Effects of cardiovascular drugs on oxygen consumption/oxygen delivery relationship in patients with congestive heart...

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 micrograms/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.