Quick and Dirty Guide to Penetrating Trauma
All penetrating objects, regardless of the type or velocity, will cause some level of tissue disruption and damage. The damage occurs as a result of two types of forces; crushing and stretching. The specific character of the object, its speed of penetration, and the type of body tissue it penetrates, will determine which mechanism of injury prevails. Penetrating trauma causes a permanent cavitation; an opening in the body caused by a force that pushes body tissues away from the path of the projectile. Body tissue with high water density such as the liver, spleen, and muscle or solid density tissue such as bone and cartilage are more likely to cause a permanent cavitation. Perforating trauma, a form of penetrating trauma, occurs when an object enters, causes its damage, and then continues on a trajectory to exit the body; usually by the path of least resistance. Both types of penetrating trauma can have devastating consequences for the victim. The most common cause of penetrating trauma in the U.S. is, you guessed it; gunshot wounds.
Penetrating Trauma & Kinetic Energy
The actual trauma from a bullet is a result of the exchange of kinetic energy between the projectile (bullet) and the human body. In the case of penetrating trauma, the object is often a bullet or a knife. However don't under estimate other significant sources of penetrating trauma like, fence posts, nails, pencils and similar sharp objects that can also cause severe penetrating trauma to the human body, causing significant injuries. The exchange of energy, in both blunt and (high/low velocity) penetrating trauma can be explained using the kinetic energy equation:
Kinetic Energy= 1/2 Mass (Weight) x Velocity (Speed)2
The complicated kinetic energy formula simply states, the greater the mass (or weight) of an object, the greater the resultant energy that is exchanged. The velocity or speed of the object however, plays a more important role, for example; doubling the speed of an object will instantly increase the kinetic energy 4 times. So in terms of ballistics, a small, fast bullet will cause more damage to the human body than a large, slow projectile will because, the velocity of the object is more important in deciding the kinetic energy exchange (therefore tissue damage), than the mass of the object is. This is why, a knife blade although larger than a bullet, tends to cause a less severe injury than a bullet.
When a projectile such as a bullet strikes the human body, it slows down and its energy is transferred to the body. This type of energy transfer can be neither created nor destroyed, it can only be changed. It is important to recall that numerous factors affect the injuries created by projectiles, including its size and shape as it travels through the body as well as, its velocity. The spin and tumble of the bullet, if there is any, fragmentation of the projectile, and the victim's distance from the gun are also factors.
Various body tissues respond differently to a projectile based on their density, resiliency, content and similar factors. The connective tissues that absorb the kinetic energy, would essentially limit tissue damage. Bones, on the other hand, rapidly break and fragment when contracted by a projectile. The effect of penetrating trauma on organs depends on the organ type; solid organs are dense and have low resiliency, making them more vulnerable to fracture with significant associated injuries. Hollow organs, on the other hand, are either fluid filled, air-filled, or both. Because of the density of fluid, opposed to air, the fluid-filled organs tend to sustain greater damage than air-filled organs, such as the lungs.
Injury to the victim begins when the tip of the projectile impacts the body tissue. The tissues are then pushed forward and laterally, subsequently colliding with the adjacent tissues, causing damage. Tearing and crushing tissues, occurring along the projectile track and from any smaller fragments that may break off from the projectile.
A shock wave follows the bullet creating a rapid change in pressure, temperature or density secondary to the projectile. In high-energy, high-velocity weapons, shock waves can sometimes approach 200 atmospheres of pressure. The shock wave generated by the bullet usually lasts only a few microseconds. However, the result can be extremely damaging. Several factors related to the bullet affect the subsequent injury, including the bullet’s profile. The profile is the size and shape of the bullet as it contacts the human body. The larger the profile, the greater will be the rate of subsequent energy exchange. Most bullets will rotate or tumble somewhat on their axis during travel. Short, high-velocity bullets tend to tumble and rotate more severely when they strike human tissue. Rifles contain grooves within the barrel (rifling) that imparts a spin on the projectile that serves to minimize yaw and tumble. Thus, the greater the tumble of a projectile, the more rapid the subsequent delivery of kinetic energy and resultant damage.
Priority 1: Scene Safety
Shooting scenes are the most chaotic, dangerous scenes we face and they may range from a single victim with assailants no longer present to mass casualty incidents or ongoing crime scenes with active shooters still at large.
When arriving at the scene of a possible shooting, consider the following:
- Is the scene safe and secure or unsafe and active?
- Is law enforcement present or do we stage, and wait?
- Has a shooter been caught and is he the only one?
- How many patients are there and how many unknown victims may be possible?
- What is their status?
- What additional resources are possibly needed?
- What is the status of local hospitals?
- What is the status of the system's surge capacity?
- Should a supervisor be requested to the scene?
- Where should initial responders stage?
- What's the best entry and exit from the scene (transport sector in an MCI)?
- Is online medical control available and aware of the situation?
