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BLAST INJURIES: the Anesthesia Provider’s Perspective

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1 BLAST INJURIES: the Anesthesia Provider’s Perspective
Linda E. Pelinka, MD, PhD Medical University of Vienna and Ludwig Boltzmann Institute for Experimental & Clinical Traumatology Vienna, Austria, European Union TRAUMA

2 Blast Injuries in the US
Texas 1947: Ammonium nitrate explosion in a ship carrying cargo of hemp, 500 killed Texas1989: Petroleum plant 23 killed, injured (mainly males aged 25-44) secondary injuries 2 miles away NYC 1993: WTC terrorist bomb 6 killed, injured Oklahoma 1995: AP Murrah building truck bomb, 167 killed (19 children)

3 „The explosion of a terrorist bomb
in the garage of the World Trade Center resulted in 6 deaths... ...but thousands could have been killed, had one tower been toppled into the other as alledgedly intended.“ Wightman JM and Gladish SL: Explosions and Blast Injuries. Ann Emerg Med, June 2001

4 BASICS what, why and how CATEGORIES Primary, secondary, tertiary and quarternary injuries, diagnosis and therapy SPECIFIC ORGAN INJURIES Lung, gut, ear, brain, extremities diagnosis and therapy

5 BASICS what, why and how

6 What is a blast? Release of energy Chemical conversion
of liquid or solid to gas

7 What causes a blast? PROPELLANTS: slower energy release DEFLAGRATION (chemical burning) Gunpowder EXPLOSIVES: instant energy release DETONATION (causes high pressure of about 4 million psi*) High energy blast wave = shock wave TNT Trinitrotoluene Composition C4 Cyclo-trimethylene-trinitramine *Psi pounds per square inch

8 What is a blast wave ? SHOCK WAVE
Sudden OVERPRESSURE of medium where blast takes place injury from sudden overpressure and thermal energy, related to magnitude and duration of blast Long duration blast wave: nuclear detonation

9 Phases of a Blast 1. Very short phase: increasing pressure
2. Longer phase: decreasing-negative pressure 3. Short phase of slightly positive pressure Massive movement of air: BLAST WIND

10 BLAST WIND Strong enough to destroy buildings 145 – 800 mph
Pressure differential 5-15 psi (pounds/sq. inch) Magnified 2-20 fold by corridors, alleys, confined spaces (corners!) Leading edge: blast front (highly pressurized, superheated molecules, supersonic speed ft/sec)

11 Mechanisms of primary blast injury
SPALLATION at liquid-gas interfaces (bowel injuries) IMPLOSION / RE-EXPANSION hollow structures („crushed egg-shell fx“ of mid-face) IRREVERSIBLE WORK by pressure differential „Aluminum can concept“: Damage done when stress = tensile strength of compressed tissue ACCELERATION / DECELERATION of organs relative to their fixation points

12 with homogenous densities (liver, spleen, tongue, eye)
Less compression and visible damage to solid organs with homogenous densities (liver, spleen, tongue, eye)

13 CATEGORIES Primary, secondary, tertiary and quarternary injuries, diagnosis and therapy

14 QUATERNARY BURNS (HOT GAS, SECONDARY FIRE) INHALATION (DUST, SMOKE) CRUSH (STRUCURES COLLAPSING) Three types of blast injuries that we will discuss PRIMARY SECONDARY and TERTIARY

15 Expected injury to unprotected victims, relative distance from a blast in open air
PBI primary blast injury

16 Primary Blast Injury Cause: direct effect of blast wave on victim (energy transfer) Injury almost exclusively to tissues of inhomogenous densities (hollow, gas containing) Read slide

17 Secondary Blast Injury
Cause: propelled debris which hits victim Treat same as any other blunt or penetrating injury

18 Tertiary Blast Injury Cause: Victim impaled or
propelled against hard surface Treatment same as for penetrating or blunt trauma (fx, crush injuries, amputations) Beslan, Chechnia September 3rd, 2004

19 Quaternary Blast Injuries
Miscellaneous collection of other mechanisms Flash burns superficial skin burns by heat of explosion Methemoglobinemia poisoning by potassium perchlorate (ammo) Acute septicemic meloidosis inhalation of contaminated soil Psychological sequelae

20 Mortality associated with use of weapons in armed conflicts, wartime atrocities, and civilian mass shootings Coupland, RM and Meddings, DR: BMJ 319, 407–410; 1999. Explosive munitions account for over 50% of all wounds sustained in military combat. The proportion of civilian casualties due to explosives is increasing as well.

