Procedural Pain and Choice of Anesthetic at Time of Polyacrylamide Hydrogel Injections for Stress Urinary Incontinence: A Randomized Controlled Trial

INTRODUCTION: Urethral bulking with polyacrylamide hydrogel (PAHG) is an FDA-approved treatment for stress urinary incontinence (SUI) due to intrinsic sphincter deficiency (ISD). While manufacturer-provided instructions recommend placement of intra-urethral anesthetic gel and/or injection of local anesthesia into the paraurethral tissues prior to injection, there is no evidence guiding preferential use of either method, and no studies have assessed how procedural anesthesia may affect the efficacy of PAHG injection, need for post-procedure catheterization or rate of PAHG re-injection. Although limited data supports the use of topical anesthesia for other in-office urogynecologic procedures, prior studies have not compared anesthetic methods for pain control. OBJECTIVE: To compare patient-reported pain scores between control (the use of topical anesthetics and paraurethral block) versus experimental (topical anesthetics alone) cohorts in women undergoing PAHG injection for the treatment of SUI and/or ISD. METHODS: This single-blinded randomized controlled trial included adult women without chronic pain conditions undergoing PAHG injection in the outpatient clinic setting of a single academic institution from 09/2023 to 08/2024. Participants were randomized to one of two anesthetic protocols: 1) control (external topical lidocaine plus prilocaine (EMLA) cream, intraurethral topical lidocaine gel, and lidocaine paraurethral block) or 2) experimental (external topical EMLA cream and intraurethral topical lidocaine gel alone). Participants were blinded to their randomization through a mock injection protocol. Pre- and post-procedural pain scores were measured using a 10-point visual analog scale (VAS). Patients unable to void post-procedure underwent catheterization with a 10-French straight catheter to remove half of bladder contents before reattempt. If still unable to void, a 12-French indwelling catheter was placed. Secondary outcomes included International Consultation on Incontinence Questionnaire–Urinary Incontinence (ICIQ-UI) scores and Patient Global Impression of Improvement (PGI-I) scores for SUI. Using pilot study data, a sample size of 52 patients was estimated to detect a difference of 1.5 between cohorts in post-procedure VAS score. A safety endpoint of 3 patients in the experimental arm requiring early termination of the procedure due to pain was set prior to study initiation. RESULTS: In total, 23 participants were enrolled (see Table 1 for participant characteristics). The study was stopped early due to meeting of the predefined safety endpoint. No patients in the control arm required early termination. The mean post-procedural VAS score was 4.5 ± 2.7 for the control arm versus 7.4 ± 2.3 for the experimental arm (p=0.002). For the three patients requiring early termination of the procedure, mean procedure-associated VAS scores were reduced from 10.0 ± 0.0 to 4.0 ± 2.6 following paraurethral block (p=0.04). There was no difference between the treatment arms with respect to procedure duration, need for PAHG re-injection, ICIQ-UI score at 2 and 12 weeks post-procedure, or PGI-I score for SUI at 2 and 12 weeks post-procedure. Participants in the experimental arm were more likely to require straight catheterization to facilitate voiding in-office (33.3% vs 0%; p=0.035) with no difference in home catheterization. CONCLUSIONS: This study presents compelling data to support the use of a paraurethral block in conjunction with topical anesthetics at the time of PAHG injection.