Blast injury

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Blast injury
MurrahBuildingInjuriesbyFloorOCB.jpg
Floor-by-floor breakdown of the injuries/deaths in the Alfred P. Murrah Federal Building from the April 1995 Oklahoma City bombing
Specialty Emergency medicine, trauma surgery

A blast injury is a complex type of physical trauma resulting from direct or indirect exposure to an explosion. [1] Blast injuries occur with the detonation of high-order explosives as well as the deflagration of low order explosives. These injuries are compounded when the explosion occurs in a confined space.

Contents

Classification

Diagram of a blast injury Anatomy of a Blast.svg
Diagram of a blast injury

Blast injuries are divided into four classes: primary, secondary, tertiary, and quaternary.

Primary injuries

Primary injuries are caused by blast overpressure waves, or shock waves. Total body disruption is the most severe and invariably fatal primary injury. [2] Primary injuries are especially likely when a person is close to an exploding munition, such as a land mine. [3] The ears are most often affected by the overpressure, followed by the lungs and the hollow organs of the gastrointestinal tract. Gastrointestinal injuries may present after a delay of hours or even days. [3] Injury from blast overpressure is a pressure and time dependent function. By increasing the pressure or its duration, the severity of injury will also increase. [3]

Extensive damage can also be inflicted upon the auditory system. The tympanic membrane (also known as the eardrum) may be perforated by the intensity of the pressure waves. Furthermore, the hair cells, the sound receptors found within the cochlea, can be permanently damaged and can result in a hearing loss of a mild to profound degree. [4] Additionally, the intensity of the pressure changes from the blast can cause injury to the blood vessels and neural pathways within the auditory system. [4] [5] Therefore, affected individuals can have auditory processing deficits while having normal hearing thresholds. The combination of these effects can lead to hearing loss, tinnitus, headache, vertigo (dizziness), and difficulty processing sound. [5]

In general, primary blast injuries are characterized by the absence of external injuries; thus internal injuries are frequently unrecognized and their severity underestimated. According to the latest experimental results, the extent and types of primary blast-induced injuries depend not only on the peak of the overpressure, but also other parameters such as number of overpressure peaks, time-lag between overpressure peaks, characteristics of the shear fronts between overpressure peaks, frequency resonance, and electromagnetic pulse, among others. There is general agreement that spalling, implosion, inertia, and pressure differentials are the main mechanisms involved in the pathogenesis of primary blast injuries. Thus, the majority of prior research focused on the mechanisms of blast injuries within gas-containing organs and organ systems such as the lungs, while primary blast-induced traumatic brain injury has remained underestimated. Blast lung refers to severe pulmonary contusion, bleeding or swelling with damage to alveoli and blood vessels, or a combination of these. [6] It is the most common cause of death among people who initially survive an explosion. [7]

Secondary injuries

Secondary injuries are ballistic trauma caused by impacts of flying shrapnels and other objects propelled by the explosion. [8] These injuries may affect any part of the body and sometimes result in penetrating trauma with visible bleeding. [9] At times the propelled object may become embedded in the body, obstructing the loss of blood to the outside. However, there may be extensive blood loss within the body cavities. Secondary blast wounds may be lethal and therefore many anti-personnel explosive devices are designed to generate fast-flying fragments.

Most casualties are caused by secondary injuries as shrapnels generally affect a larger area than the primary blast area, because debris can easily be propelled for hundreds or even thousands of meters. [8] [9] Some explosives, such as nail bombs, are deliberately designed to increase the likelihood of secondary injuries. [8] In other instances, the target provides the raw material for the fragments thrown into surrounding, e.g., shattered glass from a blasted-out window or the glass facade of a building. [8]

Tertiary injuries

Displacement of air by the explosion creates a blast wind that can throw victims against solid objects. [3] Injuries resulting from this type of traumatic impact are referred to as tertiary blast injuries. Tertiary injuries may present as some combination of blunt and penetrating trauma, including bone fractures and coup contre-coup injuries. Children are at particularly high risk of tertiary injury due to their relatively smaller body weight. [8]

Quaternary injuries

Quaternary injuries, or other miscellaneous named injuries, are all other injuries not included in the first three classes. These include flash burns, crush injuries, and respiratory injuries. [8]

