Study objective: To examine the effects of moderate hypothermia (33 degrees C), induced by surface cooling in the ED and maintained for 12 hours in the ICU, on patients with anoxic brain injury after out-of-hospital cardiac arrest.
Methods: We conducted the study in a teaching hospital in Melbourne, Victoria, Australia. Participants were 22 adults who remained unconscious after return of spontaneous circulation following out-of-hospital cardiac arrest. This treatment group was studied prospectively, and a control group of 22 similar patients was studied by retrospective chart review. Moderate hypothermia (33 degrees C) was induced in the ED by means of surface cooling and maintained for 12 hours in the ICU with rewarming to normothermia over 6 hours; control patients were maintained at normothermia.
Results: There were no significant adverse effects of induced hypothermia. Cardiovascular changes included decreased pulse rate, but there were no significant differences in mean arterial blood pressure between the two groups. Small increases in serum potassium and decreases in pH at 18 hours in the hypothermic patients compared with normothermic controls were of no clinical significance. There were no septic complications. There was a significant increase in the number of patients with good outcome (Glasgow Outcome Coma Scale category 1 or 2) with induced hypothermia (11 of 22, versus 3 of 22 for normothermic controls; P<.05), and the mortality rate was significantly lower (10 of 22 versus 17 of 22; P<.05).
Conclusion: Compared with historical normothermic controls, outcome was significantly improved and there was no increase in complications when moderate hypothermia was induced in comatose survivors of out-of-hospital cardiac arrest and maintained for 12 hours. Larger, prospective, randomized, controlled studies of induced moderate hypothermia in comatose survivors of out-of-hospital cardiac arrest are warranted.