21 Explosive Devices CONVENTIONAL WEAPONS (Grenades, bombs, rockets)
Multiple fragments Sec. blast injury Penetrating injury ANTIPERSONNEL MINES (developing countries) Traumatic amputation Detonated by only 10 lbs pressure 2000 victims every month (children) ENHANCED-BLAST MUNITIONS (fuel-air explosives) Designed to kill by primary blast War-Artillery, grenades, mortars Terrorist bombings-bombs Natural disasters- Man-made-Fuel explosions TERRORIST DEVICES (few to hundreds of pounds of explosives) Secondary and Tertiary blast injury

22 Terrorist Devices Designed to Disrupt passing vehicles
Displace vehicles Eject victims Cause gross disruption CAR BOMBS 2-6 lbs of commercial explosive Under car beneath driver´s seat Traumatic lower limb amputation Secondary fragments of metal BARE CHARGES > 20 lbs Remote detonation (radio, wire) Primary blast injury Secondary fragments of metal and debris War-Artillery, grenades, mortars Terrorist bombings-bombs Natural disasters- Man-made-Fuel explosions TRUCK BOMBS > 80 lbs Detonation creates secondary missiles from body of truck Penetrating injury, gross disruption

23 Velocity of Explosives
Initial velocity 1800m/sec Rapid deceleration due to aerodynamic drag (irregular projectile shape, no streamlining like bullet through rifle barrel) Survivors struck at velocity < 600m/sec Shimmy effect: tumbling within tissue Additional damage by environmental debris

24 Tolerance to Blast Wave in Air
radius of effect < radius of projectiles more damage if blast wave reflected by surfaces standing worse than prone enclosed space worse than open (multiple reflections) Read

25 Tolerance to Blast Wave in Water
radius of effect > radius of projectiles water inhibits movement of projectiles tension wave (cut-off wave) reflected by surface attenuates water blast wave closer to the surface augments water blast wave in greater depth more damage to deeper body regions Safer floating than treading water Safer floating on surface than treading water

26 Tolerance to Blast Wave
Repeated blasts Effects cumulative (particularly airway: loss of cilia, epithelial flattening, stripping, bleeding) sub-threshold blasts can result in injury if following close to previous blast Effect decreases with distance Blast wave travels further and Lethal radius is 3x greater in water (vs air) The blast wave travels further in water.

27 Stress wave Shear wave Longitudinal (like sound wave) Short duration
High velocity (175 mph) Stress wave Microvascular injuries Also affects hollow structures May cause limb avulsions Deformation of body wall Asynchronous movement Tearing from attachments Shear wave Transverse Long duration Low velocity (50 mph)

28 Multiple sequential posttraumatic aneurysms following high-energy injuries
Freiman S et al, J Orthop Trauma 2002 15 year-old boy Land mine in Lebanon Multiple long bone fx (external fixation) Lacerated right ant. tibial artery (grafted) 20 days later: pseudoaneurysm ulnar artery 34 days later: pseudoaneurysm peroneal artery with a-v fistula (fluoroscopically controlled embolization and placement of stents)

29 Has a patient been injured by a blast?
Primary Blast Injury Has a patient been injured by a blast? When to suspect: Type of explosion Medium of blast (air/water) Number of blasts and time between blasts Victim’s location & position to blast Enclosed area or barrier (reflected wave) Activity after blast (risk of air embolism) Ruptured tympanic membrane

30 Primary Blast Injury Lung: most common cause of
early morbidity and mortality Ear: most sensitive part of body Bowel: most common cause of delayed morbidity and mortality Read and stress each point. Ear is the best predictor of exposure but is a very low morbidity Respiratory system (severe pulmonary contusions) will be the cause of most common cause of early deaths GI tract is the most common cause of delayed death due to perforations.

31 SPECIFIC ORGAN INJURIES Lung, gut, ear, brain, extremities diagnosis and therapy

32 Blast Lung Pathophysiology
Ventilation – perfusion mismatch Increased shunt Decreased compliance Increased work of breathing

33 Blast Lung Caused by blast wave against chest wall
– not through oropharynx and trachea Symptoms Dyspnoa (“can you count to 10 in a single breath?”) Cough (dry-frothy) Hemoptysis Retrosternal pain Signs Tachypnoea Cyanosis Reduced breath sounds Dull percussion sounds Coarse crepitations Subcutaeous emphysema Retrosernal crunch (pneumo mediastinum) This is a list of findings after blast injury to the lung.

34 Blast Lung Pathology and Findings
Alveolar septa torn Hemorrhage Laceration Predeliction for Mediastinum Costo-phrenic angles “Rib markings” Pneumothorax Pneumomediastinum Subpleural cysts Interstitial emphysema Subcut. emphysema Alveolo-venous fistulae Air embolism Pulmonary edema Pulmonary contusions This is a list of findings after blast injury to the lung.

