EPINEPHRINE AND HIGH-FLOW REPERFUSION AFTER CARDIAC-ARREST IN A CANINE MODEL

Study objectives: Epinephrine has been used in cardiac arrest to Incre ase 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 cardi ac arrest. The objective of this study was to evaluate the effect of h igh-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 c ardiac arrest. Design: Prospective, randomized, double-blind, placebo- controlled study using a canine model. Interventions: Thirty mongrel d ogs 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/k g) (n=10) during reperfusion with CPB. Epinephrine or placebo was give n with the start of CPB and then every 5 minutes, followed by counters hock until ROSC or crossover at the fourth dose to high-dose epinephri ne. 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-dos e epinephrine, and in 1 of 10 given placebo. After the crossover to hi gh-dose epinephrine, ROSC was achieved in 8 of 10 dogs originally give n placebo and the remaining animal given the standard dose of epinephr ine. During early reperfusion, the high-dose group had a higher mean c oronary 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 t ime (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. C PB flow during ventricular fibrillation was 63% of baseline cardiac ou tput in all three groups. Two-hour survival was 5 of 10 in the high-do se group, 8 of 10 in the standard-dose group, and 5 of 10 in the place bo group. Conclusion: Restoration of high blood flow alone is insuffic ient to restore spontaneous circulation after prolonged cardiac arrest . Epinephrine, when administered early under high-flow conditions, inc reases coronary perfusion pressure, decreases defibrillation energy, a nd decreases time elapsed before ROSC. Higher doses of epinephrine und er conditions of high flow reperfusion do not improve 2-hour survival compared with standard-dose epinephrine.