Cyanosis

[swpm]

---

Members don't see this ad.

Barash says (5th ed, p 814) and the Connelly review book makes a point of claiming that cyanosis is evident with O2 sats of less than 80% (specifically a PaO2 of less than 50-52).

Other sources say that 5 g/dL of reduced hemoglobin (could be deoxygenated, methemoglobin, etc) is all that's needed to make someone appear cyanotic. Big Blue emphasizes this in the hypoxemia chapter, and I know I've read it elsewhere. The point being that a patient with a crit of 19 would not be cyanotic, even if his sats were 75%.

Is there any merit to the 5 g/dL threshold theory, or is it really just an O2 sat issue?

 

[Planktonmd]

If you are severely anemic and severely hypoxic you usually look gray not blue (the color of dead people).

 

[swpm]

If you are severely anemic and severely hypoxic you usually look gray not blue (the color of dead people).

Yes, point taken, and I'm sure this is the sort of debate that the likes of militarymd would call "Mental Masturbation" but two textbooks and two review books have two different answers on this issue. Obviously "cyanosis" is a continuum of "that dude looks sorta blue" to "that dude is gray and maybe we should do something, dude" ...

I just want to know which bubble to fill in on the test, as well as satisfy my curiosity.

 

[militarymd]

5 gm/dl is the box that I would fill

 

[militarymd]

PO2 does does not determine saturation on its own.

think about the different sigmoid curves that you can have....partial partial of oxygen is just that...partial pressure of Oxygen in the blood.

fetal vs sickle vs normal....all a little different.

 

[militarymd]

and yes, you're spanking it pretty good.