It is clear that trauma outcomes improve when patients are cared for in organized trauma systems. There is an outcome benefit for penetrating trauma patients taken to verified trauma centers instead of to non-trauma hospitals, either directly or with secondary transport, and there is a suggestion of even greater survival advantage for younger and sicker patients. As the trauma care system does not end with resuscitation or injury repair, neither does it begin there: Trauma care begins with the first responders in the emergency medical services (EMS) system and includes all out-of-hospital care components.

The out-of-hospital elements of the trauma system are important not only as care providers but also as drivers of notification and hospital selection, and they may be helpful in making resource utilization decisions. The system must also be designed to address access: The last well-described data show that one in seven Americans does not have access to a level I or II trauma center within 1 h, and over one quarter of the American population has such access only with helicopter transport. In addition to the systems providing initial care and transport, inclusive trauma systems must also integrate inter-facility transport systems to effect the movement of patients from non-trauma centers to trauma centers or to specialty services.

The prehospital emergency care system is largely operated by municipal agencies, with various public safety entities responding to about 95 % of the initial requests for service and over two-thirds of patient transports from those requests in the 200 largest US cities. Conversely, inter-facility transport services, both ground and air, are primarily provided by commercial operators, including hospital-sponsored, for-profit, and not-for-profit organizations.

Transport providers are generally described as basic life support, advanced life support, and critical care clinicians. Basic providers, emergency medical technicians, represent about 70 % of the over 200,000 working EMS providers in the United States. They offer stabilization and mostly noninvasive medical care. Paramedics are more advanced providers, with at least 1,200 h of training in the time-limited care of patients prior to their initial entry into the inpatient system. They provide protocol-driven care under the license of a physician, including invasive therapies such as medication administration and airway interventions.

Critical care transport teams are often part of air transport programs transporting patients to trauma centers from more remote injury sites or, more commonly, moving patients between facilities for higher levels of care. Increasingly, they also provide ground-based inter-facility critical care transport. These teams are most commonly staffed by a nurse partnered with a paramedic to leverage the blend of EMS and in-hospital critical care expertise those providers offer, but some systems partner a nurse with an in-hospital provider such as a second nurse, a respiratory therapist, or a physician. The nurses, paramedics, and respiratory therapists on these teams typically have expanded training and a greater scope of practice than their noncritical care transport counterparts. There is no optimal out-of-hospital staffing pattern or system for either EMS or inter-facility transport, due in large part to the diversity of environments in which medical transportation is provided. Systemic attention to provider quality and utilization is more important than provider or agency credentials.

The benefit of on-scene advanced life support care, either by paramedics or physicians, remains unclear. Even the oft-quoted “golden hour of trauma” is not supported by clear evidence. There is likely no single best approach. Some subsets of patients, such as those with associated severe brain injury or those with extended out-of-hospital times, may benefit from greater on-scene intervention while avoiding unnecessary delays in transport. At the same time, the care of trauma patients in urban settings may be best served by minimized out-of-hospital intervention, as transport by nonmedical providers is associated with equal, and perhaps better, outcomes than those transported by EMS.

When patients are taken to non-trauma centers or require specialty care, transfer to a higher level center improves outcomes. As patients increase in acuity and complexity, patient safety during movement requires providers with greater clinical and transport expertise. Even short in-hospital patient movements are associated with logistical and physiological complication, and the use of specialty critical care transport teams during both intra- and inter-facility transport is associated with reduced complication rates. Each trauma system must construct an appropriate model for both transport to the hospital and, as needed, transport between hospitals.

The EMS management of penetrating trauma outside the hospital is focused on accessing the patient safely, addressing immediately life-threatening injuries, minimizing secondary injury, and promptly transporting the patient to an appropriate destination.

In parallel with well-established American College of Surgeons’ advanced trauma life support guidelines, care begins with assuring a patent airway. In the overwhelming majority of cases, this can be achieved with basic life support techniques such as positioning, suctioning, or inserting an oral airway. At the other end of the spectrum, emergent cricothyrotomy is rarely indicated: It is performed in 0.004 % of all prehospital advanced life support (ALS) patients and 0.1 % of helicopter EMS patients.

Patients with significant traumatic injury may require supplemental oxygen, but high-flow oxygen is not required for all patients and can have adverse effects. The physiology of oxygen delivery describes a significant impact of a high arterial oxygen tension only in cases of severe anemia. Supplemental oxygen beyond the necessary to achieve full saturation is, at best, not beneficial. High-flow oxygen does facilitate a beneficial denitrogenation that prolongs the time to desaturation if airway management procedures are subsequently indicated.

Trauma guidelines historically emphasized the need empirically to restrict cervical spine motion until physician and, in patients with distracting injuries, radiologic evaluation. This may be overly dogmatic, and there is evolution toward less restrictive recommendations. Spinal motion restriction in penetrating trauma is associated with poorer outcomes (odds ratio of death 2.06, 95 % confidence interval 1.35–3.13): The number needed to treat for potential benefit is 1,032, while the number needed to harm is 66. Cervical spine fracture or cervical spinal cord injury is rare with penetrating trauma, occurring in between 0.11 and 1.35 % of patients, and is predictable by mechanism, presentation, and wound location. These injuries are over eight times more likely in patients with gunshot wounds than in those with stabbing injuries, and, in both situations, neurological deficit is almost always evident at the time of initial exam. The wounds associated with injury in gunshot wound patients are located between the ears and nipple, and stab wounds associated with cervical injury are those between the mandible and trapezius muscle. There may be merit in trading time to definitive trauma care for pro forma attempts at spinal motion restriction in patients who do not have neurological deficit or specific injury location.