Traumatic amputations quickly result in death, unless there are available skilled medical personnel or others with adequate training nearby who are able to quickly respond, with the ability for rapid ground or air medical evacuation to an appropriate facility in time, and with tourniquets (for compression of bleeding sites) and other needed equipment (standard, or improvised; sterile, or not) also available, to treat the injuries. Because of this, injuries of this type are generally rare, though not unheard of, in survivors. Whether survivable or not, they are often accompanied by significant other injuries. [8] The rate of eye injury may depend on the type of blast. [8] Psychiatric injury, some of which may be caused by neurological damage incurred during the blast, is the most common quaternary injury, and post-traumatic stress disorder may affect people who are otherwise completely uninjured. [8]

Mechanism

Blast injuries can result from various types of incidents ranging from industrial accidents to deliberate attacks. [9] High-order explosives produce a supersonic overpressure shock wave, while low order explosives deflagrate and do not produce an overpressure wave. A blast wave generated by an explosion starts with a single pulse of increased air pressure, lasting a few milliseconds. The negative pressure (suction) of the blast wave follows immediately after the positive wave. The duration of the blast wave depends on the type of explosive material and the distance from the point of detonation. The blast wave progresses from the source of explosion as a sphere of compressed and rapidly expanding gases, which displaces an equal volume of air at a very high velocity. The velocity of the blast wave in air may be extremely high, depending on the type and amount of the explosive used. An individual in the path of an explosion will be subjected not only to excess barometric pressure, but to pressure from the high-velocity wind traveling directly behind the shock front of the blast wave. The magnitude of damage due to the blast wave is dependent on the peak of the initial positive pressure wave, the duration of the overpressure, the medium in which it explodes, the distance from the incident blast wave, and the degree of focusing due to a confined area or walls. For example, explosions near or within hard solid surfaces become amplified two to nine times due to shock wave reflection. As a result, individuals between the blast and a building generally suffer two to three times the degree of injury compared to those in open spaces. [10]

Neurotrauma

Blast injuries can cause hidden sensory [11] and brain damage, with potential neurological and neurosensory consequences. It is a complex clinical syndrome caused by the combination of all blast effects, i.e., primary, secondary, tertiary and quaternary blast mechanisms. Blast injuries usually manifest in a form of polytrauma, i.e. injury involving multiple organs or organ systems. Bleeding from injured organs such as lungs or bowel causes a lack of oxygen in all vital organs, including the brain. Damage of the lungs reduces the surface for oxygen uptake from the air, reducing the amount of the oxygen delivered to the brain. Tissue destruction initiates the synthesis and release of hormones or mediators into the blood which, when delivered to the brain, change its function. Irritation of the nerve endings in injured peripheral tissue or organs also contributes significantly to blast-induced neurotrauma.

Individuals exposed to blast frequently manifest loss of memory of events before and after explosion, confusion, headache, impaired sense of reality, and reduced decision-making ability. Patients with brain injuries acquired in explosions often develop sudden, unexpected brain swelling and cerebral vasospasm despite continuous monitoring. However, the first symptoms of blast-induced neurotrauma (BINT) may occur months or even years after the initial event, and are therefore categorized as secondary brain injuries. [12] The broad variety of symptoms includes weight loss, hormone imbalance, chronic fatigue, headache, and problems in memory, speech and balance. These changes are often debilitating, interfering with daily activities. Because BINT in blast victims is underestimated, valuable time is often lost for preventive therapy and/or timely rehabilitation. [12]

Blast wave PTSD research

In addition to known post-traumatic stress disorder (PTSD) risk factors experienced by both civilians and military personnel in combat areas, in early 2018, 60 Minutes reported [13] that neuropathology specialist, Dr. Daniel "Dan" Perl, had conducted research on brain tissue exposed to traumatic brain injury (TBI), discovering a causal relationship between IED blast waves and PTSD. Perl was recruited to the faculty of the Uniformed Services University of the Health Sciences as a professor of pathology and to establish the Center for Neuroscience and Regenerative Medicine mandated by Congress in 2008. [14]

Casualty estimates and triage

Explosions in confined spaces or which cause structural collapse usually produce more deaths and injuries. Confined spaces include mines, buildings and large vehicles. For a rough estimate of the total casualties from an event, double the number that present in the first hour. Less injured patients often arrive first, as they take themselves to the nearest hospital. The most severely injured arrive later, via emergency services ("upside-down" triage). If there is a structural collapse, there will be more serious injuries that arrive more slowly. [15]

See also

Related Research Articles

<span class="mw-page-title-main">Hydrostatic shock</span> Controversial theory in terminal ballistics

Hydrostatic shock, also known as Hydro-shock, is the controversial concept that a penetrating projectile can produce a pressure wave that causes "remote neural damage", "subtle damage in neural tissues" and "rapid effects" in living targets. It has also been suggested that pressure wave effects can cause indirect bone fractures at a distance from the projectile path, although it was later demonstrated that indirect bone fractures are caused by temporary cavity effects.

