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Inhalation Injury

Inhalation Injury. Arek Wiktor M.D. Burn Fellow University of Colorado Hospital. Outline. Background Smoke Pathophysiology Diagnosis Treatment Specific Lethal Compounds. http://spanishlakefd.com/firealarms/. Learning Objectives. Describe the pathophysiology of inhalation injury

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Inhalation Injury

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  1. Inhalation Injury Arek Wiktor M.D. Burn Fellow University of Colorado Hospital

  2. Outline • Background • Smoke • Pathophysiology • Diagnosis • Treatment • Specific Lethal Compounds http://spanishlakefd.com/firealarms/

  3. Learning Objectives • Describe the pathophysiology of inhalation injury • How is inhalation injury diagnosed? • What adjunctive measures are used to treat inhalation injury? • What is the treatment for carbon monoxide and cyanide poisoning?

  4. A Sunday afternoon stroll thru the fire… http://www.aeromedix.com/product-exec/parent_id/1/category_id/12/product_id/1074/nm/Safe_Escape_Smoke_Hood

  5. Epidemiology • 15-30% of burn admissions have inhalation injury • Independent predictor of mortality, ↑ by 20% • Increases pneumonia risk • Leading diagnosis of those hospitalized and treated on 9/11, World Trade Center attack

  6. Anatomic Classification • Upper airway • Lower airway • Systemic toxicity http://www.monroecc.edu/depts/pstc/backup/parasan4.htm

  7. SMOKE • Variable, changes with time burning • Toxic gases and low ambient oxygen • Ingredients: Aldehydes (formaldehyde, acrolein), ammonia, hydrogen sulfide, sulfur dioxide, hydrogen chloride, hydrogen fluoride, phosgene, nitrogen dioxide, organic nitriles • Particulate matter Prien et al. Burns 1988; 14:451-460

  8. Pathophysiology • Cilia loss, respiratory epithelial sloughing • Neutrophilic infiltration • Atelectasis, occlusion by debris/edema • Pseudomembranes • Bacterial colonization at 72 hrs Hubbard et al. J Trauma 1991; 31:1477-1486

  9. Bartley et al. Drug Design, Development and Therapy. 2008; 2: 9–16.

  10. Secondary Lung Injury • Unilateral smoke inhalation damages contralateral lung • Immune response, increased permeability • Oxygen-derived free radicals • NO mediated damage (chemotactic factor neuts) • Eiscosanoids (TXA2→TXB2) • Reduced phagocytosis in macrophages

  11. Systemic Effects • Larger fluid resuscitation (2→5cc/kg/%) • Additive effect to burns • 12% pts inhalation injury alone require intubation* • 62% pts burn + inhalation injury intubated* Clark et al. J Burn Care Rehabilitation, 1990; 11:121-134

  12. Miller et al. Journal of Burn Care Research. 2009; 30(2) 249-256

  13. Diagnosis • Clinical findings: • Facial burns (96%) • Wheezing (47%) • Carbonaceous sputum (39%) • Rales (35%) • Dyspnea (27%) • Hoarsness (26%) • Tachypnea (26%) • Cough (26%) • Cough and hypersecretion (26%) DiVincenti et al. Journal of Trauma, 1971; 11:109-117

  14. NO ONE FINDING IS SUFFICIENTLY SENSITIVE OR SPECIFIC! Must use clinical judgment!

  15. Tools for Diagnosis • Bronchoscopy • Pulmonary function testing • Xenon133 lung scan

  16. Grades of Inhalation Injury Endorf and Gamelli. Journal of Burn Care and Research. 2007; 28:80-83

  17. Treatments • Airway Control • Chest physiotherapy • Suctioning • Therapeutic bronchoscopy • Ventilatory strategies • Pharmacologic adjuncts

  18. Treatment Control the Airway!!! • ≥ 40% burn • Transport http://www.burnsurgery.com/Betaweb/Modules/initial/bsinitialsec2.htm

  19. Ventilator Strategies • Airway pressure release ventilation (APRV) • Intrapulmonary percussive ventilation (IPV) • High-frequency percussive ventilation (HFPV) • High frequency oscillatory ventilation (HFOV)

  20. Single center, prospective randomized trial 2006-2009 • 387 pts screened • 31 pts HFPV, 31 pts LTV (ARDSnet) Chung et al. CCM; 2010: 38(10) 1970-1977

  21. Results • No significant difference in mortality or ventilator free days • Significant difference in “Rescue Therapy”

  22. Results • No significant difference in mortality or ventilator free days • Significant difference in “Rescue Therapy”

  23. P/F ratio vs Ventilator Mode Chung et al. CCM; 2010: 38(10) 1970-1977

  24. Study Conclusions • Study stopped for safety concerns in LTV group • Gas exchange goals met in all HFPV pts, and not in 1/3 of LTV pts • Trend for less barotrauma, less VAP, less sedation “Strict application of LTV may be suboptimal in the burn population”

  25. Pharmacologic Intervention Bartley et al. Drug Design, Development and Therapy. 2008; 2: 9–16.

  26. Pharmacologic Intervention Bartley et al. Drug Design, Development and Therapy. 2008; 2: 9–16.

  27. Airway Obstructive Casts • Mucus secretions • Denuded airway epithelial cells • Inflammatory cells • Fibrin • -Solidifies airway content • Several studies shown reduction in size of casts with fibrinolytic agents (tPA)

  28. Casts Enkhbaatar et al., 2007

  29. Theory Behind Inhaled Heparin • Animals with Burn + ARDS have decreased levels of antithrombin in plasma and BAL specimens • Heparin potentiates antithrombin by 2000x • Prevention of fibrin deposition in lungs • Heparin inhibits antihrombin’s anti-inflammatory effect - ? systemic rhAT ?

  30. Shriners Protocol Since 1990 (560+ patients treated) Mlcak RP et al. Burns, 2007;33:2-13

  31. Evidence (Pro) • Desai et al. 1998 • Pediatric burns (90 pts total) • 1985-1989 (43) vs 1990-1994 (47pts) • ↓ reintubation, atelectasis, and mortality • Miller et al. 2009 • 30 patients over 5 years, retrospective review • Tx 10,000 units heparin, 20% NA, 0.5 ml AS q4 hrs • Survival benefit, improved LIS scores, compliance • Number needed to treat 2.73

  32. Evidence (Con) • Holt et al. 2008 • Retrospective review 1999-2005, 150 pts total • Burn size, LOS, time on vent, mortality SAME • Only 68% pts had bronchoscopy, • Attending discretion which treatment to use

  33. TOXIC GASES

  34. Carbon Monoxide (CO) • CO from incomplete combustion • CO + Hb → COHb (affinity 200-250x) • LEFT shift of oxy-Hb curve (Haldane effect) • CO binding to intracellular cytochromes and metalloproteins (myoglobin) • “Two compartment” pharmacokinetics • Animal experiment 64% COHb transfusion

  35. CO Toxicity Symptoms • “Cherry-red lips, cyanosis, retinal hemorrhage”- rare • CNS and Cardiovascular • ↑ RR, ↑HR, dysrhythmias, MI, ↓BP, coma, seizures • Delayed neuropsychiatric syndrome (3-240d) • Cognitive/personality changes/parkinsonianism • Spontaneous resolution

  36. Signs and Symptoms Weaver LK. N Engl J Med 2009;360:1217-25.

  37. CO Toxicity Diagnosis • Pulse oximetry false HIGH SpO2 • Need cooximetry direct measurement of COHb • Older ABG analyzers (estimate off dissolved PO2) • MRI – lesions globus pallidus/basal ganglia/deep white matter

  38. CO Toxicity Diagnosis • Pulse oximetry false HIGH SpO2 • Need cooximetry direct measurement of COHb • Older ABG analyzers (estimate off dissolved PO2) • MRI – lesions globus pallidus/basal ganglia/deep white matter

  39. CO Toxicity Treatment • OXYGEN • Half-life COHb (min) • Carbogen – normobaric, normocapnic, hyperventilation (4.5-4.8% CO2) • Hyperbaric oxygen???

  40. Cyanide (CN) • Combustion of synthetics (plastics, foam, varnish, paints, wool, silk) • Binds to cytochrome c oxidase – dose dependent • Uncouple mitochondria • Aerobic → anaerobic = Lactic acid • Half-life 1-3 hours

  41. CN Toxicity Symptoms • Dyspnea • Tachypnea • Vomiting • Bradycardia • Hypotension • Giddiness/Coma/Siezures • Death * The smell of bitter almonds on the breath suggests exposure (cannot be detected by 60% of the population)

  42. CN Toxicity Diagnosis • No rapid assay • High lactate (>10mmol/L) (s/s, 87%/94%) • Metabolic acidosis • Elevated mixed venous saturation (<10% a-v) difference • High index of suspicion ** Also get: COHb and Methemoglobin levels

  43. CN Treatment Cyanokit (Hydroxocobalamin) • 70mg/kg dose (5g vials) • Combines with cyanide to from cyanocobalamin (Vit B12) • Red membranes/urine • Hypertension, Anaphylaxis • 5% increase COHb, interfere with HD LFTs/Cr/Fe levels

  44. Cyanide Antidote Kit (CAK) Amyl nitrite pearls, sodium nitrite, and sodium thiosulfate • Amyl nitrate and sodium nitrate induce methemoglobin • Methemoglobin+cyanide→releases cyanide from CC • Sodium thiosulfate enhances cyandide→thiocynate→renal excretion • Avoid nitrate portion in pts with inhalation injury (COHb >10%) • Vasodilation and hypotension

  45. Acquired Methemolgobinemia • NO2, NO, benzene gases → oxidation of iron • Fe2+ → Fe3+ • Shift curve to LEFT • Blood “Chocolate brown color” • Normal PaO2, pulse ox >85% • Tx: Methylene blue (1-2 mg/kg Q 30-60min)

  46. Final Thoughts • Inhalation injury is bad • Support the airway • Frequent bronchoscopy and monitoring • Different ventilatory strategies • Adjunctive measures need further investigation

  47. The Toilet Snorkel http://www.icbe.org/2006/01/18/the-toilet-snorkel/

  48. Thank You!

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