EFFECTS OF CARDIOVASCULAR DRUGS ON OXYGEN-CONSUMPTION OXYGEN DELIVERY RELATIONSHIP IN PATIENTS WITH CONGESTIVE-HEART-FAILURE

The oxygen consumption (Vo2)/oxygen delivery (Do2) relationship was analyzed in ten patients with severe congestive heart failure (CHF) and normal blood lactate levels. First dobutamine and then enoximone, after a washout period, were administered to each patient to increase cardiac output by at least 15 percent. Similar increases in Do2 were obtained with both drugs: from 285+/-46 to 393+/-87 ml/min/m2 for dobutamine, and from 285+/-54 to 392+/-99 ml/min/m2 for enoximone. However, while Vo2 did not change (132+/-24 vs 132+/-21 ml/min/m2) (Vo2/Do2 independency) with a dobutamine infusion (mean dose of 10+/-2-mu-g/kg/ min), a significant increase in Vo2 from 134+/-22 to 157+/-21 ml/min/m2 was observed with a bolus infusion of enoximone (mean dose of 1.7+/-0.5 mg/kg). These results, observed in patients with CHF without patent oxygen debt, suggest that an artefactual Vo2/Do2 dependency might be induced by the cardiovascular drug used to elevate Do2, probably because of a drug-induced oxygen demand increase.