<span class="mw-page-title-main">Head injury</span> Serious trauma to the cranium

A head injury is any injury that results in trauma to the skull or brain. The terms traumatic brain injury and head injury are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of injuries, there are many causes—including accidents, falls, physical assault, or traffic accidents—that can cause head injuries.

<span class="mw-page-title-main">Bomb</span> Explosive weapon that uses exothermic reaction

A bomb is an explosive weapon that uses the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-transmitted mechanical stress, the impact and penetration of pressure-driven projectiles, pressure damage, and explosion-generated effects. Bombs have been utilized since the 11th century starting in East Asia.

<span class="mw-page-title-main">Bleeding</span> Loss of blood escaping from the circulatory system

Bleeding, hemorrhage, haemorrhage or blood loss is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vagina or anus, or through a puncture in the skin. Hypovolemia is a massive decrease in blood volume, and death by excessive loss of blood is referred to as exsanguination. Typically, a healthy person can endure a loss of 10–15% of the total blood volume without serious medical difficulties. The stopping or controlling of bleeding is called hemostasis and is an important part of both first aid and surgery.

Overpressure is the pressure caused by a shock wave over and above normal atmospheric pressure. The shock wave may be caused by sonic boom or by explosion, and the resulting overpressure receives particular attention when measuring the effects of nuclear weapons or thermobaric bombs.

<span class="mw-page-title-main">Barotrauma</span> Injury caused by pressure

Barotrauma is physical damage to body tissues caused by a difference in pressure between a gas space inside, or in contact with, the body and the surrounding gas or liquid. The initial damage is usually due to over-stretching the tissues in tension or shear, either directly by an expansion of the gas in the closed space or by pressure difference hydrostatically transmitted through the tissue. Tissue rupture may be complicated by the introduction of gas into the local tissue or circulation through the initial trauma site, which can cause blockage of circulation at distant sites or interfere with the normal function of an organ by its presence. The term is usually applied when the gas volume involved already exists prior to decompression. Barotrama can occur during both compression and decompression events.

<span class="mw-page-title-main">Injury in humans</span> Physiological wound caused by an external source

An injury is any physiological damage to living tissue caused by immediate physical stress. Injuries to humans can occur intentionally or unintentionally and may be caused by blunt trauma, penetrating trauma, burning, toxic exposure, asphyxiation, or overexertion. Injuries can occur in any part of the body, and different symptoms are associated with different injuries.

<span class="mw-page-title-main">Bruise</span> Type of localized bleeding in tissues outside blood vessels

A bruise, also known as a contusion, is a type of hematoma of tissue, the most common cause being capillaries damaged by trauma, causing localized bleeding that extravasates into the surrounding interstitial tissues. Most bruises occur close enough to the epidermis such that the bleeding causes a visible discoloration. The bruise then remains visible until the blood is either absorbed by tissues or cleared by immune system action. Bruises which do not blanch under pressure can involve capillaries at the level of skin, subcutaneous tissue, muscle, or bone.

<span class="mw-page-title-main">Hypovolemic shock</span> Medical condition

Hypovolemic shock is a form of shock caused by severe hypovolemia. It could be the result of severe dehydration through a variety of mechanisms or blood loss. Hypovolemic shock is a medical emergency; if left untreated, the insufficient blood flow can cause damage to organs, leading to multiple organ failure.

<span class="mw-page-title-main">Traumatic brain injury</span> Injury of the brain from an external source

A traumatic brain injury (TBI), also known as an intracranial injury, is an injury to the brain caused by an external force. TBI can be classified based on severity ranging from mild traumatic brain injury (mTBI/concussion) to severe traumatic brain injury. TBI can also be characterized based on mechanism or other features. Head injury is a broader category that may involve damage to other structures such as the scalp and skull. TBI can result in physical, cognitive, social, emotional and behavioral symptoms, and outcomes can range from complete recovery to permanent disability or death.

