Toxin

Carbon Monoxide Poisoning

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Carbon Monoxide Poisoning, Carbon Monoxide

  • Epidemiology
  1. Leading cause of toxin related death in United States
  • Sources
  • Carbon Monoxide
  1. Gas powered engine
    1. Car with faulty exhaust system
    2. Passengers riding in back of a pickup truck
    3. Swimmers at back of a houseboat
    4. Propane fueled forklifts
    5. Ice skating rink Zamboni
    6. Indoor tractor pulls
  2. Home
    1. Indoor Heaters (most common cause)
      1. Furnace
      2. Home water heaters
      3. Gas heaters
      4. Pool heaters
      5. Kerosene heaters
    2. Indoor Flames
      1. Wood stoves
      2. Indoor charcoal fires
      3. Sterno fuel
    3. Tobacco smoke
      1. Tobacco Smokers
        1. Carboxyhemoglobin levels may reach 6-10%
      2. Hookah Smokers
        1. Carboxyhemoglobin levels may reach 15-20%
      3. Nonsmokers exposed to passive smoke
        1. Cigarette tip 2.5 fold greater CO than inhaled
  3. Industrial or Occupational
    1. Steel foundry
    2. Pulp paper mill
    3. Formaldehyde and coke producing plants
    4. Fire fighters
  4. Fire
    1. Building or structure fire
    2. Wilderness fire
  • Pathophysiology
  1. Carbon Monoxide Properties (no warning features that gas is present until symptoms develop)
    1. Colorless
    2. Odorless
    3. Non-irritating gas
    4. Small molecule that crosses through some barriers into closed spaces (e.g. drywall)
  2. Exposures leading to Toxicity
    1. Carbon Monoxide toxicity occurs at Ambient levels >200-500 parts per million
    2. More severe illness occurs with longer exposure times
  3. Carbon Monoxide inhalation
    1. Carbon Monoxide has a high affinity for Hemoglobin (>200-250 times higher affinity than oxygen)
    2. Displaces Oxygen and produces Carboxyhemoglobin
      1. Shifts oxygen dissociation curve left with poor delivery of any residual oxygen to tissues
      2. Functional Anemia is however not responsible for Carbon Monoxide's lethal effects
  4. Direct toxin effects of Carbon Monoxide
    1. Sodium channel activation
    2. Nitric oxide levels increase
    3. Neurotoxic
      1. Basal Ganglia (Parkinsonism)
      2. Occiput (occipital blindness)
      3. Frontal cortex (personality change)
  5. Inflammatory cascade (responsible for neurologic toxicity)
    1. White Blood Cell response
    2. Glutamic acid (inflammatory)
    3. Free radicals
  • History
  1. Multiple persons (e.g. family, coworkers, pets) in the same environment with similar symptoms
  • Symptoms
  1. Headache (88%)
  2. Dizziness (83%)
  3. Nausea (75%)
  4. Drowsiness (75%)
  5. Dry Mouth (44%)
  6. Syncope
  7. Chest Pain
  8. Shortness of Breath
  9. Myalgias
    1. Carbon Monoxide also binds myoglobin
  • Signs
  1. Cherry-red skin and mucosa
    1. Late or post-mortem finding
  2. Bounding Pulse
  3. Hypertension
  4. Muscular fasciculations
  5. Stertorous breathing
  6. Dilated pupils
  7. Convulsions
  8. Altered Mental State to coma
  9. Do not rely on Oxygen Saturations (not accurate see below)
  1. Carboxyhemoglobin: 10%
    1. Frontal Headache
  2. Carboxyhemoglobin: 20%
    1. Throbbing Headache
    2. Dyspnea on exertion
      1. Severe Hypoxemia requiring intubation may occur at this level
  3. Carboxyhemoglobin: 30%
    1. Impaired judgment
    2. Nausea or Vomiting
    3. Dizziness
    4. Visual disturbance
    5. Fatigue
  4. Carboxyhemoglobin: 40%
    1. Confusion
    2. Syncope
  5. Carboxyhemoglobin: 50%
    1. Coma
    2. Seizures
  6. Carboxyhemoglobin: 60%
    1. Hypotension
    2. Respiratory Failure
  7. Carboxyhemoglobin: 70%
    1. Death
  • Labs
  1. Blood grossly appears abnormal red color
  2. Venous Blood Gas
  3. Carboxyhemoglobin
    1. Normal background Carboxyhemoglobin is 2-3%
    2. Carboxyhemoglobin elevated >25% is significant and associated with toxicity
      1. See above for findings related to Carboxyhemoglobin levels
  4. Complete Blood Count
