Inferior mesenteric artery stump pressure: a reliable index for safe IMA ligation during abdominal aortic...

Fifty-two patients undergoing nonemergent abdominal aortic aneurysmectomy were prospectively studied to determine when the inferior mesenteric artery (IMA) could be ligated without subsequent development of ischemic colitis. Cannulation of the severed distal IMA for blood pressure measurement (IMA stump pressure) before and after aortic reconstruction was attempted in all and possible in 39 individuals. In 13 the IMA was thrombosed precluding pressure measurement. Prereconstruction and postreconstruction mean IMA stump and systemic arterial blood pressure measurements were computed and mean IMA/systemic pressure ratios were calculated. All patients underwent postoperative colonoscopy. One patient developed postoperative ischemic colitis. Her postreconstruction ratio was 0.37 and her postreconstruction mean IMA blood pressure was 33 mmHg, the only individual with a ratio and pressure less than 0.40 and 40 mmHg, respectively. Internal iliac arterial pulsations could not be restored in two patients. Although postresection indices were less than preresection indices in both, postresection indices were greater than 0.40 and 40 mmHg. In this study, if the IMA was thrombosed or if postresection pressures and ratios measured greater than 40 mmHg and 0.40 respectively, ischemic colitis did not develop following abdominal aortic aneurysmectomy. This simple test may prove useful in identifying patients at risk for developing postoperative ischemic colitis or if IMA revascularization is required.