Gunshot wounds involve the transfer of energy to a target. The damage that occurs is directly related to the amount of energy exchanged between the penetrating object and what it strikes, which relates to the projectile's mass and velocity. Other influencing factors include tissue density, the penetrating object's frontal area, and the distance between the weapon and the target.

When a bullet strikes a person, tissue is crushed. The bullet's forward movement creates a temporary tunnel that expands to a larger tunnel. The larger tunnel is considered to be a temporary "cavitation" wave. Tissues in the temporary cavity sustain damage from compression, deformation and shear. After a bullet passes through, the temporary cavity recoils to its normal position, but with a remaining cavitation, called the permanent cavity. The tissue of the permanent cavity may be damaged and nonviable. Secondary missiles, such as bullet and bone fragments, can result in additional damage.

Penetrating mechanisms of injury can be described as low, medium or high velocity. Damage from low-velocity mechanisms, such as stabbings, is often limited to the structures directly contacted. Medium-velocity mechanisms, like bullets from most types of handguns, produce less tissue destruction than high-velocity forces. High-velocity mechanisms include shots from rifles and larger military weapons.

Bullet design varies. Some are encased with hard "jackets," typically copper, to prevent the lead inside from deforming against a target. This promotes deeper penetration. Bullets that deform or fragment, such as those with soft or hollow points, may ricochet inside the body. Factors that can influence this include the location of the bullet's entry and the distance between the weapon and the victim when the weapon was fired.

Shotguns have shells containing small spherical pellets (shot) or items such as slugs or flechettes. These contents spread apart as they leave the barrel, distributing the blast energy over a wider area. At close range, shotgun injuries can be more severe than bullet injuries. At a greater range, the wider spread and lower velocity of the pellets tend to produce separated and superficial injuries.

ENTRY, EXIT

Gunshots may create both entrance and exit wounds. Entrance wounds tend to have a round shape with a surrounding margin of abrasion. Contact wounds occur when a firearm is held directly against the body and can include a muzzle imprint and soot on the skin. Close- or intermediate-range wounds may have a wider zone of powder stippling. Distant-range wounds tend to lack powder stippling and may have holes roughly equal to the calibre of the projectile fired.

Exit wounds can have a variety of appearances, including round, oval, slitlike, stellate or crescent. They may be larger than entrance wounds if the bullet expanded or tumbled on its axis, but most likely won't have gunshot residue. If an exit wound was abutted by firm support, such as clothing or furniture, it may have a circular defect and abraded margin resembling an entrance wound.

It is not always possible in the prehospital setting to determine if a wound is an entrance or exit wound. Refrain from documenting opinions, and allow forensic experts to make the determinations. Most shooting scenarios are crime scenes, and critical conclusions may be based on such interpretations. It is more important for EMS providers to identify and locate wounds and quickly manage patients. Taking the time to speculate on wound trajectory may delay the delivery of care, be detrimental to the patient's outcome and disrupt professional forensic conclusions and/or criminal prosecution.

When a bullet enters the body, numerous factors influence its path and subsequent injuries. The bullet may deform or fragment and contact more than one bone or organ. Structures that are less dense and have elasticity may sustain less damage than structures with greater density and more rigidity. For example, lung tissue has a low density with high elasticity and tends to be less damaged than muscle with higher density and some elasticity. The liver, spleen, brain and adipose tissue have little elasticity and are easily injured. Organs that are fluid-filled, such as the bladder, heart, great vessels and bowel, may rupture due to pressure waves even without direct contact with the missile. If a bone is involved, a secondary missile may form and cause additional injury.

SCENE RESPONSE

Shooting scenes may range from single victims with assailants no longer present to mass-casualty incidents or ongoing crime scenes with active shooters. Providers responding to them should work to maximize their situational awareness—what's happened, what's known, and what they might find on scene.

ARRIVAL, TRIAGE

When arriving at the scene, consider the following: Is the scene secure or active? Is law enforcement present? Has a shooter been caught? How many patients are there? What is their status? What additional resources are needed? Should ICS be initiated? What is the status of local EDs? What is the status of the system's surge capacity? Should a supervisor be updated? Should body armour be donned? Where should the initial responders stage? What's the best entry and exit? Is online medical control available? Is on-scene medical control by a physician needed? Should a mass-casualty plan be activated? Providers must be familiar with local protocols and guidelines regarding the management of gunshot wound patients, and should also be familiar with their local mass-casualty incident (MCI) plans.

When the first responding unit arrives, responders should establish command and begin an overall assessment or size-up. Using an incident command system is beneficial. ICS supports the integration of facilities, equipment, personnel, procedures and communications.

Limit providers entering the scene to the number necessary to immediately care for the patient. If a victim, including a fatality, needs to be moved to allow access to other viable patients, do it with respect to the fact that it is likely a crime scene.

