Inhaled methoxyflurane for fracture reduction in prehospital extremity trauma: an observational review of HEMS clinical practice

Abstract Background Prehospital manipulation and reduction (M&R) of traumatic limb injuries may be required before transfer to restore alignment, reduce pain and bleeding, and limit secondary neurovascular compromise. In many systems this requires intravenous procedural sedation, which is resource-intensive and not universally available. Inhaled methoxyflurane (IMF) is a portable, self-administered analgesic used within UK HEMS, but its utility as the primary agent for prehospital M&R is not well described. Methods We performed a retrospective observational review of trauma patients attended by East Anglian Air Ambulance (1 January 2019 to 31 May 2023) who received IMF to facilitate prehospital M&R of an acute limb injury. The primary outcome was successful M&R using IMF without escalation to intravenous procedural sedation; failure was inability to reduce and/or subsequent intravenous procedural sedation. Multivariable logistic regression explored associations between success and age, sex, year, pre-reduction analgesia, and anatomical site. Data are reported as n (%), median [interquartile range], and adjusted odds ratios (aOR) with 95% confidence intervals (95% CI); analyses were performed in R. Results Of 7765 patients attended, 788 received IMF and 309 met inclusion criteria. Median age was 48 [27–67] years and 160/309 (51.8%) were male. Successful M&R was achieved with IMF in 168/309 cases (54.4%); 127/141 (90.1%) failures required intravenous sedation. Increasing age (aOR 1.03 per year; 95% CI 1.02–1.05), prior opioid alone (aOR 2.50; 1.25–5.11) or opioid with paracetamol (aOR 2.19; 1.16–4.18), and patella injuries (aOR 30.12; 5.51–564.57) were independently associated with success, while femoral and tibia/fibula injuries had lower odds of success. No clinically important adverse events were recorded. Conclusions In this observational HEMS cohort selected for a trial of IMF, just over half of patients with acute traumatic limb injuries underwent prehospital manipulation and reduction without escalation to intravenous procedural sedation. Older age, pre-reduction analgesia, and patella injury were associated with success, but these findings are non-causal and should be interpreted cautiously.