Hyperbaric Question - COHb

[T-Rock]

I realize patient criteria (insurance) for HBOT in patients with CO poisoning is roughly a COHb of 25% or greater.

I’m curious though if there are any correlation tables out there that correlate COHb to the level of the patients Hemoglobin, or any formulas that do so?

The current criteria for patients of > 25% are for those with normal Hemoglobin, Males: 13.8 to 17.2 gm/dL; Female: 12.1 to 15.1 gm/dL, but what if a patients Hemoglobin is 7.3 gm/dL and their COHb is 14%?

Would that qualify the patient for treatment since their oxygen carrying capacity is greatly reduced?

A point in the right direction would be greatly appreciated!

[miclo18d]

Your question is a highly specialized situation that would probably be best answered by a hematologist. There are way too many factors to anemic blood conditions than just a low hematacrit or Hb count and the use of hyperbaric treatments.

[PedOncoDoc]

As a hematologist, I rarely see acute CO poisoning - the ED docs may have an equation to share with you. I do not, but I could see why one would need to incorporate hemoglobin level (and carrying capacity, espcially in the setting of hemoglobinopathies) into any treatment algorithm.

The other wild card is duration of both anemia and CO exposure - if both are chronic, the body will likely have compensated (to some extent) to both.

One thing to keep in mind is that if a patient is symptomatic and sufficiently anemic, a pRBC transfusion could be therapeutic against both CO poisoning and anemia, provided there is no ongoing CO exposure.

I've not seen a lot of strong data that hyperbaric O2 is more effective than high flow atmospheric O2 in this setting either - but I'd love to see any new publications on this topic.

Good luck on you search and please share what you learn!

[Doczilla]

Some places will use a cutoff value of COHgb to determine need for HBO therapy, while others use symptoms to guide treatment. Symptoms are not predictably consistent at COHgb ranges from 20-60%. We only consider HBO in CO poisoning where the patient is comatose. Even then, there is a serious lack of literature demonstrating any benefit of HBO therapy. The criteria for this are getting narrower and narrower, and unless someone publishes a study showing that it changes outcomes, HBO may go away for this indication.

I apologize that I didn't exactly answer your question.

'zilla

[T-Rock]

Thank you very much for the replies, gentlemen. The following is what I received from the Director of Hyperbaric Medicine via UHMS:

I am the director of hyperbaric medicine at Virginia Mason Medical Center.

I am not aware of any table to correct for anemia.

I would be careful not to be hard and fast in using COHb levels to treat folks. Although it easy to measure, it is likely that most of the CO toxicity is not from the COHb but more due to direct CO toxicity. Levels often drop quickly due to pre-hospital O2 especially in a patient that is intubated. If someone has LOC or other significant severe symptoms we treat them even if their level is below 25%. Recall we are not treating to just get the level down but to help reduce the CO effects on other iron containing proteins as well as reducing inflammation and oxygenating ischemic tissue.

Below are some articles that were forwarded to my email:
https://docs.google.com/viewer?a=v&pid=gmail&attid=0.1&thid=13f2ec55ce93fc44&mt=application/pdf&url=https://mail.google.com/mail/u/0/?ui%3D2%26ik%3Dfc52c1c068%26view%3Datt%26th%3D13f2 ec55ce93fc44%26attid%3D0.1%26disp%3Dsafe%26zw&sig=AHIEtbTdHro2TamFk47S_Gjyx2beXODUzg

https://docs.google.com/viewer?a=v&pid=gmail&attid=0.2&thid=13f2ec55ce93fc44&mt=application/pdf&url=https://mail.google.com/mail/u/0/?ui%3D2%26ik%3Dfc52c1c068%26view%3Datt%26th%3D13f2 ec55ce93fc44%26attid%3D0.2%26disp%3Dsafe%26zw&sig=AHIEtbTnP99LE-rZFl9cM-n4iYNLh0vC2w

https://docs.google.com/viewer?a=v&pid=gmail&attid=0.3&thid=13f2ec55ce93fc44&mt=application/pdf&url=https://mail.google.com/mail/u/0/?ui%3D2%26ik%3Dfc52c1c068%26view%3Datt%26th%3D13f2 ec55ce93fc44%26attid%3D0.3%26disp%3Dsafe%26zw&sig=AHIEtbQt8oK2fAa-MhhttM3Iq8GuOcjaSw




IMHO, I think Oxygen Content (CaO2) should be part of the evaluation criteria for HBOT.

Once levels get below 12vols%, weird things start happening at the cellular level.

In the numbers above, if a patients Hemoglobin is 7.3 gm/dL and their COHb is 14%, that would put the CaO2 at roughly a little over 8%. Considering the half life of COHb is 323 minutes, opposed to 23 minutes @ 3ATM, HBOT, IMO, would have been of benefit.

Thanks again.

Edited to add:

Below is what prompted the scenario:
http://newsfeed.time.com/2013/06/11/three-deaths-in-the-same-n-c-hotel-room-attributed-to-carbon-monoxide/

[uspsmark]

I was a hyperbaric chamber technician at the U.S. Army School of Aviation Medicine located at Fort Rucker. We had several doctors that were conducting studies back then (1988-1989) on hyperbaric oxygen therapy for wound healing. One patient had been bitten by a brown recluse spider and had a golfball sized hole where the tissue had necrotized. They had very good results in decreasing the healing time using the chamber. We never had any CO poisoning cases, but I could see where that type of oxygen therapy could be useful in that type scenario.