In multiple-patient situations, it is likely more than one response organization will be involved. Establish a chain of command as soon as possible. Use common terminology whenever possible to avoid confusion, both on the radio and in person.

Hostage and active shooter scenarios present unique challenges. The involvement of law enforcement is essential. Providers' personal safety always takes priority. EMS may be asked to stage and stand by for additional instructions. If providers are in a secure area, they should focus on caring for patients and not be hindered by whatever else is happening. If possible, the preservation of evidence will be appreciated.

The first-arriving providers to shootings will need to start triage. This process can be difficult even for veteran providers. Patient access, availability of resources, communication effectiveness and the ability to conduct accurate initial assessments are just some of the challenges. Be as accurate and thorough as possible.

There are numerous triage systems, tools and vendors available. Some systems use colours or priorities based on the patient's overall condition (e.g., red for immediate, yellow for delayed, green for minor, and black for unsalvageable). Others use a two-stage approach where responders instruct patients to walk to a specific location for additional assessment. Patients who are unable to follow this direction require further triage, usually using an approach similar to the colour/priority system. A third technique is the CUPS system, which classifies patients as C for critical, U for unstable, P for potentially unstable or S for stable.

RAPID PATIENT ASSESSMENT

When triaging gunshot wound victims, rapid patient assessment to identify life-threatening injuries is essential. Critical interventions may include airway management, pleural decompression, pressure for external haemorrhage and avoiding on-scene delays before transport.

A rapid patient assessment can be done in less than 60 seconds. In a critical gunshot wound situation, it may not be necessary, for example, to pause after opening the patient's airway to determine what intervention should be considered. Rather, once the airway is open, the patient's respiratory quality, effort and effectiveness can be quickly assessed. Providers can simultaneously begin to determine the next steps for assessment and treatment.

Working knowledge of the MARCH protocol can possibly mean the difference between life and death. MARCH prioritizes treatment so that the first responder can rapidly access the situation and rapidly apply treatment in the most critical order that care should be received.

M - MASSIVE HEMORRHAGE

- control with tourniquet. ​

A - AIRWAY

- jaw thrust or head tilt. ​

R - RESPIRATIONS

- artificial breathing, assess for chest wall trauma if no breathing. ​

C - CIRCULATION / CSPINE

- control bleeding, re-evaluate the tourniquet. And consider cervical spine immobilization. ​

H - HYPO/HYPERTHERMIA

- protect from the elements, Helicopter/Hike - create and execute a plan to stay or go

FOCUSED ASSESSMENT

After performing the initial rapid assessment, the provider may, time permitting, perform a more detailed head-to-toe assessment. This should begin with a visual inspection, followed by a hands-on assessment. Begin the assessment with a visual inspection. Observe for bruising, wounds, lacerations or hematomas. Note the appearance and alignment of the trachea and if the jugular veins appear normal or distended. When palpating, note deformity or crepitus. Does the patient appear to be in respiratory distress, with tracheal tugging?

A penetrating wound to the anterior, lateral or posterior chest, including the armpits, should be considered life-threatening until proven otherwise. In addition, a gunshot wound to the chest should never be considered isolated to a single organ or system. The path of the bullet within the thorax cannot be determined in the field. It may have ricocheted, causing a variety of injuries. Examples include hemothorax, pneumothorax, hemopneumothorax, diaphragmatic rupture, pulmonary contusion, rib fracture, subcutaneous emphysema, pneumomediastinum, thoracic wall lacerations and sternal fracture.

If two or more gunshot wounds are present, assume substantial internal damage. This is important to note, as patients with combined intrathoracic and intra-abdominal injuries have a greater chance of dying.

When anticipating potential injuries, the abdominal region may be divided into quadrants. Visualize median and transverse planes that pass through the umbilicus at right angles. This divides the abdomen into four quadrants.

A high level of suspicion is necessary with penetrating abdominal wounds. Hemodynamically stable patients with penetrating abdominal trauma may have hollow or solid organ injuries. Solid organ injury may include extensive haemorrhage; hollow organ injury can involve haemorrhage as well as the spillage of gastrointestinal contents. Hypotension, narrow pulse pressure and tachycardia suggest serious intra-abdominal injury.

In a conscious patient, pain, guarding and rebound tenderness may indicate abdominal bleeding. In an unresponsive patient, abdominal distension and bruising may be the only indications of internal bleeding. Potential internal bleeding should be considered if the patient is unresponsive, has a distended/bruised abdomen, or is tachycardic or hypotensive. Penetrating injuries to the flank or retroperitoneal area may involve the duodenum, pancreas, kidneys, ureters, bladder, colon, major abdominal vessels and rectum.

The symptoms of a gunshot wound will be influenced by numerous factors, including the type of weapon involved, type of projectile, where the patient was shot, organs/systems involved, the patient's overall condition, substance abuse and baseline health.

