1. Blast Injuries
Dr.Subhajit Sen

2. Classification of Explosives
High Order (HE) Explosive
Produce a high pressure shock wave
Examples: TNT, C-4, Semtex, dynamite
Low Order (LE) Explosive
Produce a subsonic explosion
Examples: pipe bombs, molotov cocktails
Manufactured Explosive
Standard military-issued quality-tested weapon
Improvised Explosive Device (IED)
Use a device outside its intended purpose
Made from explosives, commercial blasting supplies, fertilizer and household ingredients
Commercial jet as a guided missile
Loaded with metallic objects to inflict penetrating injury, toxic chemicals or radiological materials
Classification of Explosives – Explosives are categorized as high-order explosives or low-order explosives. HE produce a defining supersonic over-pressurization shock wave. Examples of HE include TNT, C-4, Semtex, nitroglycerin, dynamite, and ammonium nitrate fuel oil. LE create a subsonic explosion and lack HE’s over-pressurization wave, and examples of LE include pipe bombs, gunpowder, Molotov cocktails or aircraft improvised as guided missiles. Manufactured explosives are standard military-issued mass produced and quality tests weapon. Improvised devices are weapons produced in small quantities, use a device outside its intended purpose, such as converting a commercial aircraft into a guided missile. Improvised explosive devices currently used in insurgency warfare are often loaded with metallic objects to inflict penetrating injuries in crowded civilian settings.

3. Background
Explosions have the capability to cause multisystem, life-threatening injuries in single or multiple victims simultaneously
These types of events present complex triage, diagnostic, and management challenges for the ED health care provider
Explosions can produce classic injury patterns from blunt and penetrating mechanisms to several organ systems
they can also result in unique injury patterns to specific organs including lungs and CNS; and hidden pattern of injury

4. Background cont.
The extent and pattern of injuries produced by explosion are a direct result of several factors
amount and composition of the explosive material (eg, the presence of shrapnel or loose material that can be propelled), “dirt bombs”
surrounding environment (eg, the presence of intervening protective barriers)
distance between the victim and the blast
enclosed vs open space: The effects of an explosion in a closed space (e.g., a room, bus, or train) are much greater than in an open space.
delivery method if a bomb is involved
other environmental hazards
No two events are identical, and the spectrum and extent of injuries produced varies widely

7. Pathophysiology
Explosions occur when energy is transformed extremely quickly from one form –ie chemical potential energy in an explosive, to another (heat energy and kinetic energy)
The detonation of a conventional high explosive generates a blast wave that spreads out from a point source
Blast wave consists of two parts:
a shock wave of high pressure
followed closely by a blast wind

9. Types of Blast Injuries
Primary
Due to direct effect of pressure
Secondary
Due to effect of projectiles from explosion
Tertiary
Due to structural collapse and from persons being thrown from the blast wind
Quaternary
Burns, inhalation injury, exacerbations of chronic disease
Types of Blast Injuries: Primary (direct effects of pressure, either overpressurization and underpressurization, such as rupture of tympanic membranes, pulmonary damage, and rupture of hollow viscera); Secondary (effects of projectiles, causing penetrating trauma and fragmentation injuries); Tertiary (effects of structural collapse and of persons being thrown by the blast wind, causing crush injuries and blunt trauma, penetrating trauma, fractures and traumatic amputations, open or closed brain injuries); and Quaternary (burns, asphyxia, and exposure to toxic inhalants).

11. Primary Blast Injury Unique to high explosives
Due to impact of over-pressurization wave with body surfaces
Differential pressures in tissues
Organ distortion
Tensile strength of the tissue is exceeded
Tissue tearing
Primary Blast Injuries are unique to high explosives, and these basically result from the impact of the overpressurization wave with body surfaces. The injuries are caused by barotrauma, and these injuries most commonly involve air-filled organs and air-fluid interfaces. Gas-filled structures are most susceptible, such as the middle ear, the lungs, and the GI tract. Types of injuries include blast lung, TM rupture, abdominal hemorrhage and perforation, globe rupture, and concussion (TBI without physical signs of head injury). Organs are damaged by dynamic pressure changes at tissue-density (air-fluid) interfaces due to the interaction of a high frequency stress wave and a lower frequency shear wave. Rupture of the tympanic membranes, pulmonary damage and air embolization, and rupture of hollow viscera are the most important primary forms of blast injury.