<span class="mw-page-title-main">Blunt trauma</span> Trauma to the body without penetration of the skin

Blunt trauma, also known as blunt force trauma or non-penetrating trauma, describes a physical trauma due to a forceful impact without penetration of the body's surface. Blunt trauma stands in contrast with penetrating trauma, which occurs when an object pierces the skin, enters body tissue, and creates an open wound. Blunt trauma occurs due to direct physical trauma or impactful force to a body part. Such incidents often occur with road traffic collisions, assaults, sports-related injuries, and are notably common among the elderly who experience falls.

In fluid dynamics, a blast wave is the increased pressure and flow resulting from the deposition of a large amount of energy in a small, very localised volume. The flow field can be approximated as a lead shock wave, followed by a self-similar subsonic flow field. In simpler terms, a blast wave is an area of pressure expanding supersonically outward from an explosive core. It has a leading shock front of compressed gases. The blast wave is followed by a blast wind of negative gauge pressure, which sucks items back in towards the center. The blast wave is harmful especially when one is very close to the center or at a location of constructive interference. High explosives that detonate generate blast waves.

Emergency bleeding control describes actions that control bleeding from a patient who has suffered a traumatic injury or who has a medical condition that has caused bleeding. Many bleeding control techniques are taught as part of first aid throughout the world. Other advanced techniques, such as tourniquets, are taught in advanced first aid courses and are used by health professionals to prevent blood loss by arterial bleeding. To manage bleeding effectively, it is important to be able to readily identify types of wounds and types of bleeding.

<span class="mw-page-title-main">Penetrating trauma</span> Type of injury

Penetrating trauma is an open wound injury that occurs when an object pierces the skin and enters a tissue of the body, creating a deep but relatively narrow entry wound. In contrast, a blunt or non-penetrating trauma may have some deep damage, but the overlying skin is not necessarily broken and the wound is still closed to the outside environment. The penetrating object may remain in the tissues, come back out the path it entered, or pass through the full thickness of the tissues and exit from another area.

<span class="mw-page-title-main">Pulmonary contusion</span> Internal bruise of the lungs

A pulmonary contusion, also known as lung contusion, is a bruise of the lung, caused by chest trauma. As a result of damage to capillaries, blood and other fluids accumulate in the lung tissue. The excess fluid interferes with gas exchange, potentially leading to inadequate oxygen levels (hypoxia). Unlike pulmonary laceration, another type of lung injury, pulmonary contusion does not involve a cut or tear of the lung tissue.

Primary and secondary brain injury are ways to classify the injury processes that occur in brain injury. In traumatic brain injury (TBI), primary brain injury occurs during the initial insult, and results from displacement of the physical structures of the brain. Secondary brain injury occurs gradually and may involve an array of cellular processes. Secondary injury, which is not caused by mechanical damage, can result from the primary injury or be independent of it. The fact that people sometimes deteriorate after brain injury was originally taken to mean that secondary injury was occurring. It is not well understood how much of a contribution primary and secondary injuries respectively have to the clinical manifestations of TBI.

<span class="mw-page-title-main">Focal and diffuse brain injury</span> Medical condition

Focal and diffuse brain injury are ways to classify brain injury: focal injury occurs in a specific location, while diffuse injury occurs over a more widespread area. It is common for both focal and diffuse damage to occur as a result of the same event; many traumatic brain injuries have aspects of both focal and diffuse injury. Focal injuries are commonly associated with an injury in which the head strikes or is struck by an object; diffuse injuries are more often found in acceleration/deceleration injuries, in which the head does not necessarily contact anything, but brain tissue is damaged because tissue types with varying densities accelerate at different rates. In addition to physical trauma, other types of brain injury, such as stroke, can also produce focal and diffuse injuries. There may be primary and secondary brain injury processes.

Permissive hypotension or hypotensive resuscitation is the use of restrictive fluid therapy, specifically in the trauma patient, that increases systemic blood pressure without reaching normotension. The goal blood pressure for these patients is a mean arterial pressure of 40-50 mmHg or systolic blood pressure of less than or equal to 80. This goes along with certain clinical criteria. Following traumatic injury, some patients experience hypotension that is usually due to blood loss (hemorrhage) but can be due to other causes as well. In the past, physicians were very aggressive with fluid resuscitation to try to bring the blood pressure to normal values. Recent studies have found that there is some benefit to allowing specific patients to experience some degree of hypotension in certain settings. This concept does not exclude therapy by means of i.v. fluid, inotropes or vasopressors, the only restriction is to avoid completely normalizing blood pressure in a context where blood loss may be enhanced. When a person starts to bleed the body starts a natural coagulation process that eventually stops the bleed. Issues with fluid resuscitation without control of bleeding are thought to be secondary to dislodgement of the thrombus that is helping to control further bleeding. Thrombus dislodgement was found to occur at a systolic pressure greater than 80mm Hg. In addition, fluid resuscitation will dilute coagulation factors that help form and stabilize a clot, hence making it harder for the body to use its natural mechanisms to stop the bleeding. These factors are aggravated by hypothermia.

