Inhaled methoxyflurane - an explorable alternative to nitrous oxide?

Nitrous oxide is a widely used and well-established form of inhalation sedation in dentistry. Its properties have a wide margin of safety and allow for anxious, paediatric and adult patients to receive dental treatment with minimal impact upon discharge. Nitrous oxide has drawbacks, however, including its environmental impact and need for specialist equipment. Methoxyflurane is another drug which could prove to be an alternative to nitrous oxide. Methoxyflurane's use has proved popular within emergency medicine in Australia and New Zealand for its potent analgesic effects and recognition of its anxiolytic effect. As a result, its use in invasive outpatient procedures has now become popular. Unfortunately, there is very limited evidence of its use within dentistry as a form of inhalation sedation and analgesic. A wider evidence base should be established, as methoxyflurane could prove to be an effective and environmentally friendly alternative to nitrous oxide.

Environmental impact of low-dose methoxyflurane versus nitrous oxide for analgesia: how green is the 'green whistle'?

BACKGROUND

The NHS has the target of reducing its carbon emission by 80% by 2032. Part of its strategy is using pharmaceuticals with a less harmful impact on the environment. Nitrous oxide is currently used widely within the NHS. Nitrous oxide, if released into the atmosphere, has a significant environmental impact. Methoxyflurane, delivered through the Penthrox 'green whistle' device, is a short-acting analgesic and is thought to have a smaller environmental impact compared with nitrous oxide.

METHODS

Life cycle impact assessment (LCIA) of all products and processes involved in the manufacture and use of Penthrox, using data from the manufacturer, online sources and LCIA inventory Ecoinvent. These data were analysed in OpenLCA. Impact data were compared with existing data on nitrous oxide and morphine sulfate.

RESULTS

This LCIA found that Penthrox has a climate change effect of 0.84 kg carbon dioxide equivalent (CO2e). Raw materials and the production process contributed to majority of the impact of Penthrox across all categories with raw materials accounting for 34.40% of the total climate change impact. Penthrox has a climate change impact of 117.7 times less CO2e compared with Entonox. 7 mg of 100 mg/100 mL of intravenous morphine sulfate had a climate change effect of 0.01 kg CO2e.

CONCLUSIONS

This LCIA has shown that the overall 'cradle-to-grave' environmental impact of Penthrox device is better than nitrous oxide when looking specifically at climate change impact. The climate change impact for an equivalent dose of intravenous morphine was even lower. Switching to the use of inhaled methoxyflurane instead of using nitrous oxide in certain clinical situations could help the NHS to reach its carbon emission reduction target.

Use of ketamine wafer for pain management by volunteer emergency medical technicians in rural Western Australia

OBJECTIVE

To describe the use of sublingual ketamine wafers administered by volunteer emergency medical technicians (EMTs) for pain management to patients in rural Western Australia (WA).

METHODS

This retrospective cohort study included patients older than 12 years who were attended by volunteer EMTs in Esperance, Lancelin and Kalbarri, WA and received analgesic medications from 2018 to 2021. Patients who received ketamine wafers with/without other analgesics were compared to (i) patients who received only oral paracetamol and (ii) patients who received inhalational methoxyflurane without ketamine wafers with/without paracetamol.

RESULTS

The present study included 826 patients, among whom 149 patients received ketamine wafer with/without other analgesics, 82 paracetamol only and 595 methoxyflurane with/without paracetamol. Patients who received ketamine wafers were younger (median age 49 years vs 54 years for the paracetamol group vs 58 years for the methoxyflurane group), required a longer median transport interval (56 min vs 20 min vs 8 min), trauma-related (73% vs 35% vs 54%), and presented higher median initial pain score (9 vs 3 vs 8 out of 10) than those who received paracetamol and those who received methoxyflurane, respectively. Eight in the ketamine wafers group (5.4%) had a record of nausea/vomiting after the administration of ketamine wafers.

CONCLUSIONS

Sublingual ketamine wafer was administered by volunteer EMTs without any evidence of major adverse events in rural WA and deemed useful as an additional pain management option when long transport to hospital was needed. No other symptoms that may be associated with the use of ketamine were recorded.

