Effect of epidural anesthesia on colorectal anastomosis: a tonometric assessment

Epidural anesthesia is believed to benefit colorectal anastomotic blood flow because of the sympathetic blockade it produces. Our purpose is to measure with tonometry the effect of epidural anesthesia on colorectal anastomotic oxygenation.

Fifteen patients operated on for rectal cancer (radical anterior resection) were monitored postoperatively using tonometers placed in the stomach (celiac trunk), transverse colon (superior mesenteric artery), and the anastomotic area during the operation. An epidural catheter was placed at L1-2, and on the first postoperative day, 8 ml of bupivacaine (0.25 percent) was administered. The anesthetic effect extended up to T-4. Intramucosal pH (pHi) at the three locations was measured before, during, and after the epidural blockade.

Gastric and transverse colon pHi increased during the epidural blockade from 7.35 +/- 0.01 to 7.41 +/- 0.01 and from 7.34 +/- 0.02 to 7.40 +/- 0.02, respectively. The anastomotic pHi decreased from 7.3 +/- 0.02 to 7.24 +/- 0.03 under the epidural and increased up to 7.34 +/- 0.02 after withdrawal of the effect on the following day. All pHi variations were statistically significant (P < 0.05, paired Student's t-test and Wilcoxon's test), because it was the comparison between gastric and transverse colon pHi with the anastomotic pHi during the epidural (P < 0.05, one-way analysis of variance and Kruskal-Wallis tests). None of the patients developed anastomotic or other complications.

Epidural anesthesia with bupivacaine causes a significant decrease in the oxygenation-perfusion state of colorectal anastomosis in comparison with the increase in other areas of the digestive tract. Further studies need to be done to see if other epidural anesthetic-analgesic protocols also worsen colorectal anastomotic blood flow.