Prehospital emergency medicine – UK military experience

Learning objectives.

By reading this article, you should be able to:

• •Recognise the challenges of practicing military prehospital emergency medicine.
• •Explain how the patterns of injury in military prehospital situations differ from those in civilian practice.
• •Discuss how restrictions imposed by the working environment affect the military prehospital emergency medical practice.
• •Describe the training required for military prehospital emergency medicine teams.

Key points.

• •The prehospital medical emergency response team plays a key role in the care of the injured military patient.
• •The injuries encountered by military prehospital care practitioners differ from those routinely encountered in the UK.
• •The operational environment poses additional challenges to the practice of military prehospital medicine.
• •Military UK prehospital care practitioners train and work in the civilian sector when not deployed on active military duties.

Pre-Hospital Emergency Medicine (PHEM) is recognised by the General Medical Council (GMC) as a subspecialty of anaesthesia and emergency medicine. Prehospital Emergency Care (PHEC) is a commonly used term for the multidisciplinary practice of emergency care in the prehospital environment. PHEM has been practiced in the civilian and military settings for many years; recent conflicts in Iraq and Afghanistan have led to significant developments in military-PHEM (MPHEM), many of which have been adopted in civilian PHEM services.¹ This article aims to review modern practice and highlight the areas in which military practice differs most significantly from civilian models of care.

Patient population

Military-PHEC (MPHEC) teams face a different patient population from their civilian colleagues. Battlefield casualties are generally young, physically fit adults with significant physiological reserve and in whom the diagnosis of hypovolaemic shock may be masked. MPHEC teams also treat enemy combatants and local civilians who may suffer from undiagnosed endemic pathologies, including infectious diseases unfamiliar to many UK-based clinicians. Clinical interventions must be realistic and appropriate for the medical system into which casualties are ultimately discharged (e.g. civilians may be delivered to host nation hospitals where advanced levels of care cannot be sustained). All patients and those accompanying them may pose a potential risk to PHEC teams; threats may be intentional or unintentional and therefore all those individuals require to be ‘sanitised’ (searched for explosives, or other hazardous items) before assessment, treatment, and evacuation.

Patient pathology and injury patterns

UK civilian-PHEC (CPHEC) teams are dispatched to patients with a variety of acute medical, surgical, and traumatic conditions. UK civilian trauma casualties commonly present with blunt traumatic injuries resulting from motor vehicle collisions and falls. Most military patients in recent campaigns have presented with major trauma after blast injury from improvised explosive devices (IEDs), or penetrating trauma, from fragmentation injury or high-velocity gunshot wounds (GSWs).² Data from previous conflicts suggest that the majority of preventable deaths on the battlefield were caused by catastrophic extremity haemorrhage and airway obstruction.³

Blast injury

Blast injuries are thankfully still uncommon in the UK. IED attacks and blast injuries pose specific challenges to MPHEC teams and lead to significant multisystem pathology including fragmentation, ‘blast lung’, shock, coagulopathy, brain injury, and burns. Traumatic limb amputations, junctional (between or overlapping anatomical zones, e.g. pelvic/lower limb) trauma, and life-threatening haemorrhage present concurrently. Management pressures are frequently compounded by blasts involving multiple casualties. Increasingly effective personal protective equipment (PPE) for soldiers protecting the torso has generated an increased proportion of casualties with extremity, junctional, and head injuries. Head injuries are responsible for the majority of fatalities in patients who survive to admission in UK hospitals.⁴

GSWs

Military firearms (e.g. the AK47 assault rifle) fire projectiles at significantly higher velocities than the pistols most commonly involved in civilian shootings. Military GSWs therefore result in greater energy transfer to body tissues, tissue cavitation along the projectile track, and more devastating injuries, including gross contamination and large exit wounds.

Catastrophic haemorrhage

Because the majority of survivable injuries on the battlefield have been attributed to catastrophic extremity haemorrhage, there has been widespread adoption of damage control resuscitation (DCR), which prioritises control of catastrophic haemorrhage over airway management.¹ To mitigate the risk of catastrophic haemorrhage, all deploying UK service personnel are trained to apply a tourniquet proximal to the injury immediately after injury where indicated. The UK Defence Medical Service (DMS) was also an early adopter of novel haemostatic products such as Celox™ gauze (Medtrade Products Ltd., Crewe, UK) which are used in the management of life-threatening junctional haemorrhage. Multiple limb injuries, shock, and limitations in patient positioning result in extensive use of intraosseous access devices for administration of medications and fluids.