Literature review on the use of methoxyflurane in the management of pain in cancer-related procedures

INTRODUCTION

Self-administered methoxyflurane, also known as Penthrox, at a sub-anesthetic dose is a short-term, fast-acting, and safe analgesic that may provide suitable pain relief for cancer patients. This review aims to compile the existing evidence on methoxyflurane and its efficacy in reducing pain during cancer-related procedures.

METHODS

A literature search was conducted through OVID Medline and Embase. The search was limited to articles published between 2012 and 2021 and studies were included if they assessed the efficacy of methoxyflurane to reduce pain in cancer-related procedures. All types of cancer were included.

RESULTS

The literature search yielded seven studies published between 2012 and 2021. The studies analyzed assessed methoxyflurane use in prostate biopsy, colonoscopy, removal of brachytherapy rods, and bone marrow biopsy. Various research designs were employed, including three randomized controlled trials, two prospective observational studies, one retrospective, and one non-randomized controlled trial. In all, methoxyflurane has a demonstrated ability to reduce pain in these procedures.

CONCLUSION

In the limited studies available in evaluating the efficacy of methoxyflurane for reducing procedural pain during cancer-related procedures, all have demonstrated clinical equivalency or superiority. Pain relief appears to be equivalent however methoxyflurane overcomes the standard limitations of respiratory sedation and has demonstrated quicker procedural recovery times than traditional sedation methods. The accumulated data to date supports the use of methoxyflurane which can supplement or supplant current methods of analgesia in cancer-related procedures.

Trauma pain management in the emergency department: use of methoxyflurane as a patient-administered analgesic

Evidence suggests that pain is highly prevalent among patients with traumatic injuries who attend emergency departments (EDs), yet accurate assessment and management of patients with acute pain can be challenging in this setting. Effective and rapid pain management is beneficial for patients and can support timely discharge from the ED, which is particularly important in the context of the coronavirus disease 2019 (COVID-19) pandemic. This article describes a service development project that introduced the use of a patient-administered analgesic, methoxyflurane, for patients with traumatic injuries with moderate to severe pain in one ED. The author outlines the benefits and rationale for using methoxyflurane as a first-line analgesic in this patient group and describes the main elements of training sessions for emergency nurses and other ED clinicians in the administration and supervision of patient-administered methoxyflurane.

Evaluation of the effectiveness and costs of inhaled methoxyflurane versus usual analgesia for prehospital injury and trauma: non-randomised clinical study

BACKGROUND

We aimed to investigate clinical benefits and economic costs of inhaled methoxyflurane when used by ambulance staff for prehospital emergency patients with trauma. Comparison is to usual analgesic practice (UAP) in the UK in which patient records were selected if treatment had been with Entonox® or intravenous morphine or intravenous paracetamol.

METHODS

Over a 12-month evaluation period, verbal numerical pain scores (VNPS) were gathered from adults with moderate to severe trauma pain attended by ambulance staff trained in administering and supplied with methoxyflurane. Control VNPS were obtained from ambulance database records of UAP in similar patients for the same period. Statistical modelling enabled comparisons of methoxyflurane to UAP, where we employed an Ordered Probit panel regression model for pain, linked by observational rules to VNPS.

RESULTS

Overall, 96 trained paramedics and technicians from the East Midlands Ambulance Service NHS Trust (EMAS) prepared 510 doses of methoxyflurane for administration to a total of 483 patients. Comparison data extracted from the EMAS database of UAP episodes involved: 753 patients using Entonox®, 802 patients using intravenous morphine, and 278 patients using intravenous paracetamol. Modelling results included demonstration of faster pain relief with inhaled methoxyflurane (all p-values < 0.001). Methoxyflurane's time to achieve maximum pain relief was estimated to be significantly shorter: 26.4 min (95%CI 25.0-27.8) versus Entonox® 44.4 min (95%CI 39.5-49.3); 26.5 min (95%CI 25.0-27.9) versus intravenous morphine 41.8 min (95%CI 38.9-44.7); 26.5 min (95%CI 25.1-28.0) versus intravenous paracetamol 40.8 (95%CI 34.7-46.9). Scenario analyses showed that durations spent in severe pain were significantly less for methoxyflurane. Costing scenarios showed the added benefits of methoxyflurane were achieved at higher cost, eg versus Entonox® the additional cost per treated patient was estimated to be £12.30.

