Trauma and multiple injury

The importance of trauma

Injuries kill 5 million people each year, and trauma is responsible for nearly 1 in 10 deaths worldwide. It is also the leading cause of death between 15 and 29 years of age. For survivors of severe injury, resulting morbidity has a major impact on healthcare resources. Trauma is a global epidemic and places an additional burden on family members and society, as it is often a disease of the young and economically productive. Most early preventable deaths following trauma occur as a result of failure to recognise and treat haemorrhage.

The ‘golden hour’

The term ‘golden hour’ was coined by R. Adams Cowley, a US Army surgeon, to describe the period immediately after major injury during which prompt and coordinated care within a trauma system could save lives. In 1975 he stated, ‘the first hour after injury will largely determine a critically injured person’s chances for survival’. While there is no evidence to support a strictly defined period of 60 minutes from injury to definitive care, it remains a useful concept to reinforce the time-critical nature of many severe injuries and the necessity to rapidly treat exsanguination and avoid early, preventable death.

The ‘platinum 10 minutes’

An analogous concept, the ‘platinum 10 minutes’, focuses on significantly limiting scene times by the prehospital team. The absolute priority is to address immediately life-threatening physiology, followed by rapid transport to definitive care. This ‘scoop and run’ approach includes airway and breathing assessment and control, circulatory support and temporisation of massive bleeding, rather than the ‘stay and play’ philosophy which often results in futile attempts at on-scene ‘stabilisation’ in the face of rapidly deteriorating physiology.

Temporal distribution of trauma deaths

In the past, death following major injury was classically described as having a trimodal distribution; due to advancements in trauma systems and critical care, death following trauma now has a more bimodal distribution. Immediate deaths occur within seconds to minutes after injury. They are usually the result of catastrophic injury to the brain or high spinal cord, or exsanguination due to disruption of the great vessels. These deaths are generally considered unrevivable. Strategies to impact on this cohort focus on effective prevention policies such as seat-belt legislation, speed limits, automobile structural improvements and gun control. Early deaths occur within minutes to hours after injury. They are often the consequence of potentially survivable shock physiology including tension pneumothorax, cardiac tamponade and massive haemorrhage from thoracic or abdominal vascular injury. Trauma systems, which limit time from injury to definitive care through rapid transport, assessment and intervention, dramatically improve survival and reduce subsequent morbidity in this cohort. Late deaths were historically described to occur days to weeks after injury as a result of multiorgan failure or sepsis. Early optimal management, including appropriate and aggressive resuscitation, and improved techniques for managing and supporting critically injured patients have helped reduce this peak.

The introduction and development of trauma systems has had a profound effect on the cause, and therefore timing, of death following injury. Improvements in prehospital care, resuscitation, trauma surgery strategies and critical care have changed the epidemiology of trauma deaths to a new, predominantly bimodal, distribution. The first peak (immediate deaths) is not impacted by these developments. The second peak (early deaths) has been reduced in magnitude through rapid and effective care. The third peak (late deaths) no longer form a cluster as originally described; while they still occur, they result most often from a determination of futility or a survival so compromised that it is inconsistent with patient and family wishes.

Blunt trauma

Blunt trauma occurs as a direct result of crushing or shearing forces. Crushing mechanisms involve one or more of three specific phases of energy transfer: direct impact between object and patient (e.g., striking the patient with a motor vehicle), impact between patient and surrounding environment (e.g., contact with the road surface after a motor vehicle versus pedestrian collision) and contact between internal organs and supporting structures (e.g., brain striking the skull). Crush impact mechanisms cause injury through the transfer of force directly to tissue, causing disruption of cellular membranes, haemorrhage and oedema.

Shearing mechanisms are typically due to deceleration forces that cause injury at the junction between the mobile portion of an organ and an adjacent fixed portion (e.g., the relatively mobile descending thoracic aorta shears at the relatively fixed ligamentum arteriosum). Shear mechanisms cause injury from torque forces leading to the tearing of tissue and disruption of anatomic architecture, resulting in disruption of cellular membranes, haemorrhage and oedema. Frequently, high-velocity blunt trauma results in a combination of both crushing and shearing forces being applied to the body.

Mechanisms of injury resulting in blunt trauma include:

• motor vehicle collision

• pedestrian struck by motor vehicle

• bicycle crash

• falls from a height or from ground level

• interpersonal assault

Penetrating trauma

Penetrating trauma occurs when an object transfers energy to the tissue by passing through it. Although wounding objects do not always follow a straight trajectory, penetrating injuries are usually more predictable than blunt force mechanisms in terms of the extent of injury and causation of the resulting physiology. Penetrating injuries include stab wounds from a sharp implement (most commonly a knife), impalement and gunshot wounds.

Stab wounds and impalement are typically low-velocity injuries, and the injuries produced are centred around the trajectory of the offending object. Following the tract of penetration usually suffices to understand the organs that have been injured.

Ballistic injuries, such as from a gunshot wound, are much more complex, and a basic understanding of ballistics is helpful in managing such injuries. The biomechanics of wounding are based on two factors: firstly, the kinetic energy of the projectile, and secondly, the elasticity and density of the target tissue. Kinetic energy is in turn a function of projectile mass and velocity. Most civilian gunshot wounds are inflicted by low-velocity weapons (< 500 m/s). In contrast, military assault weapons are high velocity (> 1000 m/s) and result in devastating injury.

