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Toxicology Sessions – Carbon Monoxide

Jan Shoenberger, MD and Sean Nordt, MD PharmD FAAEM
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19:17
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Nurses Edition Commentary

Kathy Garvin, RN and Lisa Chavez, RN
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02:37

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EMRAP 2019 01 January Written Summary 302 KB - PDF

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Siamak M, MD -

Hi Sean, I'm a Hyperbaric/EM physician and I (nor any of my colleagues) had not heard about the comments you made about fetal Hgb and CO. Can you please share your references so that we can look into updating our pregnant CO toxicity treatment guidelines? Thanks.

Sean N. -

Thank you for message Simak. Great to hear from you.

Treatment of pregnant patients is difficult in carbon monoxide poisoning as you know. The initial concern of fetal hemoglobin being a "sink" was based on animal data but not thought to be truly accurate in humans.

Maternal carboxyhemoglobin levels are not good predictors of fetal carboxyhemoglobin levels. As a hyperbaricist who will be managing these cases I suggest you and your group discuss with your local toxicologists and/or poison center to make sure you are all on same page as your local group may feel diving at lower level is warranted before change any protocols.

The key to any patient with carbon monoxide poisoning and considering hyperbarics is in symptomatic patients including fetal distress at any concentration. As you have seen I am sure in your practice patients can have a relatively low level and be very symptomatic. Often pregnant patients have additional physical findings to consider hyperbarics beyond the pregnancy alone.

From Table in Goldfrank's Toxicologic Emergencies 10th edition on Suggested Indications for Hyperbaric Oxygen

Syncope (loss of consciousness)
Coma
Seizure
Altered mental status (GCS<15) or confusion
Carboxyhemoglobin >25%
Abnormal cerebellar function
Age ≥36 years
Prolonged CO exposure (≥24 hours)
Fetal distress in pregnancy

Fetal Distress in Pregnancy is listed rather than a lower maternal carboxyhemoglobin level.

For specific references I suggest you and your group review the chapter and individual references in Goldfrank's Toxicologic Emergencies 10th edition on Carbon Monoxide Section on Hyperbaric Oxygen Subsection Treatment of Pregnant Patients by Chris Tomaszweski. He is an emergency physician who is also toxicologist and hyperbaricist.

Of course your clinical impression of an individual patient trumps all else when considering who may benefit from hyperbarics in carbon monoxide poisoning. Dr. Tomaszweski does a nice review specifically on the basis for the initial concerns based on the animal model.

Hope that is useful.

Sean N. -

To all clinicians treating carbon monoxide poisoning including pregnant patients I recommend consulting your local toxicologist and/or poison control center for the specific management of your individual patient or patients including if your patient or patients may benefit from hyperbaric oxygen therapy. Carbon monoxide is a complex poisoning and benefits from the additional expertise of medical toxicology and/or poison center consultation.

Joel R. -

So, last time that I called poison control, they recommended me placing the patient on high flow nasal cannula instead of a NRB mask. Anyone else heard of this? It worked well and made sense, blew down a level of approximately 30% quite well.

Sean N. -

Hi Joel thank you for the message
My recommendation is 100% non-rebreather face mask with high flow oxygen. Many of these patients are going to be symptomatic and hypoxic at a cellular level as carbon monoxide impairs oxygen delivery. Standard pulse oximeters are not accurate in carbon monoxide poisoning and should not be relied upon and these patients can have elevated carboxyhemoglobin levels with normal oxygen saturation reading. As with other therapies using oxygen there is the consideration that “excess” oxygen may cause cellular damage from hyperoxia. This may be the basis of the recommendation you received about using nasal cannula although without knowing the specifics of their recommendation in the case you had hard to comment. That being said I recommend starting high flow oxygen by non-rebreather face mask particularly early in treatment and in symptomatic patients and those with elevated carboxyhemoglobin levels or if levels pending and clinically suspect. Follow carboxyhemoglobin levels as you did in your case.

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EM:RAP 2019 January Full episode audio for MD edition 226:18 min - 211 MB - M4AEM:RAP 2019 January German Edition Deutsche 103:05 min - 142 MB - MP3EM:RAP 2019 January Canadian Edition Canadian 27:18 min - 38 MB - MP3EM:RAP 2019 January Spanish Edition Español 80:39 min - 111 MB - MP3EM:RAP 2019 French Edition Français 20:32 min - 28 MB - MP3EM:RAP 2019 January Aussie Edition Australian 0:44 min - 1 MB - MP3EMRAP 2019 01 January Board Review Answers 125 KB - PDFEMRAP 2019 01 January Board Review Questions 302 KB - PDFEMRAP 2019 01 January Individual Written 655 KB - ZIPEMRAP 2019 01 January Written Summary 302 KB - PDFEM:RAP 2019 January Individual MP3 Files 204 MB - ZIP

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