12. Primary Blast Injury
Most commonly involve air-filled organs and air-fluid interfaces
Middle ear
Lungs
GI tract
Types of injuries
Blast lung
Tympanic Membrane (TM) rupture
Abdominal hemorrhage and perforation
Globe rupture
Traumatic brain injury (TBI) without physical signs of head injury

13. Secondary blast injury
caused by flying objects that strike people.
The most common cause of death in a blast event is secondary blast injuries
Terrorists often add screws, nails, and other sharp objects to bombs to increase injuries
The most common types of secondary blast injuries are:
Trauma to the head, neck, chest, abdomen, and extremities in the form of penetrating/blunt trauma
Fractures
Traumatic amputations
Soft tissue injuries
Have a low threshold for imaging studies
(plain radiographs, computed tomograms)
Wounds are grossly contaminated
Consider delayed primary closure and tetanus vaccinations

14. Fragments can travel… …a long distance….
Ship’s
Anchor
We will get back to those fragments in a little bit….
Fragments can travel… …a long distance….

15. Tertiary Blast Injuries
A tertiary blast injury is a feature of high-energy explosions
Due to persons being thrown into fixed objects by wind of explosions
Also due to structural collapse and fragmentation of building and vehicles
Structural collapse may cause extensive blunt trauma
Head injuries
Skull fractures
Bone fractures
Tertiary Blast Injuries – these result from people being thrown into fixed objects by the wind of explosions. Any body part may be affected, and fractures, traumatic amputations, and open and closed head injuries occur. Tertiary blast injuries also result from structural collapse and fragmentation of buildings and vehicles. Structural collapse and large airborne fragments lead to crush injuries and extensive blunt trauma, whereas flying fragments cause penetrating trauma. The crush syndrome is a metabolic derangement resulting from damage to muscle tissues and the subsequent release of myoglobin, urates, potassium, and phosphates. Oliguric renal failure, the most severe end point, causes the retention of potassium above and beyond that released from the damaged muscle. Appropriate treatment includes hydration and alkalinization. The compartment syndrome results from the compression that a damaged edematous muscle exerts within its inelastic sheath, which promotes local ischemia, further swelling, increased compartment pressures, decreased tissue perfusion, and further ischemia.
Crush syndrome
Compartment syndrome

16. Quaternary blast injury
related injuries encompass all other injuries caused by explosions
result of burns, smoke inhalation, or chemical agent release

17. Thermobaric weapons Fuel-air mixtures
Optimized to produce heat and blast
Secondary effects through flying fragments
Toxic detonation gases Anoxia & Gas inhalation
Particularly effective in enclosed spaces
Fireball and blast can travel around corners
Blast waves are intensified when reflected by walls and other surfaces

19. Mechanisms of Blast Injury
Category
Characteristics
Body Part Affected
Types of Injuries
Primary
Unique to HE, results from the impact of the over-pressurization wave with body surfaces. 
Gas filled structures are most susceptible - lungs, GI tract, and middle ear.
Blast lung (pulmonary barotrauma)
TM rupture and middle ear damage 
Abdominal hemorrhage and perforation - Globe (eye) rupture- Concussion (TBI without physical signs of head injury) 
Secondary
Results from flying debris and bomb fragments. 
Any body part may be affected.
Penetrating ballistic (fragmentation) or blunt injuries
Eye penetration (can be occult)
Tertiary
Results from individuals being thrown by the blast wind.
Fracture and traumatic amputation 
Closed and open brain injury
Quaternary 
All explosion-related injuries, illnesses, or diseases not due to primary, secondary, or tertiary mechanisms. 
Includes exacerbation or complications of existing conditions.
Burns (flash, partial, and full thickness)
Crush injuries
Asthma, COPD, or other breathing problems from dust, smoke, or toxic fumes
Angina, Hyperglycemia, hypertension

20. Variables Affecting Severity Primary Blast Injury
"Blast Environment" is a very important factor determining the extent of injuries.
Nearby structures may either act as a shield or may reflect the blast wave onto a casualty.
Confined environment increases damage
A blast wave that is reflected can create a peak pressure 10X greater than that of the incident wave
Blast waves inside buildings are repeatedly reflected creating a “complex blast wave”
Marked increase in injuries related to primary blast effects when explosion occurs in a closed space
Orientation of body relative to blast wave: end-on orientation minimizes injury .