The clinical relevance of this distinction is in the energy transfer and consequent tissue damage. Low-velocity weapons produce a permanent cavity (e.g., a bullet tract or stab wound) as it passes through tissue, creating relatively localized damage. In addition to local damage, however, high-velocity weapons also produce a large concussive force created from the blast effect as the missile travels through tissues at high speeds. This results in extensive tissue damage at some distance from the permanent cavity through shearing forces as a result of rapid tissue displacement and recoil.

Miscellaneous trauma

Blast injury as result of detonated explosives causes injury through several mechanisms:

• penetrating injury from fragments

• tissue disruption from shock waves

• evisceration and burns

• traumatic amputation

Burn trauma is a leading cause of accidental death, and mechanisms include:

• thermal injury

• scalds

• chemical burns

• electrical burns

• frostbite

Drownings, hangings and poisoning are often considered within the global ‘trauma’ category but typically do not require surgical assessment or intervention as part of the initial trauma evaluation. The first two mechanisms may require imaging of the cervical spine to assess for injury.

Purpose

Initial assessments of injury severity rely on rapid, clinically based evaluations of the extent of injury. They are based on patient physiology, anatomic data or, preferably, both. In field triage, injury mechanism is also a major consideration even in the absence of physiologic abnormalities. All triage aims to prioritise care and expedite transport to the most appropriate level of care or facility. Undertriaging occurs when an injured patient is taken to a facility without adequate resources. Overtriage occurs when the less severely injured patient is taken to a high-level trauma centre, bypassing a closer and adequate facility.

Injury severity scores are primarily used in clinical and health services research to allow comparison of variably injured patients across space and time, and attempt to provide a degree of reproducible objectivity to complex injury patterns and diverse populations. Injury severity scores attempt to predict the risk of morbidity and mortality for individual patients. They may be used to stratify patient cohorts when planning resource allocation or inclusion into clinical studies, and they are a useful benchmark to analyse outcome and performance improvement strategies within a facility or across a health system.

Limitations

All trauma scoring systems have limitations and are influenced by incomplete or inaccurate data. They are not absolute predictors of outcome, and some can only be applied retrospectively when detailed information is available for all injuries. Scoring systems should be regarded as broad estimates of likely outcome rather than definitive values on which to base critical decisions. They should be used as an adjunct to clinical experience, pattern recognition and protocol-driven care.

Physiologic scores

Anatomic scores

Anatomic scores define injury severity within each body region either individually or collectively. The most commonly used scores are the Abbreviated Injury Scale (AIS), which quantifies injury within distinct anatomic areas, and the Injury Severity Score (ISS), which is in turn a function of multiples of the AIS. These scores can only be applied when the full extent of injury is known and are therefore retrospective tools with which to evaluate processes of care and to gather epidemiologic information.

Combination scores

Clinical applications for trauma team activation

Injury severity, mechanism, and physiologic derangement all play a crucial role in the activation of the trauma system and team. In mature trauma systems, clear protocols exist to activate emergency medical services for field response, coordinate triage and transfer activities, and alert trauma facilities and teams to prepare for the arrival of a trauma patient. Because the extent of injury is not always apparent in the field, clearly defined and agreed-upon criteria allow unambiguous decision making and expeditious delivery of an injured patient to the most appropriate level of care. Trauma teams are typically alerted in a tiered fashion, whereby escalation can rapidly expand to include progressively specialised providers. For instance, a minor or moderately injured patient may be adequately evaluated by emergency medicine physicians, whereas a patient who clearly requires surgical consultation will have surgical and anaesthetic clinicians involved upon arrival to the trauma bay. An example of trauma activation criteria is listed in Table 9.3 . Note that under most circumstances, major trauma team activation is automatic if certain criteria for mechanism or physiology are met (such as penetrating trauma to the torso or abdomen, or hypotension in the field).

Trauma system

A trauma system is an organized, coordinated, multidisciplinary structure within a defined geographic area that delivers the full range of care to all injured patients while optimising the use of resources to reduce death and disability following injury. It includes public health services, injury prevention, emergency medical services, trauma-receiving hospitals and major trauma centres, and rehabilitation services to deliver care to a trauma patient at the right time by the right specialists through the seamless transition between each phase from ‘roadside to rehabilitation’. Importantly, it also includes research, education and systems governance as a fundamental part of injury prevention and control. The preventable death rate before implementation of a trauma system can be as high as 40%. This falls to 5% after implementing an effective trauma system and to less than 2% as the system matures. Trauma systems save lives and reduce the associated morbidity of survivors ( EBM 9.1 ).

There are five major components of a trauma system:

• 1.

  Injury epidemiology and prevention offers the greatest opportunity to reduce both the healthcare and societal burden of trauma care

• 2.

  Prehospital care is critical to delivering the right patient to the right facility at the right time.

• 3.

  Trauma centres are the hub of the network of care and must be integrated with other trauma-receiving hospitals to allow rapid interfacility transfer as needed.

• 4.

  Rehabilitation supports physical and psychological recovery to allow return to functional independence.

• 5.

  Home and follow-up care support reintegration into society and return to productivity.