[buddiage]

Reflecting on my test today, I'm trying to figure out if this was a question or not. Pretty sure it was.

[hrtprncss]

Yes, per oxyhemoglobin dissociation curve, a right or a left shift depending upon the temperature. Source: http://www.ventworld.com/resources/oxydisso/dissoc.html

Here's an interactive module where it shows the change in oxygen saturation when the only variable changing is temperature. http://www.ventworld.com/resources/o.../oxydisso.html

[buddiage]

Oh my gosh, duh.

Okay, so temperature affects O2 saturation (the higher the temp, the more requirements for metabolism I take it?) It shifts to the left...

I don't understand how there would be less O2 saturation though. If your respirations are higher, then you'd be compensating for the need for more O2 (and would they be so high as to affect CO2 and the whole pH thing??).... unless the higher temperature changes the hemoglobin, which is a protein, enough to where it doesn't want to release or grab O2...

Hmmm... I think I need to reread that.

Any help (thanks for the links) is appreciated

[cardiacRN2006]

A fever would increase O2 consumption R/T increase in metabolism.

[JenSICU_CCRN]

[quote=buddiage]Oh my gosh, duh.

Okay, so temperature affects O2 saturation (the higher the temp, the more requirements for metabolism I take it?) It shifts to the left...

I don't understand how there would be less O2 saturation though.


The shift to the left decreases hemoglobins affinity for O2 and since the o2 sat detects O2 on Hemoglobin and the Hemoglobin is pushing the O2 off of it the sat is lower. Does that make sense? If the opposite would occur, like if a pt. is cold post-op from the cold OR the O2 sat would be high since the Hemoglobin has an affinity for O2....so it is holding on to it and not releasing it to the tissues. That is why the PO2 on a post op gas looks so good. Some of our pts. (SICU Nurse here) that come over from PACU have PO2's in the high 100's due to the shifting.

Jenny

[cardiacRN2006]

Jen, that's a great explaination! I always wondered why a post op CABG had a PO2 of like 150! I always thought it was because they were bagging the heck out of them on the transport over...

[TopherSRN]

Originally Posted by cardiacRN2006

Jen, that's a great explaination! I always wondered why a post op CABG had a PO2 of like 150! I always thought it was because they were bagging the heck out of them on the transport over...

If that pO2 is off ABGs on a fresh admit then yes its because they were on 100% being bagged. If the ABGs are on a chronic that you can't get extubated then they could have a shift to the left d/t hypocapnea making their p02 be deceptively elevated. Moreoften that not though CABG's have cruddy lungs from a Hx of smoking. I've seen a handful of people with a pO2 >120 on .40, most are <90. But the initial gasses we get upon admission their pO2 is often >300 for obvious reasons.

[JenSICU_CCRN]

Originally Posted by cardiacRN2006

Jen, that's a great explaination! I always wondered why a post op CABG had a PO2 of like 150! I always thought it was because they were bagging the heck out of them on the transport over...

Well, thanks. In my CCRN studies last year, I was fascinated with the Oxyhemoglobin dissociation curve and dug deep into it. My best friend was also so interested in it, she made an educational book on it for our unit since we get pts. from PACU, fast tracked, sepsis, messed up temperature regulation, hypovolemic (trauma), and with messed up ABG's. I would imagine the high FiO2 and bagging of the pt. will contribute to the great PACU gasses too though. Listening to the Laura Gasperis DVD's I always remembered her talking about the post op gas being the best ABG a pt. will have PO2 wise-LOL.....she is so funny and her antics make things stick in your mind forever.

Jenny

[heartICU]

Originally Posted by JenSICU_CCRN

The shift to the left decreases hemoglobins affinity for O2 and since the o2 sat detects O2 on Hemoglobin and the Hemoglobin is pushing the O2 off of it the sat is lower. Does that make sense? If the opposite would occur, like if a pt. is cold post-op from the cold OR the O2 sat would be high since the Hemoglobin has an affinity for O2....so it is holding on to it and not releasing it to the tissues. That is why the PO2 on a post op gas looks so good. Some of our pts. (SICU Nurse here) that come over from PACU have PO2's in the high 100's due to the shifting.

Jenny

Actually, it is just the opposite. On the oxyhemoglobin disassociation curve, the curve shifts to the right with an increase in temperature, and that is a decreased affinity of the hemoglobin for oxygen. The saturation measures what percentage of Hgb is fully saturated. If you have a decreased affinity for oxygen, more oxygen will unload to the tissues, therefore decreasing the amount that is carried by the hemoglobin, so your pulse ox will read lower. Things that decrease hemoglobin affinity for oxygen include fever, acidosis/increased c02, decreased pH, sickle cell anemia, maternal hemoglobin, etc.

When the patient is cold, your tissues need less oxygen, so the hemoglobin has a higher affinity for oxygen, so the curve shifts to the left. Other things that shift to the left (and increase affinity) include decreased temp, increased pH, decreased Pco2, fetal hemoglobin, carboxyhemoglobin, and methemoglobin.

Make sense?

[heartICU]

Originally Posted by TopherSRN

If that pO2 is off ABGs on a fresh admit then yes its because they were on 100% being bagged.

I agree.