A brief history of analgesia in paramedic practice

Analgesia in medicine: the 1800s

Important advances in the prevention and management of pain occurred in the mid-1800s, when drugs that produced anaesthesia were first used during surgery. These drugs included nitrous oxide, ether and chloroform. The term anaesthesia means ‘without sensation’ and these drugs act to reduce the perception of pain associated with surgery. The first demonstration of anaesthesia was reportedly performed by William Morton in 1846 at the Massachusetts General Hospital in Boston (see Figure 1), and while anaesthesia was initially criticised by the medical profession, it gained popularity after the physician John Snow administered chloroform to Queen Victoria during the birth of her first child in 1853 (Caton, 1999). Ether, chloroform and nitrous oxide subsequently became popular as agents to relieve pain during surgery and dental procedures.

Advances in medicine towards the end of the 1800s were associated with other public health developments, including systems for improving the early care and transport of the sick and injured. In the UK and in Australia volunteer organisations such as St John began to form ambulance services. For example, a motorised ambulance service was established by the British Red Cross in 1914. This was followed by the establishment of a home service ambulance committee appointed by the Joint War Committee (British Red Cross, 2013). The primary aim of these early ambulance services focused on the need to provide safe transport of patients to medical care. During this time the management of pain in patients who were injured and transported by ambulance relied on techniques such as splinting fractures so that the immobilised limb was less likely to move during transport and exacerbate tissue injury, resulting in further pain. Reassurance was—and still is—an important adjunct to the alleviation of pain. However, pharmacological interventions to relieve pain only emerged in the mid-1900s.

Analgesia in paramedicine: the 1900s

Drugs that had pain-relieving or analgesic qualities were first introduced by several Australian ambulance services in the 1950s, initially in the form of trichloroethylene, a chlorinated hydrocarbon. First synthesised in 1894, trichloroethylene was discovered to have analgesic properties. Administration in an ambulance service context involved adding the liquid drug to a cotton wick in a reusable inhaler, and the patient then inhaled the vapour to produce analgesia. Although this agent gained popularity in Great Britain in the 1940s as an inexpensive analgesic and anaesthetic, particularly in the area of obstetrics (Waters et al, 1977), there is no record of its use by ambulance services in the UK. Although no longer used in Australian paramedic practice— having been discontinued in the early 1980s— trichloroethylene is still used as an industrial solvent and metal degreaser.

Analgesia in the ambulance services in the UK received little attention prior to 1970, when Baskett and Withnell (1970) first described the results of study of the use of a nitrous oxide/oxygen mix marketed as Entonox. Prior to this study, ambulance officers in the UK did not appear to have access to any agent for the relief of a patient's pain. This belief is supported by Baskett's claim that ‘it is still nearly as unpleasant for a patient to be taken to hospital with a fractured femur or acute urinary retention as it was 30 years ago,’ and that through the use of Entonox, ‘for the first time, ambulance personnel can do something specific to relieve pain’ (Baskett and Withnell, 1970).

Baskett and Withnell's seminal publication was followed by another UK study investigating and reporting on the use of nitrous oxide in the field (Wright et al, 1972). This research was followed by a report that the UK Department of Health and Social Security ‘has accepted the advice of the Ambulance Service Advisory Committee that the analgesic Entonox could be used more widely by specially trained ambulance crews without risk to the patient’ (Faculty of Anaesthetists, 1972). However, there were several contraindications associated with the use of Entonox, and ambulance officer training in the UK continued to maintain a focus on the use of distraction techniques and reassurance for the patient, along with splinting and immobilisation (National Health Service Training Authority, 1981).

During the 1970s, advanced levels of paramedic practice were implemented by ambulance services in Australia. In the UK, Professor Douglas Chamberlain devised a pilot scheme in Brighton to extend training to enable paramedic performance of advanced skills that included defibrillation and intubation (Carney, 1999). However, it would take several years before these advanced skills included the administration of opioids to manage pain.

While all ambulance services in the UK were reportedly using Entonox by 1993, the effectiveness of this agent was beginning to be questioned, with Chambers and Guly (1993) recognising a need for better pre-hospital analgesia. Difficulties in administration due to technical and communication difficulties, particularly in children and the elderly may have contributed to variations in efficacy. Other problems associated with the use of nitrous oxide include exposure of paramedics to potentially high atmospheric levels of the gas. A 1980 study found concentrations of nitrous oxide in the patient treatment area of the ambulance of ‘650–1 700 parts per million (ppm), with top concentrations up to 7 500 ppm’ (Ancker et al, 1980). In 1983, Stewart et al (1983) describe the findings of a study that detected concentrations of nitrous oxide in the ambulance of over 1 200 ppm. The Australian standard for occupational exposure to nitrous oxide is a time-weighted average maximum exposure of 25 ppm over an eight-hour working day (Safe Work Australia, 2013).

