Intramucosal-Arterial Pco2 Gradient Does Not Reflect Intestinal Dysoxia in Anemic Hypoxia

BACKGROUND:An increase in intramucosal-arterial Pco2 gradient (ΔPco2) might be caused by tissue hypoxia or by diminished blood flow. Our hypothesis was that ΔPco2 should not be altered in anemic hypoxia with preserved blood flow. METHODS:In 18 anesthetized, mechanically ventilated sheep, oxygen transport was stepwise reduced by hemorrhage (hypovolemia, n = 9) or by hemorrhage and simultaneous dextran infusion (hemodilution, n = 9). RESULTS:Hypovolemia and hemodilution produced comparable decreases in systemic and intestinal oxygen transport and uptake. However, mixed venoarterial and mesenteric venoarterial Pco2 gradients and ΔPco2 were significantly higher in hypovolemia than in hemodilution (25 ± 5 vs. 10 ± 2 mm Hg; 21 ± 6 vs. 10 ± 5 mm Hg; and 41 ± 18 vs. 14 ± 9 mm Hg, respectively; p < 0.01). CONCLUSION:ΔPco2 did not reflect intestinal dysoxia during Vo2/Do2 dependency attributable to hemodilution. Blood flow seems to be the main determinant of ΔPco2.