Carbon monoxide poisoning

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Carbon monoxide poisoning

  1. 1. • A 43 y/o woman presents with a 3-week history of intermittent headache, nausea, and fatigue. Her husband and children also have similar symptoms. They all were diagnosed with a viral syndrome by a private doctor. The symptoms began when it started to get cold. The symptoms are worse in the morning and improve while she is at work. Her V/S: 123/75, 83, 37.0, O2 98%. PE – unremarkable. What is the most appropriate next step to confirm your suspicion? a) A mono spot test b) Nasal pharyngeal swab for influenza test c) COHb level d) Lead level
  2. 2. • A 35-year-old man presents complaining of headache, weakness, nausea, and vomiting after working with paint remover in an enclosed space. Which of the following statements regarding management of this patient’s problem is TRUE? a) A special antidote kit is required b) Carboxyhemoglobin level is not helpful in this case c) Treatment must continue longer in patients with this exposure than from other sources d) The patient’s oxygen–hemoglobin dissociation curve is shifted to the right e) Severe metabolic acidosis may be present
  3. 3. Carbon Monoxide
  4. 4. Carbon Monoxide (CO)• an odorless, colorless, tasteless gas• produced by incomplete combustion of carbon materials• normally present in air at < 10 parts per million (ppm) or less; toxicity begins at 100 ppm• also an endogenous substance (normal breakdown of heme)• 200-250 times greater affinity for hemoglobin than O2• reversible binding at the iron-porphyrin center of hemoglobin, producing carboxyhemoglobin (COHb)
  5. 5. Sources of Carbon MonoxideAutomotive exhaustMotorboat exhaustPropane-fueled heatersWood- or coal-burning stoves or heatersStructure firesGasoline-powered generators or motorsNatural gas–powered heaters/furnaces/generatorsMethylene chlorideForklifts
  6. 6. Pathophysiology• Half-lives of COHb – room air: 249 - 320 minutes – 100% oxygen: 74 - 80 minutes – methylene chloride exposure: up to 13 hours• COHb level increase  relative anemia & hypoxia• There is a separate toxicity to carbon monoxide irrespective of the level of COHb.
  7. 7. Pathophysiology• 10-15% of CO is dissolved unbound into plasma >>move>> intracellular• CO inhibits cytochrome oxidase, interfering with cellular respiration and ATP generation  a relative uncoupling of oxidative phosphorylation  lactic acidosis
  8. 8. Pathophysiology• Release of guanylate cyclase & nitric oxide  endothelial dysfunction & vasodilatation  hypotension• Relative hypoxia + hypotension  ischemia- reperfusion injury in cardiac myocytes, neuronal tissue• Rhabdomyolysis, acute myocardial infarction, neuronal cell death• Cells in the basal ganglia are particularly sensitive
  9. 9. Clinical Features• Clinical presentation is highly variable• Clinical scenarios: – unconscious patient pulled from a house fire, or from a running car in a closed garage – the patient with "flu-like" symptoms – the elderly person presenting with syncope and ischemic ECG changes
  10. 10. Shannon: Haddad and Winchesters Clinical Management of Poisoning and Drug Overdose, 4th ed.
  11. 11. Shannon: Haddad and Winchesters Clinical Management of Poisoning and Drug Overdose, 4th ed.
  12. 12. • CO poisoning should always be in the dDx for 1. comatose patients 2. patients with mental status changes 3. patients with an elevated anion gap metabolic acidosis or otherwise unexplained lactic acidosis• A comatose pt removed from a fire scene should be assumed to have CO poisoning until proven otherwise, even in the absence of cutaneous or airway burns.
  13. 13. Diagnosis• blood COHb levels (using co-oximetry )• COHb serves as a marker of severity and helps to stratify pts at risk for delayed sequelae• SaO2 appear artificially high in routine ABG• Correlation between arterial and venous COHb levels is excellent  VBG sample analyzed with co-oximetry is usually sufficient
  14. 14. Diagnostic Study Findings Associated with CO Poisoning↑ COHb level (normal 0-5%; not correlate well w/symptoms)Artificially elevated oxyhemoglobin saturation using pulseoximetry (higher than the saturation on the ABG, pulseoximetry gap)↑ lactate↑ anion gap metabolic acidosis↑ CPK (rhabdomyolysis > cardiac source)↑ troponin (diffuse cardiac myonecrosis > focal CAD)Variable ECG findings—ranges from normal to injury patternBilateral globus pallidus lesions on MRINot recommend to rely solely on pulse co-oximeters to detectCO poisoning
