Violent Penetrating Trauma

 

Penetrating trauma results in a complex interplay between various mechanisms of injury. The unpredictable nature of the resulting trauma leads to many unique patient presentations. This section will focus on several factors that play into the variety seen in penetrating injury: the elements of a given injury, characteristics of penetrating objects, how those apply to gunshots/stabbings, and the assessment and management of patients with injuries secondary to violent penetrating trauma. 

 

Elements of Injury

The major elements that make up the sum injury seen with penetrating trauma are crushing, stretching, and cavitating injuries. The exact combination of these three components depends heavily on the shape, size, mass, and velocity of the penetrating object along with the type(s) of tissue the object traverses.

• CRUSHING: This is the first force experienced by the body: before any object pierces the body it exerts a crushing force to the skin and underlying muscle/organs. This same crushing force continues in front of the object as the object traverses the body. This leads to the following, a stretching force.

• STRETCHING: While the tissue at the point of impact with an object is crushed, all surrounding tissue is stretched. Just as with crushing forces, stretching forces occur all throughout an objects traversal of tissue. Due to the wider reach of the stretching force, it is responsible for damage in a wide area around the actual penetrating object.

• CAVITATION: Cavitation is the empty wound cavity that is left by an objects passage. The speed of an object is a major determinant of cavitation, as massive stretching forces caused by high-speed objects stretches large areas of tissue beyond their ability to recoil in an organized manner, resulting in large areas of shredded and missing tissue.

 

Characteristics of Penetrating Objects

The most important characteristics to consider of a penetrating object are shape, size, mass, velocity, and the tissue type that is traversed by the object. 

SHAPE/SIZE: When considered together these factors create the "cross section" of the object. Think of this as the "sharpness" or "point" of an object.

Extremely sharp penetrating objects exert extremely focused crushing force and minimal stretching force, damaging the tissue in their direct path while leaving surrounding areas unscathed. The cavitation of these injuries is minimal at best, given the low stretching force on surrounding tissue.

Blunt objects have the opposite pattern of injury, exerting crushing forces over a larger area while exerting massive stretching forces as they crush through tissue with massive amounts of force. The cavitation of these injuries is often significant due to the large amount of damaged tissue surrounding them.

Shape and size are complex, for an object with a given mass and velocity one space and size may cause fatal injury, while another may cause little more than a bruise. (a baseball moving at 45mph versus a knife moving at 45mph).

MASS: this property is closely tied to the energy of a penetrating object. More mass at a given speed = more energy. (i.e., a car moving at 60 mph vs. a basketball moving at 60 mph

If two objects are moving at the same speed, the more massive one will have more energy to crush, stretch, penetrate and then destroy tissue. High energy objects tend to cause significantly more crushing, stretching, and cavitating injury.

VELOCITY: the second determinant of energy, after mass. (Consider a bullet that has been thrown at you vs. one that is shot from a gun): 

High-velocity objects cause dramatically increased crushing and stretching force; cavitation is especially deadly in high-velocity trauma as discussed in this section under the heading "gunshot wounds."

TISSUE TYPE TRAVERSED: Tissue has varying levels of resistance to stretching and crushing trauma. 

Loose tissue such as fat or lung is very resistant to crush/stretch and can escape trauma with minimal cavitation or disruption. Alternately, dense tissue such as the muscle/liver/bone is easily destroyed by such forces and can present with impressive cavitation.

 

Gunshot and Stab Wounds

The above concepts are illustrated perfectly in wounds inflicted by some common weapons--guns and knives (or any sharp/pointed stabbing implement).

GUNSHOT WOUNDS (GSW): Gunshot wounds are the classic example of a high-velocity/low-mass object resulting in significant crushing and stretching injuries, despite the object's low size and pointed shape.

This is due to the massive cavitation induced by a high-velocity object encountering the water in the body. It creates a massive internal "explosion" as the kinetic energy of the bullet is transferred to the surrounding tissue. This crushes and stretches tissue in a wide circular pattern around the impact site, creating trauma far in excess of what the entrance wound would suggest.

The basic features of gunshot wounds:

ENTRANCE WOUNDS:

• Appear as a punched-out hole in the skin.
• The diameter of the wound is usually smaller than the bullet.  This is because the skin is elastic, and it retracts after the bullet enters the skin.
• There is an abrasion ring (sometimes called the abrasion collar) around the wound.  This is a ring of skin with the outer layer or epidermis missing, through which small amounts of blood can escape.
• Underlying tissues will not protrude.
• Tattooing or smudging (gunshot residues) may be present around the wound, depending on the distance of the shooter from the victim.

EXIT WOUNDS: 

• Exit wounds from low-velocity firearms tend to be relatively small.  They can have a variety of shapes, e.g., slit-like, X-shaped, or irregular. Exit wounds from high-velocity firearms tend to be large and destructive. 
• A typical exit wound does not have an abrasion ring.
• Underlying tissues may be protruding.
• Tattooing or smudging is always absent.

For the record, all GSWs to the abdomen require surgical exploration due to the likelihood of the bowel being perforated. If a patient is stable, even a GSW to the chest can be observed prior to determining a need for exploration (evolving anemia, hypotension = exploration). But these are post-arrival considerations. CALL TO ACTION: TRANSPORT EMERGENTLY!

