Changes in regional blood flow and pCO2 gradients during isolated abdominal aortic blood flow reduction

Objective. pCO(2) gradients are used for the assessment of splanchnic regional and local mucosal blood flow changes in experimental and clinical research. pCO(2) gradients may not parallel blood flow changes because of concomitant changes in metabolism, hemoglobin, temperature, and the Haldane effect. Design and setting. A randomized, controlled animal experiment in a university experimental research laboratory. Interventions. An extracorporeal shunt with reservoir and roller pump was inserted between the proximal and the distal abdominal aorta in 16 pigs. In animals randomized to the low-flow group (n=8) splanchnic perfusion was reduced by running the roller pump. At baseline and after 45 min of stable shunt flow superior mesenteric artery, celiac trunk, spleen artery, and portal vein blood flows and regional venous-arterial and jejunal and gastric mucosal-arterial pCO(2) gradients were measured, and the respective regional O-2 consumption rates (VO2) calculated. Measurements and results. In the low-flow group all regional blood flows and the associated VO2 decreased to roughly 50% of baseline values, and hemoglobin decreased from 7.3 (4.4-9.6) g/dl to 5.7 (4.1-8.9) g/dl. Decreasing regional blood flows were consistently associated with increasing regional and mucosal pCO(2) gradients. Conclusions. During isolated reduction in abdominal aortic blood flow there is no preferential distribution to any splanchnic vascular bed and changes in regional pCO(2) gradients reflect consistently the associated blood blow changes.