Epinephrine and high-flow reperfusion after cardiac arrest in a canine model.

STUDY OBJECTIVES: Epinephrine has been used in cardiac arrest to increase the low blood flow generated by standard CPR methods. Reperfusion with high flow such as that obtained with cardiopulmonary bypass (CPB) may obviate the need for or alter the dose of epinephrine after cardiac arrest. The objective of this study was to evaluate the effect of high-flow reperfusion after cardiac arrest with and without epinephrine on coronary perfusion pressure, defibrillation energy, restoration of spontaneous circulation (ROSC), and 2-hour survival after prolonged cardiac arrest.

DESIGN: Prospective, randomized, double-blind, placebo-controlled study using a canine model.

INTERVENTIONS: Thirty mongrel dogs were randomized to receive, after ventricular fibrillation cardiac arrest of 12 minutes' duration without CPR, placebo (n = 10), standard-dose epinephrine (.02 mg/kg) (n = 10), or high-dose epinephrine (.2 mg/kg) (n = 10) during reperfusion with CPB. Epinephrine or placebo was given with the start of CPB and then every 5 minutes, followed by countershock until ROSC or crossover at the fourth dose to high-dose epinephrine.

RESULTS: ROSC was achieved in the first 15 minutes of bypass in 10 of 10 dogs given high-dose epinephrine, in 9 of 10 given standard-dose epinephrine, and in 1 of 10 given placebo. After the crossover to high-dose epinephrine, ROSC was achieved in 8 of 10 dogs originally given placebo and the remaining animal given the standard dose of epinephrine. During early reperfusion, the high-dose group had a higher mean coronary perfusion pressure (high dose, 153 + 62 mm Hg; standard dose, 81 +/- 18 mm Hg; placebo, 51 +/- 15 mm Hg; P < .002) and a shorter mean ROSC time (high dose, 16.2 +/- 8 minutes; standard dose, 20.3 +/- 3.6 minutes; placebo, 27.9 +/- 3.2; P < .02) and required less defibrillation energy. CPB flow during ventricular fibrillation was 63% of baseline cardiac output in all three groups. Two-hour survival was 5 of 10 in the high-dose group, 8 of 10 in the standard-dose group, and 5 of 10 in the placebo group.

CONCLUSION: Restoration of high blood flow alone is insufficient to restore spontaneous circulation after prolonged cardiac arrest. Epinephrine, when administered early under high-flow conditions, increases coronary perfusion pressure, decreases defibrillation energy, and decreases time elapsed before ROSC. Higher doses of epinephrine under conditions of high-flow reperfusion do not improve 2-hour survival compared with standard-dose epinephrine.