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BLAST INJURIES: the Anesthesia Provider ’ s Perspective

BLAST INJURIES: the Anesthesia Provider ’ s Perspective

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BLAST INJURIES: the Anesthesia Provider ’ s Perspective

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  1. TRAUMA 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

  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, 130 injured (mainly males aged 25-44) secondary injuries 2 miles away • NYC 1993: WTC terrorist bomb 6 killed, 1042 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 15000 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. 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)

  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)

  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 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. Coupland, RM and Meddings, DR: BMJ 319, 407–410; 1999.

  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 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 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 standing worse than prone enclosed space worse than open (multiple reflections) • radius of effect < radius of projectiles • more damage if blast wave reflected • by surfaces

  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)

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

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

  34. 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 Blast LungPathology and Findings

  35. Blast Lung 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 1similar 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)

  38. Blast Lung Management 2similar 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) 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

  41. 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 Blast Injury to the Ear Findings

  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)

  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 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. Ultrastructural and functional characteristics of blast injury-induced neurotrauma. 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. Cernak I et al. J Trauma 50, 695–706; 2001.

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