JOURNAL OF SURGICAL RESEARCH 34, 3 1.5-3 18 (1983) Noninvasive Detection of Experimental Intestinal lschemia DANIEL S. RUSH, M.D.,’ JACQUELINE A. JORDON, B.A., CHRISTOPHER K. ZARINS, M.D., AND IRWIN H. ROSENBERG, M.D. Departments of Surgery and Medicine, The University of Chicago and The Pritzker School of Medicine, Chicago, Illinois 60637 Presented at the Annual Meeting of the Association for Academic Surgery, San Diego, California, November 7-10, 1982 INTRODUCTION Acute intestinal &hernia is associatedwith a mortality of more than 80% [2, 3, 14, 181. Periods of &hernia greater than 6 to 12 hr often commit the surgeon to an extensive re- section of gangrenous bowel from which few of these critically ill patients can recover [ 141. Delay in diagnosis is recognized as the major factor contributing to the high morbidity as- sociated with this condition [3]. Clearly, early detection is essential for the successful treat- ment of acute intestinal ischemia. No methods are currently available for the rapid, noninvasive screeningof patients at high risk for intestinal ischemia before substantial infarction has occurred. Findings by physical examination are not diagnostic, and when present, often indicate that the diagnosis has been made too late [ 14, 181.Other means of evaluation, including visceral arteriography [3], serum chemistries [4, 6, lo], radiologic appearance [ 161, dye dilution [7], intestinal radionuclide imaging [ 1, 11, 12, 131,and in- testinal ~xylose absorption [ 151, have not proved to be accurate and specific in the early detection of intestinal ischemia. Recent investigations into the metabolic re- quirements of the small intestine have dem- onstrated that glutamine is extracted from the mesenteric bloodstream as a primary meta- bolic substrate for cells of the small intestinal ’ To whom correspondence should be addressed at the Department of Surgery, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, La. 70112. mucosa [8, 9, 171.We have investigated the possibility of using the expiration of CO2 pro- duced from the oxidation of glutamine as a noninvasive metabolic indicator for the early detection of intestinal ischemia in an exper- imental model. MATERIALS AND METHODS Twenty fasted rats were anesthetized using 0.1 ml of Innovar-Vet (0.04 mg fentanyl and 2.0 mg droperidol) administered intramus- cularly and hydrated intravenously using D I0W (5 ml per kilo) administered via a fem- oral vein catheter. An arterial catheter was placed at the base of the tail for arterial pres- sure monitoring and pH determinations. Rats were then placed on a warming blanket to maintain core temperature at 37°C. Ten rats underwent a sham operation with laparot- omy, evisceration, and manipulation of the small intestine. In another ten rats, acute, to- tal, small intestinal ischemia was produced by ligation of the superior mesenteric artery at its origin and ligation of the small intestine with its adjacent mesentery at the ligament of Treitz and at the ileocecal valve. In both groups the bowel was then returned to the peritoneal cavity and the abdomen closed to prevent insensible fluid loss. Fifteen minutes later all rats were given an intravenous bolus of 0.5 &i of L-[U-‘4C]glutamine (0.0019 pmole of glutamine). A plastic hood was placed over the rat’s head and a pressure-con- trolled vacuum system bubbled expired air through a solution of 3 ml methylbenzeth- 315 0022-4804183 $1 SO Copyright Q 1983 by Academic Press, Inc. All rights of reproduction in any form reserved.