Pulmonary Inactivation of Vasopressors Following Cardiac Operations

Vasoactive drugs were infused through catheters in the right atrium and then the left atrium of 34 patients who required either vasopressor or vasodilator support following cardiac operation to determine if the route of infusion affected the aortic blood concentration of these agents. Drugs were given through the right atrium for one hour and then the left atrium for an hour. Both central aortic and pulmonary arterial blood were assayed for drug concentrations, and hemodynamic measurements were made. Sixteen patients receiving dopamine hydrochloride through the left atrium had a 36 ± 12% (± standard error of the mean) increase in aortic concentration of the drug ( p < 0.005) and a 37 ± 14% increase in cardiac index ( p < 0.005) compared with administration through the right atrium. Seven patients receiving epinephrine showed a 59 ± 21% increase in aortic concentration ( p < 0.05) and a 21 ± 10% increase in cardiac index ( p < 0.05, not significant). Eleven patients receiving sodium nitro-prusside achieved a 99 ± 25% increase in aortic concentration ( p < 0.005) and a 20 ± 7% increase in cardiac index ( p < 0.05). In all instances, significantly higher central aortic blood concentrations were achieved during left atrial (LA) versus right atrial (RA) infusions. Changes in blood concentration of the drug between the pulmonary artery and the aorta during RA infusion suggest removal or inactivation of these drugs in the pulmonary vasculature. Since one goal of treatment of cardiac dysfunction is to ensure high concentrations of vasopressor or vasodilator agents in the coronary and systemic circulations, bypassing the lungs and infusing these agents directly into the left heart may be of importance in critically ill patients following cardiac operation.