Ballistic trauma

A gunshot wound (GSW) is a penetrating injury caused by a projectile (e.g. a bullet) from a gun (typically firearm or air gun). Damages may include bleeding, bone fractures, organ damage, wound infection, loss of the ability to move part of the body and, in more severe cases, death. Damage depends on the part of the body hit, the path the bullet follows through the body, and the type and speed of the bullet. Long-term complications can include lead poisoning and post-traumatic stress disorder (PTSD).

Factors that determine rates of gun violence vary by country. These factors may include the illegal drug trade, easy access to firearms, substance misuse including alcohol, mental health problems, firearm laws, social attitudes, economic differences and occupations such as being a police officer. Where guns are more common, altercations more often end in death.

Before management begins it should be verified the area is safe. This is followed by stopping major bleeding, then assessing and supporting the airway, breathing, and circulation. Firearm laws, particularly background checks and permit to purchase, decrease the risk of death from firearms. Safer firearm storage may decrease the risk of firearm-related deaths in children.

In 2015, about a million gunshot wounds occurred from interpersonal violence. In 2016, firearms resulted in 251,000 deaths globally, up from 209,000 in 1990. Of these deaths 161,000 (64%) were the result of assault, 67,500 (27%) were the result of suicide, and 23,000 (9%) were accidents. In the United States, guns resulted in about 40,000 deaths in 2017. Firearm-related deaths are most common in males between the ages of 20 to 24 years. Economic costs due to gunshot wounds have been estimated at US$140 billion a year in the United States.

Signs and symptoms

Trauma from a gunshot wound varies widely based on the bullet, velocity, mass, entry point, trajectory, affected anatomy, and exit point. Gunshot wounds can be particularly devastating compared to other penetrating injuries because the trajectory and fragmentation of bullets can be unpredictable after entry. Moreover, gunshot wounds typically involve a large degree of nearby tissue disruption and destruction caused by the physical effects of the projectile correlated with the bullet velocity classification.

The immediate damaging effect of a gunshot wound is typically severe bleeding with the potential for hypovolemic shock, a condition characterized by inadequate delivery of oxygen to vital organs. In the case of traumatic hypovolemic shock, this failure of adequate oxygen delivery is due to blood loss, as blood is the means of delivering oxygen to the body's constituent parts. Devastating effects can result when a bullet strikes a vital organ such as the heart, lungs or liver, or damages a component of the central nervous system such as the spinal cord or brain.

Common causes of death following gunshot injury include bleeding, low oxygen caused by pneumothorax, catastrophic injury to the heart and major blood vessels, and damage to the brain or central nervous system. Non-fatal gunshot wounds frequently have mild to severe long-lasting effects, typically some form of major disfigurement such as amputation because of a severe bone fracture and may cause permanent disability. A sudden blood gush may take effect immediately from a gunshot wound if a bullet directly damages larger blood vessels, especially arteries.

Pathophysiology

The degree of tissue disruption caused by a projectile is related to the cavitation the projectile creates as it passes through tissue. A bullet with sufficient energy will have a cavitation effect in addition to the penetrating track injury. As the bullet passes through the tissue, initially crushing then lacerating, the space left forms a cavity; this is called the permanent cavity. Higher-velocity bullets create a pressure wave that forces the tissues away, creating not only a permanent cavity the size of the caliber of the bullet but a temporary cavity or secondary cavity, which is often many times larger than the bullet itself. The temporary cavity is the radial stretching of tissue around the bullet's wound track, which momentarily leaves an empty space caused by high pressures surrounding the projectile that accelerate material away from its path. The extent of cavitation, in turn, is related to the following characteristics of the projectile:
*Kinetic energy: KE = 1/2''mv''² (where ''m'' is mass and ''v'' is velocity). This helps to explain why wounds produced by projectiles of higher mass and/or higher velocity produce greater tissue disruption than projectiles of lower mass and velocity. The velocity of the bullet is a more important determinant of tissue injury. Although both mass and velocity contribute to the overall energy of the projectile, the energy is proportional to the mass while proportional to the ''square'' of its velocity. As a result, for constant velocity, if the mass is doubled, the energy is doubled; however, if the velocity of the bullet is doubled, the energy increases four times. The initial velocity of a bullet is largely dependent on the firearm. The US military commonly uses 5.56-mm bullets, which have a relatively low mass as compared with other bullets; however, the speed of these bullets is relatively fast. As a result, they produce a larger amount of kinetic energy, which is transmitted to the tissues of the target. The size of the temporary cavity is approximately proportional to the kinetic energy of the bullet and depends on the resistance of the tissue to stress. Muzzle energy, which is based on muzzle velocity, is often used for ease of comparison.
* Yaw: Handgun bullets will generally travel in a relatively straight line or make one turn if a bone is hit. Upon travel through deeper tissue, high-energy rounds may become unstable as they decelerate, and may tumble (pitch and yaw) as the energy of the projectile is absorbed, causing stretching and tearing of the surrounding tissue.
* Fragmentation: Most commonly, bullets do not fragment, and secondary damage from fragments of shattered bone is a more common complication than bullet fragments.

