Effects of epinephrine in a pig model of hypothermic cardiac arrest and closed-chest cardiopulmonary resuscitation combined with active rewarming

Objective: The aim of the current study was to assess the effects of epinep hrine in a pig model of hypothermic cardiac arrest followed by closed-chest cardiopulmonary resuscitation combined with active rewarming, simulating t he clinical management of an arrested hypothermic patient in a hospital wit hout cardiopulmonary bypass facilities. Design: Prospective, randomized ani mal study. Setting: University research laboratory. Subjects: Twelve 12- to 16-week-old domestic pigs. Interventions: Pigs were surface cooled to a bo dy core temperature of 28 degreesC. After 4 min of untreated cardiac arrest , manual closed-chest CPR and thoracic lavage with 40 degreesC warmed fluid were started. After 3 min of external chest compression animals were rando mly assigned to receive epinephrine (45, 45 and 200 mug/kg) or saline place bo in 5-min intervals. Measurements and main results: Coronary perfusion pr essure was about 15 mmHg in placebo group pigs. Coronary perfusion pressure was significantly higher after epinephrine, but restoration of spontaneous circulation was not more frequent (one of six epinephrine versus three of six saline placebo pigs, P = 0.34). After 45 mug/kg epinephrine the arteria l Po, was significantly lower when compared to the saline placebo. The thir d 200 mug/kg epinephrine dose resulted in a significantly enhanced mixed ve nous hypercarbic acidosis. Conclusions: After a short 4-min period of hypot hermic cardiac arrest, epinephrine may not be necessary to maintain coronar y perfusion pressure around the threshold usually correlating with successf ul defibrillation, even during prolonged closed-chest CPR combined with act ive rewarming. The enhanced mixed venous hypercarbic acidosis in epinephrin e-treated animals may support the argument against repeated or high dose ep inephrine administration during hypothermic CPR. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.