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Blast Injuries and Burn Care

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This is the second in a series of articles focused on best practices for burn care.

Development of this article began in December 2012. In the immediate aftermath of the Boston Marathon bombings, additional lessons will emerge to be applied to the science of managing these types of incidents. We would like to acknowledge the actions of those who heard the call for help and responded quickly on April 15. It is obvious that extensive planning in the months and weeks before, staging of resources and response actions lessened the severity of this horrific event.

There can be multiple sources of blast injuries.1–4 Was a blast accidental or intentional? Although scene safety is central to all responses, an intentional blast has greater potential for risk to responders than most response scenarios.2

Blasts can produce horrific injuries to patients, with the burn component and amputations being the most obvious at first contact.2,4–8 It is with this fact in mind that blast injury was included in this series. While burn injuries are a priority, the primary cause of morbidity and mortality is the impact of the overpressurization force (blast wave) on the body. This blast wave can produce pulmonary damage (to include a condition described as blast lung, air emboli, pneumothorax and hemothorax), rupture of the tympanic membrane (eardrum) or hollow viscus (organ) injury. Though the rupture of the tympanic membrane is not a true emergency, as a finding it should sharply raise your suspicion of the potential for critical concomitant lung or viscus injuries.9–11

Conversely, however, the absence of tympanic membrane injury does not clear your patient of other potentially critical injuries.
Following an explosion, patient injuries may result from blunt force, projectile trauma or the thermal wave, or any combination. Injuries include airway complications, exsanguination, and orthopedic and burn injuries. Burn injuries should be managed immediately after or concurrently with the immediate life threats of airway compromise and hemorrhage.5,7

When a scene involves a blast injury, expeditiously remove patient and begin transport to a hospital. Protect the airway and cervical spine and control life-threatening hemorrhage. Otherwise, defer care and a more detailed assessment until the patient is in the ambulance. During your assessment, if there are signs the patient was carrying the source of the blast, notify law enforcement immediately. Most likely, a law enforcement officer will accompany you and your patient to the hospital.

Defining a Blast/Explosion

A blast or explosion happens when a chemical conversion occurs that changes a solid or liquid to highly pressurized gases in an extreme manner with substantial instantaneous release of gas and heat.17 This rapid expansion of gases compresses the surrounding air, creating incredible waves of pressure that move out from the point of explosion. This blast wave dissipates and disperses as it encounters more stable air and moves across solid or liquid surfaces. The friction of the blast wave encountering the stable air and other stationary objects aids in slowing and dispersing it. However, the closer an object or person is to the point of the explosion, the more likely this incredible energy (which includes a thermal component) will be absorbed by that person or item. Items that are either a part of an explosion or carried by the blast wave are called shrapnel. Blast injuries are primarily produced by one or more of the three direct components of a blast: the blast wave, the thermal component or shrapnel.

If the blast wave is limited in the area where it can rapidly expand, the pressure it produces can be concentrated or amplified. Examples of this scenario include blasts in confined spaces like on a bus, in a narrow street between tall buildings, or in a hallway with closed doors. Even in a semi-open area such as a street, if a blast occurs next to a building, the remaining area of less resistance (the street and sidewalks) will be struck by the concentrated or amplified blast wave. Another way to think about this is that a patient is far more likely to survive a car-bomb blast 100 feet away if it explodes in an open field rather than an alley between two tall buildings.

In addition to distance, shielding is also a key factor in determining the likelihood of injury. The greater your distance from the point of explosion, the more likely you are to survive. If you are standing behind a fixed solid object (shielding) that can either dissipate or deflect the blast wave or deflect objects propelled by the blast, you are more likely to survive the blast as well.

Though certain chemical reactions are hotter than others, all blast waves include a thermal component. Furthermore, the temperature of this blast wave varies, depending on the agent used for the blast. Nevertheless, it is this thermal aspect that produces significant burn injuries.

If a blast occurs underwater, there is a compounding effect of the energy as the blast wave attempts to pass through water, which is greater in density than air. However, it also dissipates more quickly, and the shrapnel travels a shorter distance as friction reduces its velocity.

Scene Size-up

When your response includes the report of an explosion, your scene size-up must include trying to better understand if it’s the result of an accidental or intentional act. Either situation may pose a risk to responders. Additionally, explosion scenes will likely be chaotic, and this information may not be initially available. Explosions may result in buildings, including nearby structures, becoming unsteady and unsafe. In addition to the undermined structural stability, rubble and other debris may also pose an airborne threat. Do not attempt a rescue you are not trained, equipped and prepared to undertake; always await responders who have that equipment and expertise.

