Abstract 2411: A Randomized, Controlled Trial Comparing the Arctic Sun to Standard Cooling for Hypothermia After Cardiac Arrest
Hypothermia therapy improves neurological outcome following out-of-hospital cardiac arrest (OOHCA). Standard surface cooling (SC) with ice packs and cold water blankets is readily available, but is labor intensive and often overcools the patient. The Arctic Sun® (AS) surface cooling system uses enhanced energy transfer pads and close computer control of patient temperature (temp). The objective of this study was to compare the AS to SC for treatment of patients with OOHCA. We hypothesized that a greater proportion of patients treated using the AS would reach 34°C within 4 hours of starting cooling (primary outcome) and AS treated patients would be less likely to be out of target range (32–34°C) during 24 hours of cooling than patients treated with SC. This multicenter trial enrolled unresponsive, hemodynamically stable patients resuscitated from witnessed OOHCA of presumed cardiac cause, with any initial rhythm. After randomization, sedation and paralysis, cooling devices were set to a target temp of 33.5°C and core temperature was monitored continuously. Assuming that 60% of SC treated patients will reach 34°C within 4 hours, a sample size of 64 has 80%power (α = 0.05) to identify a 30% absolute increase in the primary outcome. Thirty-four AS and 30 SC subjects were enrolled; three (2 AS, 1 SC) were withdrawn prior to initiating cooling. Overall, 75% of AS patients vs. 55% of SC patients reached 34°C within 4 hours (95% CI of the increase -4% to 43%). The mean (SD) time to 34°C was 200 (78) min for the AS group and 275 (195) min for the SC group. While 28/29 SC patients had a recorded temp outside of range, only 9/32 AC patients were out of range (Relative Risk=3.4; 95% CI 2.0 to 6.0). The rates of serious adverse events during cooling were similar (13% AS, 22% SC; p=0.3). The rate of Cerebral Performance Category of 1 or 2 recorded at final follow-up was similar (47% AS, 34% SC, p=0.4). In conclusion, the AS and SC are both safe and effective for inducing hypothermia. The AS may cool more quickly, but a lower than expected primary outcome rate in both groups limited our power to evaluate the primary outcome difference. After reaching 34°, AS patients were less likely to be out of range. Long-term neurological outcome was good among these comatose survivors of cardiac arrest.