STAB WOUNDS: Stab wounds are an example of a high-mass/low-velocity object causing massive trauma.

The injury pattern of a stabbing wound results from a moderate amount of energy concentrated on a minute point, allowing for the concentration of otherwise mild crushing forces into a microscopic area, easily pushing through tissue and damaging all structures it comes across.

Knife wounds are extremely serious due to the inability of the body to resist the extreme forces at the tip of the knife. Most forms of trauma will spare the relatively tough blood vessels/nerves, but stabbing trauma easily transects these structures.

Somewhat unintuitively, while solid fixed tissues such as the liver, kidneys, and body wall are highly likely to be damaged if they lie in the knifes trajectory, the free-floating bowels are less likely to be injured than with a bullet, as these "free-floaters" tend to get pushed or "twist" out of the way. 

CALL TO ACTION: TRANSPORT EMERGENTLY! You cannot determine what will happen emergently because you cannot see what is happening "below sea level," that is, below the skin, except deduce it indirectly with worsening vital signs. 

 

Assessment and Management: ABC(DE)s 

As with most forms of severe trauma, the management of penetrating trauma focuses on the management of the ABCs (airway, breathing, circulation) but also extends to D and E (disability and exposure) due to the complex and multifactorial nature of injuries secondary to violent penetrating injury. 

AIRWAY: Penetrating trauma to the head and/or neck has a high risk of airway compromise due to direct structural damage and "mass effects," expanding collections of blood/fluid that compress the air passages.

Opening the airway via modified jaw-thrust may be necessary as C-spine trauma is common in high-energy penetrating injuries to the head and neck. The modification of the jaw thrust that makes it modified is establishing in-line stabilization of the head and neck to move the jaw forward with a minimum head extension.

For abdominal penetrating injury, C-spine stabilization has not shown benefit unless clear neurological deficits (signs of spinal injury) are present. Always consider the use of mechanical airways (nasopharyngeal/oropharyngeal, portable suction, and endotracheal) as your jurisdiction allows. Remembering that nasopharyngeal airways are contraindicated in facial trauma.

BREATHING: Along with respiratory effort, breathing should be assessed as you open/assess a patient's airway: rate, quality, depth, and accessory muscle use are the key elements of breathing.

Palpation of the thorax and auscultation for lung sounds in both lungs and the neck is essential to reveal any hidden injury or pneumothorax in patients with penetrating trauma. 100% oxygen at 12-15 L/min via non-rebreather is the standard respiratory intervention in severe penetrating trauma. Positive pressure ventilation via Bag-Valve-Mask may be necessary depending on the patient's underlying injuries. 

CIRCULATION: A rapid assessment of both peripheral and central pulses can provide a solid estimate of a patient's perfusion and blood pressure while giving additional information on pulse rate, regularity, and quality.

• Radial pulse presence indicates an approximate systolic BP of at least 80 mmHg.
• Femoral pulse presence is associated with a systolic BP of at least 70 mmHg.
• Carotid pulse is associated with a systolic BP of at least 60 mmHg.

Because the pulse is palpable when peripheral pulses are absent (< 70 mmHg), the carotid is the best place to check for a pulse in an unconscious adult trauma patient.

• Skin: 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. Cool, pale, ashen, and/or moist skin is abnormal. Capillary refill time below 2 seconds also argues for sufficient perfusion.

 DISABILITY: A rapid physical and mental neurological test is sufficient to assess the presence of significant disability.

Physically, a rapid assessment may include testing the patient's grip and ability to dorsal/plantar flex the feet for evaluation of extremity movement and sensation. Loss of sensation and/or paralysis are the most alarming findings that indicate the disruption of nerves. Reassessment is also important, as changes in findings over time should be noted.

The potential disability resulting from trauma to the central nervous system (especially the head) should be assessed using the AVPU or GSC scales. The AVPU scale is far more practical in potentially chaotic trauma situations. The AVPU scale is as follows: Is the patient Alert and conversational, responsive to Verbal stimuli only, responsive to Painful stimuli only, or wholly Unresponsive? The GCS should be used to more accurately evaluate the possibility of disability when time permits.

EXPOSURE (and secondary assessment): The complete exposure of any patient with penetrating trauma is essential. Undress the patient for an evaluation of all skin surfaces. This is essential to avoid missing any injuries that are not a component of the primary presentation. If cutting off the clothing, cut along seams so as to not destroy forensic evidence (bullet holes, etc.).

The DCAPBLTS assessment (Deformity, Contusions, Abrasions, Penetrations, Bruising, Tenderness, Lacerations, and Swelling) is a common acronym to work through during the secondary assessment and a reminder of what one would expect to find in common penetrating injury.

NOTE: That in the case of wounds sustained from a violent encounter. It is important to preserve evidence, thorough documentation of all injuries is essential, and careful preservation of the victim's clothing is required.

If possible, cut along seams and place clothing in a paper bag for law enforcement to take custody of. Never discard any clothing, leave it with officers on scene or transport it with the patient to the ER.