The immediately life-threatening injuries associated with breathing addressed in the primary survey are tension pneumothorax and open pneumothorax. A tension pneumothorax can be managed in the out-of-hospital setting by needle decompression. The usual intravenous catheter is too short to reach the pleural space in up to a third of trauma patients, so providers should consider the use of a catheter of at least 3.25 in. in length in order to optimize success rates. An open pneumothorax can be covered with a three-sided dressing, and the patient monitored carefully for the accumulation of air and subsequent development of a tension pneumothorax.

One significant controversy in out-of-hospital trauma care is the role of airway capture to assist breathing. It is clear that hypoventilating patients should have assisted ventilation, and mechanical ventilation in shock states beneficially redistributes the cardiac output consumed by work of breathing to increase mixed venous oxygen saturation independently of arterial oxygen content. Appropriate ventilation may be important overall: The mortality of intubated trauma patients, both with and without brain injury, is significantly increased when they arrive at the trauma center with an abnormal pCO₂. The optimal timing and methods for achieving these goals, however, are less clear.

Endotracheal intubation is a core paramedic skill, but there is some suggestion that skill maintenance is difficult. Paramedics in large urban systems may have only a single intubation opportunity every year, and the overall success rate for paramedic prehospital intubation may be unsatisfyingly low and accompanied by high complication rates. Specialty teams with high scrutiny, good quality improvement programs, and close supervision can be successful at the invasive airway capture. Procedure success rates by paramedics with sedation-assisted intubation are about 77 %, rising to 96 % with the use of neuromuscular-blocking agents.

Although procedural success can be achieved, there is little certainty of improved outcomes with routine and widespread paramedic out-of-hospital intubation. For example, the only subgroups of patients shown to have improved outcomes following out-of-hospital intubation for traumatic brain injury were those subsequently transported by a helicopter critical care transport team. There is no specific outcome evaluation of out-of-hospital intubation in patients with penetrating trauma.

Prevention of adverse events in patients with endotracheal tubes being placed or in place is essential. The incidence of hypoxia during paramedic intubation may be as high as 56 %, and there is some suggestion that true procedure success is not technical success, but rather the avoidance of that hypoxia. The importance of careful ventilation has already been described. The addition of end-tidal carbon dioxide measurement devices for confirming endotracheal tube placement and for the ongoing monitoring of correct placement clearly improves out-of-hospital outcomes. Anesthesia standards recommend capnography for patients with airway appliances and for spontaneously breathing patients with sedation, yet adherence to this standard of care has significant room for improvement in the prehospital environment. It may be, ultimately, that the “benefit” of endotracheal intubation comes not from the procedure, but from patient selection, the prevention of intra-procedure complications, and careful post-procedure care.

There are a number of blind insertion airways, variations on an esophageal tube or a laryngeal mask, which can be used when patients are frankly hypoventilating. These devices, especially the esophageal tube airways, are designed to be used by providers trained to basic skill levels, to have high success rates, and to have few complications.

As the primary survey progresses to circulation, the lifesaving intervention is to arrest hemorrhage. Direct pressure continues to be the primary means of hemorrhage control. Specialized trauma dressings for the purpose of providing effective, continuous direct pressure exist. These dressings combine an absorbent pad and compression banding to provide direct pressure without relying on caretakers, which may be a benefit for the resource-limited prehospital arena.

In cases where direct pressure fails, placement of a tourniquet is indicated. Tourniquets have played a pivotal role in reducing battlefield loss of life from injury to under 13 %, with an 85 % reduction in death from uncontrolled extremity bleeding. There is a shift from improvised devices to purpose-built tourniquets, the most common of which involves a Velcro® strap combined with a plastic windlass device. A tourniquet device with a width of at least 1 in. ensures adequate tamponade deep vasculature while avoiding tissue injury underlying the placement site, and tourniquet placement for up to 16 h without long-term complications may be possible. It is considered best practice to write the placement time on the device, as well as to convey the information in verbal and written patient handoff.

For vascular injuries that are not amenable to tourniquet placement due to their location, particularly proximal femoral injuries and penetrating wounds to the pelvis, research is being performed on pneumatic compression devices which might be able to provide adequate pressure to occlude vasculature at the level of the femoral artery bifurcation and above.

Penetrating injuries deep within the soft tissues pose a particular challenge to achieving hemostasis. Military experience with hemostatic agents has translated into the civilian environment. These products, initially developed as powders and pastes, have since evolved into impregnated gauze dressings that encourage clot formation at the site of injury. Guidelines from civilian medicine, military medicine, and the Hartford Consensus for public and emergency services preparedness for active shooter and terrorism incidents recommend the use of tourniquets and hemostatic agents.

The question of prehospital fluid resuscitation for penetrating trauma appears to be well settled: There is no benefit to prehospital volume resuscitation in trauma patients with bleeding and without brain injury, and there is increased mortality in the subgroups with penetrating trauma or hypotension. Massive crystalloid resuscitation is clearly associated with coagulopathy, increased hemorrhage, and the development of the abdominal compartment syndrome.

Uncertainty about fluid resuscitation remains for patients who have associated brain injury or extended out-of-hospital times. For patients with brain injury, outcomes are clearly associated with the maintenance of cerebral perfusion pressure, with a goal of maintaining a mean arterial pressure of at least 80 mmHg. There is a paucity of guidance about the point at which the deleterious effects of persistent shock from delayed resuscitation for patients with prolonged out-of-hospital times begin to outweigh the hemorrhagic and coagulopathic risks associated with volume repletion.