Impact of Anesthesia Agents and Patient Factors on Postoperative Urinary Retention Following Urethral Polyacrylamide Hydrogel Injection for Urinary Incontinence

INTRODUCTION: Urethral polyacrylamide hydrogel injection (Bulkamid™) is used to treat stress urinary incontinence (SUI) or stress-predominant mixed urinary incontinence. This procedure can be performed in-office with local anesthesia or in the operating room with monitored anesthesia care (MAC). A well-known complication of this procedure is immediate postoperative urinary retention (POUR) with reported rates as high as 20%. Prior literature suggests that MAC may be a risk factor for POUR. OBJECTIVE: The objective of this study was to characterize immediate POUR in patients who underwent MAC during polyacrylamide hydrogel injection. METHODS: A retrospective review was conducted on women over 18 years old who underwent urethral polyacrylamide hydrogel injections (Bulkamid™) for SUI or stress-predominant mixed urinary incontinence between January 2021 to December 2023 at a single tertiary care center under MAC. Patients who underwent any concurrent procedure at the time of urethral bulking were excluded. Immediate POUR was defined as the inability to void after four hours of passive filling necessitating placement of a 10 French Foley catheter. Comparisons were made using Fisher’s exact test and Chi2 test as appropriate for nominal variables, and Mann–Whitney test for continuous variables. RESULTS: One hundred and six patients met inclusion criteria (Table 1). POUR was identified in twenty-four patients (22.6%). The average amount retained upon straight catheterization was 486.3±155.8 mL. Concurrent use of an overactive bladder medication, prior intradetrusor botulinum toxin, sacral neuromodulation, or midurethral sling did not appear to increase the risk of POUR (Table 2). Lower body mass index (BMI) was significantly associated with POUR (25.8±4.6 vs 30.6±6.8, p=0.001). There was a trend towards older age (65.5±15.1 vs 59.3±14.3, p=0.064). The use of intraoperative anesthetics, including propofol, midazolam, or fentanyl, did not significantly affect rates of POUR (p=0.91, 0.81, and 0.89, respectively). A subset of 26 patients received a paralytic (rocuronium) intraoperatively, with 14 receiving a reversal agent (sugammadex) at the conclusion of the case. Neither the use of rocuronium nor sugammadex was associated with risk of immediate POUR (p=0.27, 0.58). On multivariate analysis, after controlling for parity, prior treatments, and anesthetic use, BMI ≤ 25 was associated with 4.5-fold increased risk of POUR (p=0.02) and age ≥65 was associated with 2.8-fold increased risk of POUR (p=0.09). CONCLUSIONS: A BMI ≤25 may be a notable risk factor for immediate POUR following urethral polyacrylamide hydrogel injection. There were no statistically significant differences in risk for immediate POUR based on the anesthesia medication received intraoperatively. The use of a neuromuscular blockade with or without reversal agent did not appear to impact rates of POUR. Age ≥65 may be associated with POUR, but this did not reach statistical significance. Further studies are needed to elucidate if other aspects are associated with urinary retention.Table 1Table 2