As part of DCR, MPHEC teams resuscitate shocked casualties using warmed blood products, which have been shown to be associated with improved outcome.⁵ Patients are warmed to normothermia and tranexamic acid administered. These interventions are now becoming adopted by many UK civilian PHEC teams, although some still use crystalloid solutions, despite their known association with worsening coagulopathy.⁶ Unsurprisingly, the mean injury severity score of patients in recent conflicts has often been in excess of typical civilian trauma casualties.⁷ It is speculated that the number of ‘unexpected survivors’ identified amongst UK casualties in the recent Afghanistan conflict is partly attributable to the adoption of this aggressive approach to the management of catastrophic haemorrhage.

Prehospital care network

Prehospital critical care teams operate within a network of care-providers. CPHEC is initially provided by community first-responders, paramedics, helicopter emergency medicine services, and volunteer solo doctors.⁹ In the military, care is provided by a combination of non-specialist team medics, specialist field medics, primary care doctors, and specialist MPHEC teams such as Medical Emergency Response Team (MERT) as described in the Operational Care Pathway.¹⁰

Figure 1 has been adapted by authors from the Operational Care Pathway.¹⁰ The ‘hot zone’ is a non-permissive environment with an immediate threat to responding personnel. The ‘warm zone’ is a semi-permissive environment, where a specific secondary threat to personnel exists; these zones are dynamic but convenient to consider when planning medical operations. Deployed hospital care includes surgical and critical care capability. Role two (R2) units are typically small and mobile, but close to the warm zone and at risk from enemy contact. Larger, role three (R3) facilities have a greater capacity and are usually further away from the warm zone and therefore more secure. Tactical evacuation (TACEVAC) describes the movement of patients between deployed hospital care facilities. Strategic evacuation (STRATEVAC) is the movement of patients from the operational theatre to a first world-standard medical facility, designated a role four (R4) facility, usually in the UK.

Fig 1.

Schematic representation of configuration of military casualty evacuation resources in a deployed operational theatre.

Point of injury

Unlike civilian casualties, military casualties commonly receive life-saving interventions (e.g. tourniquet application) within minutes of injury, performed by soldiers with no professional medical training. More advanced interventions can be offered by ‘team medics’ (soldiers who have attended a 3-day medical course) and ‘field medics’ (providing medical care as their primary role after more than a year of medical training). Aggressive early haemorrhage control interventions may attenuate cardiovascular collapse and delay requirements for more advanced prehospital interventions.¹¹ This may allow casualties with previously unsurvivable injuries to survive until the arrival of a PHEC team.

Medical evacuation

Medical evacuation (MEDEVAC) requests are processed to allow intelligent tasking of the most appropriate medical resources available. Tactical Field Care describes interventions necessary to save or stabilise life whilst awaiting MEDEVAC: they are practiced in accordance with principles taught during the Battlefield Advanced Trauma Life Support (BATLS) course. Before the arrival of a MEDEVAC team, the area must be secured, potentially delaying the deployment and arrival of medical teams. The designated receiving medical facility will depend on the clinical needs of the patients, geographical proximity, capabilities of the transfer mode, and escorting team.

Clinical timelines

Many UK CPHEC teams are capable of deploying rapidly to incident scenes. It can be anticipated that there will be a delay in MPHEC teams accessing casualties during the early stages of expeditionary military operations because of the large distances involved and enemy activity at the scene. Under these circumstances, prolonged field care (PFC) is instituted. PFC comprises ongoing organ support (e.g. reassessing haemorrhage control, airway suctioning, titration of fluid stocks to optimise cardiac output etc.) and also nursing care such as management of pressure areas, temperature, analgesia, and monitoring fluid balance. Prolonged timelines are likely to represent the experience of UK rural air ambulances or secondary transfer team. To deliver PFC, MPHEC teams need appropriate additional training and resources. MEDEVAC is provided by the MERT and is usually the first available asset able to offer critical care interventions.

Treatment platforms

Because of the variable nature of the threat and terrain, MPHEC teams deploy various modes of transport or ‘platforms’. Practitioners may work with tracked or wheeled vehicles when responding by land; a range of landing craft, ridged inflatables and large boats at sea, and a selection of both rotary and fixed wing aircraft. All these pose unique challenges as a treatment environment and unlike civilian air ambulances, are rarely configured as dedicated medical assets. Personnel and equipment are stowed in a largely improvised fashion, resulting in partly compromised ergonomics. Smaller military transports (e.g. Wildcat helicopter) have similar dimensions to a civilian air ambulance, whereas support helicopters (e.g. Chinook) are larger and can accommodate more personnel, equipment, and casualties (Fig. 2). Large helicopters allow 360° access to casualties and their size allows them to accommodate large numbers of casualties when the situation demands. MPHEC teams may care for up to eight critically ill patients in transit, placing severe challenges on equipment, space, and command and control resources.

Fig 2.

