Prehospital Care for Medical Emergencies and Trauma

Background

The heritage of the modern emergency medical service (EMS) can be traced to the late 1700s with the approach to triage and forward patient retrieval of Napoleon’s chief surgeon, Dominique Jean Larrey. Later, in 1832, in London, transport carriages were introduced for cholera patients. The rationale for the introduction of such carriages was that the “curative process commences the instant the patient is put into the carriage.” Americans adopted this concept during the American Civil War, when General Jonathan Letterman, a Union military surgeon, created the first organized system in the United States to transport injured patients. Civilian EMS systems in the United States evolved subsequently—with the first one forming in Cincinnati in 1865.

It was nearly a century later in the 1960s when changes in medical technology and knowledge joined forces with political will to formalize the concept of prehospital care. In the early 1960s, two major clinical advances occurred—cardiopulmonary resuscitation (CPR) for life support of the patient in cardiac arrest, and the development of portable external defibrillators. These two advancements provided the foundation of advanced cardiac life support (ACLS). This, in turn, led to the concept of trained community members to respond to emergencies to improve outcome.

In 1965, President Lyndon Johnson created the President’s Committee for Traffic Safety, which published the report Health, Medical Care, and Transportation of the Injured . It identified motor vehicle crashes as a significant public health concern. The committee recommended a national program to reduce highway deaths and injuries. Additionally, in 1966, a report was released by the National Academy of Sciences titled Accidental Death and Disability: The Neglected Disease of Modern Society . It emphasized the need to address the quality of prehospital emergency medical care as it recognized that ambulances were ill-equipped and inappropriately staffed.

These two documents paved the way for the Highway Safety Act of 1966, which was passed by Congress and ultimately led to the formation of the National Highway Traffic Safety Administration (NHTSA) within the Department of Transportation. The NHTSA developed a national EMS curriculum which, in 1969, became the standard for emergency medical technician (EMT) training in the United States. In 1973, Congress further passed the EMS Systems Act, granting funds for the development of regional EMS systems. As a result, various states established a total of approximately 300 EMS regions with associated federal support. In the United States, the responsibility of EMS then shifted from federal to state level in 1981, which created heterogeneity in the system.

During the same period of time, EMS and prehospital medical systems were similarly evolving in most developed countries outside the United States. All had unique aspects and points of difference, mostly influenced by the local geography, political will, origin, and resources. The fundamental mission of EMS systems remained common—to deliver the best possible prehospital care to the right patients, in the right timeframe, and to transport them safely to a higher level of care.

Some systems evolved to be predominantly staffed by physicians, while others were staffed almost exclusively by paramedics with no to very minor physician involvement, and most fell somewhere between the two—with at least the capacity for a combined physician-paramedic crew.

Emergency Medical Technician and Paramedic-Based Emergency Medical Service Systems

Specially trained EMTs and paramedics form the bulk of the workforce of EMS systems in North America and in many other developed nations. Under U.S. law, physicians, functioning as EMS directors, are required to approve the medical operations of the EMS systems they oversee. This includes communication, clinical operations, and governance.

In the United States, there are three levels of EMTs based on their level of education and training: EMT-basic (EMT-B), EMT-intermediate (EMT-I), and EMT-paramedic (EMT-P). The primary focus of the EMT-B is to provide basic emergency medical care (using BLS skills) and transportation to a healthcare system. They typically staff nonemergency ambulances and may also respond to nonemergency calls. EMT-I practitioners, or advanced EMTs, provide basic and limited advanced emergency medical care and transportation. They are regulated differently and their skills range between BLS and ALS depending on state regulations. EMT-P is the highest skillset within EMTs in the United States. They undergo intensive 1- to 2-year training in advanced prehospital emergency care. They are ALS trained and can perform procedures such as endotracheal intubation, administration of drugs, and manual defibrillation.

In many other countries, paramedics are required to complete bachelor-level university degrees and are nationally or regionally registered by regulatory bodies—in a similar way that medical practitioners are licensed. In some regions, such as in most states of Australia and in many countries in Western Europe, intensive care paramedics have advanced skills in complex medical and trauma management as well as casualty access and rescue skills.

Primary Survey and Initial Assessment at the Scene

The primary survey is usually performed in the same ABCDE (airway-breathing-circulation, disability-exposure) mnemonic format that is widely known from ACLS. Since 2010, the American Heart Association has recommended changing their ABC approach (airway-breathing-compressions) to CAB (compressions-airway-breathing), emphasizing circulation prior to airway. This is particularly relevant for someone in cardiac arrest to bring focus to chest compressions. It is also relevant to the trauma patient suffering critical bleeding. If you can hear the bleeding, you should stop it first!

The approach, therefore, in the prehospital major trauma patient is C-ABCDE. Strategies for prehospital management of critical hemorrhage are discussed in more detail elsewhere in the chapter, but broadly, options include direct pressure, deep wound packing, use of novel hemostatics (there are several on the market), and tourniquets for extremity hemorrhage (the Combat Application Tourniquet [CAT] is the most widely used). Specific techniques can be used for major maxillofacial hemorrhage, which include nasal packing, or balloon tamponade devices (such as the Rapid Rhino), dental splints, and immobilization of the jaw with a hard, cervical spinal collar.

Novel approaches using resuscitative endovascular balloon occlusion of the aorta (REBOA) to manage critical bleeding in pelvic trauma in the absence of chest trauma are not yet widespread. Indeed, prehospital REBOA has been used successfully on only one documented occasion by London’s Air Ambulance. It remains an area of significant controversy and of limited evidence.

