ASSESSMENT OF ANASTOMOTIC RELIABILITY WITH PULSE OXIMETRY IN GRADED INTESTINAL ISCHEMIA - AN EXPERIMENTAL-STUDY IN DOGS

Background/Purpose: Pulse oximetry has been proposed as an appropriate and feasible technique in the assessment of intestinal ischemia in re cent years. In this study the authors aimed to assess the reliability of anastomoses in the dog small intestine in which there is graded irr eversible ischemia as measured by pulse oxymeter. Methods: In a contro l group of four dogs, without any devascularization, three small bowel anastomoses were formed in each dog. The study group consisted of 12 dogs. In each animal three intestinal segments with different levels o f ischemia were created by ligating the marginal vessels proximally an d distally in sequence beginning from the midpoint of the segmental va scular arcade. Preanastomotic pulse oximeter readings between 80% and 90% were assigned to mild ischemia, 70% and 80% to moderate, and 60% a nd 70% to severe ischemia group. Pulse oximetry measurements were obta ined from probes applied to the antimesenteric serosal surfaces at the midpoint of small intestinal segments. A total of 48 intestinal segme nts (12 nonischemic in the control group and 36 with three different l evels of ischemia in the study group) were transected in the midpoint and anastomosed in double layers. Postanastomotic Sao(2) values were a lso noted. The anastomoses were evaluated 48 hours later macroscopical ly if there was any leakage, and biopsy specimens were obtained for hi stopathologic ischemic gradings. All results were studied statisticall y. Results: Histopathologic grades between each group were statistical ly different (P < .01 for each comparison) except for control and mild ischemia groups (P > .05), worsening as the level of ischemia increas ed. Pre-and postanastomotic pulse oximetry measurements correlated ver y well with the histological gradings(r = -0.90, P < .001 and r = -0.9 3, P < 0.001 respectively). Number of anastomotic leakages were none i n control, one in mild, nine in moderate, and 12 (all of the anastomos es) in severe ischemia groups. In the moderate ischemia group with an average preanastomotic pulse reading of 76.75%, each of the leaking an astomoses had a postanastomotic pulse measurement of lower than 70%. T he finding that the difference between histopathologic grades of contr ol and mild ischemia groups with average preanastomotic pulse measurem ents of 96% and 85%, respectively is not statistically significant ena bles us to suggest that a saturation of al least 85% is necessary for a reliable anastomosis. Conclusion: These results suggest clearly that anastomotic reliability can be predicted objectively with pulse oxime try.