Blast-related ocular trauma comprises a specialized subgroup blast injuries which cause penetrating and blunt force injuries to the eye and its structure. The incidence of ocular trauma due to blast forces has increased dramatically with the introduction of new explosives technology into modern warfare. The availability of these volatile materials, coupled with the tactics of contemporary terrorism, has caused a rise in the number of homemade bombs capable of extreme physical harm.

Acoustic trauma is the sustainment of an injury to the eardrum as a result of a very loud noise. Its scope usually covers loud noises with a short duration, such as an explosion, gunshot or a burst of loud shouting. Quieter sounds that are concentrated in a narrow frequency may also cause damage to specific frequency receptors. The range of severity can vary from pain to hearing loss.

References

  1. ↑ Blast Injury Translating Research Into Operational Medicine. James H. Stuhmiller, PhD. Edited by William R. Santee, PhD Karl E. Friedl, PhD, Colonel, US Army. Borden institute (2010)
  2. ↑ Kristi L. Koenig; Carl H. Schultz (18 April 2016). Koenig and Schultz's Disaster Medicine: Comprehensive Principles and Practices. Cambridge University Press. pp. 469–470. ISBN   978-1-316-47292-7.
  3. 1 2 3 4 Chapter 1: Weapons Effects and Parachute Injuries, pp. 1–15 in Emergency War Surgery (2004)
  4. 1 2 Choi, Chul-Hee (2012). "Mechanisms and Treatment of Blast Induced Hearing Loss". Korean Journal of Audiology. 16 (3): 103–107. doi:10.7874/kja.2012.16.3.103. PMC   3936657 . PMID   24653882.
  5. 1 2 Gallun, F (2012). "Implications of blast exposure for central auditory function: a review". Journal of Rehabilitation Research and Development. 49 (7): 1059–1074. doi: 10.1682/JRRD.2010.09.0166 . PMID   23341279.
  6. ↑ Sasser SM, Sattin RW, Hunt RC, Krohmer J (2006). "Blast lung injury". Prehosp Emerg Care. 10 (2): 165–72. doi:10.1080/10903120500540912. PMID   16531371. S2CID   2912045.
  7. ↑ Born CT (2005). "Blast trauma: The fourth weapon of mass destruction". Scandinavian Journal of Surgery. 94 (4): 279–85. doi: 10.1177/145749690509400406 . PMID   16425623. S2CID   44680290.
  8. 1 2 3 4 5 6 7 8 9 Keyes, Daniel C. (2005). Medical response to terrorism: preparedness and clinical practice. Lippincott Williams & Wilkins. pp. 201–202. ISBN   978-0-7817-4986-2.
  9. 1 2 3 Wolf, Stephen (July 23, 2009). "Blast injuries". The Lancet. 374 (9687): 405–15. doi:10.1016/S0140-6736(09)60257-9. PMID   19631372. S2CID   13746434.
  10. ↑ Marks, ME (2002). The Emergency Responder's Guide to Terrorism. Red Hat Publishing Co., Inc. pp. 30–2. ISBN   1-932235-00-0.
  11. ↑ Lawson, B. D., & Rupert, A. H. (2010). Vestibular aspects of head injury and recommendations for evaluation and rehabilitation following exposure to severe changes in head velocity ambient pressure. In Proceedings of the Human Performance at Sea Symposium. University of Strathclyde, Glasgow, UK.
  12. 1 2 Cernak, I., and L. J. Noble-Haeusslein. 2010. Traumatic brain injury: An overview of pathobiology with emphasis on military populations. J Cereb Blood Flow Metab 30(2):255-266.
  13. ↑ Pelley, Scott "How IEDs may be physically causing PTSD"; 60 Minutes, 1 April 2018.
  14. ↑ USUHS Archived 2019-07-08 at the Wayback Machine Center for Neuroscience and Regenerative Medicine; Uniformed Services University; Bethesda, Maryland.
  15. ↑ "Explosions and Blast Injuries: A Primer for Clinicians" (PDF). CDC. Retrieved 2013-12-29.. Occasionally updated.
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