CONCLUSION

When administered to adults with moderate or severe pain due to trauma inhaled methoxyflurane reduced pain more rapidly and to a greater extent than Entonox® and parenteral analgesics. Inclusion of inhaled methoxyflurane to the suite of prehospital analgesics provides a clinically useful addition, but one that is costlier per treated patient.

[Acute pain management : the role of inhaled methoxyflurane in clinical practice]

Since 2018, a new analgesic drug has been made available in Switzerland : methoxyflurane. This halogenated gas, controlled by the patient, offers a very effective analgesic effect comparable to opiates. Known since the 1960s and used mainly in pre-hospital emergency medicine in Australia and New Zealand, its use in Europe is increasing alongside standard analgesic treatments in the traumatic setting. Administered by inhalation, it does not require an intravenous access, which is ideal in prehospital emergency situations. This treatment could be used for the management of acute pain of various origins, such as renal lithiasis, or to facilitate different procedures, such as closed fracture reduction or chest tube insertion. Its indications are growing and its use will probably become commonplace with clinicians in a near future.

Multimodal oral analgesia for non-severe trauma patients: evaluation of a triage-nurse directed protocol combining methoxyflurane, paracetamol and oxycodone

Insufficient analgesia affects around 50% of emergency department patients. The use of a protocol helps to reduce the risk of oligoanalgesia in this context. Our objective was to describe the feasibility and efficacy of a multimodal analgesia protocol (combining paracetamol, oxycodone, and inhaled methoxyflurane) initiated by triage nurse. We performed a prospective, observational study in an emergency department (Grenoble Alpes University Hospital, France) between December 2017 and April 2018. Adult non-severe trauma patients with a numerical pain rating scale (NRS) score ≥ 4 were included. The primary efficacy criterion was the proportion of patients with an NRS score ≤ 3 at 15 min. Pain intensity was measured for 60 min and during radiography. Data on adverse events and satisfaction were recorded. A total of 200 adult patients were included (median [interquartile range (IQR)] age: 32 [23-49] years; 126 men (63%)). Sixty-six patients (33%) reported an NRS score ≤ 3 at 15 min. The time required to achieve a decrease of at least 2 points in the NRS score was 10 (5-20) min. The median [IQR] pain intensity was 4 [2-5] before radiography and 4 [2-6] during radiography. Adverse events were frequent (n = 128, 64%). No serious adverse events were reported. The patients and caregivers reported good levels of satisfaction. The administration of a nurse-driven multimodal analgesia protocol (combining paracetamol, oxycodone, and methoxyflurane) was feasible on admission to the emergency department. It rapidly produced long-lasting analgesia in adult trauma patients.Trial registration: NCT03380247.

Methoxyflurane Versus Standard of Care for Acute Trauma-Related Pain in the Emergency Setting: Protocol for a Randomised, Controlled Study in Italy (MEDITA)

Introduction

Low-dose methoxyflurane, administered via a hand-held inhaler, has been used for short-term pain relief in emergency medicine in Australia and New Zealand for over 40 years, and was recently approved in Europe for the rapid relief of moderate-to-severe trauma-related pain in adults. There is currently a lack of data for methoxyflurane versus active comparators, therefore this trial will investigate the efficacy and safety of inhaled methoxyflurane compared with standard of care (SoC) in the treatment of acute trauma-related pain in pre-hospital and ED settings in Italy.

Methods

MEDITA (Methoxyflurane in Emergency Department in ITAly) is a Phase IIIb, prospective, randomised, active-controlled, parallel-group, open-label, multicentre trial. A total of 272 adult patients with moderate-to-severe pain [score ≥ 4 on the Numerical Rating Scale (NRS)] due to limb trauma will be randomised 1:1 to receive 3 mL methoxyflurane (self-administered by the patient via inhalation under supervision of a trained person) or medications that currently comprise the SoC in Italy [intravenous (IV) morphine for severe pain (NRS ≥ 7); IV paracetamol or ketoprofen for moderate pain (NRS 4–6)], administered as soon as possible after randomisation.

