title: Assessment of gut mucosal perfusion and colonic tissue blood flow during abdominal aortic surgery with gastric tonometry and laser Doppler flowmetry.
abstract: The objective of this study was to investigate the effect of infrarenal aortic cross-clamping and unclamping on gut mucosal perfusion by gastric tonometry and on sigmoid colonic tissue blood flow by laser Doppler flowmetry during abdominal aortic surgery. This was a prospective before-and-after intervention comparison study in a university hospital of 8 male patients, aged 57-87, undergoing elective infrarenal abdominal aortic surgery. Each patient was pretreated with ranitidine. Following general anesthesia, a nasogastric tonometer was inserted into the stomach. The balloon of the tonometer was filled with 2.5 mL of normal saline for gas tension and pH analysis. This process was repeated before and after aortic cross-clamping and unclamping. Gastric mucosal pHi was calculated with the Henderson-Hasselbalch equation from the arterial Hco3- and the tonometrically measured mucosal Pco2. A laser Doppler flow probe was placed in contact with the serosa of the sigmoid colon against the mesentery after the abdomen was opened. Sigmoid colonic tissue blood flow (SCBF) was assessed by the laser Doppler flowmeter. Gastric mucosal pHi by gastric tonometry and colonic tissue blood flow by laser Doppler flowmetry were measured before and after aortic cross-clamping and unclamping. Gastric mucosal pHi decreased significantly 30 minutes after aortic cross-clamping (7.37 +/-0.07) (p < 0.01), 60 minutes after aortic cross-clamping (7.39 +/-0.08) (p < 0.05), and 30 minutes after aortic unclamping (7.37 +/-0.08) (p < 0.01), compared with pHi before aortic cross-clamping (7.50 +/-0.06). Gastric mucosal pHi increased to the original level 60 minutes after aortic unclamping (7.46 +/-0.08). Since a gastric mucosal pH above 7.35 is considered normal, these mean values of pHi were clinically insignificant. However, gastric mucosal pHi decreased below 7.32 in 5 patients during abdominal aortic surgery. Gastric mucosal pHi decreased further to 7.30 in 1 patient following aortic cross-clamping and below 7.30 in 3 patients 30 minutes after aortic unclamping. SCBF decreased significantly after aortic cross-clamping (28.1 +/-4.8 mL/min/100 g) compared with the value before aortic cross-clamping (51.9 +/-11.3 mL/min/100 g) (p < 0.01). Following aortic unclamping, SCBF returned to 41.7 +/-7.4 mL/min/100 g. It is concluded that transient episodes of significant intestinal mucosal ischemia may have been encountered occasionally in patients undergoing abdominal aortic surgery, but a sigmoid colonic tissue blood flow of 41.7 +/-7.4 mL/min/100 g was sufficient to prevent postoperative ischemic colitis regardless of whether there was ligation or no ligation of inferior mesenteric artery among the studied population since none of the patients developed clinically significant ischemic colitis.
authors.affiliation: Department of Anesthesiology, Medical College of Virginia of Virginia Commonwealth University, Richmond, VA 23298-0541, USA.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Nakatsuka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017544:Aortic Aneurysm, Abdominal / Q000601:surgery*; D001794:Blood Pressure; D002302:Cardiac Output; D012809:Colon, Sigmoid / Q000098:blood supply*; D003250:Constriction; D005260:Female; D005753:Gastric Mucosa / Q000098:blood supply*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000098:blood supply*; D007432:Intraoperative Period; D017078:Laser-Doppler Flowmetry; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies