The term 'trauma' is used to describe injuries caused by external force through accidents, violence or acts of self-harm. Injuries are broadly categorised by the mechanism of injury. In penetrating injuries, the skin is breached by a sharp object such as a knife or glass, causing external and potential internal bleeding, and in blunt injuries, the skin is normally unbroken and the force of the injury damages the skin or internal organs.
Blunt and penetrating injuries may cause severe bleeding and subsequent reduction in blood volume (hypovolaemia), which can lead to hypovolaemic shock (circulatory failure as a result of inadequate blood volume). If uncorrected, hypovolaemia will initially lead to inadequate perfusion and oxygenation of tissues and will subsequently cause permanent damage to vital organs and multiple organ failure, which is one of the major causes of death in trauma patients.
Data from the Office for National Statistics on the causes of death in England and Wales in 2000 state that 15,462 deaths were caused by injury. The Royal College of Surgeons suggests that about 14,500 fatalities arose from 545,000 trauma admissions in the UK in 1988. Department of Transport Statistics for motor vehicle crashes in England and Wales in 1998 reported that there were about 320,000 injuries involving road vehicles and around 3,400 deaths. Blunt injuries account for most of the trauma in the UK – there are about 10 times as many blunt as penetrating injuries.
Ambulance services across the UK differ in their composition and may comprise emergency medical technicians (EMTs) trained in basic life support (BLS), paramedics (emergency medical specialists) trained in advanced life support (ALS), or a combination of EMTs and paramedics. BLS involves establishing a clear airway, starting expired-air resuscitation in the absence of breathing, and starting external chest compression in the absence of a carotid pulse. ALS includes immediate procedures such as defibrillation, the administration of oxygen and cardioactive drugs, monitoring of the electrocardiogram, endotracheal intubation and setting up of an intravenous infusion in a large peripheral or central vein. The British Association for Immediate Care (BASICS) also provides a service of voluntary doctors who are qualified in emergency medicine and equipped to attend accident scenes. Cannulation and administration of intravenous (IV) fluid can be undertaken by doctors or paramedics trained in ALS and may be initiated at the accident scene, in the ambulance en route to hospital, or in the accident and emergency department.
Ambulance crews are usually the first healthcare professionals to attend an accident scene, where they assess the general physiological state of the patient to determine which pre-hospital interventions are needed. The evaluation includes an assessment of the degree of blood loss and whether bleeding is controlled or uncontrolled. This involves identifying possible sites of bleeding (which may be external or internal) and assessing whether there is a radial or central pulse. Other indicators of haemorrhage in adults are tachycardia, peripheral vasoconstriction and reduced blood pressure (if more than 750 ml of blood is lost). The severity of hypovolaemic shock in adults is classified according to the volume of blood lost, from class 1 when it is less than 750 ml, to class 4 when it is more than 2,000 ml.