Concerns regarding environmental exposure to high levels of nitrous oxide were addressed by a position paper published by the National Association of Emergency Medical Services Physicians (NAEMSP) in 1990. This reinforced the need to use scavenging systems and adequate ventilation while nitrous oxide is used within the ambulance (NAEMSP, 1990). However, difficulties in maintaining safe environmental exposure standards of nitrous oxide contributed to the decision by the Ambulance Service of New South Wales to withdraw this agent from use in 2001.

A new era of analgesia: opioids

Morphine has long been recognised as the standard against which other analgesics are measured. However, its introduction in the pre-hospital or ambulance setting has faced several barriers, including legislative controls restricting the possession and administration of opioids. The evolution of pain relief in the UK has been challenging, in part due to regulations controlling the use of certain classes of drug. Ambulance staff are subject to Department of Health Acts of Parliament such as the Misuse of Drugs Act 1971 (c.38), the Misuse of Drugs Regulations 2001 (no. 3998), the Medicines Act 1968 (c.67).

While one barrier has involved pragmatic legislative issues relating to the prescription and security of opioids, some resistance was likely to be based on the fallacious claims that ‘the relatively long action of the drug may hinder accurate diagnosis on arrival at hospital by masking pain’ (Baskett and Withnell, 1970). The fear that opioids mask symptoms and make diagnosis more difficult has been refuted by evidence that demonstrates that the relief of pain may enhance the diagnostic process (Macintyre et al, 2010). Opioids have significant adverse effects, including respiratory depression. However, concerns may have been amplified by the publication of case studies from primary care and hospital settings documenting adverse outcomes accompanied by statements such as ‘I hesitate to think how many patients have died in the ambulance on the way to hospital of unsuspected hypoventilation rather than from their myocardial disease’ (Caradoc-Davies, 1981). There is scant evidence of adverse outcomes associated with the use of opioids to manage pain in the paramedic practice setting.

Further barriers may have been associated with Baskett's claim that unreliability of drug absorption and excretion is ‘accentuated in the accident and emergency situation.’ Furthermore, the author also cites ‘unfortunate and increasing addiction problems’ to conclude that ‘it is obvious that the opiates are impossible to consider as a satisfactory analgesic in these conditions’ (Baskett, 1972). While this has subsequently proved to be untrue, these fears may have contributed to delays in the introduction of morphine in some ambulance services.

Concerns about complications such as morphine-induced respiratory depression as well as early legislative barriers led UK ambulance services to consider other analgesics instead of morphine. Nalbuphine, a synthetic opioid with agonist-antagonist properties, appeared to be an ideal drug to address these concerns, according to a study that investigated the administration of this drug by paramedics in England (Chambers and Guly, 1994). Nalbuphine produces analgesia by acting as a k-opioid receptor agonist, while antagonising µ-receptors. The latter effect helps to explain the drug's relative lack of respiratory depression and euphoria.

Nalbuphine was subsequently the subject of several studies of its use in the pre-hospital setting (Gray et al, 1997; Hyland-McGuire and Guly, 1998; Woollard et al, 2002). However, the introduction of this drug was criticised by emergency physicians, with a series of case reports describing instances where excessive amounts of morphine were needed to achieve pain relief in patients given nalbuphine in the field (Houlihan et al, 1999). The author proposed that the antagonist action of nalbuphine on µ-opioid receptors was the cause of the ineffectiveness of morphine at normal therapeutic doses. Despite this criticism the drug subsequently became a common paramedic-administered opioid throughout UK ambulance services, but has never been used by ambulance services in Australia.

Despite these developments, by 1993, only five (of 65) ambulance services in the UK were using analgesia other than Entonox. Analgesics used by these services were nalbuphine (n=3), diclofenac (n=1), and diamorphine (n=1) (Chambers and Guly, 1993). While legislative restrictions account for some of these findings, the reluctance of ambulance services medical advisors to support paramedic-administered opioids was noted to be a major barrier by the study authors.

Nalbuphine was used by ambulance services in the UK until 2004, when the Joint Royal Colleges Ambulance Liaison Committee (JRCALC) produced an urgent notice to all ambulance services announcing that the manufacturer was withdrawing this drug. This notice acknowledged that, while nalbuphine had previously been the mainstay of parenteral analgesia within UK ambulance services, this drug was not used in other clinical settings, as pure agonist opioid drugs are preferred. As such, the JRCALC advised ambulance services that morphine should be used in place of nalbuphine (JRCALC, 2004). Morphine is now commonly used by UK ambulance services. To facilitate the use of this drug the JRCALC has established the Group Authority for the Possession of Controlled Drugs for NHS ambulance Trusts and paramedics employed (2008). This enables paramedics to operate under a Patient Group Directive which is strictly controlled.

In Australia, morphine was introduced to paramedic practice in the states of Victoria and New South Wales in the 1980s, but at that time, only the most highly qualified paramedics were authorised to administer the drug to patients with pain, mainly due to concerns regarding patient safety. Authority to administer morphine was extended to all paramedics in the state of Victoria following the introduction of advanced life support training in 2000, which was established as the base level qualification for all paramedics in the ambulance service in that state.

