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.