11/6/2013 Oxygen Hemoglobin Carbon Monoxide CO-Hgb 4 11/6/2013 - PowerPoint PPT Presentation

11/6/2013 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 February 20, 2003 deaths/yr • Majority due to smoke inhalation 100 killed • Associated with high morbidity and 230 injured mortality 1

11/6/2013 Case Study Kiss nightclub fire Jan, 2013 • 40-year old male pulled from an enclosed fire. He is confused and agitated. He arrives in your 233 killed Many from smoke emergency department disoriented and in inhalation 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

11/6/2013 Objectives for this talk Carbon monoxide (CO) • Colorless, odorless, non-irritant gas • Produced anytime a carbon- • We will focus on the systemic toxicity of containing substance is burned inhaled toxic gases • House fires, leaking furnaces, • Carbon Monoxide portable generators • Cyanide Carbon monoxide (CO) • Common serious poisoning • 15,000 - 40,000 cases/year in U.S • Over 2,000 deaths CO Pathophysiology • High incidence of permanent neurologic sequelae 3

11/6/2013 Oxygen Hemoglobin Carbon Monoxide CO-Hgb 4

11/6/2013 1. Functional Anemia 2. Shift in Oxygen Hgb Dissociation Curve 100 100 Percent Saturation Hgb Percent Saturation Hgb 50 50 alveoli 40 80 120 40 80 120 0 0 Oxygen Partial Pressure (mmHg) Oxygen Partial Pressure (mmHg) 5

11/6/2013 100 100 Percent Saturation Hgb Percent Saturation Hgb 50 50 tissues tissues alveoli alveoli 0 40 80 120 0 40 80 120 Oxygen Partial Pressure (mmHg) Oxygen Partial Pressure (mmHg) 100 100 Percent Saturation Hgb Percent Saturation Hgb 50 50 tissues tissues alveoli alveoli 40 80 40 80 0 120 0 120 Oxygen Partial Pressure (mmHg) Oxygen Partial Pressure (mmHg) 6

11/6/2013 CO Pathophysiology 100 • Binds to hemoglobin Percent Saturation Hgb • 250:1 compared wtih O2 50 • Functional anemia • Changes hemoglobin such that it wont give up oxygen tissues alveoli 0 40 80 120 Oxygen Partial Pressure (mmHg) 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 vomiting • Intracellular myoglobin? • Confusion • Intracellular cytochrome? • Post anoxic inflammatory injury 7

11/6/2013 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 8

11/6/2013 Pearl Traditionally CO only measurable through CO-oximetry can be performed on either venous CO-oximetry or arterial blood samples Pearl Clues to the diagnosis 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? 9

11/6/2013 Outcome after CO Poisoning Carboxyhemoglobin levels COHgb % Symptoms* • Survivors of severe poisoning may have < 5% None, or mild headache permanent “hard” sequelae. 10-20% Headache, dyspnea on exertion • Vegetative state 30-40% Severe headache, fatigue, • Parkinsonism irritability, dizziness 40-50% Confusion, collapse 50-60% Coma, convulsions *Note: correlation between COHgb levels and symptoms is poor Case Continued... Outcome after CO Poisoning • Survivors of severe poisoning may have • Laboratory Data: permanent “hard” sequelae. • Vegetative state • VBG: pH 6.8, pO2 = 75, • Parkinsonism • Lactate = 16 mmol/L • COHgb = 20% • Subtle cognitive deficits • CXR negative • Memory impairment • Head CT negative • Irritability • Moodiness • Difficulty concentrating 10

11/6/2013 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

11/6/2013 Pitfall Dont forget about Cyanide !! Cyanide: Pathophysiology Patients exposed to carbon monoxide are likely to be exposed to cyanide Electron Transport Chain Electron Transport Chain e - Mitochondrial Matrix NADH 12

11/6/2013 Electron Transport Chain Electron Transport Chain H+ H+ H+ e- e - H+ H+ H+ NADH NADH Electron Transport Chain Electron Transport Chain cytochrome aa3 CN ADP ADP H+ ATP ATP NADH NADH H+ H+ 13

11/6/2013 Symptoms and Signs Electron Transport Chain • Dizziness cytochrome aa3 CN • Headache, nausea, vomiting • Dyspnea • Tachycardia, hypotension • Coma, seizures, death ADP ATP NADH Pitfall Clinical clues to the diagnosis Lactic Acidosis • Cyanide levels are not readily available! Elevated mixed venous pO2 Cardiovascular collapse 14

11/6/2013 Pearl Case Continued... Laboratory Data: VBG: pH 6.8, pO2 = 75, Lactate = 16 mmol/L Consider CN toxicity in the smoke inhalation patient with lactate > 10 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

11/6/2013 Cyanide Antidote Kit Treatment of CN Poisoning • Removal from source • 100% oxygen by tight-fitting mask/ET tube • Cyanide antidote kit? • Hydroxocobalamin? Cyanide Antidote Kit Nitrites 16

11/6/2013 Nitrites Nitrites Nitrites Pitfall Problem: • Administration of nitrites to the patient with concurrent CO and CN (1) Hypotension poisoning (2) Methemoglobinemia 17

11/6/2013 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

11/6/2013 Hydroxocobolamin • Side effects: – Red Skin, secretions 2-7 days – Nausea, vomiting – Occasional HTN and muscle twitching from Clin Toxicol 2006; 14.17 73 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: Oxygen Treatment Approx T 1/2 of COHgb • Does HBO therapy reduce the ¥ Room air 5-6 hrs ¥ 100% Oxygen 45-90 min incidence of subtle cognitive deficits? ¥ Hyperbaric oxygen 20-30 min 19

11/6/2013 Multiplace chamber - Jacobi Hospital NY Multiplace chamber - Jacobi Hospital NY Monoplace chamber Monoplace chamber 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! 20

11/6/2013 Which of the following treatments should Consider HBO if: be rendered to our patient? • Loss of consciousness (1,2) • COHbg > 25% (1,2) • Age > 36 yrs (1) • (A) Nitrites • Metabolic acidosis • (B) Sodium thiosulfate • Cerebellar findings on Exam (2) • (C) Hydroxocobalamin • (D) Hyperbaric oxygen therapy (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 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. 21

11/6/2013 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 • Consider HBO victims • New antidote: hydroxocobalamin Questions? 22