Cardiorespiratory responses to an i.v. infusion of dobutamine in the intact anaesthetized dog.

The cardiorespiratory responses to an i.v. infusion of dobutamine hydrochloride were assessed in eight anaesthetized, mechanically ventilated dogs. As the rate of infusion of dobutamine was increased from 2 to 30 microgram kg-1 min-1, there was a progressive decrease in arterial pressure, pulmonary wedge pressure and arterial pH. There was a significant decrease in arterial oxygen tension at the greater doses of dobutamine (15 and 30 microgram kg-1 min-1) from initial control values. Carbon dioxide output, arterial carbon dioxide tension, venous admixture and oxygen consumption increased during the infusion of dobutamine. However, oxygen supply increased further so that the oxygen consumption; supply ratio decreased. It is concluded that dobutamine may decrease arterial oxygen tension, but that the increased cardiac output and decreased arterial pH produced by dobutamine may increase oxygen supply to the tissues in spite of this.