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 How is inhalation injury diagnosed? What adjunctive measures are used to treat inhalation injury? What is the treatment for carbon monoxide and cyanide poisoning? 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 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 Anatomic Classification Upper airway Lower airway Systemic toxicity http://www.monroecc.edu/depts/pstc/backup/parasan4.htm 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 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 Bartley et al. Drug Design, Development and Therapy. 2008; 2: 9–16. 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 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 Miller et al. Journal of Burn Care Research. 2009; 30(2) 249-256 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 NO ONE FINDING IS SUFFICIENTLY SENSITIVE OR SPECIFIC! Must use clinical judgment! Tools for Diagnosis Bronchoscopy Pulmonary function testing Xenon133 lung scan Grades of Inhalation Injury Endorf and Gamelli. Journal of Burn Care and Research. 2007; 28:80-83 Treatments Airway Control Chest physiotherapy Suctioning Therapeutic bronchoscopy Ventilatory strategies Pharmacologic adjuncts Treatment Control the Airway!!! ≥ 40% burn Transport http://www.burnsurgery.com/Betaweb/Modules/initial/bsinitialsec2.htm Ventilator Strategies Airway pressure release ventilation (APRV) Intrapulmonary percussive ventilation (IPV) High-frequency percussive ventilation (HFPV) High frequency oscillatory ventilation (HFOV) 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 Results No significant difference in mortality or ventilator free days Significant difference in “Rescue Therapy” Results No significant difference in mortality or ventilator free days Significant difference in “Rescue Therapy” P/F ratio vs Ventilator Mode Chung et al. CCM; 2010: 38(10) 1970-1977 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” Pharmacologic Intervention Bartley et al. Drug Design, Development and Therapy. 2008; 2: 9–16. Pharmacologic Intervention Bartley et al. Drug Design, Development and Therapy. 2008; 2: 9–16. 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) Casts Enkhbaatar et al., 2007 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 antiinflammatory effect - ? systemic rhAT ? Shriners Protocol Since 1990 (560+ patients treated) Mlcak RP et al. Burns, 2007;33:2-13 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 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 TOXIC GASES 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 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 Signs and Symptoms Weaver LK. N Engl J Med 2009;360:1217-25. 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 COHb Symptoms % 0-5 Normal 15-20 Headache, confusion, fatigue 20-40 Hallucination, vision Δ’s 40-60 Combative, coma 60 + Cardiopulmonary arrest 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 COHb Symptoms % 0-5 Normal 15-20 Headache, confusion, fatigue 20-40 Hallucination, vision Δ’s 40-60 Combative, coma 60 + Cardiopulmonary arrest CO Toxicity Treatment OXYGEN Half-life COHb (min) RA 1ATM 100% O2 100% O2 2.5 ATM Male 240 47 22 Female 168 33 15 Carbogen – normobaric, normocapnic, hyperventilation (4.54.8% CO2) Hyperbaric oxygen??? 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 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) 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 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 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 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) Final Thoughts Inhalation injury is bad Support the airway Frequent bronchoscopy and monitoring Different ventilatory strategies Adjunctive measures need further investigation The Toilet Snorkel http://www.icbe.org/2006/01/18/the-toilet-snorkel/ Thank You! 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?