21. Primary blast injury
Direct trauma
Amputations
Death
Hollow organ damage
Ear
Lung
GI tract
Air embolism is 1o cause of sudden death due to blast

23. TM Injury TM - structure most frequently injured by blast
TM rupture
Ossicle dislocation
Disruption of oval or round window
Symptoms may include hearing loss, tinnitus, vertigo, bleeding from external canal, mucopurulent otorrhea
Otologic exam and audiometry for all
TM rupture is sensitive marker, but absence does not exclude other organ injury

24. Ear
Middle ear:
Ruptured tympanic membrane (TM)
Temporary conductive hearing loss
Inner ear:
Temporary sensory hearing loss
Permanent sensory hearing loss

25. Blast Lung Lung – 2nd most susceptible organ to blast injury
Most common fatal primary blast injury among initial survivors
Pulmonary barotrauma includes
Pulmonary contusions
Hemothorax
Pneumothorax
Pneumomediastinum
Systemic air embolism
Free radical associated injuries
DIC
Clinical triad of apnea, bradycardia, and hypotension
Signs usually at initial presentation but may manifest as late as 48 hours after explosion
Should be suspected if dyspnea, cough, hemoptysis, or chest pain
The lung is the second most susceptible organ to primary blast injury. It is the most common fatal primary blast injury among initial survivors, and pulmonary barotraumas includes pulmonary contusions, systemic air embolism, and free radical associated injuries such as thrmobosis, lipoxygenation, and disseminated intravascular coagulation (DIC).

26. Blast Lung Radiographic findings
Bihilar “butterfly” pattern
Pneumothorax or hemothorax
Pneumomediastinum and subcutaneous emphysema
Prophylactic chest tube if blast lung suspected
Signs or blast lung are usually present at the time of initial evaluation, but they have been reported as late as 48 hours after the explosion. Blast ling is characterized by the clinical triad of apnea, bradycardia, and hypotension. It should be suspected in anyone who presents with dyspnea, cough, hemoptysis, or chest pain following blast exposure. Pressure differentials across the alveolar-capillary interface cause disruption, hemorrhage, pulmonary contusion (appears as bihilar “butterfly” pattern on chest radiograph), pneumothorax, hemothorax, pneumomediastinum, and subcutaneous emphysema. Pulmonary injuries vary from selected petechiae to confluent hemorrhages. Immediate onset of pulmonary edema carries a grave prognosis. A prophylactic chest tube is recommended before general anesthesia or air transport if blast lung is suspected. Blast lung is the most common fatal injury among initial survivors. Pulmonary barotraumas is the most common critical injury to people close to a blast center, whether civilian or military.
Systemic acute gas embolism from pulmonary disruption may occlude blood vessels of the brain or spinal cord, and injury to the CNS from acute gas embolism needs to be differentiated from the direct effects of head trauma and concussion.

27. Tension Pneumothorax

28. Pulmonary injury
The chest-wall acceleration causes a brief but powerful force transmitted to the underlying lungs as a stress wave.
This picture shows a mild degree of localized pulmonary contusion, which would be easily survivable in a human. These only cause minor problems with oxygen diffusion.
What do you think these parallel bands are? In the old days, this pattern used to be called “rib markings” but has since been shown to represent intercostal spaces, which can be accelerated more than the bony ribs.
Blood vessels stretched and torn causing pulmonary contusion
Mild interstitial hemorrhage with minor oxygen diffusion problems
Bruises on lungs produced when primary blast wave rapidly accelerates ribs into underlying lung tissue

