Medical Minute: CO Poisoning

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October 14, 2014 by dailybolusoflr

By Ryan Circh, MD

Pathophysiology:
  • CO binds hemoglobin 200x more tightly than oxygen.
  • 85% will bind O2, the rest will dissolve in plasma.
  • CO can inhibit cytochrome oxidase like cyanide (interfering with cellular metabolism).
  • Endothelial damage, triggering an inflammatory response.
  • CO can cause nitric oxide release resulting in vasodilation and hypotension.
  • Hypoxia and hypotension can lead to MI, neuronal death, rhabdomyolysis.

Symptoms:
  • Flu-like symptoms
  • Headache
  • Nausea
  • Dizziness
  • Confusion
  • Dyspnea
  • Seizures
  • Syncope
  • Focal neuro deficits
  • Coma

History
  • Typically around fall, winter months when heater use increased
  • Ask about exposure to heaters, fires, or gas/propane-powered motors in closed spaces.
  • Multiple family members may have varying degrees of similar symptoms.

Diagnosis:
  • Consider CO poisoning in non-specific symptoms
  • Ask about CO detectors in homes
  • Pulse ox will be normal as COHb absorbs at the same wavelength
  • COHb level from ABG/VBG, do not need arterial sample
  • COHb doesn’t always correlate with symptoms or outcomes
  • Labs may help give a clue to degree of poisoning: metabolic anion gap lactic acidosis

Treatment:
  • Oxygen
  • Room air half-life 200 minutes, 100% FiO2 80 minutes
  • Mild-moderate symptoms 100% facemask
  • Severe inbutaion
  • Extreme hyperbaric oxygen
  • Indication for hyperbarics: ataxia, seizure, focal neuro deficits, chest pain, dyspnea, EKG changes, or COHb over 25%
  • Pregnancy for COHb >15%

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