Methoxyflurane versus usual Analgesia for Prehospital Injury & Trauma

INTERVENTION: Ambulance clinicians will be randomised following initial training on trial procedures. Paramedics and EMTs will be allocated into two equal blocks, and individuals in each block randomised into intervention or control arms by the trial statistician using computer generated simple randomisation method. Participants randomised to the intervention arm will then receive training on how to use methoxyflurane (Penthrox), its side effects and adverse reaction reporting process. Methoxyflurane will be administered according to its current licence, one bottle of 3 mL PENTHROX vapourised in a PENTHROX inhaler self‐administered under supervision of a person trained in its administration. On finishing the 3 mL dose another 3 mL may be used. Dose should not exceed 6 mL in a single administration. The control arm is standard or usual analgesia administered in the East Midlands Ambulance Service NHS Trust, which is morphine (intravenous or oral), paracetamol (intravenous) nitrous oxide and oxygen (1:1) mixture (Entonox), or non‐steroidal anti‐inflammatory. Of these analgesics only Entonox can be administered by Emergency Medical Technicians as usual analgesia. CONDITION: Pre‐hospital pain management for patients in moderate to sever pain from injury or trauma ; Signs and Symptoms PRIMARY OUTCOME: Pain measured using the verbal numerical pain score (VNPS), which is used as standard method of assessment for all patients attended by East Midlands Ambulance Service NHS Trust. Baseline pain scores will be taken as standard prior to the administration of any analgesia, 5 minutes after initial analgesia and again at 30 minutes or arrival at the emergency department whichever is sooner. SECONDARY OUTCOME: 1. Incremental cost effectiveness ratio (including the drug costs, costs of associated consumables, cylinder rental, number cylinders used, refilling and maintenance costs (regarding Entonox) in addition to requirements for duplication of resources at scene (i.e. EMT crew having to call paramedic back‐up for purposes of stronger analgesic requirements) and also the necessity to take the patient to ED if given an opioid); 2. Tolerability of methoxyflurane; 3. Proportion of patients in whom pain between baseline, pain 5 minutes after administration and at final (i.e. after 30 minutes or at arrival at ED) is reduced; 4. Time to addition of second analgesic versus current standard of care (Entonox); 5. Percentage of patients with a = 30% reduction in baseline pain at first and subsequent timepoints/measurements INCLUSION CRITERIA: Ambulance staff: 1. Qualified Paramedic or Emergency Medical Technician contracted by East Midlands Ambulance Service NHS Trust Patients: 1. Adult aged 18 years and above 2. Emergency attendance by ambulance paramedic or EMT 3. In moderate to severe pain (VNPS 4‐10) due to trauma (injury) and associated pain