Intraluminal pCO₂: A reliable indicator of intestinal ischemia

A reliable, objective method to determine small bowel ischemia intraoperatively has not been developed. These experiments examined the relationship between intraluminal pCO₂ (IL pCO₂), intestinal blood flow, and degree of ischemic mucosal injury. IL pCO₂ was measured with a clinical mass spectrometer using Teflon catheters calibrated in tissue mode; transmural intestinal blood flow was measured with radioactive microspheres. Anesthetized rabbits (N = 24) were cannulated for microsphere injections and mass spectrometer catheters were placed in the lumen of the small bowel. Blood flow was determined prior to superior mesenteric artery occlusion and then at 30, 60, or 180 min after occlusion. In control animals the superior mesenteric artery was not clamped. Intestinal biopsies were taken at the time of each blood flow determination and microscopic injury was graded from 1 (normal) to 4 (complete epithelial slough). There was a strong linear correlation between the IL pCO₂ and the histologic grade of injury (r = 0.778, P < 0.001). These results show that intestinal ischemia due to superior mesenteric artery occlusion causes a rapid, sustained rise in small bowel IL pCO₂ that correlates with the degree of mucosal injury. These experiments suggest that this technology may provide a superior method to assess intestinal perfusion.