    1. Leukocytosis
  • Precautions
  1. Oxygen Saturation (Pulse Oximeter) data is inaccurate
    1. Does not distinguish Carboxyhemoglobin from oxygenated Hemoglobin
  2. Drywall does not deter Carbon Monoxide
    1. Carbon Monoxide diffuses across drywall and may permeate separated rooms in multi-tenant housing
  3. Consider concurrent Cyanide toxicity in structure fires
    1. Smoke Inhalation and Lactic Acid >8 suggests cyanide Poisoning
    2. Especially with Altered Level of Consciousness
  4. Start oxygen while awaiting lab testing results if higher level of suspicion
    1. Start 100% oxygen via non-rebreather
  5. Hyperglycemia is a Neurotoxin and worsens outcomes
    1. Consider Insulin for Glucose >300 mg/dl
  1. Criteria
    1. Carboxyhemoglobin <30%
    2. No Neurologic or Cardiovascular Impairment
  2. Management
    1. Oxygen 100% Non-Rebreathing Mask
      1. Continue until Carboxyhemoglobin <5%
      2. Carbon Monoxide decreases 50% in 6 hours on room air
      3. Carbon Monoxide decreases 50% in 60 minutes on Non-Rebreather Mask
      4. Carbon Monoxide decreases 50% in 30 minutes on 100% oxygen while intubated
    2. Admission criteria
      1. All patients with Carboxyhemoglobin >25%
      2. Underlying heart disease
  1. Criteria
    1. Carboxyhemoglobin: 30-40%
    2. No Neurologic Impairment
  2. Management
    1. Oxygen 100% Non-Rebreathing Mask
      1. Continue until Carboxyhemoglobin <5% (see above)
    2. Admission to telemetry (cardiovascular monitor)
    3. Consider hyperbaric oxygen (see below)
      1. Cerebellar signs
      2. Focal neurologic deficit
      3. Persistent severe Headache
      4. Loss of consciousness, Seizure or coma
      5. Glasgow Coma Scale (GCS) <15
      6. Age >36 years old
      7. Prolonged Carbon Monoxide exposure
    4. Venous Blood Gas
      1. Determine acid-base status
  1. Criteria
    1. Carboxyhemoglobin: >40%
    2. Neurologic Impairment
  2. Management
    1. Oxygen 100% Non-Rebreathing Mask
      1. Continue until Carboxyhemoglobin <5% (see above)
    2. Admission to telemetry (cardiovascular monitor)
    3. Endotracheal Intubation may be required due to severe Hypoxemia
    4. Venous Blood Gas
      1. Follow acid-base status
    5. Extracorporeal Membrane Oxygenation (VA-ECMO)
      1. Indicated in refractory cardiovascular collapse
    6. Hyperbaric oxygen chamber
      1. Mechanism
        1. Carbon Monoxide decreases 50% in 20-30 minutes on hyperbaric oxygen at 2.8 atm
        2. Allows oxygen to dissolve in blood at a much greater extent (beyond Hemoglobin binding)
        3. Decreases inflammatory cascade
        4. Decreases reperfusion injury
      2. Efficacy
        1. Decreases risk of delayed neuropsychiatric effects
          1. Reduces risk of personality change, Parkinsonism, cognitive effects
        2. Better short-term and long-term cognitive outcome
        3. Weaver (2002) N Engl J Med 347:1057-67 [PubMed]
      3. Criteria
        1. Ideally performed within 6 hours of presentation
        2. Chamber immediately available OR
        3. No improvement in 4 hours
          1. Cardiovascular status
          2. Neurologic status
  • Complications
  1. Hypoxic Encephalopathy
    1. Cognitive effects may persist for weeks to months or even permanently
    2. Parkinsonism
    3. Occipital blindness
    4. Personality change
  2. Coronary ischemia or myocadial infarction
  3. Increased risk of Coronary Artery Disease
    1. Henry (2006) JAMA 295(4): 398-402 [PubMed]
  • Prevention
  1. Adequate Ventilation
  2. Carbon Monoxide detectors
    1. Alarm sounds when Ambient Carbon Monoxide levels are >50 parts per million
    2. Carbon Monoxide toxicity occurs at Ambient levels >200-500 parts per million
  • References
  1. Moayedi and Swaminathan in Herbert (2016) EM:Rap 16(7): 13-14
  2. Nordt and Shoenberger in Herbert (2019) EM:Rap 19(1): 4-6
  3. Reisdorf (1996) in Tintinelli (1996)
  4. (1995) MMWR Morb Mortal Wkly Rep 44:765-7 [PubMed]