- Is there a potential for the situation worsen?
- Is medical control by an emergency physician needed on scene?
- Should a mass casualty plan be activated?
Providers must be familiar with local protocols and guidelines regarding management of gunshot wound patients, and should also be familiar with their local mass-casualty incident (MCI) plans. Take the time to review and prepare, check out the Quick and Dirty Guide to START triage.
A rapid patient assessment should be done in less than 60 seconds.
When triaging a gunshot wound victim, rapid patient assessment to identify life-threatening injuries is crucial. Critical interventions include airway management, pleural decompression, pressure for external hemorrhage and avoiding on-scene delays before transport. In a critical gunshot wound situation, 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.
ABCDE of Penetrating Trauma
If the patient's airway is at risk, rapid intervention is critical. The airway may need to be opened using a modified jaw-thrust, especially if cervical spine injury is suspected. Additional management may include inserting a nasopharyngeal, oropharyngeal or advanced airway depending on local protocols. Early airway management is priority where there has been a gunshot wound to the chest, neck, or abdomen with an expanding hematoma. Severe bleeding, swelling and dysfunction from the assault on the body will quickly begin to cause complications that are hard for the traumatized systems to overcome. In this situation, the airway can become extremely difficult to manage. As the patient's airway is opened, evaluate breathing and respiratory effort simultaneously. Observe respiratory rate, quality, and depth, and note accessory muscle use. Assess breath sounds as soon as it is practical to do. Depending on the situation, providers may want to perform auscultation after palpating the thorax, as palpation may reveal tenderness and/or crepitus. Palpate with caution to avoid injury from possible fractured bones and bullet fragments.
Circulation can be quickly assessed using common pulse locations. Evaluate for presence, rate, regularity, quality, and estimated BP when needed. Pulses can be used to estimate blood pressure in an emergency, until the pressure can be properly evaluated.
- Radial pulse presence indicates an approximate systolic BP of at least 80 mmHg
- Brachial or femoral pulse presence is associated with a systolic BP of 70 mmHg
- Carotid pulse is associated with a systolic BP of 60 mmHg
The patient's skin can also be a good indicator of circulatory status. Skin that is warm, dry, and pink is indicative of adequate perfusion. Abnormal findings include skin that is cool, pale, ashen, and/or moist. Cap refill time of < or = 2 seconds reveals the presence of peripheral circulation quickly. It is crucial to perform a rapid assessment of the patient's neuro status, ASAP. A simple scale to use is the AVPU scale (alert, responsive to verbal stimuli, responsive to painful stimuli, or unresponsive). The GCS should be used to evaluate the possible disability of the patient. Proper evaluation of the patient includes assessing for the possibility of paralysis. A rapid assessment may include grip testing and dorsal/plantar flex evaluation for extremity movement and sensation.
It is essential to expose the patient for inspection, as the assessment continues. This is important in the case of an assault victim, as the clothing or other items worn by the victim may hide a potential entry or exit wound. Inspect the victim for the presence of external hemorrhage, wounds from powder burns and DCAPBTLS (Deformity, Contusions, Abrasions, Penetrations, Bruising, Tenderness, Lacerations, and Swelling). When clothing is removed, avoid cutting through any holes caused by a projectile or blood/tissue. If possible, cut along the seams of the victims clothing and place in a plastic bag. The clothing may become valuable evidence later, so never discard clothing of any type. Leave it on scene if LE is present or transport it with the patient to the ER and advise staff that it may be evidence.
The prehospital management of a patient with a GSW may vary from region to region, but will always focus on supportive care and a safe, rapid transport. As an initial step, give high flow oxygen early in the treatment modality. Managing a gunshot wound involving the head, will probably require airway management and direct pressure for any external hemorrhage. Depending on the mechanism and anatomy involved, airway management may be very challenging. Airway adjuncts, including portable suction, should always be readily 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. As always, know your local protocol. Tracheal involvement may require advanced airway procedures, such as intubation.
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, potential for internal injury, potential for internal and external blood loss, and patient's overall condition. If the patient has sustained an open chest wound, an occlusive dressing should be used. 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 proper technique for a needle decompression can be found in The Quick and Dirty Guide to Chest Trauma as well as, an awesome 10-minute video explaining Needle Decompression.
With any gunshot wound, establish at least one large bore intravenous line. Aggressive IV fluid administration to maintain or reach normotension is discouraged in patients with penetrating injury unless the patient shows serious signs and symptoms of severe shock or prolonged transport is expected. There may be select cases in which permissive hypotension is preferred over fluid administration intended to maintain a normal blood pressure. So, administer fluids by the latest local protocols. Whenever possible, prevent the patient from cooling to the point of shivering. When clothing is removed and IV fluids are administered, hypothermia can be accidentally induced. Pre-warmed blankets and fluids may help avoid hypothermia and shock. Hopefully, this table explaining the various stages of shock will help!