Once critical bleeding has been identified and temporarily controlled, moving through the remainder of the primary survey in a rapid yet methodical way is warranted. If there is airway (A) obstruction, the obstruction should be cleared and the airway secured if necessary. While it will often be appropriate to perform a rapid sequence intubation in the prehospital environment, it may not always be necessary or beneficial. A balance must be struck between delaying transfer, likely disposition once in hospital, distance to definitive care, and skillset available. Most prehospital services continue to secure the cervical spine with a hard collar for transport and this would be applied at this time.

Breathing (B) becomes the next priority; after the airway is cleared and possibly secured, a patient’s breathing is assessed by observing respiratory rate, pattern, and degree of chest rise and fall. Supplemental oxygen and assisted ventilation may be indicated. Immediately reversible causes of potentially fatal chest trauma, such as tension pneumothoraces, may also be identified and treated with minimal delay to patient transfer. In the case of tension pneumothoraces, many advanced prehospital services (especially those with medical-paramedic HEMS crews) have adopted a finger thoracostomy approach to chest decompression, rather than needle thoracostomy, to achieve a more definitive endpoint early and minimize the risk of reaccumulation of the pneumothorax in transit. Of course, this definitive care may not be available prehospital in all jurisdictions.

Circulation (C) is next assessed by palpating pulses, checking for heart rate, pulse quality and regularity, measuring blood pressure, and again assessing for sources of hemorrhage. As an approximation, a palpable carotid pulse corresponds to a systolic blood pressure of at least 70 mm Hg, and a palpable radial pulse to a systolic blood pressure of 80 to 90 mm Hg.

Also, as part of the primary survey, large-bore intravenous access is obtained. Early fluid management in the trauma patient has been a contentious issue in trauma management for many years. There has been much discussion in the scientific and prehospital literature in relation to the role of crystalloid fluid in the early resuscitation of the trauma patient. Over the past decade there has been a significant shift away from the aggressive use of crystalloid and a shift toward early administration of blood products in the prehospital environment. Some prehospital retrieval services carry red cells only, whereas some (particularly in the United Kingdom) also carry freeze-dried plasma products. In the trauma patient with no concomitant head injury, achieving a systolic blood pressure of 90 mm Hg is ideal (so-called “permissive hypotension”). The only caveat to this blood pressure target is in the head-injured patient. If head injury is present or suspected, then hypotension should be avoided. Indeed, available evidence suggests that in the presence of severe head injury, a single episode of systolic hypotension below 90 mm Hg may double mortality.

As part of the assessment of circulation, suspected long bone fractures can be immobilized with CT-6 (or equivalent) splints and the patient may be packaged in a vacuum mat for transport. If the prehospital team has the capability and expertise, an extended focused assessment with sonography in trauma (e-FAST) exam can be performed as part of the circulatory assessment. This may assist in identifying pneumothoraces before transport and may also reveal other major sources of bleeding that can be relayed to the receiving center.

Disability (D) is measured using the Glasgow Coma Scale (GCS). The GCS is made up of three parts: eyes, verbal response, and motor response. The best patient response is recorded. In the GCS, a maximum of 4 points are allocated for eye opening, 1 being unresponsive and 4 being eyes open; a maximum of 5 points are allocated to verbal response, with 1 being unresponsive and 5 being alert and oriented; and a maximum of 6 points are allocated to motor response, with 1 being unresponsive and 6 for the patient who obeys commands. The highest possible score is 15 and the lowest score possible is 3. As a general rule, patients with GCS score of 8 to 9 have alteration in their conscious state significant enough so as to no longer have the ability to protect their own airway. Assessment of exposure and environment (E) and measures to defend core body temperature completes the primary survey and patient packaging process.

It is important to note that the management of the trauma patient in the prehospital environment relies on concurrent activity within the team. The key to prehospital diagnosis and treatment is the initiation of important treatment as problems are identified, while minimizing unnecessary time spent at the scene. The focus of professional prehospital teams is avoiding the “therapeutic vacuum,” or time where nothing useful is happening for the patient.

On arrival, and having assessed the scene, the prehospital care team must rapidly obtain a relevant and focused history of the patient and the events surrounding the incident. In the case of trauma, the ATMIST and AMPLE mnemonics provide a useful framework for gathering key initial information. ATMIST stands for age, time of incident, mechanism of injury, injuries sustained, vital signs (initial and subsequent), and treatment given so far. The AMPLE approach can then be applied to gather specific and relevant history. AMPLE stands for allergies, medications (regular and acute), past history, last meal (menses, tetanus injection) and the events surrounding the injury.

Out-of-Hospital Cardiac Arrest

Survival from sudden cardiac arrest is highly dependent on early CPR and early defibrillation. Communities have placed an increasing emphasis on bystander CPR, community accessible AEDs, and rapid response of EMS providers.

When the EMS arrives on the scene, the “Universal Treatment Algorithm” is started. Chest compressions continue until cardiac monitoring is placed and it is determined whether defibrillation is appropriate. Pharmacotherapy and airway management remain poorly defined. Optimal airway management in OHCA has not been established, and studies have shown that resuscitation with medications increases likelihood of the return of spontaneous circulation (ROSC) without improved outcome.

The likelihood of ROSC will depend in large part on the etiology of the cardiac arrest as well as the presence of adequate bystander CPR. By far the most common cause of OHCA is from cardiac pathology.