smoke and burns
TRANSCRIPT
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SMOKE INHALATION AND FIRE TOXICOLOGY
Steven A. Godwin MD
University of Florida /HSC
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Background
• Account for 50% of fire deaths
• Multiple factors contribute to M and M– Local pulmonary insult– Inhaled pulmonary and systemic toxins– Asphyxia
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Mechanisms of Local Pulmonary Injury
• Thermal Injury
• Chemical Injury
• Multifactorial
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Thermal Injury
• Rarely affects parenchyma
• Damages primarily mucous membranes
• Initial 24 hours is key
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Chemical Injury
• Physical properties– anatomic location
– extent of absorption
• Length of exposure
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Physical Properties of Chemical Inhalants
• Upper airway irritants– Larger, highly water soluble particles
• Alveolar injury– Associated with less water solubility
and smaller particles
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Multifactorial Injury
• Respiratory epithelium necrosis
• Cilia inactivation
• Type II pneumocytes and alveolar macrophage destruction
• Capillary leak syndrome
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Systemic Fire Toxins
• Chemical asphyxiantsCarbon monoxide
Cyanide
• Simple asphyxiantsNitrogen Argon Hydrogen
Methane Helium
Ethane Carbon dioxide
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Chemical Asphyxiants
• Carbon monoxide– Colorless, tasteless, odorless gas
– Leading cause of reported toxicologic deaths
– Byproduct of incomplete combustion
– Pyrolysis of any carbon containing material
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Mechanism of CO Toxicity
• CO competes with oxygen binding to hemoglobin, myoglobin, and cytochrome oxidase
• Results in global hypoxia, muscle ischemia, and cellular hypoxia
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CO Toxicity
• Impaired O2 off-loading
• Leftward shift of oxygen dissociation curve
• Fetal tissue at increased risk
• Neurologic and cardiovascular systems primarily affected
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Physical Findings and Carboxyhemoglobin levels
• O %
• 10 %
• 20 %
• 30 %
• 40 %
• 50 %
• 60-70 %
No symptoms
Frontal HA
HA, DOE
N/V, dizziness, blurred vision, poor judgement
Confusion, syncope
Coma, seizures
Hypotension, death
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Pediatric Exposures
• Up to 17 % of acute exposures die
• Up to 48 % of acute exposures may require CPR
• Newborns at highest risk
• Confused for colic
• Implicated in some cases of SIDS
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Cyanide Toxicity
• Suspect in fires involving synthetics– wool, silk, nylon, paper, upholstery,
plastics, polyurethane, asphalt
• Victims have bitter almond breath odor
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Mechanisms of CN Toxicity
• Inhibits ATP production by binding with the ferric moiety of cytochrome oxidase
• Blockade in the mitochondrial O2
• Severe hypoxia despite presence of O2
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Presentation of CN Toxicity
• Mimick signs of hypoxia without cyanosis
• Physical signs are non-specific: may include hyperventilation, anxiety, decreased LOC, seizure, coma, cardiac arrhythmias
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Clinical Clues
• History most important clue
• Suspect in any patient found to be comatose, bradycardic, and severely acidotic w/o findings of cyanosis or hypoxia
• Diagnosis supported by bright- red retinal vessels, oral burns and odor
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Initial Evaluation in Smoke Inhalation
• History, History, History, History
• A,B,Cs
• PE:
HEENT: retinal veins, mucous membranes, facial burns, singed nasal hairs or presence of carbonaceous sputum, dysphonia
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Initial Evaluation in Smoke Inhalation
• PE continued:
Neck: stridor
Cardiovascular: ectopy
Pulmonary: wheezing and rales
Skin: cherry red discoloration, burns, chemical exposures, bullae
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Airway Evaluation
• Fiberoptic evaluation recommended in significant exposures due to unreliable physical signs
• Close observation with low threshold for intubation
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Laboratory
• Essential test: ABG with co-oximetry COHb level
Urine pregnancy test Chest x-ray
• Additional test to consider Electrolytes CPK levels
CBC Urine myoglobin
Coagulation studies
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ABG and Pulse Oximetry
• Beware the saturation gap– Ask for measured oxygen saturation
– May calculate poor man’s (UMC) COHb level
• Evaluate severe acidosis
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Initial Management
• 100 % Oxygen
• Airway evaluation with brochoscopy if indicated
• Supportive care with treatment of burns
• No role for steroids or antibiotics
• Observation period depends on exposure
