RELATIONSHIP BETWEEN OXYGEN-UPTAKE AND OXYGEN DELIVERY IN SEPTIC PATIENTS - EFFECTS OF PROSTACYCLIN VERSUS DOBUTAMINE

Objective: To compare the effects of prostacyclin (PGI2) and dobutamin e on the relationship between oxygen delivery (DO2) and oxygen uptake (VO2) in stable septic patients. Design: Prospective study using a cro ssover 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 VO 2 were calculated before and after a 20-min infusion of 5 ng/kg/min of PGI2 followed or preceded by 5 mug/kg/min of dobutamine. Measurements and Main Results: Both medications increased cardiac output significa ntly. At the dose used, PGI2 infusion reduced mean arterial pressure f rom 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 variab les. 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% t o 28.5 +/- 7.8%, p < .01). The responses to these medications were sim ilar in survivors and nonsurvivors. Conclusions: PGI2 and dobutamine a t the doses used have similar effects on oxygen extraction in critical ly ill septic patients, but dobutamine increases DO2 more consistently and is better tolerated than prostacyclin.