Methoxyflurane analgesia for outpatient hysteroscopy: A double-blind, randomised, controlled trial

Despite clinical and economic benefits, pain during outpatient hysteroscopy (OPH) remains a barrier to use. There is a lack of evidence to support routine use of one analgesic over another versus no analgesic.

To study the efficacy and safety of methoxyflurane analgesia during OPH.

A single-centre, randomised, double-blind, placebo-controlled experiment was performed; 90 patients were randomly assigned (1:1). Participants allocated to the treatment group (cases) received 3 mL of methoxyflurane through an inhaler. The control group received a placebo. The primary outcome was a mean difference in pain, via a change in Visual Analog Scale (VAS) score from baseline at diagnostic hysteroscopy. Secondary outcomes were a mean difference in VAS score with any subsequent operative procedures; a mean difference in VAS score at 15 min post-procedure; participant and clinician-reported adverse effects and events; and participant-reported procedure acceptability, adjuvant nitrous oxide (N₂O₂) use and a composite of 'distress'.

During diagnostic hysteroscopy, there was a mean difference of 11.5 mm/100 (95% confidence interval (CI) 0.08-22.95), P = 0.05, with the lower score in the cases, compared with controls. During subsequent operative procedures, there was a mean difference of 15 mm/100 (95% CI 2.71-28.22), P = 0.02, with the lower pain score in the cases, compared with controls. There was no significant difference in pain 15 min post-procedure, participant- and clinician- reported adverse effects and events, procedure acceptability and the 'distress' composite.

Methoxyflurane significantly reduced pain during OPH compared with placebo, for diagnostic as well as operative procedures. Furthermore, methoxyflurane was well tolerated, with no adverse events.