(115) RANDOMIZED CONTROLLED TRIAL OF METHOXYFLURANE AND LOCAL ANESTHESIA VS. LOCAL ANESTHESIA ONLY FOR SCROTAL SURGERY
Authors: Shah J , Chung D , Dhillon H , Fidel M , Bal D , Roque C , Ko Y , Patel P 
Published: December 2024

Abstract

Introduction
There is a growing recognition within urologic care of the benefits of utilizing procedures performed under local anesthesia in an ambulatory setting. This approach not only mitigates the risks associated with general or spinal anesthesia but also addresses concerns related to increased wait times and enhances accessibility for patients. Building upon previous research indicating the viability of local anesthesia (LA) in penoscrotal procedures, there is a growing interest in exploring complementary approaches to further optimize patient outcomes. However, despite the efficacy of LA alone, factors such as needle phobia, anxiety, and prior negative experiences can impact its effectiveness. Short-acting, inhaled anesthetics like methoxyflurane have shown efficacy in trauma care and as an anxiolytic during medical procedures, especially at low doses. They provide advantages such as enabling spontaneous ventilation and maintaining airway reflexes, with a faster onset and longer-lasting analgesic effects compared to nitrous oxide. This makes methoxyflurane particularly advantageous for ambulatory surgery.

Objective
This randomized controlled trial aims to investigate whether incorporating inhaled methoxyflurane as an adjunct to LA improves pain tolerance and reduces anxiety levels compared to LA alone.

Methods
Patients aged 18-65 undergoing scrotal procedures (hydrocelectomy, spermatocelectomy, epididymectomy) are eligible for recruitment. Exclusion criteria include a history of substance use disorder, renal impairment, liver dysfunction, hypersensitivity to methoxyflurane or related agents, and personal or family history of malignant hyperthermia. Participants will be randomly assigned to either the LA-only control group (administered with a 50/50 lidocaine and bupivacaine mixture) or the methoxyflurane + LA group. Baseline demographics will be collected with a validated 6-question STAI short form for anxiety assessment, and self-reported pain levels and scrotal procedure history. Post-procedure, participants will immediately rate procedural pain and anxiety levels, with follow-up assessments for adverse events conducted 2-4 weeks later. Data analysis will employ descriptive statistics and Welch’s t-tests to evaluate outcomes. This study is expected to be completed in September of 2024.

Results
A total of 12 patients have been recruited thus far with an average age of 65.3 ± 13.6 in the methoxyflurane group (n = 7) and 39.0 ± 12.6 in the control group (n = 5, p = 0.007). Baseline pain levels self-reported by the methoxyflurane group averaged 1.1 ± 2.3, while the control group reported 2.4 ± 2.3 (p = 0.37) on a scale of 1 (no pain), 10 (maximal pain). Similarly, baseline anxiety levels, as measured by the STAI, were 10.7 ± 3.5 for the methoxyflurane group and 11.6 ± 5.4 for the control group (p = 0.76) on a scale of 4 to 24. During the procedure, the methoxyflurane group reported procedural pain and anxiety levels of 0.28 ± 0.75 and 0, respectively, compared to 1.4 ± 1.7 and 1.6 ± 1.7 in the control group (p = 0.22, p = 0.09). No adverse events were reported. Post-procedural follow-up calls are scheduled as more participants become eligible within the designated timeframe.

Conclusions
Our pilot study endeavours to shed light on the potential benefits of incorporating methoxyflurane as an adjunct to LA for scrotal procedures. Our preliminary results demonstrate safety of methoxyflurane with no adverse events reported.

Disclosure
Any of the authors act as a consultant, employee or shareholder of an industry for: Boston Scientific.