High dose naloxone does not improve cerebral or myocardial blood flow during cardiopulmonary resuscitation in pigs

In a prospective, randomized, placebo-controlled, double-blind trial we tested the hypothesis that naloxone given during cardiopulmonary resuscitation (CPR) enhances cerebral and myocardial blood flow. Twenty-one anesthetized, normoventilated pigs were instrumented for measurements of right atrial and aortic pressures, and regional organ blood flow (radiolabeled microspheres). After 5 min of untreated fibrillatory arrest, CPR was commenced using a pneumatic chest compressor/ventilator. With onset of CPR, an i.v. bolus of 40 μg/kg b.w. of epinephrine was given, followed by an infusion of 0.4 μg/kg per min. After 5 min of CPR, either naloxone, 10 mg/kg b.w. (group N, n=11) or normal saline (group S, n=10) was given i.v. Prior to, and after 1, 15, and 30 min of CPR, hemodynamic and blood flow measurements were obtained. After 30 min of CPR, mean arterial pressure was significantly higher in group N (26±5 vs. 13±3 mmHg, P