Caliber: The caliber of a handgun or rifle is typically described as the diameter of the bore, although this can sometimes vary depending on how the diameter is measured. For example, a 0.38 bullet refers to a bullet that can be fired along a bore that measures 0.38 inches in diameter. The caliber is expressed in inches in the United States (e.g., 0.45 inches) or millimeter (mm) in other countries (e.g., 9 mm).

The extremity compartment syndrome is an acute, limb, and potentially life-threatening emergency that occurs when the pressure in a muscle compartment increases to levels that cause reduced tissue perfusion resulting in ischemic damage to the muscles and nerves.

Elderly patients have limited respiratory reserve and often decompensate rapidly and unexpectedly. Liberal early endotracheal intubation should be considered. Good preoxygenation should be a priority whenever possible.

Facial injuries are common and can involve both soft tissue injury and bony injury. These often occur because of motor vehicle collisions, secondary to direct impact against the windshield, steering wheel, or dashboard, as well as from broken glass fragments, causing lacerations and eye injuries. Many facial injuries also occur because of physical assault or because of falls to the head and face, especially in the elderly, who are less able to protect their face while falling.

Head trauma is the most common cause of death and permanent disability following trauma. Blunt head injury is usually the result of motor vehicle collisions, auto versus pedestrian collisions, or falls from significant heights. Gunshot wounds cause the vast majority of penetrating head injuries, although stab wounds and impalement injuries may also be seen.

Splints should be used to temporarily immobilize possible fractures and dislocations during the evaluation and management of life- and limb-threatening injuries.

Orthopedic injuries are found in approximately 85% of blunt trauma victims; thus knowledge of their evaluation and treatment is important. Some of these injuries are also acutely life- or limb-threatening and need to be treated in an expedited fashion. Despite the importance of early treatment, the standard primary survey promulgated by the ATLS course is necessary to detect other injuries that have a higher priority. During the primary survey, the only attention to musculoskeletal injury is acute hemorrhage control with direct pressure.

Pediatric trauma is a leading cause of morbidity and mortality in children. Although the principles of the initial evaluation and management are the same as in adult patients, it is important to take into account the anatomic and physiologic differences, which may affect the clinical presentation, investigations, and management of the pediatric trauma patient.

When attempts at orotracheal intubation or airway rescue techniques (e.g., laryngeal mask airway) have failed in a patient who cannot oxygenate or ventilate, cricothyroidotomy is the emergency surgical airway of choice. It can be performed open or percutaneously. The approach should be dictated by the proceduralist’s preference and experience.

Central venous access is obtained via the internal jugular vein (IJV), subclavian vein (SCV), or femoral vein.

Intraosseous (IO) infusion is based on the principle that medullary veins of long bones remain patent during shock and hypovolemia.

In traumatic cardiac arrest, especially due to hemorrhage or cardiac tamponade, external cardiac compression has no role in the emergency room.