Mass Casualties from Gunshot Attack
Gunshot injuries include violence-related, unintentional, and self-inflicted injuries. The majority of these injuries are caused by handguns. Although most gunshot attacks involve only one victim, there have been several well-publicized cases in which multiple persons were killed or injured in a single event. On December 14, 2012, it took less than 10 minutes to complete the deadliest school shooting in U.S. history, resulting in 27 dead (including the shooter) at Sandy Hook Elementary School in Newtown, Connecticut. The deadliest mass shooting in U.S. history, in which a gunman killed 59 people and injured nearly 700 others at a concert in Las Vegas, Nevada, on October 1, 2017, was completed in only 15 minutes.
Firearm injury results from tissue crush and tissue stretch. As a projectile travels through tissue, it crushes all tissue in its path and creates a permanent cavity. Additionally, tissue adjacent to the path of the projectile is stretched away from the permanent cavity, creating a temporary cavity. Highly elastic tissues, such as lung or muscle tissues, suffer little injury from tissue stretch, whereas this mechanism greatly disrupts inelastic tissues such as bone, brain, or liver, increasing the severity of injury caused by an individual projectile.
Firearms include two basic types: rifled firearms and shotguns ( Fig. 1). A rifled firearm (e.g., pistol or rifle) has spiral grooves in its barrel that impart a spin on the projectile, stabilizing its flight and increasing the firearm’s accuracy. When the cartridge is fired, the burning of the propellant generates gas in a contained space, and the pressure generated by the gas propels the bullet forward. The bullet accelerates while inside the barrel, reaches its maximum speed upon exit (muzzle velocity), and heads toward its target. As the bullet enters tissue, it begins to tumble and deform. Depending on the makeup of the bullet and the properties of the tissue through which it travels, it may expand, fragment, or remain in one piece.
Rifles and handguns have grooves in the barrel (called rifling), which make bullets spin when fired. Shotgun barrels typically have no grooves and are called smoothbore.
Shotguns have a smooth barrel that discharges hot gases, wad, and either multiple projectiles or a single projectile (rifled slug). The distance from the muzzle of the shotgun to the point of impact is a key determinant of the magnitude of injury. At short range (less than 6 m), a shot charge containing multiple projectiles results in a single surface wound that communicates with a deep underlying wound with massive tissue destruction. At this short range, tissue impact deforms the individual pellets, increasing their original cross section with a concomitant increase in tissue crush and surface-wound size. The multiple closely adjacent wound channels create additive tissue stretch, resulting in severe tissue disruption. The amount of pellet deformation and tissue destruction gradually decreases as the distance of the impact range increases. When the impact range exceeds 7 m, the multiple projectiles result in numerous discrete wounds that are not associated with underlying massive tissue destruction. Rifled slugs, designed for killing larger animals, follow the same ballistic patterns as single projectiles from rifled firearms, except insofar as they have a much larger cross-sectional area and confer a correspondingly greater amount of damage from tissue crush.
Pore-Incident Actions
Hospital, emergency department, and outpatient facilities should all have general disaster plans in place in the event of an attack. Mass casualty events require coordination of local, state, and federal public safety resources. Both emergency medical service (EMS)- and hospital-based triage systems may need to be altered in the event of a large number of patients seeking medical care within a brief period of time. Health care providers should practice universal precautions. In the event of multiple casualties, triaging of the victims at the scene and on arrival to the hospital will be necessary. Protocols for triaging of victims are part of a properly prepared disaster plan. Disaster plans should be in place, and personnel should be familiar with the plans so that when an event does occur, a minimum of confusion will ensue.
Post-Incident Actions
First responders and EMS personnel should confirm the scene is safe before evaluating casualties at the site of the event. Increasing numbers of state and local EMS departments have tactical EMS-trained personnel who are able to provide initial first aid to victims and first responders before the scene has been secured. A joint commission between the American College of Surgery and the Federal Bureau of Investigation created the “Hartford Consensus,” which describes methods to minimize loss of life in these instances. Their core recommendations are contained in the acronym THREAT (Threat suppression, Hemorrhage control, Rapid Evacuation to safety, Assessment by medical providers, Transport to definitive care).
If a large number of casualties are identified and a disaster needs to be declared, the proper channels must be notified and triage protocols instituted. Receiving hospitals should be given as much advance notice as possible to ensure that hospital personnel will be ready to handle the influx of patients. A “reverse triage” scenario may develop in which individuals with minor injuries rapidly self-extricate and self-present to first responders or local hospitals, straining resources before the more severely injured patients arrive. Early psychological assessment and intervention for victims, bystanders, and personnel responding to the scene may help mitigate long-term mental health consequences from the incident.
