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Does Inhaled Methoxyflurane Implement Fast and Efficient Pain Management in Trauma Patients? A Systematic Review and Meta-Analysis.

ABSTRACT:

Introduction

Evidence on the use of inhaled methoxyflurane in the management of trauma pain is conflicting and obfuscated. This study aimed to determine the efficacy and safety of inhaled methoxyflurane for trauma pain on the basis of published randomized controlled trials (RCTs).

Methods

RCTs assessing the efficacy of methoxyflurane in adults or adolescents with acute trauma pain published in PubMed, Web of Science, Embase, Cochrane Library, and Google Scholar were searched. The control groups were those that received placebo or standard analgesic treatment (SAT). The primary outcome was the change from baseline in pain scores during the first 30 min of treatment. Secondary outcomes included time to first pain relief, the proportion of patients experiencing pain relief, rescue analgesia rate, the treatment satisfaction of patients and investigators, and the methoxyflurane-related treatment-emergent adverse events (TEAEs).

Results

A total of nine RCTs (1806 patients) were identified. Results revealed that methoxyflurane provided a clinically unimportant benefit by improving the mean difference of change from baseline in pain intensity (from - 0.44 to - 1.23 cm, p < 0.001) at various time points within the first 20 min compared to control treatment. Besides, methoxyflurane decreased the time of onset of pain relief (mean difference - 5.29 min; 95% CI - 6.97 to - 3.62) and the proportion of patients who needed rescue analgesic medication (risk ratio 1.41; 95% CI 1.17-1.70) despite it increasing the risk of non-severe TEAEs (risk ratio 3.09; 95% CI 1.72-5.57). Notably, the benefit of almost all secondary pain-related outcomes was rendered clinically nonsignificant between methoxyflurane and SAT strata besides the time of onset of pain relief. The quality of evidence was low or very low in all outcomes.

Conclusions

In emergency situations without effective therapy, this systematic review and meta-analysis provides low-quality evidence that methoxyflurane can be used as a rapid-acting and effective treatment for acute trauma pain, although its utilization is associated a risk of non-severe TEAEs. However, the current evidence does not support the notion that inhaled methoxyflurane offered superior analgesic efficacy to SAT.

Clinical trial number

PROSPERO registration number CRD42020223000.

SUBMITTER: Liu H

PROVIDER: S-EPMC8119536 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Methoxyflurane is an inhaled analgesic administered via a disposable inhaler which has been used in Australia for over 40 years for the management of pain associated with trauma and for medical procedures in children and adults. Now available in 16 countries worldwide, it is licensed in Europe for moderate to severe pain associated with trauma in conscious adults, although additional applications are being made to widen the range of approved indications. Considering these ongoing developments, we reviewed the available evidence on clinical usage and safety of inhaled analgesic methoxyflurane in trauma pain and in medical procedures in both adults and children. Published data on methoxyflurane in trauma and procedural pain show it to be effective, well tolerated, and highly rated by patients, providing rapid onset of analgesia. Methoxyflurane has a well-established safety profile; adverse events are usually brief and self-limiting, and no clinically significant effects on vital signs or consciousness levels have been reported. Nephrotoxicity previously associated with methoxyflurane at high anesthetic doses is not reported with low analgesic doses. Although two large retrospective comparative studies in the prehospital setting showed inhaled analgesic methoxyflurane to be less effective than intravenous morphine and intranasal fentanyl, this should be balanced against the administration, supervision times, and safety profile of these agents. Given the limitations of currently available analgesic agents in the prehospital and emergency department settings, the ease of use and portability of methoxyflurane combined with its rapid onset of effective pain relief and favorable safety profile make it a useful nonopioid option for pain management. Except for the STOP! study, which formed the basis for approval in trauma pain in Europe, and a few smaller randomized controlled trials (RCTs), much of the available data are observational or retrospective, and further RCTs are currently underway to provide more robust data.

