INCREASED VENOUS-ARTERIAL CARBON-DIOXIDE TENSION DIFFERENCE DURING SEVERE SEPSIS IN RATS

Objective: To test the hypothesis that decreases in blood flow during septic shock lead to increases in the venous-arterial PCO2 difference in a rat model of sepsis. Design: Prospective, randomized, controlled experimental study. Setting: Research laboratory. Subjects: Fifteen Sp rague-Dawley rats. Interventions: Severe sepsis was induced by cecal l igation and perforation. Ten animals were randomized to no treatment o r fluid infusion to maintain the cardiac output at baseline values. An additional five rats served as sham-operated controls. Measurements a nd Main Results: Hemodynamic measurements, arterial and central venous blood gases were obtained at baseline, and then at 3 hrs and 6 hrs af ter abdominal surgery. In the five septic rats that did not receive vo lume infusion, cardiac output decreased from 331 +/- 32 to 172 +/- 9 m L/min/kg (p < .001). This decrease in cardiac output was associated wi th an increase of 13 +/- 2 torr (1.7 +/- 0.2 kPa) in the venous-arteri al PCO2 difference (p < .001). Furthermore, the venous-arterial PCO2 g radient correlated linearly with the cardiac output in the same animal s (r(2) = 52, p < .001). In the septic animals that received volume in fusion and in sham animals, cardiac output and the venous-arterial PCO 2 remained unchanged from baseline at 6 hrs. Conclusion: We conclude t hat the increase in the venous-arterial PCO2 gradient in severe sepsis appears to be related to reductions in cardiac output.