Sigmoid intramural pH for prediction of ischemic colitis during aortic surgery. A comparison with risk factors and inferior mesenteric artery stump pressures.

We compared intramural pH (pHI) measured through a silicone balloon placed in the lumen of the sigmoid colon with risk factor analysis and inferior mesenteric artery (IMA) stump pressures as predictors of ischemic colitis in 34 patients undergoing elective or emergency operations on the abdominal aorta. All patients had preoperative and postoperative flexible sigmoidoscopy, IMA stump pressure measurements, and serial measurements of pHI. Logistic regression analysis showed that aortic aneurysm, age, and stenosis of the superior mesenteric artery were the only risk factors that bore a statistical relationship to ischemic colitis. Ligation of a patent IMA did not increase the likelihood of ischemic colitis. The IMA stump pressure criteria for predicting ischemic colitis were absent in nine of the ten patients in whom ischemic colitis developed and were present in five of the 24 in whom it did not develop. Intraoperative pHI dropped below 6.86 in all three patients in whom severe ischemic colitis developed. Mild colitis developed in seven patients whose minimum pH was 6.99 +/- 0.12 (mean +/- SD). No colitis developed in the remaining 24, whose minimum pH was 7.21 +/- 0.13. Thus, stump pressure is not a reliable means of predicting ischemic colitis. Aortic aneurysm, age, and superior mesenteric artery stenosis were significant risk factors. The average minimum intraoperative pHI and its duration were the best predictors for the development of ischemic colitis.