29. Blast Abdominal Injury
Intestinal barotrauma more common with underwater air blast
Colon – visceral organ most frequently affected with Hematomata in bowel wall & Intraluminal hemorrhage
Mesenteric ischemia from gas embolism may cause delayed rupture/perforation of large or small intestine
Solid organ injury less likely
Signs and symptoms (maybe delayed)
Abdominal pain, nausea, vomiting, hematemesis
Rectal pain and tenesmus
Testicular pain
Unexplained hypovolemia
Blast abdominal injury should be suspected in anyone exposed to a explosion with abdominal pain, nausea, vomiting, hematemesis, rectal pain, tenesmus, testicular pain, unexplained hypovolemia, or any finding suggestive of an acute abdomen. The colon is the visceral organ most frequently affected by a primary blast injury, and rupture of the colon and small intestine may occur as an immediate result of a blast. Mesenteric ischemia or infarct can cause delayed rupture of the large or small intestine. Note that clinical signs of blast-related abdominal injury may be initially silent until signs of acute abdomen or sepsis are advanced. Intestinal barotraumas is more common with underwater than air blast injuries. Rupture, infarction, ischemia, and hemorrhage of solid organs such as the liver, spleen, and kidney are generally associated with very high blast forces or proximity of the patient to the blast center.

30. Blast Abdominal Injury Identifying Abdominal Injury
Serial abdominal examinations
Serial hematocrit determinations
Diagnostic studies
USG
Peritoneal lavage CT
CXR
If not hemodynamically compromised, CT can:
1) identify pneumothoraces not seen on chest x-ray;
2) can quantify pulmonary contusions;
3) detect intraperitoneal blood (if > mL);
4) find pneumoperitoneum (dissected from chest or from GI);
5) characterize actual organ injury (but not bowel well).
Ultrasound can:
1) rapidly identify large amounts of intraperitoneal blood.
Diagnostic peritoneal tap & lavage can:
1) rapidly identify large amounts of intraperitoneal blood;
2) identify hollow-organ injury better than CT or ultrasound

31. Blast Brain Injuries
Primary blast waves can cause concussions or mild traumatic brain injury (MTBI) without a direct blow to the head due to barotrauma and gas embolism
Signs and symptoms include headache, fatigue, poor concentration, lethargy, anxiety, and insomnia
Consider the proximity of the victim to the blast particularly when given complaints of:
Loss of consciousness
Headache
Fatigue
Poor concentration, lethargy, amnesia
Symptoms of concussion and post traumatic stress disorder (PTSD) can be similar
Primary blast injury to the eye include rupture of the globe, serous retinitis, and hyphema lid laceration, traumatic cataracts injury to optic nerve . Primary blast injuries to the brain include concussion as well as barotraumas caused by acute gas embolism. Consider the proximity of the victim to the blast particularly when given complaints of headache, fatigue, poor concentration, lethargy, depression, anxiety, insomnia, or other constitutional symptoms. Loss of consciousness and coup and countercoup injuries formerly were considered secondary and tertiary injuries, but with the increased use of body armor in the military, damage to the CNS after an explosion has been increasingly attributed to the direct effects of the blast.

32. Arterial gas embolism in liver
air bubbles enter blood stream and travel to brain or heart causing stroke or heart attack
Cerebral circulation
Stroke
Seizures
Altered mental status
Coronary circulation
Dysrhythmias
Ischemia or infarction
Cardiogenic shock
Torn interfaces between the airways and the pulmonary venous circuit can lead to air entering the left heart and being ejected to the systemic circulation. This may be more likely to occur under two additional circumstances:
1) low pulmonary vascular pressure (egg, shock)
2) high airway pressure (egg, PPV)
Arterial emboli can go anywhere, but they are the worst if they lodge in the cerebral or coronary arteries. Any symptom or sign of a stroke or a heart attack may be manifest.
The pulmonary-vagal reflex is likely the cause of immediate loss of consciousness, but AGE is an early cause of LOC. It is also the most common cause of death in the first hour after immediate survival.
Systemic acute gas embolism from pulmonary disruption may occlude blood vessels of the brain or spinal cord, and injury to the CNS from acute gas embolism needs to be differentiated from the direct effects of head trauma and concussion.
Arterial gas embolism in liver

