Abnormal ABG's and intubation

ZASHAGALKA, RN · May 18, 2006

Hi,
I am working on a case study and am having trouble with one of the questions.
Ok so the patients ABG's are pH 7.3, 02 48, CO2 55, HCO3 30. Patient has received little relief from nebulizer, dyspneic positions, breathing exercises. This is his second day in hospital. He presented to the ER with SOB, temp 100.2, cough with green-brown phlem, increased pulse, BP and resp.
The doctor has ordered for him to be intubated.
The question is:
What are the indicators in these ABG's that signify the need for intubation?
I get that he is retaining too much CO2 but I just don't know how to word my answer.
Any help would be greatly appreciated.
Jenn:selfbonk:

Not just increased CO2 but decreased PO2 - at this point increased O2 without mechanical asst (intubation or bipap) is just likely to cause respiratory depression and not actually lead to the exchange that would increase PO2 systemically.

Pt appears to be compensating Ph-wise but the inadequate O2 is going to soon catch up - even to that compensation - without relief.

So, your main problem AT THE MOMENT isn't the CO2 but the O2. Unfortunately, at that CO2 level, you aren't going to be able to push higher oxygenation without ventilatory support.

Sounds like the scenario is asking you to look at and show that you understand the oxyhemoglobin dissociation curve.

From a textbook: "The standard curve is shifted to the right by an increase in temperature, 2,3-DPG, or PCO2, or a decrease in pH. The curve is shifted to the left by the opposite of these conditions. A rightward shift, by definition, causes a decrease in the affinity of hemoglobin for oxygen. This makes it harder for the hemoglobin to bind to oxygen (requiring a higher partial pressure to achieve the same oxygen saturation), but it makes it easier for the hemoglobin to release bound oxygen. "

The indications for intubation are increased PCO2, and fever WITH A DEMONSTRATED decrease in PO2 indicating a right-ward shift in the oxyhemoglobin dissociation curve creating a dangerous decrease in the affinity of hemoglobin for oxygen. Intubation is indicated to provide mechanical asst gas exchange in order to decrease PCO2 and reverse the rightward shift in the curve, thereby restoring a more normal hemoglobin affinity for oxygen which would create an increase in PO2.

~faith,

Timothy.

McGyverRN · May 18, 2006

Those numbers aren't great, but I would think the doc may try Bipap (with O2 bled in) before intubation. Bipap is a mask that exerts inspiratory and expiratory pressure, helping the gas exchange to occur. I have seen many patients with numbers like that improve greatly with Bipap.

Daytonite, BSN, RN · May 18, 2006

here are a couple of pages from a critical care tutorial for medical students that may help you out:

http://www.ccmtutorials.com/rs/intubate/in_vent3.htm - evaluating a patient in respiratory distress

http://www.ccmtutorials.com/rs/intubate/in_vent4.htm - deciding when to intubate and ventilate

EastCoast · May 18, 2006

THough the patient has gotten by for 2 days with this ABG I think that the

pO2 of 48 is concerning. If this was my patient i'd do the following...

repeat the ABG. It's alarming to see a pO 2 of 48 without significant change in PH even with compensation unless he has COPD.

Also, what is the Percent sat?? if it is less than 85 percent I'd say that meets criteria for intubation. While BIpap/Cpap is an option his Pco is not significantly high enough for him to blow off the CO2 nor will it be beneficial if he needs pulmonary toileting and needs to clear secretions.

If he has gone 2 days with a PO2 of 48 and a low o2 sat i'd worry about anoxic brain injury.

What we do not have is whether this man has COPD or restrictive lung disease as a baseline. In this case I'd not be alarmed by the gas but would consider bipap. In this case trying to improve his o2 conventionally may be dangerous as he may be able to tolerate the po/co level (it's near 50 /50) with a near normal ph and where by giving him O2 would cause further demise as mentioned above by losing his respiratory drive.

In short though, i'd likely intubate him as it sounds like he needs to rest on a vent.

luvmypatients · May 18, 2006

THANKS EVERYONE!!!!!!!!!!!!