Induction of prehospital therapeutic hypothermia after resuscitation from nonventricular fibrillation cardiac arrest*.

OBJECTIVE: To evaluate the effects on temperature and outcome at hospital discharge of a pre-hospital rapid infusion of large volume, ice-cold intravenous Hartmann's solution in patients with out-of-hospital cardiac arrest and an initial cardiac rhythm of asystole or pulseless electrical activity.

DESIGN: Prospective, randomized, controlled clinical trial.

SETTING: Pre-hospital emergency medical service and 12 critical care units in Melbourne, Australia.

PATIENTS: One hundred and sixty three patients who had been resuscitated from cardiac arrest with an initial cardiac rhythm of asystole or pulseless electrical activity.

INTERVENTIONS: : Patients were randomized to either pre-hospital cooling using a rapid infusion of up to two litres ice-cold Hartmann's solution (82 patients) or cooling after hospital admission (81 patients). The planned duration of therapeutic hypothermia (32 °C-34 °C) in both groups was 24 hrs.

MEASUREMENTS AND MAIN RESULTS: Patients allocated to pre-hospital cooling received a median of 1500 ml of ice-cold fluid. This resulted in a mean decrease in core temperature of 1.4 °C compared with 0.2 °C in hospital cooled patients (p < .001). The time to therapeutic hypothermia (<34 °C) was 3.2 hrs in the pre-hospital cooled group compared with 4.8 hrs in the hospital cooled group (p = .0328). Both groups received a mean of 15 hrs cooling in the hospital and only 7 patients in each group were cooled for 24 hrs. Overall, there was no difference in outcomes at hospital discharge with favorable outcome (discharge from hospital to home or rehabilitation) in 10 of 82 (12%) in the pre-hospital cooled patients, compared with 7 of 81 (9%) in the hospital cooled patients (p = .50). In the patients with a cardiac cause of the arrest, 8 of 47 patients (17%) who received pre-hospital cooling had a favorable outcome at hospital discharge compared with 3 of 43 (7%) in the hospital cooled group (p = .146).

CONCLUSIONS: In adults who have been resuscitated from out-of-hospital cardiac arrest with an initial cardiac rhythm of asystole or pulseless electrical activity, pre-hospital cooling using a rapid infusion of large-volume, ice cold intravenous Hartmann's solution decreases core temperature at hospital arrival and decreases the time to therapeutic hypothermia. In patients with a cardiac cause of the arrest, this treatment may increase the rate of favorable outcome at hospital discharge. Further larger studies should evaluate the effects of pre-hospital cooling when the initial cardiac rhythm is asystole or pulseless electrical activity, particularly in patients with a cardiac cause of the arrest.