35 Blast Lung APNOEA BRADYCARDIA HYPOTENSION
acute cardiovascular reflex triad transmitted by the vagal nerve APNOEA BRADYCARDIA HYPOTENSION RJ Guy, J Trauma 1998

36 Blast Lung Open-air blast in Beirut
0.6% of initial survivors had blast lung. Confined-space blast in Jerusalem 35% of initial survivors had blast lung. Frykberg ER et al: The 1983 Beirut Airport terrorist bombing. Ann Surg 1989

37 Blast Lung Management 1 similar to that of lung contusion
Airway maintanance, C-spine control Decompression of pneumothorax Prophylactic chest drains Breathing spontaneous if possible High flow oxygen (15 L/min) Follow standard Airway, Breathing, Circulation plans Place a chest tube if a pneumothorax is present (or may consider if patient will be air transported) Treat all with oxygen. If a ventilator is required, use a low volume strategy (keep plateau pressure < 30)

38 Blast Lung Management 2 similar to that of lung contusion
If intubation is unavoidable Unilateral lung ventilation, high frequency ventilation, Extra-Corporeal Membrane Oxygenation (ECMO) Low tidal volume (peak pressure <30) Reversion to spont. breathing ASAP Beware of AAE (anesthesia, aircraft) Follow standard Airway, Breathing, Circulation plans Place a chest tube if a pneumothorax is present (or may consider if patient will be air transported) Treat all with oxygen. If a ventilator is required, use a low volume strategy (keep plateau pressure < 30) AAC acute air embolism

39 Localization of massive hemoptysis
90° counter-clockwise without head rotation for left lung Bleeding from Alternatives: Univent tube Double lumen tube left lung right lung

40 Blast Injury to the Ear Symptoms
Hearing loss, high-pitched tinnitus common initially, usually improves Pain temporary, may last for weeks Dizziness rare, usually post-concussive Bleeding Read

41 Blast Injury to the Ear Findings
Outside-in tympanic membrane rupture in 70% of patients Foreign material in ear Cholesteatoma by implanted keratinizing squamous cells Ossicular injury dislocation, fracture, avascular necrosis

42 Blast Injury to the Ear: The London Bridge Incident
Walsh RM et al, J Accident & Emergency Med 1995 12 patients required treatment for ear injuries 3 of these patients had perforated ear drums with persistent loss of hearing 9 patients had short term loss of hearing and tinnitus (4 hrs - 4 wks) None had balance problems

43 Treatment of Blast Injury to the Ear
85% of peforations heal spontaneously Surgery (grafting) for large perforations (>80% of surface area) No need for immediate surgery (<1yr) No need for prophylactic antibiotics Long term review for cholesteatoma

44 Blast Injury to the Bowel
Combined intra-abdominal stress and shear waves: Hematoma & tear of the mesentery & bowel Immediate rupture of the bowel Stretching, ischemia, transmural weakening Late transmural necrosis – late rupture – septic MOF Detection may be difficult (silent for days, delayed rupture) Read

45 Blast Injury to the Bowel
Examination Delayed diagnostic peritoneal lavage probably most sensitive CT and ultrasound unreliable Treatment Abdominal exploration and repair Beware of risk of air embolism in patient under general anesthesia

46 Blast Injury to the Bowel
Signs and symptoms Nausea and vomiting Hematemesis (rare) Rectal pain Testicular pain Abdominal tenderness, guarding Absent bowel sounds Hypovolemia Signs and symptoms Nausea and vomiting Hematemesis (rare) Rectal pain Testicular pain Abdominal tenderness, guarding Absent bowel sounds Hypovolemia

47 Blast–induced neurotrauma: A myth becomes reality.
Cernak I, Presented at the 7th International Neurotrauma Symposium. Medimond International Proceedings, Bologna, Italy, 2004. In the past, research has focused on blast injuries to gas-containing organs (lung, ear, gastrointestinal tract), perhaps because the brain was believed to be protected by the skull.

48 Traumatic brain injury in the war zone.
Okie, S. N. Engl. J. Med. 352, 2043–2047; 2005. More recent research indicates that TBI is a common consequence of blast injury. TBI accounts for a larger proportion of casualties among soldiers surviving wounds sustained in combat in Iraq and Afghanistan than in previous conflicts.

49 Cernak I et al. J Trauma 50, 695–706; 2001.
Ultrastructural and functional characteristics of blast injury-induced neurotrauma. Cernak I et al. J Trauma 50, 695–706; 2001. Reactive gliosis and neuronal swelling and cytoplasmic vacuolation were observed in the hippocampus of rats subjected to thoracic blast injury even if the head was protected.

50 Cernak I et al. Brain Inj. 15, 593–612; 2001.
Cognitive deficits following blast injury-induced neurotrauma: possible involvement of nitric oxide. Cernak I et al. Brain Inj. 15, 593–612; 2001. Cognitive impairment and oxidative stress also were observed after blast injury in rats.

