Smoke inhalation 2/1/2013. Disclosures. Smoke Inhalation. Case Study

Transcription

1 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, killed 230 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% 1

2 What type of injuries do you expect? Objectives for this talk Thermal burns to the upper airway Chemical injury to the upper airway Chemical injury to the lower airway Systemic affects of absorbed poisons 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 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 Carbon Monoxide CO Pathophysiology 2

3 CO-Hgb 1. Functional Anemia CO Pathophysiology 2. Shift in Oxygen Hgb Dissociation Curve 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 3

4 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 Pearl Traditionally CO only measurable through CO-oximetry CO-oximetry can be performed on either venous or arterial blood samples 4

5 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? 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 5

6 Pitfall Question: are there any other systemic toxins found in smoke? Tendency to focus on CO as the diagnosis San Francisco Great Earthquake and Fire Consider this Hydrogen cyanide gas produced in combustion of : Consider this 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 likely to be exposed to cyanide Cyanide: Pathophysiology 6

7 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 Pearl Lactic Acidosis Elevated mixed venous po2 Consider CN toxicity in the smoke 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! 7

8 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 8

9 Pitfall Sodium thiosulfate 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 53 from Clin Toxicol 2006;

10 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 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! 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 10

11 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? 11