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Initial Management
• Healthy asymptomatic patients with normal blood gases may be discharged
• Exposure to agents with low solubility (phosgene) need longer observation
• Exposure to local irritants (hydrogen chloride, sulfur dioxide) treat symptomatically and observe
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CO Management
• Rules of thumb for the elimination half-life of CO
Room air 240-320 minutes
100 % oxygen at 1 atm 60-90minutes
HBOT with 3 atm 23 minutes
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Hyperbaric Therapy
• Dalton’s Law:Pt=PO2 + PN2 + Px
– States the ratio of gases doesn’t change despite the change in total pressure
– The individual partial pressures do change
• Increases Oxygen content to 6.8 %
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CO Management
• Guidelines for Hyperbaric therapy– COHb > 25%– COHb > 15% in patient with coronary dz– COHb > 15% or with symptoms in pregnancy– COHb > 15% in a young child
EKG changes pO2 < 60 mmHg
Metabolic acidosis Abnormal thermoregulation
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CO Management
• Goals of oxygen therapy in mild exposures:– Treat until COHb level < 5 % and
asymptomatic
– Admit patients with cardiac dz for observation
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CN Management
• Lilly Cyanide Kit– Amyl nitrite
– Sodium nitrite
– Sodium thiosulfate
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Mechanism of Action of Antidote Kit
• Amyl nitrite and sodium nitrite converts Hb > methemoglobin > binds CN > cyanomethemoglobin > rhodenase metabolizes CN to thiocyanate
(enhanced by sodium thiosulfate) > renal excretion of sodium thiocyanate
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Hydroxycobalamin
• Non- toxic
• Binds CN and is excreted by kidneys as cyanocobalamin
• Used in Europe
• Awaiting FDA approval
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Outpatient Burn Care• 1st Degree
– Superficial Burns
• 2nd Degree
– Superficial Partial Thickness
– Deep Partial Thickness• 3rd Degree
– Full Thickness
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Superficial Burns
• Superficial epidermis only
• Painful, erythematous and w/o blisters
• Usually due to sunlight or short flash
• No Scar
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2nd Degree Burns
• Superficial Partial Thickness– Full epidermis and may involve
dermis
– Red, blistered, weeping, and painfull
– Often scalds and short flashes
– No scarring
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2nd Degree Burns
• Deep Partial Thickness– Usually spares deep dermal structures– Severe blistering or waxy appearance– Often confused with full thickness– Scar on healing
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3rd Degree Burns
• Destruction of dermal layer
• Flames, scalds, and chemical and electrical contact
• White, charred inelastic skin
• Thrombosed vessels
• Scar with contractures
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Second Degree Depth of Burn
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Third Degree Depth of Burn
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Minor Burn Management
• The 5 Cs:– Cut
– Cool
– Clean– Chemoprophylaxis - bacitracin, Silver
Sulfadiazine
– Cover
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Don’t Forget Pain Control!!
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Major Burn Evaluation
• Adult Body Surface Area: “Rule of Nines”
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Major Burn Evaluation
• Pediatric Body Surface Area: “Rule of Nines”
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Severe Burn Management
• Airway– Assess for injury and establish control
early
• Breathing
• Circulation– Fluid Resuscitation
– Monitor Urine Output
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Fluid Resuscitation
• Rule of thumb:– 1 ml of urine / kg / hr for children under
30kg
– 30-50 ml /kg / hr output for adults
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Parkland Formula: Only a Guideline
• Estimate of fluid requirements in partial and full thickness burns
• 2-4 ml / kg / % BSA burn over first 24 hours
• 50% of Ringer’s Lactate give over 1st 8 hours with rest administered over next 16 hours
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Criteria for Transfer
• Partial / Full thickness burns greater than 10% BSA in patients > 55 yo and < 10 yo.
• All other age groups with burns > 20 % BSA• Partial / Full thickness burns to face, hands, eyes,
ears, feet, genitalia, or perineum or those overlying major joints
• 5% Full thickness in any age group• Significant electrical burns • Significant chemical burns
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Criteria for Transfer
• Inhalation injury• Burn injury in patients with complicating co-
morbid illnesses• Children in facilities lacking appropriate resources
to aid in rehab• Patients requiring special long term support
including children in abuse cases
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Questions
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