Those who can evacuate on their own or with the aid of others who are either uninjured or have minor injuries will either await your response or self-transport to a nearby or trusted medical facility or clinician. Scene safety can include debris issues regardless of the nature of the blast. A blast is more likely to be a mass-casualty incident than most of your typical alarms. Your scene size-up should include an estimate of the number of injured.

Be prepared to be confronted by multiple patients and request appropriate additional ambulances and other resources as needed. If a blast is significant, there could be considerable loss of life in the immediate area. This scene could include detached limbs, penetrating trauma, significant blood loss and deformation of the survivors as well as those killed.

Initial Triage

Triage of patients includes the typical assessments you would use to determine who is critical (red tags), who has potentially serious injuries (yellow tags), who has minor injuries (green tags) and who is either dead or has nonsurvivable injuries (black tags).

All common triage systems include some assessment series that involves positioning the airway to include breathing and life-threatening hemorrhage assessment.

Moving from triage of the group to care for individual patients, the primary survey is consistent with a trauma assessment: airway, breathing, circulation, disability and exposure. The secondary assessment should pay particular attention to head, thorax, abdomen and extremities for injuries produced by the concussion aspect of the blast wave, the thermal aspect, and shrapnel that may have contused or penetrated the patient.

One of the more delicate parts of the body is the tympanic membrane (eardrum). It is quite sensitive to pressure, and for patients impacted by a blast wave, there is a reasonable chance the most seriously injured will have damage to or rupture of the tympanic membrane. This can be identified by blood in the ear canal or loss of hearing.9,11 Visible blood in one or both ear canals or sudden hearing loss indicates the patient was likely to have been in the immediate area of the blast and should be considered serious (yellow-tagged) until further evaluated.

While EMS professionals have a typical routine for assessing potential trauma patients (and this article will not suggest you change that approach), there are several key areas of focus when assessing and managing blast-injured patients.

Common life-threatening injuries to be aware of include closed head injuries and cervical spine injuries. With the chest, pay close attention for the possibility of pneumothorax, hemothorax or tension pneumothorax (caused by rapidly changing pressures created by the blast wave). For the abdominal area, it is important to note that hollow organs, such as the spleen and stomach, may be damaged by the rapidly changing pressures. For a ruptured spleen (upper left quadrant), there will be point tenderness and other typical signs associated with exsanguination. If you suspect solid viscus injury, it is also reasonable to suspect and continue to reevaluate for hollow viscus injury.18

Assess the pelvis for stability and all extremities for deformity and stability. Additionally, the blast wave can lead to fractures caused by propelled objects, the wave itself or a patient being thrown against a fixed object. An overall assessment should include looking for damage produced by shrapnel and burn injuries.

Depending on the source of the explosion, the blast wave may include very hot air that creates critical burn injures at the point of contacting the patient. For some of the more catastrophic blast scenarios, this could create a profound number of burn-injured patients. Blast-injured patients commonly have significant burns that become the focus of clinicians. Although burns can be life-threatening, do not lose sight of the principle concern for loss of life, the underlying traumatic injury.

Types of Explosions

Accidental Explosions
The most common explosion is accidental. Several case study explosions available for review in the U.S. over the past 15 years include the 1999 Jahn Foundry explosion in Massachusetts,19 2008 Savannah sugar factory fire20 and 2003 West Pharmaceutical fire/explosion in North Carolina.21 Even when the cause of an explosion is accidental, it is imperative that responders recognize that the conditions that led to the initial explosion (such as a gas leak) may still be present and could lead to a second explosion. All involved in the area where the blast occurred, if they can, typically will attempt to move as far away as they safely can.

Do not attempt to rescue those you are not trained and equipped to rescue. Establish a safe perimeter and remain there until those with the training and equipment needed for a rescue arrive.

Intentional Explosions
If there are indications an explosion was intentional, the next greatest concern is the threat for a secondary device. Evaluate surroundings for suspicious items such as unattended backpacks, packages or vehicles. Do not enter a scene that has not been cleared. If you find yourself in a scene you determine is potentially dangerous, identify the quickest/safest route back out to a safe area.

Intentional explosions can include a host of hazards for responders. Additional improvised explosive devices may have delayed timers or be remotely triggered once responders arrive. If there’s any indication of an intentional blast, stay at a safe distance. If you have already begun patient care before recognizing an intentional blast, back away to what is identified as a safe perimeter. Ideally, take the patient with you.