Planned Outcomes

Pain intensity will be measured using a 100-mm visual analogue scale (VAS) at baseline (time of randomisation) and at intervals up to 30 min. Time of onset of pain relief as reported by the patient and use of rescue medication will be recorded. The patient will rate the efficacy and the healthcare professional will rate the practicality of study treatment at 30 min after randomisation using a 5-point Likert scale. Adverse events will be recorded until safety follow-up at 14 ± 2 days. Vital signs will be measured at baseline, 10 and 30 min. The primary aim is to demonstrate non-inferiority of methoxyflurane versus SoC for the change in VAS pain intensity from baseline (randomisation) to 3, 5 and 10 min.

Trial Registration

EudraCT number: 2017-001565-25. Clinicaltrials.gov identifier: NCT03585374.

Funding

Mundipharma Pharmaceuticals srl.

Electronic supplementary material

The online version of this article (10.1007/s12325-018-0830-x) contains supplementary material, which is available to authorized users.

[Application of penthrox preparation in patients with traumatic disease]

Indications for preparation Pentrox application in injured persons, suffering traumatic disease, were substantiated. The pain syndrome dynamics while conducting analgesia, was investigated, using simple verbal scale.

Is methoxyflurane a suitable battlefield analgesic?

Anecdotal reports of mechanical failure of morphine autojets have triggered a review of possible alternatives. Methoxyflurane is one such alternative already widely used by the Australian and New Zealand Defence Forces. The potential benefits and likely significant drawbacks of methoxyflurane are reviewed with the aim of stimulating discussion.

A pilot study of inhaled methoxyflurane for procedural analgesia in children

BACKGROUND

Methoxyflurane (MF), a potent volatile anesthetic, can be used as an analgesic in subanesthetic concentrations. In Australia, MF is extensively used in children and adults as an analgesic in the prehospital setting via a hand-held inhaler device. We conducted a pilot study to explore its use as a patient controlled analgesic for painful procedures in children in the emergency department (ED).

METHODS

This is a prospective observational case series of children aged 5 years and older requiring procedural analgesia for brief painful procedures. Pain scores, depth of sedation, adverse events and patient, parent and staff satisfaction were assessed as well as consumption of MF measured.

RESULTS

Fourteen patients (aged 6-13 years) received MF mainly for extremity injuries. Amount of MF consumed ranged from 0.36 to 3.06 g per patient inhaled over 4-25 min. There were no serious adverse events. No patient was deeply sedated. Five patients had mild brief self-resolving adverse events including agitation, euphoria, blurry vision, dizziness and cough. Four patients with fractures with initial high pain scores (> or =6) received MF for bridging analgesia with large drops in pain scores. Four patients who required fracture reductions with initial low scores did not achieve adequate analgesia. The remaining six patients had painful procedures undertaken with satisfactory analgesia.

CONCLUSIONS

On the basis of this small pilot study of MF use in children in the ED, this agent appears to be a powerful analgesic. MF seems most useful as a self-titrated bridging analgesic agent in patients after extremity trauma. It appears less useful as a procedural agent when patients are unable to anticipate and achieve a sufficient level of analgesia before painful stimulus infliction. Pre- and intraprocedure coaching is an important aspect of its use especially if initial pain scores are low.

Energy metabolism in anesthetized children with burns

Energy dynamics in 10 burned children were studied to determine cause and effect relationships between rates of heat production, heat loss and plasma catecholamine concentrations when thermoregulatory responses were depressed by methoxyflurane anesthesia. Rapid cooling of the burned children was due to increased heat loss during the period of anesthesia. Heat production increased significantly, although not enough to counterbalance the increased heat loss reflecting a block in central thermoregulation by general anesthesia. Mean plasma catecholamine concentrations decreased during general anesthesia as compared with baseline values. Heat production attempted to track heat loss during a period in which plasma catecholamine levels declined. An increased rate of heat loss is concluded to be primary stimulus for increased metabolic acitvity after thermal injury.

Methoxyflurane analgesia for burns dressings

The requirements for analgesia for burns dressings are discussed.

Methoxyflurane has proved satisfactory in a clinical trial, and can be administered by one of two types of vaporizer.

The possibility of nephrotoxicity due to methoxyflurane has not been eliminated.