Endoluminal pulse oximetry combined with tonometry to monitor the perfusion of the sigmoid during and after resection of abdominal aortic aneurysm.

Early detection of colonic ischaemia after aortic grafting is essential if mortality is to be decreased when this complication develops. The aim of this study was to determine changes in the sigmoid colon during and after abdominal aortic grafting using endoluminal pulse oximetry (SmO2). Oxygen saturation was measured on the mucosa (SmO2) and serosa (SsO2) of 20 sequential patients undergoing elective surgery for abdominal aortic aneurysm; intramural pHi was also measured. Initially, all patients had a normal SmO2 in the sigmoid; however, before cross-clamping eight patients had a reduction in the SmO2. The pulse curve disappeared immediately after cross-clamping in 15 patients, with only five still showing a pulse curve in the sigmoid colon. Before declamping, 13 patients regained their pulse curve. The intraluminal pHi showed a large interindividual variation (2 S.D. approximately 0.4). Patients were classified into three groups according to SmO2: group A, no pulse; group B, diminished saturation (< 90%); and group C, normal saturation (> or = 90%). There was significant correlation with the pHi after cross-clamping in all groups. One patient who developed ischaemia of the sigmoid colon demonstrated a prolonged reduction in the SmO2, a decreased perioperative pHi, and an increased oxygen saturation in the inferior mesenteric vein during cross-clamping.