33. Treatment for Arterial Gas Embolism
Recompression with 100% oxygen
Left lateral recumbent position
Hyperbaric oxygen (HBO) is definitive
Aspirin may be helpful in AGE -may reduce inflammation-mediated injury in pulmonary barotrauma
Patients thought to have acute gas embolism (AGE) require recompression treatment. Place patients on 100% oxygen by tight-fitting face mask and, if possible, place them in the left lateral recumbent position. Trendelenburg (head down) position is no longer recommended. Of course, other causes of symptoms (eg, traumatic CNS injury) must be excluded. Hyperbaric oxygen (HBO) treatment is the definitive procedure. Transfer of the patient may be required. Research suggests that aspirin is helpful in AGE. Aspirin may reduce inflammation-mediated injury in pulmonary barotrauma as well. It may, however, be unwise to give an antiplatelet agent to a patient with acute trauma.

34. Other Primary Blast Injuries Eye
Globe rupture
serous retinitis
hyphema
lid laceration
traumatic cataracts
injury to optic nerve
Signs and symptoms include eye pain, foreign body sensation, blurred vision, decreased vision, drainage

35. Primary blast injury is lethal…
Primary blast injury is lethal…. But SECONDARY blast injuries are the real killer of explosions.
Fragments from munitions (design)
Fragments from “spiked” terrorist bomb (Nails, Glass, Unique IED’s…)
Fragments from blast environment
Glass fragments are a common cause of injury/death related to blast in civilian settings
From the bomber…
At least one paper reports infections from bomber fragments….
Glass causes up to 50% of secondary blast injuries

38. Crush Injury: Definition
An injury sustained when a body part is subjected to a high degree or prolonged presence of force or pressure
Acute traumatic ischemia, with or without associated injuries, causing insult to tissues

39. Crush Syndrome
Term used to describe the systems manifestations of crush injury after reperfusion of affected body parts
May occur in absence of trauma and evolve in the absence of early signs or symptoms
Arterial thrombosis or embolism
Severe anemia
Toxins
Legitimate medications and drugs of abuse
Systemic effects are due to rhabdomyolysis and reperfusion of hypoxic and damaged tissues
major cause of early mortality

40. Crush Syndrome : Pathophysiology
Reperfusion
Rhabdomyolysis
Skeletal muscle damage greatest after reperfusion
Superoxide radicals produced during reperfusion attacks free fatty acids, producing cellular edema, death, and necrosis
Na-K-ATP pump exchanges intracellular sodium for calcium with further derangement of intracellular metabolism
Efflux from damaged muscle cells of:
Potassium
Purines
Lactic Acid
Phosphate
Myoglobin
Thromboplastin
Creatine

41. Crush Syndrome: Pathophysiology
Resultant effects of derangements due to rhabdomyolysis and reperfusion
Potassium  Hyperkalemia Arrhythmias
Calcium  Hypocalcemia Arrhythmias
Phosphate  Hyperphosphatemia Renal damage
Myoglobin  Myoglobinemia Renal damage
Fluid shifts  Hypovolemia Renal failure
Reperfusion  Free radicals Renal damage
Purines  Hyperuricemia Renal damage
Hypoxemia  Lactic acid Acidosis
Thromboplastin Complement system DIC
Creatinine  Elevated serum levels, Azotemia
Sodium 

42. Crush Syndrome: Clinical Presentation
General condition of a patient with crush injury dictated by other injuries, delay in extrication, environmental conditions
Common presentations
Hypothermia or hyperthermia
Dehydration/shock
Mental status varies from alert to comatose
Affected part (usually limb)
Tense edema and decreased sensation
Overlying skin may be shiny, contused, necrotic
May have penetrating wounds (worse diagnosis)

43. Crush Syndrome: Treatment
Fluid resuscitation
Brisk diuresis
Diagnose and treat other metabolic derangements
Hyperkalemia
Hypocalcemia
Treat tissue damage
Pain control
Agitation

44. Crush Injury: Compartment Syndrome
Is a collection of localized signs and symptoms that result when the perfusion pressure falls below the tissue pressure in a closed anatomic space for sufficient time to compromise circulation and function of tissues involved
Areas most affected
Lower extremities
Upper extremities
Pelvis
Gluteal region
Abdominal muscles

