Objective: To compare the effects of prostacyclin (PGI2) and dobutamine on the relationship between oxygen delivery (DO2) and oxygen uptake (VO2) in stable septic patients.
Design: Prospective study using a crossover design with alternate order of medications.
Patients: Seventeen patients with documented sepsis and a stable hemodynamic status with normal blood lactate concentrations. Eleven patients were mechanically ventilated. Eight patients eventually died.
Interventions: DO2 and VO2 were calculated before and after a 20-min infusion of 5 ng/kg/min of PGI2 followed or preceded by 5 micrograms/kg/min of dobutamine.
Measurements and main results: Both medications increased cardiac output significantly. At the dose used, PGI2 infusion reduced mean arterial pressure from 90.8 +/- 16.8 to 81.5 +/- 17.3 mm Hg (p < .01) and PaO2 from 97 +/- 25 torr to 82 +/- 22 torr (from 12.9 +/- 3.3 to 10.9 +/- 2.9 kPa) (p < .01) and increased venous admixture from 17.5 +/- 0.6% to 23.8 +/- 8.2% (p < .01). Dobutamine had no significant influence on these variables. PGI2 increased DO2 by 19% (from 470 +/- 105 to 557 +/- 117 mL/min/m2, p < .01) while dobutamine increased DO2 by 27% (from 463 +/- 103 to 589 +/- 156 mL/min/m2, p < .01). PGI2 increased VO2 by 5% (from 148 +/- 38 to 155 +/- 36 mL/min/m2) while dobutamine increased VO2 by 10% (from 146 +/- 36 to 161 +/- 41 mL/min/m2, p < .01). Accordingly, there was an identical decrease in oxygen extraction with PGI2 (from 32.4 +/- 8.2% to 28.6 +/- 7.1%, p < .01) and dobutamine (from 32.4 +/- 8.3% to 28.5 +/- 7.8%, p < .01). The responses to these medications were similar in survivors and nonsurvivors.
Conclusions: PGI2 and dobutamine at the doses used have similar effects on oxygen extraction in critically ill, septic patients, but dobutamine increases DO2 more consistently and is better tolerated than prostacyclin.