Monitor and reassess vital signs throughout the incident. If they're available and time allows, apply cardiac monitoring and pulse oximetry. Changes in vital signs, including pre-and post-fluid bolus administration, should be documented and reported to the receiving hospital. When possible, obtain the patient's medical history, but do not invest excessive time.

TREATMENT

The prehospital management of patients with gunshot wounds may vary but will focus on supportive care and rapid transport. As an initial step, since any compromise to perfusion will directly affect oxygen delivery, give supplemental oxygen early.

Management of a gunshot wound to the head may include airway management and direct pressure for external haemorrhage. Depending on the mechanism and anatomy involved, airway management may be challenging. Adjuncts, including suction, should always be available. Although cervical spine immobilization may be indicated in select cases, the literature has not found a clear benefit to immobilizing victims of penetrating trauma, and recent studies have suggested possible harm. Consult your local protocols.

Management of a gunshot wound to the neck will be influenced by numerous factors. Providers may need to address active external haemorrhage, potential internal haemorrhage, tracheal compromise resulting in airway compromise, and open penetrating neck wounds. External bleeding may require direct pressure. An open wound may require the application of an occlusive dressing. Tracheal involvement may require advanced airway procedures such as intubation through the penetrating neck injury. C-spine immobilization may be indicated.

With a gunshot wound to the chest, patient management will depend in part on the suspected injury. Providers will need to consider the reported mechanism of injury, the potential for internal injury, the potential for internal and external blood loss, and the patient's overall condition. If the patient has sustained an open chest wound, an occlusive dressing may be needed.

These patients may have a variety of internal thoracic injuries. In cases of tension pneumothorax or tension hemopneumothorax, immediate intervention is indicated. Many EMS systems allow providers to perform chest decompression with needle thoracostomy. The technique involves inserting a large-bore catheter in the anterior chest between the second or third intercostal margin of the ribs on the affected side or between the fourth and fifth ribs laterally at what is often referred to as the midaxillary line. Once the catheter has been introduced, the air is released from the thorax, and the pressure within becomes equalized. This allows for improvements in air exchange and circulation.

   With penetrating thoracic trauma, consider fluid administration. Fluid selection, rate of administration and the amount administered will depend on local protocols, provider judgment and the patient's overall condition. There is still controversy regarding the ideal goal for blood pressure in the shooting victim. Some say higher blood pressures promote bleeding from injury sites; others argue permissive hypotension may compromise adequate perfusion. A summary of the current literature suggests an SBP of at least 90 mmHg, but not a lot higher, is a reasonable goal. The type of fluids to use is also the subject of debate. At this time, the literature best supports crystalloid solution (normal saline or lactated Ringer's) for these patients.

Treatment of a gunshot wound to the abdomen may include bandaging, direct pressure and the use of an occlusive dressing. The location of the wound and the patient's overall condition will influence specific treatment, including fluid administration. As with thoracic trauma, fluid selection, rate of administration and amount administered will rely on local protocols, provider judgment, and overall condition.

Treatment for gunshot wounds to the extremities will vary. With a suspected fracture, immobilize per local protocols. In many cases, pain relief will be indicated. Manage open extremity wounds and external haemorrhages with direct pressure and bandaging. Consider penetrating trauma in the mid-femur or higher to be life-threatening until proven otherwise.

With gunshot wounds to the head, neck, chest, abdomen, pelvis or thigh, establish at least one intravenous line. Fluid options may include crystalloids, colloids and blood substitutes. Hypertonic crystalloid solutions, such as hypertonic saline/dextran and hypertonic saline, have been considered as well. The literature has not shown advantages to hypertonic saline or colloid solutions in trauma patients, so crystalloids appear to be a reasonable approach at this time.

Administer fluids by local protocols. Aggressive IV fluid administration to maintain or reach normotension is discouraged in patients with penetrating injury unless the patient manifests severe shock or prolonged transport is expected. There may be select cases in which permissive hypotension is preferred over fluid administration intended to maintain normal blood pressure.

Whenever possible, prevent the patient from cooling to the point of shivering. When clothing is removed and IV fluids are administered, hypothermia can be induced. Prewarmed blankets and fluids may help avoid this. While there is research looking at the potential benefit of hypothermia in certain cases, intentionally inducing prehospital hypothermia on penetrating trauma patients is not an agreed-upon standard of care.

Contact the receiving hospital(s) as soon as possible. Early notification can play a critical role in ensuring timely and appropriate resources are available for your patient. Items to communicate include the number of patients, types of injuries and potential injury severity. Protocols should be clear regarding which hospitals are capable of managing gunshot wound victims.

Disclaimer: This article has been developed for educational purposes only. It is not a substitute for professional medical advice. Should you have questions or concerns about any topic described here, please consult your medical professional.