded that moderate therapeutic hypothermia led to a higher percentage of patients surviving with a favorable neurologic outcome, and they noted that previous research in this area has found mixed results. “Cardiac arrest is a highly heterogeneous entity, and many factors may affect the efficacy of hypothermia,” they wrote. They calculated that based on the study results the number needed to treat (NNT) with hypothermia to have one additional patient survive with a CPC of 1 or 2 would be 22, compared to NNTs to prevent one patient death of 15 for bystander CPR and 112 for epinephrine.

The study did have a number of limitations, including that a substantial proportion of patients had body temperatures above 38 °C and that the study used targeted temperature management for 56 to 64 hours in the hypothermia group and for 48 hours in the normothermia group. “Last, the fragility index value of 1 for our trial indicates that an outcome change in a single patient would make the difference in the primary outcome nonsignificant,” the authors said.

An article in the July ACP Hospitalist covered how targeted temperature management has affected cognitive outcomes after cardiac arrest.