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Smoke inhalation Craig Smollin MDAssociate Medical Director,

California Poison Control Center, SFAssistant Professor of Emergency Medicine

University of California, San Francisco

Disclosures

• No financial relationship to any commercial products discussed in this talk

• Fires account for approx 3,250 U.S. deaths/yr

• Majority due to smoke inhalation

• Associated with high morbidity and mortality

Smoke Inhalation

Station night club fireRhode IslandFebruary 20, 2003

100 killed230 injured

Case Study

• 40-year old male pulled from an enclosed fire.

He is confused and agitated. He arrives in your

emergency department disoriented and in

moderate distress, coughing up soot and

complaining of difficulty breathing.

• VS: BP 90/60, HR 120, RR 30, O2 sat 95%

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What type of injuries do you expect?

• Thermal burns to the upper airway

• Chemical injury to the upper airway

• Chemical injury to the lower airway

• Systemic affects of absorbed poisons

Objectives for this talk

• We will focus on the systemic toxicity of inhaled toxic gases

• Carbon Monoxide

• Cyanide

Carbon monoxide (CO)

• Colorless, odorless, non-irritant gas

• Produced anytime a carbon-containing substance is burned

• House fires, leaking furnaces, portable generators

Carbon monoxide (CO)

• Common serious poisoning

• 15,000 - 40,000 cases/year in U.S

• Over 2,000 deaths

• High incidence of permanent neurologic sequelae

CO Pathophysiology

Carbon Monoxide

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CO-Hgb 1. Functional Anemia

2. Shift in Oxygen HgbDissociation Curve

CO Pathophysiology

• Binds to hemoglobin

• 250:1 compared wtih O2

• Functional anemia

• Changes hemoglobin such that it wont give up oxygen

CO Pathophysiology• Binds to hemoglobin

• 250:1 compared wtih O2

• Functional anemia

• Shifts O2-Hemoglobin dissociation curve to left

• Other toxic effects

• Intracellular myoglobin?

• Intracellular cytochrome?

• Post anoxic inflammatory injury

Symptoms and Signs

• Nonspecific

• Headache

• Dizziness

• Malaise

• Nausea and vomiting

• Confusion

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Pitfall

• The diagnosis of carbon monoxide poisoning is easily overlooked!

Clues to the diagnosis

Cherry-red color

Multiple victims

Pulse oximetry?

ABGs?

Pulse oximetry

Pitfall - Pulse oximetry reading will be normal in CO poisoning

Arterial blood gas

Pitfall - pO2 by arterial blood gas will be normal in CO poisoning

Traditionally CO only measurable through CO-oximetry

Pearl

CO-oximetry can be performed on either venous or arterial blood samples

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Clues to the diagnosis

Cherry-red color

Multiple victims

Pulse oximetry?

ABGs?

Pearl

You must have a high index of suspicion and send a CO-Hgb level by CO-oximetry

Carboxyhemoglobin levels

COHgb %< 5%

10-20%

30-40%

40-50%50-60%

Symptoms*None, or mild headacheHeadache, dyspnea on

exertionSevere headache, fatigue,

irritability, dizziness Confusion, collapseComa, convulsions

*Note: correlation between COHgb levels and symptoms is poor

Outcome after CO Poisoning

• Survivors of severe poisoning may have permanent “hard” sequelae.

• Vegetative state

• Parkinsonism

• Survivors of severe poisoning may have permanent “hard” sequelae.

• Vegetative state

• Parkinsonism

• Subtle cognitive deficits

• Memory impairment

• Irritability

• Moodiness

• Difficulty concentrating

Outcome after CO Poisoning Case Continued...

• Laboratory Data:

• VBG: pH 6.8, pO2 = 75,

• Lactate = 16 mmol/L

• COHgb = 20%

• CXR negative

• Head CT negative

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Pitfall

•Tendency to focus on CO as the diagnosis

San Francisco 1906 - Great Earthquake and Fire

Question: are there any other systemic toxins found in smoke?

