Disclosures Smoke inhalation Craig Smollin MD Associate Medical Director, California Poison Control Center, SF Assistant Professor of Emergency Medicine University of California, San Francisco No financial relationship to any commercial products discussed in this talk Smoke Inhalation Fires account for approx 3,250 U.S. deaths/yr Majority due to smoke inhalation Associated with high morbidity and mortality Station night club fire Rhode Island February 20, 2003 100 killed 230 injured 1
Case Study Kiss nightclub fire Jan, 2013 233 killed Many from smoke inhalation 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% 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 From http://lifeinthefastlane.com/ 2
Objectives for this talk Carbon monoxide (CO) We will focus on the systemic toxicity of inhaled toxic gases Carbon Monoxide Cyanide Colorless, odorless, non-irritant gas Produced anytime a carboncontaining 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 3
Oxygen Hemoglobin Carbon Monoxide CO-Hgb 4
1. Functional Anemia 2. Shift in Oxygen Hgb Dissociation Curve 100 100 Percent Saturation Hgb 50 Percent Saturation Hgb 50 alveoli 0 40 80 120 0 40 80 120 Oxygen Partial Pressure (mmhg) Oxygen Partial Pressure (mmhg) 5
100 100 Percent Saturation Hgb 50 Percent Saturation Hgb 50 tissues alveoli tissues alveoli 0 40 80 120 0 40 80 120 Oxygen Partial Pressure (mmhg) Oxygen Partial Pressure (mmhg) 100 100 Percent Saturation Hgb 50 Percent Saturation Hgb 50 tissues alveoli tissues alveoli 0 40 80 120 0 40 80 120 Oxygen Partial Pressure (mmhg) Oxygen Partial Pressure (mmhg) 6
100 CO Pathophysiology Percent Saturation Hgb 50 tissues alveoli Binds to hemoglobin 250:1 compared wtih O2 Functional anemia Changes hemoglobin such that it wont give up oxygen 0 40 80 120 Oxygen Partial Pressure (mmhg) 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 7
Pitfall Clues to the diagnosis The diagnosis of carbon monoxide poisoning is easily overlooked! Cherry-red color Multiple victims Pulse oximetry? ABGs? Pulse oximetry Arterial blood gas Pitfall - Pulse oximetry reading will be normal in CO poisoning Pitfall - po2 by arterial blood gas will be normal in CO poisoning 8
Pearl Traditionally CO only measurable through CO-oximetry CO-oximetry can be performed on either venous or arterial blood samples Clues to the diagnosis Pearl Cherry-red color Multiple victims You must have a high index of suspicion and send a CO-Hgb level by CO-oximetry Pulse oximetry? ABGs? 9
Carboxyhemoglobin levels Outcome after CO Poisoning COHgb % < 5% 10-20% 30-40% 40-50% 50-60% Symptoms* None, or mild headache Headache, dyspnea on exertion Severe headache, fatigue, irritability, dizziness Confusion, collapse Coma, convulsions Survivors of severe poisoning may have permanent hard sequelae. Vegetative state Parkinsonism *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 Subtle cognitive deficits Memory impairment Irritability Moodiness Difficulty concentrating Case Continued... Laboratory Data: VBG: ph 6.8, po2 = 75, Lactate = 16 mmol/l COHgb = 20% CXR negative Head CT negative 10
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 combustion of : Hydrogen cyanide gas produced in combustion of : Paper Silk Wool Plastic Cotton Probability of HCN production/exposure is high 11
Pitfall Dont forget about Cyanide!! Patients exposed to carbon monoxide are likely to be exposed to cyanide Cyanide: Pathophysiology Electron Transport Chain Electron Transport Chain Mitochondrial Matrix e- NADH 12
Electron Transport Chain Electron Transport Chain H+ H+ H+ e- e- NADH H+ H+ H+ NADH Electron Transport Chain Electron Transport Chain CN cytochrome aa3 NADH ADP H+ H+ H+ ATP NADH ADP ATP 13
Electron Transport Chain Symptoms and Signs NADH CN cytochrome aa3 ADP ATP Dizziness Headache, nausea, vomiting Dyspnea Tachycardia, hypotension Coma, seizures, death Pitfall Clinical clues to the diagnosis Cyanide levels are not readily available! Lactic Acidosis Elevated mixed venous po2 Cardiovascular collapse 14
Pearl Consider CN toxicity in the smoke inhalation patient with lactate > 10 Case Continued... 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! Treatment Which of the following treatments should be rendered to our patient? (A) Nitrites (B) Sodium thiosulfate (C) Hydroxocobalamin (D) Hyperbaric oxygen therapy 15
Treatment of CN Poisoning Cyanide Antidote Kit Removal from source 100% oxygen by tight-fitting mask/et tube Cyanide antidote kit? Hydroxocobalamin? Cyanide Antidote Kit Nitrites 16
Nitrites Nitrites Nitrites Pitfall Problem: (1) Hypotension (2) Methemoglobinemia Administration of nitrites to the patient with concurrent CO and CN poisoning 17
Cyanide Antidote Kit 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) 18
Hydroxocobolamin Side effects: Red Skin, secretions 2-7 days Nausea, vomiting Occasional HTN and muscle twitching 73 from Clin Toxicol 2006; 14.17 Treatment of CO Poisoning Removal from source 100% oxygen by tight-fitting mask/et tube Hyperbaric oxygen? Oxygen Treatment Approx T 1/2 of COHgb Room air 5-6 hrs 100% Oxygen 45-90 min Hyperbaric oxygen 20-30 min 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? 19
Multiplace chamber - Jacobi Hospital NY Monoplace chamber Weighing the Evidence: HBO vs NBO Weighing the Evidence: HBO vs NBO Weaver et al. Thom et. al. Scheinkestel et. al. Raphael et. al Weaver et al. Thom et. al.? Scheinkestel et. al. Raphael et. al YES NO YES NO Naturally, experts disagree on interpretation! 20
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 Which of the following treatments should be rendered to our patient? Case Conclusion... (A) Nitrites (no) (B) Sodium thiosulfate (maybe) (C) Hydroxocobalamin (probably better) (D) Hyperbaric oxygen therapy (consider) 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. 21
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? 22