Help with complicated acid base balance

[Teacher17]

I cared for a patient that had the following ABG's

Ph- 7.39 (normal but compensated)

PCO2- 54 (high, indicating respiratory acidosis)

HCO3- 33 (high, metabolic alkalosis)

Pa02- 31 Base Excess of 7

She has CHF, was hospitalized for an exacerbation and shortness of breath. Currently on 1L via nasal canula.

I understand that one is compensating for the other. She has many other s/s leading to kidney failure, so I am hesitant to say that the kidneys are actually compensating. Perhaps the HCO3 is increasing because the kidneys can no longer filter it out properly?

She is experiencing pulmonary edema, which explains her raised CO2 as she can no longer excrete it properly.

This leads me to think it is something like compensated (on accident?) respiratory acidosis. However, my research seems to be indicating that because her BE is 7, it is indicative that the primary issue is her metabolic alkalosis which I don't understand how that can be the primary problem. Any help understanding this would be greatly appreciated.

[Triddin]

My first thought is her pao2 = yikes. She's sob, rr is likely high hence a higher co2, which could be compensating for metabolic alkalosis or a side effect of not having enough oxygenation. Give her some lasix, increase her fio2, try Bipap if not contraindicated and follow up with another abg. It's hard to take abgs like this as a stand-alone. It's important to look at the trends as well as the patient condition. Did this patient look like they were struggling to breathe? Was this a worsened abg? How were her kidney function tests? Aki or ckd or both? History of copd/smoking?

[Triddin]

Sorry. Early morning brain. Increased rr = decreased co2

[Here.I.Stand, BSN, RN]

I would say with the pH being closer to acidotic than alkalotic it's a compensated acidosis, and respiratory because of the high CO2 (vs a low HCO3, which would be the case with a metabolic acidosis).

Plus, look at her history: are there any conditions that notoriously cause CO2 retention? A kidney injury doesn't necessarily mean zero function either... otherwise everyone with an elevated BUN/Cr would be on dialysis. And you do have a high HCO3... the kidneys excrete HCO3 to raise the pH, correct? That is exactly how our body compensates for a respiratory acidosis.