  15. 15. Neuroimaging• CT brain: change in 12 h of CO exposure + LOC• Symmetric low-density areas at globus pallidus, putamen, caudate nuclei• CT changes in 24 h  poor outcome• Not influence patient management• Reserved for patients who show poor response or have an equivocal diagnosis• MRI appears to be superior
  16. 16. www.learningradiology.com
  17. 17. Bilateral hypodensity in the globus pallidus and hippocampal regions on admission CT. Coric V et al. J Neurol Neurosurg Psychiatry 1998;65:245- 247©1998 by BMJ Publishing Group Ltd
  18. 18. Other Tests• Neuron-specific enolase or S100B and CSF myelin basic protein are markers for CO neurotoxicity• More useful to determine prognosis than diagnosis
  19. 19. Treatment• Immediate removal from the contaminated environment• Initial resuscitation steps• Supplemental oxygen (conc. ≈ FiO2 1.0) immediately …and for at least 4 hours• Severely poisoned pts >> continuous cardiac monitoring, an IV line established, and an ECG performed.
  20. 20. Hyperbaric Oxygen (HBO) Therapy• Enhance elimination of COHb (reduces the half- life to ≈ 30 min)• Increases amount of dissolved O2 in plasma• Reduces CO binding to other heme-containing proteins• Questionable benefit over normobaric oxygen• May reduce incidence of neurologic sequelae• The question of who will benefit most, and when to refer, remains controversial.
  21. 21. Commonly Utilized Indications for Referral forHyperbaric Oxygen TreatmentSyncopeConfusion/altered mental statusSeizureComaFocal neurologic deficitPregnancy with COHb level >15%Blood level >25%Evidence of acute myocardial ischemia Tintinallis Emergency Medicine: A Comprehensive Study Guide, 7th ed.
  22. 22. HBO Therapy• The patient needs to be clinically stable (+ secure airway, stable hemodynamic) before referral or transport for HBO.• Complications: – Pneumothorax – Barotrauma to the ears – Seizures from oxygen toxicity (usually with prolonged or multiple treatments) – Gas embolism
  23. 23. Disposition ConsiderationsSymptom Severity Disposition CommentsMinimal or no Home Assess safety issuessymptomsHeadache Home after Administer 100% O2 in EDVomiting symptom Observe 4 hElevated CO level resolution Assess safety issuesAtaxia, seizure, Hospitalize Administer 100% O2 in EDsyncope, chest Consult with CO level, comorbidpain, focal hyperbaric conditions—includingneurologic deficit, specialist pregnancy—and age; stabilitydyspnea, ECG of the patient must bechanges considered if considering transfer for hyperbaric oxygen Tintinallis Emergency Medicine: A Comprehensive Study Guide, 7th ed.
  24. 24. Special Populations• Children: – more susceptible (↑fetal hemoglobin, ↑metabolic rate) – HBO - good safety profile• Elderly: – higher risk from poisoning (esp. serious comorbid) – CAD – low COHb (4-6%) can cause ECG changes & myocardial ischemia
  25. 25. Special Populations• Pregnant pts: – HBO therapy if they meet criteria or if there are signs of fetal distress – Normobaric oxygen therapy should be prolonged (slower elimination of CO from the fetus)
  26. 26. Thank You
  27. 27. • A 43 y/o woman presents with a 3-week history of intermittent headache, nausea, and fatigue. Her husband and children also have similar symptoms. They all were diagnosed with a viral syndrome by a private doctor. The symptoms began when it started to get cold. The symptoms are worse in the morning and improve while she is at work. Her V/S: 123/75, 83, 37.0, O2 98%. PE – unremarkable. What is the most appropriate next step to confirm your suspicion? a) A mono spot test b) Nasal pharyngeal swab for influenza test c) COHb level d) Lead level
  28. 28. • A 35-year-old man presents complaining of headache, weakness, nausea, and vomiting after working with paint remover in an enclosed space. Which of the following statements regarding management of this patient’s problem is TRUE? a) A special antidote kit is required b) Carboxyhemoglobin level is not helpful in this case c) Treatment must continue longer in patients with this exposure than from other sources d) The patient’s oxygen–hemoglobin dissociation curve is shifted to the right e) Severe metabolic acidosis may be present

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