Interior view of an RAF Chinook helicopter configured in MERT role in Afghanistan.

PHEC team roles

UK air ambulance teams mostly conduct primary transfers (deploy to incident scenes via helicopter or road, transferring patients by helicopter or land ambulance). MPHEC teams undertake an extended range of roles including secondary transfers (from one deployed medical facility to another), or deploy to and reinforce a static primary care facility and provide an advanced resuscitation capability when MEDEVAC deployment cannot be guaranteed. These roles require a broader skillset, including prolonged transfer and maintenance of anaesthesia which are well-suited to clinicians with an anaesthesia and critical care background.

Team composition

The optimum team mix for civilian or MPHEC teams is unclear and compositions vary. Physician-led teams are capable of delivering a broader complement of technical skills (e.g. anaesthesia, thoracotomy, advanced analgesia), but also deliver clinical leadership and decision-making, which is critical in high-performing medical teams.¹² Future MERT deployments are likely to consist of a mission specific team of two to four personnel, based on the anticipated level of care required. Unlike most UK civilian PHEC services, the DMS employs paramedics and emergency department nurses to perform MEDEVAC, rather than critical care paramedics. The team is usually augmented by a doctor to provide a critical care capability, depending on the nature of the deployment.

Treatment models

Historically, PHEC teams have adopted two different treatment models, whilst some MPHEC teams have pioneered a third approach.

‘Scoop-and-run’

This model focuses efforts on transporting the patient to a medical treatment facility as rapidly as possible. After a rapid initial assessment and packaging, patients are conveyed to the nearest appropriate facility, with clinical interventions limited to those that are achievable on the platform used (e.g. fluid and drug administration). Scoop-and-run is commonly used by civilian PHEC teams operating, unable to deliver advanced resuscitation techniques, when the scene is close to a medical facility and when the casualty is physiologically unstable with a time-critical condition. This strategy was widely used during by MPHEC teams in conflicts in Vietnam and The Falkland Islands.

‘Stay-and-play’

This approach prioritises delivering clinical interventions at the scene, before packaging the casualty and transporting to a medical facility. This is more commonly used by physician-led PHEC teams who are able to provide advanced interventions and operate on small transfer platforms (e.g. civilian air ambulance). This reduces the clinical timelines for delivering critical care interventions (e.g. PHEA, thoracostomy/thoracotomy etc.) but can delay arrival at a medical facility. Physician-led teams adopt this approach when presented with a sick casualty likely to benefit from rapid on-scene intervention and there is a likelihood the casualty will deteriorate en route to hospital (e.g. obtunded, head-injured casualty requiring a definitive airway). It is less-commonly used in the military, where the battlefield is often too hazardous for MPHEC teams to remain at the scene.

‘Scoop-and-play’

This approach has been developed by the UK MERT during recent operations in Afghanistan. It is characterised by the rapid transfer of casualties from the battlefield to a medical facility, with resuscitation occurring in transit. This is only feasible for MPHEC teams on large transport platforms (e.g. Chinook helicopter). It minimises both time to arrival at hospital and time from injury to advanced resuscitation interventions. Civilian PHEC teams rarely have access to transport vehicles large enough to make this feasible.

Novel hybrid resuscitation

Haemorrhage remains a significant cause of avoidable death for both civilian and military trauma patients. Volume resuscitation remains a key component of the management of these patients and despite limited evidence for its validity, hypotensive resuscitation is widely practiced by PHEC teams. Hypotensive resuscitation is speculated to mitigate the risk posed by non-compressible haemorrhage before the patient reaches a surgical team.13, 14 Current UK CPHEC guidelines are to resuscitate to the return of a central pulse.¹³ MPHEC teams resuscitate to a radial pulse (except in head injuries and paediatric patients, where normotension is targeted) for a maximum of 1 hour following injury, at which point normotension is targeted. This is termed novel hybrid resuscitation and is informed by experimental evidence showing that, in blast injuries in particular, prolonged hypotension may increase mortality.¹⁵

Environment

PPE

Healthcare providers are used to wearing PPE, to mitigate the risk of contamination with bodily fluids. The prehospital environment poses many additional environmental hazards. Civilian PHEC teams may encounter these at roadside incidents where protective clothing, helmets, and other measures are mandated whilst operating around damaged vehicles.

MPHEC teams frequently operate in austere combat environments, where additional hazards include ballistic projectiles from enemy forces and blast from explosive threats at incident scenes. Medics wear ballistic body armour, helmets, and survival equipment (e.g. personal weapons, water, ammunition, and personal radios), The weight of this equipment requires MPHEC team members to be physically fit to avoid fatigue and injury; its bulk impairs movement, balance, and positioning. PPE worn by casualties may hinder their handling, exposure, and positioning (e.g. when supine, the ballistic back plates worn by casualties cause hyperextension of the neck, making laryngoscopy difficult).

