A prospective, randomized, blinded study was conducted to evaluate the efficacy of standard compared with high-dose epinephrine in cardiac arrest in dogs. Twenty-five mongrel dogs were anesthetized and monitored by central venous catheter, intra-arterial catheter, and ECG. A left lateral thoracotomy was performed, and the proximal left anterior descending artery was ligated. After ten minutes of myocardial ischemia, ventricular fibrillation was obtained by application of 6-V AC. Mechanical ventilation was stopped. Total arrest time was ten minutes. All animals were randomized into one of five resuscitation protocols; each protocol was identical except for the dose and route of epinephrine administration. Group 1 animals comprised the control group and received normal saline. Group 2 and 3 animals received epinephrine in doses of 0.014 mg/kg by central venous and intracardiac injection, respectively. Group 4 and 5 animals received epinephrine in doses of 0.071 mg/kg by central venous and intracardiac injection, respectively. None of the dogs receiving normal saline had a return of spontaneous circulation, defined as a spontaneous systolic blood pressure of more than 50 mm Hg. Nine of the ten animals from groups 2 and 3 and all of the ten animals from groups 4 and 5 had a return of spontaneous circulation. However, animals receiving the standard dose of epinephrine had a significantly longer resuscitation time compared with the high-dose group (P = .05) and required more doses of epinephrine for successful resuscitation than did animals receiving high doses (P less than .02).(ABSTRACT TRUNCATED AT 250 WORDS)