Clinical Presentation
As previously described, tissue injury results from direct crush by the projectile and by being stretched and deformed by the energy of the projectile’s passage. The most important determinant of injury is the tissue the bullet crushes. The tissue that is crushed corresponds to the permanent cavity formed by the bullet. Injury created by the temporary cavity depends on the elasticity of the tissue injured and becomes more important with higher-energy bullets.
Medical Treatment Of Casualties
Initial evaluation of persons with gunshot wounds is similar to that of any multi-trauma victim, with initial evaluation of the MARCH protocol, followed by the secondary survey and ongoing monitoring, including vital signs, electrocardiographic monitoring, and pulse oximetry.
However, unlike blast wounds and blunt trauma, gunshot wounds tend to be isolated. The focus of the examination is the detection of penetrating or perforating injuries. A careful examination of the patient including the back, under the hair, the axillae, and the gluteal folds will help identify injuries. It is often difficult to differentiate entrance from exit wounds. Although it is often thought that the smaller wound must be the entrance wound, this is not always true, particularly with high-velocity rounds.
A patient with two bullet wounds may have sustained a single injury with exit of the projectile, or two separate injuries with retained projectiles. Radiographs of the areas a bullet is thought to have traversed are indicated to identify the position of any retained projectiles. Laboratory studies should be ordered as clinically indicated. Evidence preservation and chain of custody of evidence should be considered when removing clothing from patients being evaluated.
Evaluation, resuscitation, and ongoing management should proceed as for any other multitrauma victim in both the prehospital setting and the emergency department. The management of gunshot wounds is best conducted in consultation with a trauma surgeon. If adequate resources are unavailable, the decision to transfer the patient should be made early in the course of treatment.
Wounds that may have crossed the mediastinum require a thorough evaluation, even in a stable patient. In this setting, injury to the aorta, heart, pericardium, and esophagus must be ruled out. Patients who present with unstable vital signs or who become unstable during evaluation should receive bilateral tube thoracostomies. The presence of pericardial tamponade should also be considered; bedside ultrasound can rapidly identify this pathology. Surgical exploration is often indicated in these patients.
Patients with penetrating gunshot wounds to the abdomen require exploratory laparotomy, even in the presence of stable vital signs. Stable patients with back or flank wounds can be evaluated by computed tomography and observation, but these patients may also benefit from surgical exploration. This decision must be made in conjunction with a trauma surgeon.
Injuries to the extremities require evaluation of the distal neurovascular status. A bullet does not need to transect a vessel to cause injury, as the temporary cavity may precipitate an arterial dissection, and compartment syndrome may result from swelling of the injured area. Angiography is indicated if arterial injury is suspected. Fractures from a gunshot wound should be treated as open fractures with early administration of antibiotics. Debridement of devitalized soft tissue is often necessary.
Penetrating gunshot wounds to the head are often not survivable. For patients with this type of injury who arrive at the hospital alive, consultation with a neurosurgeon is indicated. Injuries to the spine can occur even when the bullet does not actually pass through the vertebral canal. Use of steroids is not indicated for penetrating cord injuries. Additionally, the presence of a central nervous system injury should not delay assessment for the presence of thoracoabdominal injuries that can be rapidly fatal.
Unique Considerations
Gunshot wounds must be reported to the appropriate authorities. In most cases, shootings become the subject of a criminal investigation by law enforcement authorities. Therefore, the medical record and patient property should be preserved as evidence. If patient clothing is cut, care should be used to avoid cutting through portions a bullet might have gone through.
Any material that needs to be saved for law enforcement authorities should be placed in paper bags, because plastic bags will trap moisture, which can degrade evidence. The location of all wounds identified should be recorded in the medical record, including comments on the presence of any powder residue observed surrounding the wound. If a bullet is recovered, avoid making any markings on the sides of the bullet, because this will interfere with forensic evaluation of rifling patterns. Any marking of recovered bullets that may be necessary for the preservation of chain of custody should be at the nose or base.
As a bystander, you are in the best position to provide first care and are a critical beginning to the emergency medical system. The Essential Casualty Care course will teach you how to manage those injuries while waiting for first responders. This course goes beyond the Stop the Bleed curriculum by addressing other preventable causes of death and will teach you how to use most public-access haemorrhage control kits. It also is consistent with the Tactical Emergency Casualty Care Committee’s Active Bystander Guidelines.