Communication/assessment challenges

Extremes of noise, vibration, and temperature on military transport vehicles can degrade the ability of MPHEC teams to operate. High noise levels mandate the wearing of ear protection and communication by radio or non-verbal means. MPHEC teams commonly operate at night, when for tactical reasons, white torchlight is unsuitable. Low light further hinders team communication and therefore MPHEC teams train extensively to develop robust communication strategies and protocol-driven treatment pathways. Operating under red or blue torchlight prevents effective discrimination between colours, impairing assessment of patient skin colour and quantification of external bleeding; colour-coded medical equipment (e.g. colorimetric end-tidal CO₂ detectors) may become uninterpretable and some digital displays unreadable.

Patient assessment is challenging in the prehospital environment. CPHEC teams usually assess patients before packaging and transport; MPHEC teams may only be able to assess their patients in transit aboard a dark, noisy, and vibrating vehicle. MPHEC teams modify their approach to patient assessment accordingly.

Catastrophic haemorrhage is difficult to detect in low or red ambient light conditions, and thresholds to intervene are reduced to prevent death from haemorrhage. Airway assessment is challenging and visual cues such as the misting of a facemask with respiration and the use of non-invasive ETCO₂ monitoring are more valuable than conventional clinical signs which are difficult to detect. In-flight chest examination is limited to inspection for injuries and symmetry of movement; measuring the ventilatory frequency is difficult, and chest percussion and auscultation are impossible. Assessment of the circulation is focused on identifying the presence and cause of hypovolaemic shock. It may be difficult to diagnose in transit, where palpation of pulses is problematic because of vibration. Skin colour may be indeterminate in low light levels and non-invasive blood pressure measurement devices may be unreliable. Shock diagnosis often relies on a combination of heart rate (measured via adhesive defibrillator pads), injury pattern, and mechanism. Neurological assessment is often simplified and measuring a formal Glasgow Coma Score largely impossible. Significant spinal cord injury may be diagnosed acutely; subtle neurological pathology may not be revealed until later. Pain assessment is difficult and may be reliant on interpreting casualty behaviour and facial expressions.

Training pathway

The Faculty of Pre-Hospital Care of the Royal College of Surgeons of Edinburgh (RCSEd) define CPHEC providers according to their competency levels. These are summarised in the PHEM Skills Framework by nine levels of care1, 2, 3, 4, 5, 6, 7, 8, 9; Level 9 practitioners are the most senior clinicians with managerial responsibility (e.g. clinical director). Level 8 practitioners are typically consultants in anaesthesia or emergency medicine with postgraduate training in PHEM. MPHEM physicians operate within a similar framework and like their civilian colleagues, study for the Fellowship in Immediate Medical Care, awarded by the RCSEd. New civilian and military PHEM physicians in training undertake a GMC-accredited, subspecialty training programme in PHEM whilst seconded to a civilian air ambulance organisation.

MPHEM consultants receive training to operate in a deployed MPHEC team. This includes military prehospital trauma training delivered by the BATLS and MPHEC courses, consolidated by individual and team training during the MERT Course. The MERT course teaches MPHEC teams to manage critically ill military casualties under arduous and challenging conditions and includes in-flight training serials on support helicopters. Crew resource management and non-technical skills are a core focus in the preparation of MPHEC practitioners and are intensively coached and assessed during the MERT Course. The MPHEC training pathway includes additional training in survival, underwater escape training, chemical, biological, radiological, and nuclear medicine, and core military skills such as personal weapon training. Novel techniques using virtual reality simulation are also being explored and may provide an environment for individualised and portable training in the near future.¹⁶

Conclusion

PHEM is a subspecialty of anaesthesia that presents many challenges to the anaesthetist. MPHEM is particularly unique with respect to the volume and acuity of presenting casualties and by the high prevalence of penetrating and blast injuries, which are unfamiliar to most UK-based practitioners. The hazardous and austere environments demand that teams implement robust and effective strategies to deliver care to multiple casualties, under hostile, austere, and varied conditions.

Declaration of interest

No declaration of interest to be declared.

MCQs

The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.

Biographies

Lt Col Rich Reed FRCA RAMC is a Military Consultant in anaesthesia and critical care doctor for Devon Air Ambulance. He is Clinical Director for the Medical Emergency Response Team Course and has deployed operationally on several occasions.

Surg Lt Cdr Sebastian Bourn FRCA RN is a specialty trainee in anaesthesia in the South East Scotland and Northern deanery and a specialty trainee in prehospital emergency medicine for the Great North Air Ambulance (North East programme).

Matrix codes: 1B04, 2A02, 3A10