Tox Time: Carbon Monoxide

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November 21, 2017 by jtreb

Beebe Bluff is a 28 yo F brought in by EMS after a house fire. She is 5 months pregnant. ABC intact, GCS 15, dexi 130. She is currently complaining of a headache and some shortness of breath. Secondary survey shows soot on her clothes and a cherry red color to her skin, but is otherwise unremarkable.  

What: Carbon monoxide poisoning. Patients will present with a host of nonspecific symptoms including headache, nausea, dizziness, and altered mental status (ranging from confusion to coma). Myocardial injury is common as well.


Who:   -Victims of house fires

-Propane-powered vehicle operators

-Those with hot water heaters, indoor heaters or indoor hibachi

-Individuals in enclosed garages (accidental or suicide attempts)


How:  Short answer: Hemoglobin likes CO more than O2

Less short answer: Hemoglobin binds carbon monoxide with higher affinity than it does oxygen; in fact, the affinity is so high ,that oxygen can’t displace the carbon monoxide, and a left shift occurs on the oxyhemoglobin dissociation curve


Clues: -Normal/high SaO2 (the SaO2 only detects hemoglobin saturation, not hemoglobin saturated with oxygen)

-Normal PO2 (dissolved content of oxygen is unchanged)

-Clustered presentation (the whole family is sick, even the dog!)

-Cherry red skin color


Management: As always, ABCs first. Co-oximetry can detect an elevated carboxyemoglobin level, and use of an abg is preferred to a vbg. Be sure to also screen for other toxins like cyanide as well. Check an EKG and troponin to rule out myocardial injury, especially in people with a pre-existing coronary artery disease. A “classic” but rarely seen complication is hemorrhage of the basal ganglia in carbon monoxide poisoning. Contacting your local poison control is always helpful, as well.

Initial treatment involves:

-High flow oxygen via nonrebreather (to decrease the half-life of carboxyhemoglobin from 320 minutes to around 90 minutes). If necessary, intubation and ventilation with 100% oxygen is an option.

2) Hyperbaric oxygen will decrease the half-life of carboxyhemoglobin even further to around 30 minutes. Recommendations for HBO include:

-Evidence of end-organ damage

-Carboxyhemoglobin level >25 or >15 in pregnant women

-Loss of consciousness, coma, or seizures

-Evidence of myocardial ischemia or dysrhythmias



Centers for Disease Control and Prevention. Carbon Monoxide Poisoning. CDC 2017. Accessed at

Clardy P, Manaker S, and Perry H. Carbon monoxide poisoning. UpToDate 2017. Accessed at


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