45. Compartment Syndrome Suggestive clinical findings
Similar settings to crush injury, but may also occur with subacute trauma
Bone fractures
High velocity penetrating injury to muscles in closed compartment with extensive tissue disruption
Can also occur in subacute fashion due to prolonged immobilization on hard surface

46. Compartment Syndrome: Pathophysiology
Significant muscle mass damage
Typically occurs in major muscle groups enclosed by inelastic, fibrous sheaths
Tissue/muscle damage results in edema in a closed volume space
Progressive cycle of edema, perfusion compromise, tissue hypoxia and cellular derangement, further edema, etc.
Untreated, will produce same effects as crush injury

47. Compartment Syndrome: Clinical Presentation
The 5 P’s
Pain
Pallor
Paresthesia
Paralysis
Pulselessness
Progression of symptoms
(sometimes the 6th P)

48. Compartment Syndrome: Treatment
Measuring compartment pressures
Use of Ketamine
Fasciotomies: Fasciotomies are a definitive treatment, but tissue pressure at which it is required is controversial

49. Mortality/Morbidity Mortality rates vary widely between incidents
Immediate death/injury rates higher for bombings involving structural collapse (25%)
confined space (8%)
open air detonations (4%).

50. Mortality/Morbidity
Unique patterns of injury are found in all bombing types. Injury is caused both by direct blast overpressure (primary blast injury) and by a variety of associated factors.
Enclosed-space explosions, including those occurring in busses, and in-water explosions produce more primary blast injury.
Explosions leading to structure collapse produce more orthopedic injuries.
Land mine injuries are associated with a high risk of below- and above-the-knee amputations.

51. Mortality/Morbidity
Presence of tympanic membrane (TM) rupture indicates that a high-pressure wave (at least 40 kilopascal [kPa], 6 psi) was present and may correlate with more dangerous organ injury.
Theoretically, at an overpressure of 100 kPa (15 psi), the threshold for lung injury, TM routinely ruptures.

52. Overview of Explosive-Related Injuries
System
Injury or Condition
Auditory
TM rupture, ossicular disruption, cochlear damage, foreign body 
Eye, Orbit, Face
Perforated globe, foreign body, air embolism, fractures
Respiratory
Blast lung, hemothorax, pneumothorax, pulmonary contusion and hemorrhage, A-V fistulas (source of air embolism), airway epithelial damage, aspiration pneumonitis, sepsis
Digestive
Bowel perforation, hemorrhage, ruptured liver or spleen, sepsis, mesenteric ischemia from air embolism
Circulatory
Cardiac contusion, myocardial infarction from air embolism, shock, vasovagal hypotension, peripheral vascular injury
CNS Injury
Concussion, closed and open brain injury, spinal cord injury, air embolism-induced injury 
Renal Injury
Renal contusion, laceration, acute renal failure due to rhabdomyolysis, hypotension, and hypovolemia
Extremity Injury
Traumatic amputation, fractures, crush injuries, compartment syndrome, burns, cuts, lacerations, acute arterial occlusion, air embolism-induced injury 

54. General Considerations
Half of all initial casualties seek medical care over first hour
Expect upside down triage
Most severely injured arrive after less injured who bypass EMS and self-transport to closest hospitals
Secondary devices
Initial explosion attracts law enforcement and rescue personnel who will be injured by second explosion
Terrorist attacks in civilian settings tend to have a biphasic distribution of mortality – high immediate rates of death followed by low early and late mortality rates.
Rarely have civilian providers faced a battlefield approach to triage or sorting. Initial stabilization of victims of blast injury like that of other trauma victims, includes assessment and management of the airway, breathing, and circulation. Half of all initial casualties will seek medical care over a one-hour period. This can be useful to predict demand for care and resource needs. Expect an upside down triage—the most severely injured arrive after the less injured, who bypass ENS triage and go directly to the closest hospitals. Another ominous consideration is the tactic of setting dual explosion, since the initial explosion may be a ploy to attract law enforcement and resuce personnel, followed by a second device designed to injure rescuers. Moreover, EMS personnel should check for radiation and chemical contamination at the scene of a deliberate attack.
Few US health professionals have experience with explosive-related injuries, as Vietnam era physicians are retiring, and until the last decade, the US was largely spared of the scourge of mega-terrorist attacks.

