A gunshot wound (GSW) is a form of ballistic trauma resulting from a projectile, typically a bullet, fired from a firearm. This injury is characterized by the rapid transfer of kinetic energy from the projectile into the body’s tissues. The damage extends beyond the direct path of the bullet, often leading to severe internal injuries, blood loss, and physiological shock. A GSW is a medical emergency requiring rapid intervention.
How Kinetic Energy Creates Damage
The mechanism of tissue destruction in a gunshot wound is governed by the projectile’s kinetic energy. Kinetic energy is calculated using the formula \(KE = 1/2mv^2\), where \(m\) is the mass and \(v\) is the velocity of the bullet. Because velocity is squared, a small increase in projectile speed results in a disproportionately larger increase in destructive energy transferred upon impact.
As the bullet travels through the body, it crushes and lacerates tissue directly in its path, creating the permanent cavity. The dimensions of this cavity are determined by the bullet’s caliber and whether it deforms or fragments. The most destructive effect comes from the rapid energy transfer that pushes tissue radially outward from the bullet’s track, creating a momentary, pulsating space known as the temporary cavity.
The temporary cavity can expand to be many times the diameter of the projectile, subjecting surrounding tissues to extreme stretching and pressure. Tissues that are relatively inelastic, such as the liver or brain, are highly vulnerable to this stretching and may rupture, causing damage far from the bullet’s direct path. More elastic tissues, like muscle and lung, tolerate this temporary displacement better.
Categorizing Gunshot Wounds
Gunshot wounds are categorized based on whether the projectile remains within the body or passes completely through. A penetrating wound occurs when the bullet enters the body but does not exit, meaning all of the projectile’s kinetic energy is absorbed by the target. A perforating wound involves both an entry and an exit wound, indicating the projectile passed entirely through the tissue.
The appearance of the skin defect can distinguish between the two primary wound types. Entry wounds are typically smaller and more uniform than exit wounds because the skin is pushed inward and stretched before being punctured. They often feature an abrasion collar, a ring of scraped skin around the defect caused by the bullet’s friction as it enters.
Conversely, exit wounds are generally larger and more irregular because the bullet, often having tumbled, fragmented, or deformed, pushes tissue outward as it leaves the body. The edges of an exit wound are usually everted, or turned outward, and they lack the distinct residue features found at the entry site.
Factors Influencing Severity
The severity of a gunshot wound is influenced by a combination of ballistic, anatomical, and range-related factors. Ballistic factors include the bullet’s caliber and design, such as whether it is a full metal jacket, which tends to penetrate, or a hollow-point, which is designed to expand and transfer energy more aggressively. The exponential relationship of velocity to kinetic energy means a high-velocity rifle round causes significantly more widespread tissue destruction than a lower-velocity handgun round of similar mass.
Anatomical location is a major determinant of outcome, as injuries to the central nervous system, heart, or major blood vessels can be immediately life-threatening. Even a low-energy projectile can be fatal if it transects a large artery or vein, leading to rapid hemorrhage. Furthermore, less elastic organs, such as the liver or spleen, are more prone to extensive damage from the temporary cavitation effect.
The distance between the muzzle and the target also dictates the wound’s characteristics and potential for contamination. Contact wounds occur when the muzzle is pressed directly against the skin, forcing gas, soot, and flame into the wound. Intermediate-range wounds are characterized by tattooing or stippling, which are pinpoint abrasions caused by unburnt powder grains embedding in the skin. Distant-range wounds only show the mechanical effect of the bullet, lacking the soot or tattooing residue entirely.
Immediate Stabilization and Care
The immediate medical response to a gunshot wound follows established trauma protocols, prioritizing the stabilization of life-threatening conditions. The initial and most time-sensitive goal is hemorrhage control, as significant blood loss can lead to rapid shock and death. This is achieved through direct pressure on external wounds or the application of tourniquets for severe extremity bleeding.
Simultaneously, medical personnel must assess and manage the patient’s airway and breathing to ensure adequate oxygenation. Once initial stabilization is achieved, a rapid survey is performed to identify all injuries, including any hidden internal bleeding or organ damage. The patient is then quickly prepared for transport to a surgical facility where definitive care, often involving operative repair, can address the full extent of the ballistic trauma.