A comparative study of extra- and intraluminal sigmoid colonic tonometry to detect colonic hypoperfusion after operation for abdominal aortic aneurysm

Objectives: There is no ideal method to monitor colonic perfusion after abdominal aortic aneurysm (AAA) repair. The aim was to evaluate extraluminal sigmoid colon tonometry, comparing with the established intraluminal method.

Methods: Eighteen patients were monitored with both methods, 10 after elective and eight after ruptured AAA repair. One tonometric catheter was placed inside the sigmoid colon (intraluminal) and another extraluminally in close contact with the serosa of the sigmoid colon (extraluminal). Intra- and extraluminal partial pressure of carbon dioxide (pCO(2)) were measured every 10 min during 48 h postoperatively, 1536 simultaneous measurements. Intraluminal pH (pHi) and extraluminal pH (pHe) were calculated, and intra-abdominal pressure (IAP) was measured, every 4 h. Colonic ischaemia was defined as pHi ≤ 7.1.

Results: Mean pHi was 7.18 ± 0.11 and mean pHe was 7.28 ± 0.09. With a pHe cut-off value of ≤ 7.2, the sensitivity and specificity to detect colonic ischaemia were 95% and 95%, respectively. Accuracy was 95% and the positive and negative predictive values 0.80 and 0.99, respectively. The positive likelihood ratio was 19 and the negative likelihood ratio 0.05.

Conclusion: Extraluminal tonometry may serve as a screening test: A pHe-value < 7.2 indicates suspected colonic ischaemia, meriting further investigation. It was not able to evaluate the severity of ischaemia.