51 Blast-Induced Brain Injury and Posttraumatic Hypotension and Hypoxemia
Dewitt DS and Prough DS. J Neurotrauma 2008 Hemorrhage accounted for approximately 50% of combat deaths, and the lungs are one of the primary organs damaged by blast overpressure. Thus, it is likely that blast-induced lung injury and/or hemorrhage leads to hypotensive and hypoxemic secondary brain injury in a significant number of combatants exposed to blast overpressure injury.

52 Blast-Induced Brain Injury and Posttraumatic Hypotension and Hypoxemia
Dewitt DS and Prough DS. J Neurotrauma 2008 Unfortunately, the paucity of reproducible animal models of blast injury has limited research on the pathophysiology of blast injury and many important features have not been investigated: Cerebral blood flow, cerebral vascular reactivity to blast-induced brain injury, effects of hemorrhagic or hypoxemic posttraumatic insults on the blast-injured CNS.

53 Blast-Induced Brain Injury and Posttraumatic Hypotension and Hypoxemia
Dewitt DS and Prough DS. J Neurotrauma 2008 Reactive oxygen species (ROS) are produced by TBI. Superoxide radicals combine with nitric oxide, another ROS produced by blast injury, to form peroxy- nitrite, a powerful oxidant that impairs cerebral vascular responses.

54 SECONDARY BRAIN DAMAGE VICIOUS CYCLE
ICP CBV CPP CBF AUTOREGULATION

55 Functional Impairments
Pseudoanurysms Intracerebral hemorrhage & vasospasm Increased BBB permeability edema Diffuse axonal damage impaired information processing Regional malperfusion motor/sensory malfunction Cognitive deficits retro/anterograde amnesia, confusion, indecisiveness Ropper A. N Engl J Med 2011; 364/22:

56 Surgical Team’s experience in Operation Iraqi Freedom.
Patel TH et al.J Trauma 57, 201–207; 2004. Improvements in body armor, transport and battlefield surgical care have all contributed to increased survival.

57 Musculoskeletal Blast Injury
Most common injury in modern warfare Secondary injury (debris projectiles) Surgical debridement Excision of non-viable tissue Drainage Delayed closure

58 Chitosan-based hemostatic dressing: experience in current combat.
Wedmore I, Holcomb JB et al. J Trauma 60, 655–658; 2006. Hemostatic dressings, bandages or pads filled with substances that promote clotting, have been very effective in reducing hemorrhage. bandages containing chitosan, a carbohydrate Derived from chitin, were 100% successful in stopping or reducing hemorrhage from external wounds in Operation Iraqi Freedom.

59 Potentially Fatal Traumatic Amputation
Debris propelled upward along tissue planes Compartment injury Contamination Sepsis

60 Blast Wave-induced Fracture
Contaminated with bacteria High risk of infection Tetanus prophylaxis ASAP Antibiotic prophylaxis ASAP Major threats: Gas gangrene, Pseudomonas

61 Blast Injury and Air Embolism Main cause of immediate and early death Signs and symptoms depend on vascular bed affected Signs and symptoms EKG: Arrhythmia, ischemia Somnolence, headache, Motor and/or sensory loss Vertigo, ataxia Seizures Facial or tongue blanching Transient blindness Read

62 Treatment of Air Embolism
Avoid/treat low vascular pressure Avoid high airway pressure Avoid head-down position Administer oxygen Hyperbaric oxygen therapy ASAP e.g. after hemorrhage e.g. resuscitation with PPV increases intra-cranial pressure promotes embolism to coronary vessels reduces volume of bubbles improves blood flow to tissues

63 Problems following Blast Injury
Combination: primary, secondary, tertiary, quaternary Combination of chemical and biological injury Toxic gas inhalation Read

64 TAKE HOME MESSAGES

65 AIRWAY Mentally altered Intubation to safeguard airway
Sponteneous breathing if possible Hemoptysis Unilateral ventilation of less injured lung

66 BREATHING Lung contusion 100% oxygen, PEEP+PPV if necessary
Unilateral ventilation of better lung avoids barotrauma in compliance mismatch Pneumothorax Additional chest drains

67 CIRCULATION Hypovolemic shock Normalize pre-load to avoid AAE
As much fluid as necessary As little fluid as possible Cardiogenic shock Coronary AAE semi/left-lateral decubitus position hyperbaric oxygen

68 CONSIDER PRIMARY INJURY IN ALL BLAST VICTIMS
LUNG INJURY presents early Exclude before general anesthesia and air transport ABDOMINAL INJURY presents late May be silent until sepsis is advanced EAR INJURY is easily overlooked Source of significant morbidity and litigation

69 Blast - induced Air Embolism main cause of early death
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