Discussion

Explosions force responders to confront and manage chaotic scenes. Those who can self-evacuate from blasts generally will and meet you as you arrive. Those who cannot may be aided or carried to an area considered safe. A disproportionate number of those with minor injuries may self-evacuate to nearby hospitals. This could potentially engage and tie up resources for those with less serious injuries and further complicate your response and destination choices. The CDC has developed multiple resources for responders and hospitals to aid in the response to blast injuries.32 Information from those resources was included in this work.

One such example is the difference between high-order (HE) and low-order (LE) explosives. With HE, the nature of the blast can be substantially more complicated, with more injuries and widespread damage than with LE. However, in the chaos of triage and treatment for initial patients, knowing the difference in explosive type will not change the care you provide.

Significant information and resources are also available regarding a span of subtopics from improvised bombs and blast injury patterns to concussive wave patterns. Additionally, guides are available online from the CDC that include stratification of injuries based on proximity to the point of ignition (primary, secondary, tertiary and quaternary; see “Blast Injury Types”). Those references provide a greater level of detail than is offered in this paper. The focus of this work is to provide information that is useful, concise and consistent with current standards of systematically managing patients with combined burn/traumatic injuries.

Conclusion

Patients with blast injuries are difficult to manage because their most obvious injuries may not be the most likely to contribute to their mortality. From full-thickness burns to partial and full amputations, blast injury survivors may present with graphic injuries. Nevertheless, death could also be caused by something less obvious, such as a pulmonary contusion, tension pneumothorax or hollow organ rupture produced by the shock wave.
Your initial assessment may reveal only subtle signs of a much greater underlying injury. While burn-injured patients are best managed at burn centers, they must first be cleared of potential traumatic injuries before they are transferred or transported. (The exception is when the closest trauma center is colocated with a burn center. Nevertheless, although this is a recommendation, always follow your local protocol.)

Blast Injury Types

Primary: Injury from overpressurization force (blast wave) impacting the body surface. Tympanic membrane (eardrum) rupture, pulmonary damage and air embolization, hollow viscus injury.
Secondary: Injury from projectiles (flying debris, bomb fragments, shrapnel). Penetrating trauma, fragmentation injuries, blunt trauma.
Tertiary: injuries from displacement of victim by the blast wind. Blunt or penetrating trauma, fractures, traumatic amputations.
Quaternary: All other injuries from the blast, to include crush injuries, burns, asphyxia, toxic exposures and exacerbations of chronic illness.
Adapted from: www.emergency.cdc.gov/BlastInjuries

Blast Injuries: Key Issues to Ask/Determine

Nature of device: Chemical/agent, quantity.
Method of delivery: Incendiary, explosive.
Nature of environment:

  • Open area, enclosed space, water or confined area.
  • Distance from blast;
  • Shielding/protective barrier;
  • Other environmental hazards.

For a blast in liquid or under water, the concussion is exacerbated due to the density of the liquid. However, shrapnel is less likely to be dispersed over a wide area.

For a blast in open air, the wave is unidirectional. It comes from the blast area and disperses as the force moves away from the point of explosion. In a confined area such as a bus or an alley, the blast wave is concussive, reciprocating (back and forth motion) and amplified.

Evaluate for: Blunt trauma; crush injury or compartment syndrome; penetrating injuries; pneumothorax or tension pneumothorax; head injuries, to include traumatic brain injury or concussion; tympanic membrane (eardrum) rupture; fractures; and abdominal hemorrhage or organ perforation (hollow organs are most vulnerable).

The most common cause of death: shock wave leading to blast lung, viscus (organ) damage, and debris propelled by the blast that acts as shrapnel.

Low- and High-Order Explosives

Low-order explosive materials (LE) deflagrate, meaning the explosion begins with a flame and is a product of a combustible substance and an oxidant. The slow burn (measured in cm/sec. up to m/sec.) is less than the speed of sound. However, the energy released can be amplified with pressure or within a confined space such as a rocket tube or the barrel of a gun. One advantage with the relatively slow burn of LEs is that they can be used as propellants. An example includes gunpowder for bullets or pyrotechnics. The propellant in the two solid fuel rockets attached on each side of the space shuttle’s liquid fuel tank was LE material.

