Pre-hospital emergency medicine

Introduction

Ambulance services have traditionally had the primary role of providing rapid stretcher transport of patients to an emergency department (ED). Increasingly, paramedics are also trained to provide emergency medical care prior to hospital arrival in a wide range of life-threatening illnesses with the expectation that earlier treatment will improve patient outcomes.

Dispatch

Many countries have a single telephone number for immediate access to the ambulance service in cases of emergency, such as 911 in North America, 999 in the United Kingdom and 000 in Australasia. However, the accurate dispatch of the correct ambulance skill set in the optimal time frame is complex. It is inappropriate to dispatch all ambulances on a ‘code 1’ (lights and sirens) response to all callers, since this entails some level of risk to the paramedics and other road users. On the other hand, it may be difficult to accurately identify life-threatening illnesses or injuries using information gained from telephone communication alone, especially from bystanders. Also, the dispatch of paramedics with advanced life support training to routine cases where these skills are not required may make them unavailable for a subsequent call to a patient with a time-critical emergency.

In order to have consistent, accurate dispatch of the appropriate skill set in the optimal time frame, many ambulance services are now using computer-aided dispatch programs. These programs have structured questions for use by call takers with limited medical training. Pivotal to accurate telephone dispatch is identification of the chief complaint, followed by subsequent structured questions to determine the severity of the illness. The answers to these questions allow the computerized system to recommend the optimal paramedic skill set and priority of response. This computer algorithm is medically determined according to local protocols and practices and provides consistency of dispatch.

Most ambulance services have at least four dispatch codes. A code 1 (or local equivalent terminology) is used for conditions that are considered immediately life threatening. For these, emergency warning devices (lights and sirens) are routinely used. The possibility of lifesaving therapy arriving as soon as possible is judged as outweighing the potential hazard of a rapid response. In a code 2 (or equivalent) response, the condition is regarded as being urgent and emergency warning devices may be used only when traffic is heavy. In a code 3 response, an attendance by ambulance within an hour is deemed medically appropriate. Finally, a non-emergency or ‘booked’ call is a transport arranged at a designated time negotiated by the caller and the ambulance service.

Despite continuous developments in computer algorithms, accurate telephone identification of life-threatening conditions may be difficult. For example, identification of patients who are deceased (beyond resuscitation), in cardiac arrest or experiencing an acute coronary syndrome has been shown to lack the very high sensitivity and specificity that might be expected.

The dispatch centre also has a role for telephone instructions on bystander CPR and first aid. For conditions that are regarded as non-urgent, the dispatch centre may transfer the call to a referral service for the provision of a medical response other that an emergency ambulance. This might include dispatch of a district nurse for a home visit, the provision of simple medical advice with instructions to see a family physician or advice to attend an ED if symptoms persist.

Clinical skills

Ambulance treatment protocols vary considerably around the world. Since there are few randomized controlled trials to provide high-quality evidence-based guidance for pre-hospital care, there is still much controversy and considerable variation in the ambulance skill set required by different ambulance services.

Many ambulance services provide a number of different skill sets, dispatching ambulance officers trained in basic life support (including defibrillation) to non-emergency or urgent cases (ambulance paramedics) and more highly trained officers (designated as advanced life-support paramedics or intensive-care paramedics) to patients with an immediately life-threatening condition for which advanced life-support skills may be appropriate. In addition, ambulances services may co-respond with other emergency services (such as firefighters) to provide rapid-response defibrillation and assist with basic life support.

The evidence for some of the more common pre-hospital interventions is outlined in the following sections.

Trauma care

Pre-hospital trauma care may be considered as either basic trauma life support (clearing of the airway, assisted ventilation with a bag/mask, administration of supplemental oxygen, control of external haemorrhage, spinal immobilization, splinting of fractures and the administration of inhaled analgesics) or advanced trauma life support (ATLS), including intubation of the trachea, intravenous (IV) fluid therapy, decompression of tension pneumothorax and the administration of IV analgesia.