Cardiac index vs oxygen-derived parameters for rational use of dobutamine in patients with congestive heart failure

In patients with congestive heart failure (CHF), catecholaminergic agents may exert thermogenic effects that limit their beneficial effects in terms of global tissue oxygenation. Oxygen extraction ratio (O2ER) or mixed venous blood saturation (SvO2) might take into account better than cardiac index (CI) the resultant effect of such agents on peripheral oxygenation. We tested this hypothesis in a series of 20 patients with severe CHF and normal blood lactate levels undergoing pulmonary artery catheterization and receiving incremental doses of dobutamine: 0 (Do), 5 (D5), 10 (D10), and 15 micrograms/kg/min (D15). A significant dose-effect relationship (p < 0.01) was found between dose of dobutamine and CI (CI = 0.06 dose + 1.82). By contrast, no dose-effect relationship was observed between dobutamine dose and either O2ER or SvO2. Indeed, a biphasic profile was observed for O2ER and SvO2. From D0 to D10, O2ER decreased (from 45 +/- 6 to 35 +/- 7 percent) and SvO2 increased (from 52 +/- 7 to 62 +/- 7 percent). From D10 to D15, no further change was observed for both parameters. This latter finding was related to a significant increase in VO2 at D15 (p < 0.01). In these normolactatemic patients with unchanged VO2 from D0 to D10 while DO2 linearly increased (from D0 to D15), the increase in VO2 at D15 was probably due to an increase in oxygen demand induced by the drug. Our results suggest that dobutamine at a dose of 15 micrograms/kg/min can induce an increase in O2 demand that might offset the improvement in CI. Thus, in patients with CHF, oxygen-derived parameters such as O2ER and SvO2 should be more appropriate than CI to assess the efficacy of dobutamine.