Utility of anesthetic block for endometrial ablation pain: a randomized controlled trial.

BACKGROUND

Second-generation endometrial ablation has been demonstrated safe for abnormal uterine bleeding treatment, in premenopausal women who have completed childbearing, in short-stay surgical centers and in physicians' offices. However, no standard regarding anesthesia exists, and practice varies depending on physician or patient preference and hospital policy and setting.

OBJECTIVE

The aim of this study was to evaluate whether local anesthetic, in combination with general anesthesia, affects postoperative pain and associated narcotic use following endometrial ablation.

MATERIALS AND METHODS

This was a single-center single-blind randomized controlled trial conducted in an academic-affiliated community hospital. A total of 84 English-speaking premenopausal women, aged 30 to 55 years, who were undergoing outpatient endometrial ablation for benign disease were randomized to receive standardized paracervical injection of 20 mL 0.25% bupivacaine (treatment group) or 20 mL normal saline solution (control group) upon completion of ablation. The study was designed to test a 40% 1-hour mean visual analog scale (VAS) pain score difference with an average standard deviation of 75% of both groups' mean VAS scores, using a 2-tailed test, a type I error of 5%, and statistical power of 80%. A sample of 36 patients per study group was required. Assuming a 15% attrition rate, the study enrolled 42 patients per study arm randomized in blocks of 2 (84 total). Two-tailed cross-tabulations with Fisher exact significance values where appropriate and Student t tests were used to compare patient characteristics. Backward stepwise regressions were conducted to control for confounding.

RESULTS

Between April 2016 and February 2017, a total of 108 women scheduled for endometrial ablation were screened (refusals, n = 21; ineligible, n = 3) to determine whether there were meaningful differences in postoperative VAS pain scores and postoperative narcotic use. Of the 84 randomized women, 2 age-ineligible women were excluded. Intent-to-treat analyses included 1 incorrect randomization (in which the provider consciously decided to provide analgesia regardless of the protocol, after which the provider was excluded from further study participation) and 3 women having no ablation because of operative difficulties. Three were lost to second-day follow-up. Treatment group patients (n = 41) experienced 1.3 points lower 1-hour postoperative VAS pain scores than the control group (n = 41, P = .02). The difference diminished by 4 hours (P = .31) and was negligible by 8 hours (P = .62). Treatment group patients used 3.6 less morphine equivalents of postoperative pain medication (P = .05). Regression analyses controlled for confounding reduced the 1-hour postoperative treatment group pain score difference to 0.8 (confidence interval [CI], -0.6 to 0.1) but slightly increased the average postoperative morphine equivalents to 3.7 (CI, -6.8 to -0.7).

CONCLUSION

This randomized controlled trial found that local anesthetic with low risk for complications, used in conjunction with general anesthesia, decreased postoperative pain at 1 hour and significantly reduced postoperative narcotic use following endometrial ablation. Further research is needed to determine whether the study results are generalizable and whether post procedure is the best time to administer the paracervical block to decrease endometrial ablation pain.