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

Abstract

Background: 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.

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

Materials and methods: 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'.

Results: 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.

Conclusions: 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.