Methoxyflurane analgesia for burns dressings

The use of methoxyflurane (Penthrox®) for procedural analgesia in the emergency department and pre-hospital environment

Background

Methoxyflurane is an inhaled analgesic agent licensed in the United Kingdom for the relief of moderate to severe pain in conscious patients with trauma. Methoxyflurane has been widely used by Australian ambulance services since the 1970s.

Aims

Primary aim: To assess the efficacy of methoxyflurane for procedural analgesia in the emergency department and pre-hospital environment. Secondary aims: to assess the efficacy of methoxyflurane for analgesia in the emergency department and pre-hospital environment; to assess the safety of methoxyflurane as an analgesic.

Method

A literature search of Medline, EMBASE, CINAHL and Cochrane databases was performed. A total of 59 articles were reviewed.

Results

One study using methoxyflurane for procedural analgesia in the emergency department was found. Multiple studies demonstrate the use of methoxyflurane for procedural analgesia for painful procedures outside the emergency department. Compared to other analgesics, methoxyflurane provides adequate analgesia. Overall, methoxyflurane is inferior to fentanyl or morphine, but it provides quicker onset analgesia compared to fentanyl and tramadol. It provides similar analgesia to nitrous oxide. Nephrotoxicity is dose dependent. Used in the analgesic doses, the risk of clinically significant kidney injury is negligible. Rare cases of unpredictable, severe hepatitis are reported.

Discussion

The efficacy of methoxyflurane and its acceptability to patients and clinicians has been shown in a number of studies. As would be expected in any procedural analgesic choice, patient and clinician factors and the procedure planned are all important considerations. Compared to other analgesic agents, methoxyflurane performs favourably with a low chance of adverse events.

Conclusion

Methoxyflurane is an efficacious analgesic agent in the emergency department and pre-hospital environment. It is easily portable and has a rapid onset. Methoxyflurane is suitable for use in procedural analgesia and as a bridging analgesic agent. Risks to the patient from renal or hepatic injury, cardiorespiratory depression or malignant hyperthermia are low.

STOP!: a randomised, double-blind, placebo-controlled study of the efficacy and safety of methoxyflurane for the treatment of acute pain

Objective

To evaluate the short-term efficacy and safety of methoxyflurane for the treatment of acute pain in patients presenting to an emergency department (ED) with minor trauma.

Methods

STOP! was a randomised, double-blind, multicentre, placebo-controlled study conducted at six sites in the UK. A total of 300 patients, 90 of whom were adolescent patients (age 12–17 years), were randomised 150:150 to receive either methoxyflurane via a Penthrox inhaler or placebo. The primary end point of the study was the change in pain intensity as measured using the visual analogue scale (VAS) from baseline to 5, 10, 15 and 20 min after the start of study drug inhalation. Patients were supplied with one inhaler containing 3 mL methoxyflurane or 5 mL placebo after enrolment and initial assessments. Age group (adolescent/adult) and baseline VAS score were controlled for in the statistical analyses.

Results

A total of 149 patients received methoxyflurane, and 149 patients received placebo. Demographic and baseline characteristics were comparable between the groups. Methoxyflurane reduced pain severity significantly more than placebo (p<0.0001) at all time points tested, with the greatest estimated treatment effect of −18.5 mm (adjusted change from baseline) seen at 15 min after the start of treatment. Methoxyflurane was well tolerated, with the majority of adverse reactions being mild, transient and in line with anticipated pharmacological action.

Conclusion

The results of this study suggest that methoxyflurane administered via the Penthrox inhaler is an efficacious, safe, and rapidly acting analgesic.

Trial registration number:

NCT01420159.

Inhaled methoxyflurane for pain and anxiety relief during burn wound care procedures: an Australian case series

Pain is a common and significant feature of burn injury. The use of intravenous opioids forms the mainstay of procedural burn pain management, but in an outpatient setting, the demand for novel agents that do not require parenteral access, are easy to administer and have a rapid onset are urgently needed. One such agent is the inhaled anaesthetic agent, methoxyflurane (MF). The aim of this study was to conduct a pilot investigation into the clinical effectiveness of MF inhaler on pain and anxiety scores in patients undergoing burn wound care procedures in an outpatient setting. A prospective case series involved recruiting patients undergoing a burn wound care procedure in an ambulatory burn care setting. Pain and anxiety were assessed using numerical rating scales. Overall, median numerical pain rating score was significantly higher post-dressing [pre-dressing: 2; interquartile range (IQR): 1-3 versus post-dressing: 3; IQR 1·5-4; P = 0·01], whereas median numerical anxiety score significantly reduced following the dressing (pre-dressing: 5; IQR 4-7 versus post-dressing: 2; IQR 1-2; P < 0·001). Our study suggests that there is a role for MF in the pain management armamentarium in those undergoing burn care procedures in the ambulatory care setting. However, there is an urgent need for larger case series and randomised controlled trials to determine its overall clinical effectiveness.

