The use of dopamine to correct the reduced cardiac output resulting from positive end-expiratory pressure

Abstract

Listen

Translate article

PEEP has become widely used in patients with acute respiratory failure to increase arterial oxygenation. Despite a beneficial effect on the arterial oxygen content, PEEP may result in a substantial decrease in the cardiac output. This study was undertaken to determine the effectiveness of dopamine in correcting a PEEP-induced decreased cardiac output and to determine if, in increasing the cardiac output, the pulmonary shunt is affected. In 12 anesthetized, mechanically ventilated dogs the cardiac output and shunt were determined simultaneously. After control values were obtained, 10 cm of water PEEP was begun and a dopamine infusion was given for 3 hours. The infusion rate was adjusted to maintain the cardiac output near control levels, the average dose being 17.6 μg/kg/min. With the addition of PEEP, there was a decrease in the cardiac output, an increase in the pulmonary vascular resistance, and no change in the shunt. With the infusion of dopamine, the cardiac output returned to control; there was an increase in the shunt and a decrease in the pulmonary vascular resistance. When the dopamine was discontinued, there was a decrease in the cardiac output and the shunt to predopamine levels, but there was no change in pulmonary vascular resistance. On stopping PEEP, there was no change in the shunt but there was an increase in the cardiac output and a decrease in the pulmonary vascular resistance. These studies show that dopamine can correct the reduced cardiac output resulting from PEEP but that in doing so it produces a substantial increase in the pulmonary shunt. The rapid onset of the shunt with dopamine and the equally rapid decrease in the shunt on discontinuing dopamine suggests a redistribution of the increased pulmonary blood flow or the opening of anatomical arteriovenous shunts. Similar hemodynamic effects have been observed in man and it is suggested that those treating critically ill patients be aware of a possible increase in the shunt when dopamine is used to correct a decreased cardiac output in patients receiving PEEP.