Diagnosis

Classification

Gunshot wounds are classified according to the speed of the projectile using the Gustilo open fracture classification:

*Low-velocity: Less than 1,100 ft/s (340 m/s)

Low velocity wounds are typical of small caliber handguns and display wound patterns like Gustilo Anderson Type 1 or 2 wounds

*Medium-velocity: Between 1,200 ft/s (340 m/s) and 2,000 ft/s (610 m/s)
These are more typical of shotgun blasts or higher caliber handguns like magnums. The risk of infection from these types of wounds can vary depending on the type and pattern of bullets fired as well as the distance from the firearm.
*High-velocity: Between 2,000 ft/s (610 m/s) and 3,500 ft/s (1,100 m/s)

Usually caused by powerful assault or hunting rifles and usually display wound pattern similar to Gustilo Anderson Type 3 wounds. The risk of infection is especially high due to the large area of injury and destroyed tissue.

Bullets from handguns are sometimes less than but with modern pistol loads, they usually are slightly above , while bullets from most modern rifles exceed . One recently developed class of firearm projectiles is the hyper-velocity bullet, such cartridges are usually either wildcats made for achieving such high speed or purpose-built factory ammunition with the same goal in mind. Examples of hyper velocity cartridges include the .220 Swift, .17 Remington and .17 Mach IV cartridges. The US military commonly uses 5.56mm bullets, which have a relatively low mass as compared with other bullets (40-62 grains); however, the speed of these bullets is relatively fast (Approximately , placing them in the high velocity category). As a result, they produce a larger amount of kinetic energy, which is transmitted to the tissues of the target. However, one must remember that high kinetic energy does not necessarily equate to high stopping power, as incapacitation usually results from remote wounding effects such as bleeding, rather than raw energy transfer. High energy does indeed result in more tissue disruption, which plays a role in incapacitation, but other factors such as wound size and shot placement play as big of, if not a bigger role in stopping power and thus, effectiveness. Muzzle velocity does not consider the effect of aerodynamic drag on the flight of the bullet for the sake of ease of comparison.

Prevention

Medical organizations in the United States recommend a criminal background check being held before a person buys a gun and that a person who has convictions for crimes of violence should not be permitted to buy a gun. Safe storage of firearms is recommended, as well as better mental health care and removal of guns from those at risk of suicide. In an effort to prevent mass shootings greater regulations on guns that can rapidly fire many bullets is recommended.

Management

Initial assessment for a gunshot wound is approached in the same way as other acute trauma using the advanced trauma life support (ATLS) protocol. These include:
* A) Airway - Assess and protect airway and potentially the cervical spine
* B) Breathing - Maintain adequate ventilation and oxygenation
* C) Circulation - Assess for and control bleeding to maintain organ perfusion including focused assessment with sonography for trauma (FAST)
* D) Disability - Perform basic neurological exam including Glasgow Coma Scale (GCS)
* E) Exposure - Expose entire body and search for any missed injuries, entry points, and exit points while maintaining body temperature
Depending on the extent of injury, management can range from urgent surgical intervention to observation. As such, any history from the scene such as gun type, shots fired, shot direction and distance, blood loss on scene, and pre-hospital vitals signs can be very helpful in directing management. Unstable people with signs of bleeding that cannot be controlled during the initial evaluation require immediate surgical exploration in the operating room. Otherwise, management protocols are generally dictated by anatomic entry point and anticipated trajectory.

Neck

A gunshot wound to the neck can be particularly dangerous because of the high number of vital anatomical structures contained within a small space. The neck contains the larynx, trachea, pharynx, esophagus, vasculature (carotid

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