The current state of analgesia practice

Although the efficacy and safety of morphine in treating moderate to severe pain has been demonstrated, a need for analgesics for mild to moderate pain led to the introduction of other analgesic options. Other drugs currently used to relieve pain in paramedic practice include methoxyflurane, a volatile analgesic and anaesthetic widely used in anaesthesia during the 1960s to 70s (Komesaroff, 1995; Ball and Westhorpe, 2007). Although evidence of dose-dependent nephrotoxicity (Cousins et al, 1974) lead to restrictions of its use in some countries, it remains a popular analgesic agent in health settings in Australia and New Zealand, where it is licenced for use as an analgesic.

Methoxyflurane is an effective analgesia in children with moderate to severe pain, but has been found to be less effective in comparison with both morphine and fentanyl (Bendall et al, 2011). The drug has been shown to be effective in relieving pain in adults, and produces few adverse effects (Buntine et al, 2007). However, the drug is not currently approved for use in the UK.

Limited drug options for pain relief are currently available to UK ambulance staff. Most ambulance trusts carry liquid paracetamol, entonox, and morphine in oral and parenteral forms. These drugs have been shown to be effective in managing acute pain, but may be ineffective or inappropriate for managing specific types of pain such as migraine, where other classes of drug may be more effective (Derry et al, 2012).

One Trust currently provides co-codamol (codeine phosphate and paracetamol) as part of the paramedic formulary. It is of note that most specialist paramedics in primary care carry a wider range of drugs used to relieve pain or to manage the cause of the pain. These include anti-fungals such as nystatin for oral candidiasis; anti-spasmodics such as hyoscine butylbromide, codeine phosphate, co-codamol and dihydrocodeine; glycerine suppositories for pain from constipation; antacids such as lansoprazole; local anaesthetics for wound closure; rizatriptan for acute migraine; diazepam for acute muscle spasm; non-steroidal anti-inflammatory drugs such as diclofenac and ibuprofen (often given with paracetamol for greater analgesic effect); and steroids (prednisolone) in the context of temporal arteritis (Nicholls and Hawkes-Frost, 2012).

Specialist paramedics in critical care in the UK are authorised to administer IV paracetamol, intra-nasal diamorphine, fentanyl, lignocaine for either local anaesthesia or regional nerve blocks, and ketamine, used in small analgesic doses and larger sedation doses. Currently, these are only administered in the presence of a physician-led team. However, the results of a paramedic-initiated trial of ketamine in the East of England Ambulance Service NHS Trust is due to be published in 2014.

In Australia, morphine is now commonly used to manage moderate to severe pain in paramedic practice. Paramedics are also using intranasal fentanyl for both adults and children in a number of jurisdictions, and the efficacy of this drug by the intranasal route has been described in the literature (Bendall et al, 2011; Fleischman et al, 2010; Middleton et al, 2010). Ketamine is also used in some settings, and the combined use of morphine and ketamine has been studied and published (Jennings et al, 2011; 2012).

The future

As the role of the paramedic continues to evolve to include responsibilities for primary care in the community, partnerships with organisations such as the British Pain Society and Painaustralia will help to ensure that paramedics are included in health networks that provide multidisciplinary care for patients living with pain. Health partnerships will be pivotal in influencing decisions that enable safe and effective pain strategies including the inclusion of a wider range of pain management options.

It is important that pain management practice addresses the needs of special populations. These include individuals experiencing chronic pain, those at extremes of age and individuals with communication difficulties that limit their ability to express their pain, including patients with cognitive impairment due to disease such as dementia. For example, technology now enables paramedics to assess pain in a patient with severe dementia using an iPhone or Android smartphone application (British Geriatrics Society, 2013).

Examples of strategies to address the needs of vulnerable patients include discussions with the British Pain Society that have resulted in recommendations to ambulance Trusts regarding the use of intra-nasal diamorphine for children with severe pain. Support for paramedic administration of this controlled drug will be crucial as this opioid is not currently included in the controlled drug formulary that UK paramedics are licensed to possess or supply.

Future opportunities for research into pain management options include the use of adjunct therapies such as transcutaneous electrical nerve stimulation (Simpson et al, 2013); acupressure (Kober et al, 2002; Lang et al, 2007), and regional analgesia using techniques such as a fascia iliaca block (Australian New Zealand Clinical Trials Registry, June 2010). Chronic pain is an area that deserves a higher priority in paramedic practice, as paramedics will inevitably care for patients with complex pain syndromes and cancer-related pain. There are opportunities for paramedics to be involved in the care of these individuals, particularly during an exacerbation of pain that may have triggered a call for assistance.

Paramedic pain management practice has been transformed over the past three decades from basic interventions and a limited range of pain management options, to the advanced practitioner that currently has a broader scope of practice that may include referral rights. However, the efficacy and safety of this specialised area of practice must be supported by a broader curriculum to develop the knowledge and skills required to care for individuals with pain (Charlton, 2005). An increased range of analgesic options will be unlikely to result in significant improvements in paramedic pain management practice unless there is an associated investment in education and clinical audit of practice using valid and reliable clinical indicators to ensure that practice achieves and continues to meet contemporary standards of care.