55. General Management Focus on two exams Otoscopic exam Pulse oximetry
If ruptured TM, chest radiography and eight hour observation recommended
Primary blast injury notorious for delayed presentation
If non ruptured TM and no other symptoms, may conditionally exclude other serious primary blast injuries
Pulse oximetry
Decreased oxygen saturation signals early blast lung even before symptoms
Management of specific injuries – Treatment of patients after blasts focuses on two examinations. First, portable otoscopes are used to identify rupture of the tympanic membranes. If the tympanic membranes are intact, serious primary blast injuries can be conditionally excluded, in the absence of other symptoms such as dyspnea, respiratory distress, and acute abdominal pain. Patients with rupture of the tympanic membranes should undergo radiography of the chest and should be observed for at least eight hours, as clinically indicated, since primary blast injuries are notorious for their delayed onset. Second, these victims should be monitored by sequentially measuring their oxygen saturation by pulse oximetry. Decreased oxygen saturation probably signals early blast lung even before symptoms begin.

56. Guidelines for Admission
High risk patients who require admission
Significant burns
Suspected air embolism
Radiation
Sharpnel contamination
Abnormal vital signs
Abnormal lung examination findings
Clinical or radiographic evidence of pulmonary contusion or pneumothorax
Abdominal pain or vomiting
Penetrating injuries to the thorax, abdomen, neck, or cranial cavity
High risk patients who require admission
Significant burns, suspected air embolism, radiation or WP contamination, abnormal vital signs, abnormal lung examination findings, clinical or radiographic evidence of pulmonary contusion or pneumothorax abdominal pain vomiting evidence of renal contusion or hypoxia penetrating injuries to the thorax abdomen neck or cranial cavity

57. Guidelines for Disposition
Limited data prevent establishing optimal duration of observation
Low risk and may be discharged with strict precautions after 4hrs of observation:
Persons exposed to open-space explosions with no apparent significant injury, normal vital signs and unremarkable lung and abdominal examination
Moderate risk and should be observed for longer periods of time for delayed complications:
Persons exposed to closed-space explosion or in-water explosions
Persons with TM rupture
Guidelines for disposition - Limited data prevent establishing the optimal duration of observation.
Persons exposed to open-space explosions who have no apparent significant injury and with normal vital signs and unremarkable lung and abdominal examinations generally can be discharged after 4 hours with instructions to return to the ED if shortness of breath, abdominal pain, vomiting, or other symptoms occur.
Persons exposed to significant closed-space explosions, in-water explosions, and those who incur TM rupture are at higher risk of delayed complications. These patients should receive more intensive observation over a longer period. Motivated, reliable, and completely asymptomatic patients may be sent home after 4 hours of observation.
Admit to the hospital all patients with significant burns, suspected air embolism, radiation or WP contamination, abnormal vital signs, abnormal lung examination findings, clinical or radiographic evidence of pulmonary contusion or pneumothorax, abdominal pain, vomiting, evidence of renal contusion/hypoxia, or penetrating injuries to the thorax, abdomen, neck or cranial cavity.

58. Special Populations Pediatric trauma Pregnancy
Increased use of Intensive Care Unit (ICU) resources
Higher injury severity scores (ISS)
Longer hospital stays
Pregnancy
Direct injury to fetus is uncommon
Fetus protected by amniotic fluid
Risk for placental abruption
If blast in second or third trimester admit labor to delivery for fetal monitoring
Children who are victims of terrorism require more resources of ICUs, have higher ISS, and have longer hospital stays than children who survived traumatic events unrelated to terrorism.
During pregnancy, the direct injury of the fetus by the blast is uncommon, as the fetus is apparently protected by amniotic fluid. However, its attachment to the placenta is at risk, if the blast wave affects the high-density uterine wall and the lower-density placental medium, causing placental abruption. For women exposed to blasts in the second and third trimester of pregnancy, admission to the labor and delivery area for fetal monitoring is recommended.