Perioperative Topical Nitrate and Sphincter Function in Patients Undergoing Transanal Stapled Anastomosis: A Randomized, Placebo-Controlled, Double-Blinded Trial

PURPOSE: The use of transanal stapling devices may impair continence because of digital dilatation and/or instrumentation. This study assessed the effect of pharmacological dilatation of the sphincter prior to stapler insertion. METHODS: A randomized, placebo-controlled, double-blinded study of 60 patients undergoing transanal stapled anastomosis was undertaken. Consenting patients were randomly assigned to receive a single intraoperative dose of topical 0.2 percent nitroglycerin (glyceryl trinitrate) ointment or nitroglycerin-free placebo. All patients were assessed preoperatively and postoperatively by clinical methods (Wexner incontinence scores and examination), anorectal manometry by a station pull-through technique, and endoanal ultrasonography. RESULTS: Intraoperative mean (±SEM) resting pressures (mmHg) were significantly reduced by nitroglycerin compared with prenitroglycerin levels (9.9 ± 0.9 vs 50.5 ± 2.7; P = 0.002) or controls (56.0 ± 3.2; P = 0.001). Twenty-one of the 28 controls (75 percent) but only 4 of the 32 patients in the nitroglycerin group (12.5 percent) required digital dilatation to insert the stapling instrument (P = 0.003). Squeeze pressures were unaltered by the intervention but mean resting pressures were higher in the nitroglycerin group postoperatively (52.9 ± 3.2 - 31. 6 ± 1.3 = 21.3 mmHg; 95 percent confidence interval, 14-27). Incontinence scores were lower in the nitroglycerin group at the 3-month (1.1 ± 0.2 vs. 4.6 ± 0.3; P = 0.003) and 12-month (0.9 ± 0.1 vs. 4.4 ± 0.3; P = 0.002) clinic visits. CONCLUSION: Preoperative nitroglycerin dilatation protects sphincter function in patients undergoing transanal stapled anastomoses.