2/1/2013

Disclosures

Smoke inhalation • No financial relationship to any commercial products discussed in this Craig Smollin MD talk Associate Medical Director, California Poison Control Center, SF Assistant Professor of Emergency Medicine University of California, San Francisco

Smoke Inhalation

Station night club fire • Fires account for approx 3,250 U.S. Rhode Island deaths/yr February 20, 2003 • Majority due to smoke inhalation 100 killed 230 injured • Associated with high morbidity and mortality

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%

1 2/1/2013

What type of injuries do you expect? Objectives for this talk

• Thermal burns to the upper airway • Chemical injury to the upper airway • We will focus on the systemic toxicity of inhaled toxic gases • Chemical injury to the lower airway • Systemic affects of absorbed poisons • • Cyanide

Carbon monoxide (CO) Carbon monoxide (CO)

• Colorless, odorless, non-irritant gas • Common serious poisoning • Produced anytime a carbon- • 15,000 - 40,000 cases/year in U.S containing substance is burned • Over 2,000 deaths • House fires, leaking furnaces, • High incidence of permanent portable generators neurologic sequelae

Carbon Monoxide

CO Pathophysiology

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CO-Hgb 1. Functional Anemia

CO Pathophysiology

• Binds to hemoglobin • 250:1 compared wtih O2 • Functional anemia • Changes hemoglobin such that it wont give up 2. Shift in Oxygen Hgb Dissociation Curve

CO Pathophysiology Symptoms and Signs • Binds to hemoglobin 250:1 compared wtih O2 • • Nonspecific Functional anemia • • Headache Shifts O2-Hemoglobin dissociation • Dizziness curve to left • Malaise • Other toxic effects • Nausea and • Intracellular myoglobin? • Confusion • Intracellular cytochrome? • • Post anoxic inflammatory injury

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Pitfall Clues to the diagnosis

Cherry-red color • The diagnosis of carbon monoxide poisoning is easily overlooked! Multiple victims

Pulse oximetry?

ABGs?

Pulse oximetry Arterial blood gas

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

Pearl

Traditionally CO only measurable through CO-oximetry CO-oximetry can be performed on either venous or arterial blood samples

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Clues to the diagnosis Pearl

Cherry-red color You must have a high index of suspicion and Multiple victims send a CO-Hgb level by CO-oximetry

Pulse oximetry?

ABGs?

Carboxyhemoglobin levels Outcome after CO Poisoning

COHgb % Symptoms* < 5% None, or mild headache • Survivors of severe poisoning may have 10-20% Headache, dyspnea on permanent “hard” sequelae. exertion 30-40% Severe headache, fatigue, • Vegetative state irritability, dizziness Parkinsonism 40-50% Confusion, collapse • 50-60% Coma, convulsions

*Note: correlation between COHgb levels and symptoms is poor

Outcome after CO Poisoning Case Continued... • Survivors of severe poisoning may have permanent “hard” sequelae. • Laboratory Data: • Vegetative state • VBG: pH 6.8, pO2 = 75, • Lactate = 16 mmol/L • Parkinsonism • COHgb = 20% • Subtle cognitive deficits • CXR negative • Memory impairment • Head CT negative • Irritability • Moodiness • Difficulty concentrating

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

•Tendency to focus on CO as the diagnosis

San Francisco 1906 - Great Earthquake and Fire

Consider this… Consider this…

• Hydrogen cyanide gas produced in of : • Hydrogen cyanide gas produced in combustion of :

Paper Silk Wool Plastic Cotton

• Probability of HCN production/exposure is high

Pitfall

Dont forget about Cyanide !! Patients exposed to carbon monoxide are Cyanide: Pathophysiology likely to be exposed to cyanide

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Symptoms and Signs Pitfall

• Dizziness • Headache, nausea, vomiting • Dyspnea • Cyanide levels are not readily available! • Tachycardia, hypotension • Coma, seizures, death

Clinical clues to the diagnosis Pearl

Lactic Acidosis Consider CN toxicity in the smoke Elevated mixed venous pO2 inhalation patient with lactate > 10

Cardiovascular collapse

Case Continued... Treatment

Laboratory Data: VBG: pH 6.8, pO2 = 75, Lactate = 16 mmol/L COHgb = 20% CXR negative HCT negative Our patient likely exposed to both CO and CN!

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

• Removal from source • (A) Nitrites • 100% oxygen by tight-fitting mask/ET tube • (B) Sodium thiosulfate • Cyanide antidote kit? • (C) Hydroxocobalamin • Hydroxocobalamin? • (D) Hyperbaric oxygen therapy

Cyanide Antidote Kit Nitrites

Nitrites Nitrites

Problem:

(1) Hypotension

(2) Methemoglobinemia

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Sodium thiosulfate Pitfall

• Administration of nitrites to the patient with concurrent CO and CN poisoning

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)

Hydroxocobolamin

• Side effects: – Red Skin, secretions 2-7 days – Nausea, vomiting – Occasional HTN and muscle twitching

from Clin Toxicol 2006; 14.17 53

9 2/1/2013

Treatment of CO Poisoning Hyperbaric oxygen • Speedier removal of CO • Removal from source • Provides oxygen independent of Hgb • 100% oxygen by tight-fitting mask/ET • Benefit to the injured brain? tube • About 1500 patients treated/year in • Hyperbaric oxygen? U.S. • Million dollar question: • Does HBO therapy reduce the incidence of subtle cognitive deficits?

Weighing the Evidence: HBO vs NBO Weighing the Evidence: HBO vs NBO

Weaver et al. Scheinkestel et. al. Weaver et al. Scheinkestel et. al. ? Thom et. al. Raphael et. al Thom et. al. Raphael et. al

YES NO YES NO Naturally, experts disagree on interpretation!

Which of the following treatments should Consider HBO if: be rendered to our patient? • Loss of consciousness (1,2) • COHbg > 25% (1,2) • (A) Nitrites • Age > 36 yrs (1) • Metabolic acidosis • (B) Sodium thiosulfate • Cerebellar findings on Exam (2) • (C) Hydroxocobalamin (1) Weaver et al: Am J Resp Crit Care Med 2008; 178:314 • (D) Hyperbaric oxygen therapy (2) Weaver et al: NEJM 2002; 347:1057 • Also, pregnancy (fetus more at risk)

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

Patient intubated and placed on 100% oxygen. Received hydroxocobalamin for presumed CN • (A) Nitrites (no) exposure (lactate >10 mmol/L). HBO was • (B) Sodium thiosulfate (maybe) considered but decided against because • (C) Hydroxocobalamin (probably better) nearest chamber was at great distance and • (D) Hyperbaric oxygen therapy (consider) patient unstable.

Take home points Take home points • Cyanide Carbon monoxide • • Often accompanies CO in smoke • Nonspecific symptoms inhalation • pO2 and conventional pulse ox • Elevated lactate and mixed venous normal pO2 • Treat with oxygen • Avoid nitrites in smoke inhalation victims • Consider HBO • New antidote: hydroxocobalamin

Questions?

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