Project description:BackgroundMore than 75% of patients presenting to the Emergency Department are suffering symptoms of pain. Despite this, 67% will not receive any analgesia. Methoxyflurane is a fluorinated hydrocarbon gas which has analgesic properties when inhaled. Penthrox is a methoxyflurane autoinhaler recently licenced in Europe. Its ease of administration, safety, and fast onset of action make it of particular relevance to emergency medicine. Additionally, outside the hospital, it has the advantage of increased temperature stability and portability over current standard care. New evidence of its efficacy is emerging; however, currently, its use in Europe is not widespread. The objective of this study will be to systematically evaluate the evidence on inhaled methoxyflurane to determine if it is a superior analgesia in the acute trauma setting.MethodsWe designed and registered a study protocol for a systematic review and meta-analysis on randomised controlled trials, comparing inhaled methoxyflurane and either placebo or standard care. A comprehensive search will be conducted from database inception onwards in MEDLINE, Embase, and the Cochrane CENTRAL database, concurrent with a search of the grey literature for other relevant studies, including clinical trial databases. Only randomised controlled trials will be included. No limitations will be imposed on publication status or language of publication. The primary outcome will be mean difference in patient-reported pain at time points within the first 30 min of administration. Secondary outcomes will be mean difference in time to clinically significant pain relief and relative risk of adverse effects. Two reviewers will independently screen all returned studies and collect data. Disagreements will be resolved through discussion or referral to a third reviewer. Individual study methodological quality will be appraised using an appropriate tool. If feasible, we will conduct a random effects meta-analysis; if this is not possible, we will construct a narrative synthesis.DiscussionThis systematic review will summarise the best available evidence and definitively establish if inhaled methoxyflurane is a superior analgesia to standard care in the acute trauma setting. This knowledge will directly impact emergency care in the UK and worldwide and may require amendments to European pain relief guidelines.Systematic review registrationPROSPERO CRD42020189119 .

Project description:Purpose:Opioid analgesics remain the cornerstone of treatment for severe trauma pain in the emergency setting, but there are barriers to their use. This post hoc analysis of a previously reported trial (MEDITA) investigated the efficacy and safety of low-dose methoxyflurane versus intravenous (IV) morphine for severe trauma pain. Patients and Methods:MEDITA was a Phase IIIb, randomized, active-controlled, parallel-group, open-label study in Italian pre-hospital units and emergency departments (EudraCT: 2017-001565-25; NCT03585374). Adult patients (N=272) with moderate-to-severe trauma pain (score ?4 on the Numerical Rating Scale [NRS]) were randomized 1:1 to inhaled methoxyflurane (3 mL) or standard analgesic treatment (SAT; IV paracetamol 1g or ketoprofen 100mg for moderate pain [NRS 4-6] and IV morphine 0.1mg/kg for severe pain [NRS ?7]). Analyses were performed for the severe pain subgroup. The primary efficacy variable was the overall change from baseline in visual analog scale (VAS) pain intensity at 3, 5 and 10min post-randomization. Non-inferiority of methoxyflurane versus morphine was concluded if the upper 95% confidence interval (CI) for the treatment difference was <1; superiority was concluded if the upper 95% CI was <0. Results:Ninety-three patients (methoxyflurane: 49; SAT: 44) were included in the severe pain intention-to-treat population. The reduction in VAS pain intensity over the first 10min was superior for methoxyflurane versus morphine (adjusted mean treatment difference: -5.54mm; 95% CI: -10.49, -0.59mm; p=0.029). Median time to onset of pain relief was 9min for methoxyflurane and 15min for morphine. Patients rated treatment efficacy and physicians rated treatment practicality "Excellent" or "Very good" for more methoxyflurane-treated patients (42.8% and 67.3%) than morphine-treated patients (18.1% and 22.8%). Adverse events, all non-serious, were reported in 20.4% of methoxyflurane-treated patients and in 4.8% of morphine-treated patients. Conclusion:Methoxyflurane provided superior short-term pain relief to IV morphine in patients with severe trauma pain and offers an effective non-narcotic treatment option.

Project description:PurposeAcute trauma pain management in the elderly population is a challenge. Inhaled methoxyflurane represents a promising treatment option; however, data in the elderly population are limited.Patients and methodsSubgroup, post hoc analysis including 69 patients aged ≥65 years from a randomized, active-controlled, open-label study in the emergency setting. Key inclusion criterion was moderate-to-severe pain (Numerical Rating Scale [NRS] score ≥ 4]) secondary to trauma in a single limb. Patients received inhaled methoxyflurane (3 mL) or standard analgesic treatment (SAT; IV paracetamol 1 g or ketoprofen 100 mg for moderate pain [NRS 4-6] and IV morphine 0.1mg/kg for severe pain [NRS ≥7]). The primary endpoint was the overall change in visual analog scale (VAS) pain intensity from randomization to the next 3, 5, and 10 min. Secondary endpoints included time to onset of pain relief (TOPR), efficacy up to 30 min, judgment of operators and patients, and safety.ResultsPain reduction over time was similar in both groups. Median TOPR was shorter for methoxyflurane (9 min; 95% CI: 7.8, 10.2 min) than SAT (15 min; 95% CI: 10.2, 19.8 min). In terms of treatment satisfaction, patients and operators rated treatment efficacy and practicality, respectively, as "Excellent" or "Very good" 5.7 times and 3.4 times more frequently than SAT. A similar rate of adverse events (methoxyflurane: 6 events; SAT: 7 events) was recorded, all non-serious. No clinically significant changes in vital signs parameters were observed, and methoxyflurane did not result in cases of bradycardia or hypotension.ConclusionIn elderly patients with trauma pain, inhaled methoxyflurane shows similar pain relief and safety compared to SAT, offering advantages in terms of onset of effect and user's satisfaction. Although this analysis presents some methodological limitations, it provides the first specific evidence of the use of inhaled methoxyflurane in the elderly population.Trial registrationEudraCT number: 2017-001565-25; Clinicaltrials.gov identifier NCT03585374.