Review article: Efficacy and safety of methoxyflurane analgesia in the emergency department and prehospital setting

This article reviews the evidence for the analgesic efficacy of methoxyflurane in both prehospital and ED settings, as well as the adverse event profile associated with methoxyflurane use. Although there are no published controlled trials of methoxyflurane in sub-anaesthetic doses, available data indicate that it is an efficacious analgesic. There is inadequate evidence regarding its use as an agent for procedural pain. Despite the potential for renal impairment evident when it was used in anaesthetic doses, no significant adverse effects have been reported in the literature, neither in patients nor occupationally, when the dose used is limited to that currently recommended.

Prehospital analgesia in adults using inhaled methoxyflurane

OBJECTIVE

For many years, ambulance services throughout Australia have been administering methoxyflurane as a first-line analgesic agent. However, there is a paucity of literature regarding its efficacy, safety and usage profile. The present study was designed to examine the efficacy of methoxyflurane in adults.

METHODS

An observational case series was conducted over a 10 month period. Adults to whom methoxyflurane was administered while traveling by ambulance to an urban teaching hospital were enrolled. Data analysed included indications for use, verbal numerical pain scores, depth of sedation and adverse effects. Data were collected via paramedic, patient and ED staff surveys.

RESULTS

Eighty-three adult patients were enrolled over a 10 month period. A mean reduction in verbal numerical rating scale (VNRS) scores of 2.47 +/- 0.24 (on a 10-point scale) was recorded 5 min post methoxyflurane, with a total reduction of 3.21 +/- 0.24 at time of arrival at the ED. Both VNRS scores were significantly different from baseline (P < 0.0001). Fifteen patients (18.1%, 95% CI 9.8-26.4%) reported mild side-effects either during or shortly after administration. A total of 68 (81.9%, 95% CI 72.0-89.5%) of the paramedics and 60 (72.3%, 95% CI 61.4-81.6%) of the patients interviewed said that they felt satisfied with the level of analgesia provided by methoxyflurane.

CONCLUSION

The use of methoxyflurane as a prehospital analgesic significantly reduced pain in patients, with no significant side-effects attributed to its use. The majority of patients and paramedics interviewed were satisfied with its effects and indicated a willingness to use it again.

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.

Inhaled methoxyflurane as a prehospital analgesic in children

OBJECTIVE

Despite widespread use of methoxyflurane as an inhaled analgesic by ambulance services in Australia there are no published data as to its use pattern, efficacy and safety in the prehospital setting. We set out to characterize methoxyflurane use in children in the prehospital setting.

METHODS

An observational case series was conducted over an 8 month period. Children who received methoxyflurane while being transported to a tertiary children's hospital by ambulance were enrolled. We analysed indications for use, verbal numerical pain scores, adverse events and depth of sedation based on paramedic, patient, parent and ED staff surveys and review of ambulance care records.

RESULTS

During the study period 105 patients were enrolled with an age range of 15 months to 17 years (median age 11 years). Methoxyflurane was mainly used for extremity injuries (82%). Paramedic pain scores dropped from a mean of 7.9 (95% confidence interval [CI] 7.5-8.3) prior to methoxyflurane use to 4.5 (95% CI 3.9-5.0) at 2-5 min and to 3.2 (95% CI 2.8-3.7) at 10 min. There were no serious adverse events (one-sided 97.5% CI 0-3%). Mild adverse events occurred in 38 patients (36.2%; 95% CI 27.0-46.1%). Five of 15 (33.3%) patients under 5 years of age were deeply sedated.

CONCLUSION

In the present paediatric case series methoxyflurane appears to be an efficacious analgesic with a low adverse events profile. In young children in particular it can briefly lead to deep sedation.

Management of pain during debridement: a survey of U.S. burn units

To determine how burn pain is assessed and managed during debridement, questionnaires were sent to 151 U.S. burn facilities. 181 staff members from 93 burn units responded. For a typical adult patient, most respondents preferred a narcotic, but the dosages varied widely without a corresponding variation in assessed pain. The assessment of pain also did not vary with the type of analgesia used or the route of administration (i.v., i.m., p.o or gas). Half the respondents used psychotropic drugs in conjunction with narcotics, but without a reduction in dosage of the narcotic or a reduction in assessed pain. For a typical burned child, although more respondents recommended using no narcotics or no psychotropics or no analgesics at all, the assessed pain for children and adults was the same, i.e. in the moderate range. Pain during debridement was rate as more severe by those with less job experience and by those who gave higher dosages of analgesics before the procedure. The survey's findings indicate a need to reevaluate current analgesic practices for debridement and to document pain and pain relief.

Aspects of management of the burned child

This paper presents some principles and practical aspects of the management of children with burn injuries.

Special problems of respiratory tract damage and later problems in fluid and electrolyte therapy are discussed.

Various difficulties for the anaesthetist are outlined and the authors’ methods in preoperative, intraoperative and postoperative management are detailed.