Effects of dobutamine on oxygen consumption in septic patients. Direct versus indirect determinations

Dobutamine has been proposed as a means of disclosing a pathologic oxygen supply (DO2) dependency in critically ill patients. Like other catecholamines, however, dobutamine might increase cellular metabolism, so that oxygen consumption (VO2) would increase regardless of the presence or absence of a supply dependency. This study investigated the effects of graded doses of dobutamine on VO2 in stable, septic patients. Since it has been suggested that the use of reverse Fick equation to determine VO2 can induce a spurious VO2/DO2 dependency owing to a mathematical coupling of data, we determined VO2 both by respiratory gas analysis (VO2DIR) and from the reverse Fick equation (VO2INDIR). In 12 adult patients with signs of sepsis but an otherwise stable hemodynamic status (normal blood lactate levels, and no change in vasoactive drugs or fluid administration for at least 2 h), a dobutamine infusion was administered at a dose of up to 10 micrograms/kg/min in increments of 2 micrograms/kg/min every 10 min. Complete hemodynamic and gas measurements were obtained at baseline, at each dose of dobutamine, and 20 min after discontinuation of the infusion. All of the measured parameters were similar at baseline and after discontinuation of the dobutamine infusion. Dobutamine induced a dose-related increase in the cardiac index (from 3.84 +/- 0.97 to 6.19 +/- 1.56 L/min/m2, p < 0.01) and DO2 (from 501 +/- 123 to 801 +/- 219 ml/min/m2, p < 0.01). Both VO2DIR and VO2INDIR increased, from 161 +/- 37 to 183 +/- 40 ml/min/m2 and from 140 +/- 29 to 168 +/- 42 ml/min/m2, respectively (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)