Consider this…

• Hydrogen cyanide gas produced in combustion of :

Consider this…

• Hydrogen cyanide gas produced in combustion of :

• Probability of HCN production/exposure is high

Paper Silk Wool Plastic Cotton

Pitfall

Dont forget about Cyanide !!Patients exposed to carbon monoxide are

likely to be exposed to cyanideCyanide: Pathophysiology

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Symptoms and Signs

• Dizziness

• Headache, nausea, vomiting

• Dyspnea

• Tachycardia, hypotension

• Coma, seizures, death

Pitfall

• Cyanide levels are not readily available!

Clinical clues to the diagnosis

Lactic Acidosis

Elevated mixed venous pO2

Cardiovascular collapse

Pearl

Consider CN toxicity in the smoke inhalation patient with lactate > 10

Case Continued...

Our patient likely exposed to both CO and CN!

Laboratory Data:

VBG: pH 6.8, pO2 = 75,

Lactate = 16 mmol/L

COHgb = 20%

CXR negative

HCT negative

Treatment

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Which of the following treatments should be given to our patient?

• (A) Nitrites

• (B) Sodium thiosulfate

• (C) Hydroxocobalamin

• (D) Hyperbaric oxygen therapy

Treatment of CN Poisoning

• Removal from source

• 100% oxygen by tight-fitting mask/ET tube

• Cyanide antidote kit?

• Hydroxocobalamin?

Cyanide Antidote Kit Nitrites

Nitrites Nitrites

Problem:

(1) Hypotension

(2) Methemoglobinemia

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Pitfall

• Administration of nitrites to thepatient with concurrent CO and CNpoisoning

Sodium thiosulfate

Sodium thiosulfate Hydroxocobolamin

• Combines with CN to form Vitamin B12.

• Appears to be effective and safe

• Preferred drug for CN due to smoke inhalation (safer than nitrites)

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Hydroxocobolamin

• Side effects:

– Red Skin, secretions 2-7 days

– Nausea, vomiting

– Occasional HTN and muscle twitching

from Clin Toxicol 2006; 14.17

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Treatment of CO Poisoning

• Removal from source

• 100% oxygen by tight-fitting mask/ET tube

• Hyperbaric oxygen?

Hyperbaric oxygen• Speedier removal of CO

• Provides oxygen independent of Hgb

• Benefit to the injured brain?

• About 1500 patients treated/year in U.S.

• Million dollar question:

• Does HBO therapy reduce the incidence of subtle cognitive deficits?

Weighing the Evidence: HBO vs NBO

YES NO

Thom et. al.

Weaver et al.

Raphael et. al

Scheinkestel et. al.

YES NO

Thom et. al.

Weaver et al.

Raphael et. al

Scheinkestel et. al.

?

Naturally, experts disagree on interpretation!

Weighing the Evidence: HBO vs NBO

Consider HBO if:

• Loss of consciousness (1,2)

• COHbg > 25% (1,2)

• Age > 36 yrs (1)

• Metabolic acidosis

• Cerebellar findings on Exam (2)

(1) Weaver et al: Am J Resp Crit Care Med 2008; 178:314(2) Weaver et al: NEJM 2002; 347:1057

• Also, pregnancy (fetus more at risk)

Which of the following treatments should be rendered to our patient?

• (A) Nitrites

• (B) Sodium thiosulfate

• (C) Hydroxocobalamin

• (D) Hyperbaric oxygen therapy

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Which of the following treatments should be rendered to our patient?

• (A) Nitrites (no)

• (B) Sodium thiosulfate (maybe)

• (C) Hydroxocobalamin (probably better)

• (D) Hyperbaric oxygen therapy (consider)

Case Conclusion...

Patient intubated and placed on 100% oxygen.

Received hydroxocobalamin for presumed CN

exposure (lactate >10 mmol/L). HBO was

considered but decided against because

nearest chamber was at great distance and

patient unstable.

Take home points

• Carbon monoxide

• Nonspecific symptoms

• pO2 and conventional pulse ox normal

• Treat with oxygen

• Consider HBO

Take home points• Cyanide

• Often accompanies CO in smoke inhalation

• Elevated lactate and mixed venous pO2

• Avoid nitrites in smoke inhalation victims

• New antidote: hydroxocobalamin

Questions?