Surveillance to detect colonic ischemia with extraluminal pH measurement after open surgery for abdominal aortic aneurysm

Objective: Colonic ischemia (CI) is a life-threatening complication after aortic surgery. Postoperative surveillance of colonic perfusion may be warranted. The aim was to evaluate the safety and feasibility of postoperative extraluminal pH measurement (pHe) using colonic tonometry after open abdominal aortic aneurysm (AAA) repair. Methods: Before closing the abdomen after open AAA repair, a tonometric catheter was placed transabdominally in contact with the sigmoid colon serosa, similar to a drainage catheter. Extraluminal partial pressure of carbon dioxide was measured postoperatively and combined with arterial blood gas analysis, the pHe was calculated. The measurements were repeated every four hours alongside simultaneous intra-abdominal pressure measurements. The threshold for colonic malperfusion was set at pHe<7.2. Results: Twenty-seven patients were monitored, twelve operated on for ruptured AAA and fifteen for intact AAA. Four patients developed clinically significant CI requiring surgical treatment, all of which were preceded by prolonged (>5h) pHe<7.2 indicating malperfusion. A fifth patient, who during monitoring had a lowest pHe of 7.21, developed mild colonic ischemia with onset after completion of monitoring, which was successfully managed conservatively. Seven patients who had brief durations (<5h) of pHe<7.2 did not develop clinical signs of CI or any related adverse events. Conclusions: Measurements of pHe using colonic tonometry indicated malperfusion in all patients who developed clinically significant CI. Shorter duration of low pHe was well tolerated without any signs of CI. Measurement of pHe was safe and reliable for surveillance of colonic perfusion after open aortic surgery, indicating a promising technique, but larger studies are needed