Pilot study to assess the feasibility of self-administered, low-dose methoxyflurane for cystoscopic procedures.

INTRODUCTION: Methoxyflurane (MEOF) (Penthrox™) is an inhaled, self-administered, non-opioid analgesic approved by Health Canada for the short-term relief of moderate to severe acute pain associated with trauma or interventional medical procedures. In this pilot study, we evaluated the feasibility of using MEOF as an anesthetic agent in 11 patients undergoing outpatient cystoscopic procedures.

METHODS: The average duration of the procedure was 24 (range 20-35) minutes and this included 10 minutes of administration time of the drug and five minutes of wait time before the procedure. The average monitoring time from start to end of the procedure was 23 (range 20-35) minutes and this included 15 minutes of monitoring post-procedure. On a scale of 0-10, patients on average rated the pain 4/10 (standard deviation [SD] 2.6).

RESULTS: Global performance was on average 3/4 (SD 1.3) for the patients and 3/4 (SD 1.1) for the operator. Of the 11 patients, four reported adverse events; two experienced euphoria, one experienced dizziness, and one was unable to tolerate the medication. Two patients noted their adverse events to be of moderate intensity, while the other two were of mild intensity. None of the adverse events was deemed serious.

CONCLUSIONS: Our findings in this pilot study provide proof of principle for the design of a randomized control trial to evaluate MEOF as an anesthetic in an outpatient cystoscopic procedural setting. As more urologic procedures are being performed in an outpatient setting, this may offer significant clinical benefit.