High-order explosive materials (HE) detonate, meaning the explosion travels faster than the speed of sound (measured generally in km/sec.). This detonation produces an incredible shock wave and widespread damage. HE materials are typically used in military applications or for industrial use, such as mining. For military applications, one of the more common examples is known as a plastic explosive version of Composition C, referred to as C4. Other typical HE examples include trinitrotoluene (TNT) and pentaerythritol tetranitrate (PETN).17

Terrorist Use of Explosives

The first truck bomb in the U.S. involved a local resident who used dynamite to blow up his truck and collapse part of a school, killing 40 children in 1927 in Bath, MI.22,23 There were multiple accounts of dynamite bombs being used onboard airplanes in the 1950s and 1960s. One of note included a briefcase bomb on a flight from New York to Miami in 1960. The bomb was detonated as the airplane flew over Wilmington, NC, blowing a hole in the fuselage. The pilots attempted to turn back to the airport in Wilmington, but the aircraft crashed just south of the city in the town of Bolivia, killing all on board.24
The combining of fertilizer (active ingredient: ammonium nitrate) and fuel oil or diesel fuel can produce a significant explosion. The bombing of Oklahoma City’s Murrah Federal Building in 1995 included a large rental truck filled with fertilizer and diesel fuel, detonated remotely. It killed 168 in the building (including one responder.)25–28 Note that a specific mixture of ammonium nitrate and fuel oil (ANFO) is sold for mining and quarrying. While similar in composition, ANFO is a commercially sold product and is not a “fertilizer bomb.”

These explosives are today referred to as improvised explosive devices (IEDs). Given the overwhelming superiority of conventional forces of the U.S. military and allies throughout the Iraq and Afghanistan conflicts, those in opposition have often resorted to using IEDs. These ranged from pipe bombs to attaching detonators to artillery shells and burying them alongside highways.

Improvised Nuclear Devices

A great potential threat faced by responders is the use of an improvised nuclear device (IND).12 The consequences of INDs could be far greater than those of any other hazard faced today in the U.S.13–15 The blast and burn injury potential for such a disaster far exceeds current capacities for absorbing a surge of patients.16 Although the likelihood is quite remote, an IND detonation is the worst-case scenario. Thus, if large-scale efforts are aimed at creating a framework to manage the general aspects of such a catastrophe, scalability and flexibility will make other responses more manageable and successful regardless of the size of the disaster.

Battlefield Lessons

Battlefield medicine from the Iraq and Afghanistan conflicts has contributed greatly to improving how we care for acutely injured patients, including those with with burn and blast injuries.29,30 The importance of this information and its translation to improved civilian patient care cannot be overstated.

In World War II and, to a lesser extent, the Korean and Vietnam conflicts, these patients would typically die of their injuries. With the rapid improvement in helmets and body armor, those areas left less protected are where injuries are now concentrated. Thus, survivors of armed conflict today are more likely to have chronic issues associated with large burns and partial or complete amputation in the months and years following the injury.31 As with other injuries more likely encountered in civilian life, the first battle is saving a life. The next is improving its quality.

References
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29. Cancio LC, Horvath EE, Barillo DJ, et al. Burn support for Operation Iraqi Freedom and related operations, 2003 to 2004. J Burn Care Rehabil, Mar–Apr 2005; 26(2):151–61.
30. Chung KK, Blackbourne LH, Wolf SE, et al. Evolution of burn resuscitation in operation Iraqi freedom. J Burn Care Res, 2006 Sep–Oct; 27(5): 606–11.
31. Ramasamy MA, Hill CA, Masouros S, et al. Outcomes of IED foot and ankle blast injuries. J Bone Joint Surg, 2013 Mar 6; 95(5): e251–7.
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Randy D. Kearns, DHA, MSA, NREMT-P (ret.), is program director for the North Carolina Burn Disaster Program and administrator of the EMS Performance Improvement Center at the University of North Carolina School of Medicine.

Charles B. Cairns, MD, FACEP, FAHA, is a professor and chair of emergency medicine at the University of North Carolina School of Medicine.

James H. Holmes, IV, MD, FACS, is director of the Wake Forest Baptist Medical Center’s Burn Center and associate professor of surgery at the Wake Forest School of Medicine.

Preston B. Rich, MD, MBA, FACS, is a professor of surgery and chief of trauma, critical care and emergency surgery at the University of North Carolina School of Medicine, as well as a firefighter and medical advisor for the Chapel Hill (NC) Fire Department.

Bruce A. Cairns, MD, FACS, is director of the North Carolina Jaycee Burn Center and the John Stackhouse Distinguished Professor of Surgery/Microbiology and Immunology at the University of North Carolina School of Medicine.

 

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