SYSTEMIC AND REGIONAL PCO(2) GRADIENTS AS MARKERS OF INTESTINAL ISCHEMIA

Objective: We evaluated the response of mixed venous-arterial carbon d ioxide (pCO(2)) to severe intestinal ischaemia produced by gradual occ lusion of the superior mesenteric artery (SMA). Design: Prospective, c ontrolled, experimental study. Setting: Animal research laboratory. Su bjects: Twelve domestic pigs, Interventions: SMA blood flow was reduce d by 40 %, 70 % and 100 % from the baseline at 60-min intervals. Measu rements and main results: Haemodynamics were monitored continuously an d blood gas values were determined at 30-min intervals. During the SMA occlusion we observed the development of intramucosal acidosis, incre ased splanchnic oxygen extraction and an increased portal venous-arter ial lactate gradient indicative of splanchnic hypoperfusion and intest inal ischaemia. Intramucosal-arterial (p < 0.001), intramucosal-portal venous (p < 0.01) and portal venous-arterial (p < 0.01) pCO(2) gradie nts increased during the SMA occlusion, whereas the mixed venous-arter ial pCO(2) gradient remained unchanged. The mixed venous-arterial pCO( 2) gradient did not correlate with the intramucosal-arterial pCO(2) gr adient (r = 0.13), portal venous-arterial lactate gradient (r = 0.10) or splanchnic oxygen extraction (r = 0,14). The portal venous-arterial pCO(2) gradient correlated with the portal venous-arterial lactate gr adient (r = 0.75, p < 0.001) and splanchnic oxygen extraction (r = 0.7 9,p < 0.001), but not with the intramucosal-arterial pCO(2) gradient ( r = 0,35), Conclusion: Despite clear evidence of severe splanchnic hyp operfusion, as shown by regional hypercarbia and lactate production, t he mixed venous-arterial pCO(2) gradient did not reflect splanchnic hy poperfusion.