Is Epinephrine Contraindicated During Cardiopulmonary Resuscitation?

Abstract

Background Why pulmonary gas exchange deteriorates after administration of epinephrine during cardiopulmonary resuscitation (CPR) is unclear. Methods and Results Forty-four anesthetized swine received an infusion of six inert gases. Animals underwent ventricular fibrillation with CPR and intravenous administration of saline (control), epinephrine (15 μg/kg), or methoxamine (150 μg/kg). Cardiac output, aortic blood pressure, pH, and arterial oxygen saturation were recorded. Distributions of V̇ a and Q̇ were determined by the multiple inert gas elimination technique. Ventricular fibrillation and CPR caused significant decreases in cardiac output, aortic blood pressure, and arterial pH. With epinephrine (versus saline), diastolic blood pressure was significantly higher (23±7 versus 8±4 mm Hg), but the increase in shunt (from 7±4% to 29±17%) and the reduction in Sa o 2 (from 99.7% to 76.8%) were significantly larger. Also, the increase in dead space was greater and elimination of CO 2 less. There were no differences between animals given methoxamine or saline, except for increased diastolic blood pressure. Conclusions During experimental ventricular fibrillation and CPR, epinephrine increased intrapulmonary shunt ≈300% more than saline or methoxamine and significantly reduced arterial oxygen saturation. We suspect that the β-adrenergic receptor activity of epinephrine attenuated hypoxic pulmonary vasoconstriction. Methoxamine is as effective a pressor as epinephrine for CPR and devoid of β-adrenergic activity. We recommend that such an agent be considered, instead of epinephrine, for CPR.