Methoxyflurane for outpatient hysteroscopy: a randomised, double-blind, controlled trial
Description
Design: Single-centre, randomised, double-blind, placebo-controlled study. Intervention: 45 participants allocated to the treatment group received 3 ml methoxyflurane through an inhaler during their procedure. 45 patients in the control group received a placebo inhaler. Outcomes related to change in visusal analog pain scores, adverse effects and events and the requirement for supplemental inhaled pain relief.
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Steps to reproduce
The offsite research pharmacist created the randomisation schedule and prepared the identical opaque trial boxes. They used a computer-generated 1:1 sequence. Within the box there was the plastic-sealed Penthrox inhaler and a methoxyflurane vial, along with the paper with the randomisation outcome. The procedure involved at least three clinicians: the blinded hysteroscopist, the blinded nurse and the unblinded nurse who prepared the inhaler. Upon recruitment by the hysteroscopist, the box was allocated sequentially and the unblinded nurse would take it into an adjoining room to prepare the inhaler. The unblinded nurse was barred from informing anyone about the allocation, or offering the patient supplemental analgesia. Cases would receive a Penthrox inhaler with 3ml of methoxyflurane within and controls received a Penthrox inhaler with a drop of methoxyflurane on the outside (to support blinding with the typical fragrance). Procedure The procedure was performed with the patient in low lithotomy. We used a 30 degree, 4mm rigid hysteroscope (Karl Storz Germany). Room temperature Hartmann’s solution was used on a 150mmmHg pressure bag. We used no touch vaginoscopy, then hydrodilatation of the cervix. For operative procedures such as small polyps or retrieval of foreign bodies, hysteroscopic microscissors or micrograspers were applied via the working channel of the hysteroscope. For procedures like endometrial biopsies or intrauterine device insertion, we inserted a bivalve speculum vaginally. If a tenaculum needed to be placed, 34mg lignocaine and 1:1000 adrenaline (LIgnospan 1.7ml) was infiltrated to the anterior cervix via a 25-gauge needle prior to tenaculum application. We used Mirena intrauterine systems, Medgyn Endosamplers TM or Cooper Surgical Pipelles, as required. For specimens that were not retrievable with micrograspers (usually due to >1cm size), we applied a MyoSure LITE Manual Hysteroscopic Tissue Removal System. We chose the Visual Analog Scale (VAS) to record patient pain levels (8). Participants used a pen to mark along a 100mm line representing their pain severity. 0mm represented no pain and 100mm represented the worst possible pain. We analysed participants’ VAS scores according to the change from their baseline pelvic pain (9). A blinded nurse guided the participants on when to score their pain. The VAS with diagnostic procedures was taken either immediately after the scope was removed, or (if required) before the introduction of operative instruments. The participant was asked to refer to the worst pain during the procedure.