Project description:BackgroundWe 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.MethodsOver 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.ResultsOverall, 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.ConclusionWhen 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.

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Project description:Introduction:The undertreatment of acute pain presents a significant challenge in the Emergency Department. This post hoc subgroup analysis of a previously reported randomized controlled UK study reports the efficacy and safety of low-dose methoxyflurane analgesia in treating adolescent patients with moderate-to-severe trauma pain. Patients and methods:Three hundred patients (96 in the adolescent subgroup) aged ?12 years requiring analgesia for acute trauma pain (pain score of 4-7 on the Numerical Rating Scale) at triage were randomized 1:1 to methoxyflurane (up to 6 mL) or placebo (normal saline), both administered using a Penthrox® inhaler. The patient could request rescue medication (paracetamol/opioids) at any time. The primary endpoint was the change from baseline in visual analog scale (VAS) pain intensity. Results:Mean VAS pain score for the adolescent subgroup at baseline was ~ 61 mm. Adjusted mean change in VAS pain intensity from baseline to 5, 10, 15, and 20 minutes was -24.5, -28.1, -31.6, and -31.7 mm for methoxyflurane and -14.6, -18.8, -19.2, and -23.7 mm for placebo, with a statistically significant treatment effect in favor of methoxyflurane overall across all four time points (-9.9 mm; 95% CI: -17.4, -2.4 mm; P=0.0104). Median time to first pain relief was significantly shorter with methoxyflurane (1 minute) than placebo (3 minutes, P<0.0001). Pain relief was reported within 1-10 inhalations in 95.7% of methoxyflurane-treated patients and 64.6% of placebo-treated patients. Rescue medication was requested by two (4.3%) methoxyflurane-treated patients and three (6.3%) placebo-treated patients. Over 95% of patients, physicians, and nurses rated methoxyflurane treatment as "Excellent", "Very Good" or "Good" compared with between 64% and 68% for placebo. The incidence of adverse events was higher with methoxyflurane (51%) than placebo (42%), mostly comprising mild/transient dizziness and headache. Conclusion:This subgroup analysis shows that low-dose inhaled methoxyflurane is a rapid-acting and effective analgesic in adolescent patients presenting with moderate-to-severe trauma pain. Trial registration:Clinicaltrials.gov identifier: NCT01420159, EudraCT number: 2011-000338-12.

Project description:IntroductionThe inhalational analgesic low-dose methoxyflurane has been widely used by Australian ambulance services since 1975 and is now approved in Europe for emergency relief of moderate-to-severe trauma-related pain in conscious adult patients. The use of methoxyflurane in hostile environments is of special interest given its portability, ease of use and rapid onset of action. This trial will investigate the efficacy, tolerability and practicality of use of inhaled methoxyflurane in patients with moderate-to-severe trauma-related pain rescued from hostile mountainous environments by the Helicopter Emergency Medical Service (HEMS) in Italy.MethodsMETEORA is a phase IIIb, prospective, single-arm, multicentre trial. Approximately 200 adult patients with a pain score of at least 4 on the numerical rating scale (NRS) due to limb trauma rescued by HEMS will be enrolled. Patients will receive up to 2 × 3 mL methoxyflurane, self-administered by the patient by inhalation under medical supervision. Rescue medication will be permitted if required.Planned outcomesPain intensity will be measured using a 100-mm visual analogue scale (VAS) at baseline, at 5, 10, 15, 20, 30, 45 and 60 min after the start of methoxyflurane inhalation and when positioning the patient on a spinal board or stretcher; and also using the NRS at enrolment and at 10 min. Use of rescue medication (yes/no) will be recorded. The patient will rate efficacy and the healthcare professional will rate practicality of methoxyflurane treatment at 30 and 60 min using a 5-point Likert scale. Vital signs will be measured at baseline, 10, 30 and 60 min. Assessments after 30 min will only be performed for patients using a second inhaler. Adverse events will be recorded until safety follow-up at 3 ± 1 days. The primary endpoint is the percentage of patients achieving at least 30% improvement from baseline in VAS pain intensity within the first 10 min of methoxyflurane administration.Trial registrationEudraCT number: 2017-004601-40.FundingMundipharma Pharmaceuticals, srl. Plain language summary available for this article.