Mild Therapeuric Hypothermia to Improve the Neurologic Outcome After Cardiac Arrest - HACA
The Hypothermia After Cardiac Arrest (HACA) was a randomized multicenter trial with blinded assessment of the outcome designed to determine whether mild systemic hypothermia increases the rate of neurologic recovery after resuscitation from cardiac arrest due to ventricular fibrillation.
Mild hypothermia increases the rate of neurologic recovery after resuscitation from cardiac arrest due to ventricular fibrillation.
Patients Screened: 3,551
Patients Enrolled: 275
NYHA Class: III or IV 11%
Mean Follow Up: 6 months
Mean Patient Age: 49 to 67
Mean Ejection Fraction: N/A
Patients seen consecutively in the emergency department, in whom spontaneous circulation had been restored after cardiac arrest, were eligible for the study. The inclusion criteria were a witnessed cardiac arrest, ventricular fibrillation or a nonperfusing ventricular tachycardia as the initial cardiac rhythm, a presumed cardiac origin of the arrest, an age of 18-75 years, an estimated interval of 5-15 minutes from the patient’s collapse to the first attempt at resuscitation by emergency medical personnel, and an interval of no more than 60 minutes from collapse to restoration of spontaneous circulation.
Patients were excluded if they met any of the following criteria: a tympanic membrane temperature below 30°C on admission, a comatose state before the cardiac arrest due to the administration of drugs that depress the central nervous system, pregnancy, response to verbal commands after the return of spontaneous circulation and before randomization, evidence of hypotension (mean arterial pressure <60 mm Hg) for more than 30 minutes after the return of spontaneous circulation and before randomization, evidence of hypoxemia (arterial oxygen saturation <85%) for more than 15 minutes after the return of spontaneous circulation and before randomization, a terminal illness that preceded the arrest, factors that made participation in follow-up unlikely, enrollment in another study, the occurrence of cardiac arrest after the arrival of emergency medical personnel, or a known pre-existing coagulopathy
A favorable neurologic outcome within six months after cardiac arrest
Mortality within six months and the rate of complications within seven days
Patients who had been resuscitated after cardiac arrest from ventricular fibrillation were randomly assigned to undergo therapeutic hypothermia (target temperature, 32°C to 34°C, measured in the bladder) over a period of 24 hours or to receive standard treatment with normothermia. Therapeutic hypothermia was induced with the use of an external cooling device and ice packs were used if the temperature goal was not achieved.
All patients received standard intensive care according to a detailed protocol. Midazolam and fentanyl were used for sedation. To avoid shivering, paralysis was induced by the intravenous administration of pancuronium (0.1 mg per kilogram) every two hours, for a total of 32 hours.
A total of 3,551 patients were assessed for eligibility. Two hundred and seventy-five were enrolled, with 137 patients randomly assigned to the hypothermia group and 138 to the normothermia group. Seventy-five of the 136 patients in the hypothermia group for whom data were available (55%) had a favorable neurologic outcome, as compared with 54 of 137 (39%) in the hypothermia group (risk ratio 1.40, 95% confidence interval 1.08-1.81).
Mortality at six months was 41% in the hypothermia group (56 of 137 patients died), as compared with 55% in the normothermia group (76 of 138 patients, risk ratio 0.74, 95% confidence interval 0.58-0.95). The complication rate did not differ significantly between the two groups.
Among patients who have been successfully resuscitated after cardiac arrest due to ventricular fibrillation, therapeutic mild hypothermia was associated with increased rates of a favorable neurologic outcome and reduced mortality.
Hypothermia after Cardiac Arrest Study Group. Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. N Engl J Med 2002;346:549-56.
Keywords: Temperature, Tachycardia, Ventricular, Hypothermia, Cardiopulmonary Resuscitation, Ventricular Fibrillation, Coronary Disease, Urinary Bladder, Heart Arrest, Ice
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