Bicarbonate HC03 - As High as 43?

[NurseSonata]

I haven't seen this before - and was wondering if this is common?

I have a 72yo PT with COPD. Very fragile - multiple health problems. She is a chronic CO2 retainer. 24/7 02. Her HC03 has been as high 39 mmol/L previously over the years, but she seems to live a relatively normal life (within her range) despite being SOB, etc.

Routine blood work today uncovered serum bicarbonates (HC03) of 43 mmol/L. The only difference between today and any other testing day is that she was asleep when blood work was taken and was also laying flat (which she shouldn't have been - long story). She is usually sitting up and talking when bloods are taken, so I wonder if this would make a difference (sleep versus wide awake and talking?) and also laying flat versus sitting up? Her urine output is also much lower than normal (despite a good eGFR). No diabetes, etc.

Normal ranges in our facility are 20-32 mmol/L for HC03.

I"m wondering if others have had PTs with HC03 levels this high?

Am interested in hearing the experiences of others. Thanks in advance.

[Wile E Coyote, ASN, RN]

I could see a sleeping, prone COPD'er retaining more CO2 from baseline long enough to bump her serum Bicarb if in said hypoventilating state long enough (several hours, overnight, etc).

As far as pure #'s I've absolutely seen HCO3 baselines well above 43, particularly at end-stage.

For non-respiratory driven causes, I'd start by looking at the rest of her lytes, any new meds, & her hydration status.

Is this an acute hospital patient or some other status?

[LovingLife123]

Did you do a blood gas to see what her CO2 and O2 were?

[KRVRN, BSN, RN]

Pt sounds very compensated. CO2 and pH?

[NurseSonata]

No ABGs were taken at the time - as just routine bloods. 02 Sats 88% on 1 L/min. Sats a bit lower than usual for this PT, but since she was laying flat and sleeping, not surprising.

[NurseSonata]

No blood pH was taken at the time - so this is why just looking at this alone is a bit like stabbing in the dark. Sodium and Chloride lower than normal ranges - so definitely compensating.

[LovingLife123]

We can all guess and are probably right that her body was compensating for a high CO2 level but unless you can see the actual numbers, you don't know that is what the cause of the high bicarb levels. Could there have been something else going on with this patient?

It's just hard not seeing the whole picture. It is a very high level, but not unheard of. That's why I would want to investigate further and be sure of the cause.

[AgentBeast, MSN, RN]

Very normal in chronic COPD patient's

[SouthpawRN]

No blood pH was taken at the time - so this is why just looking at this alone is a bit like stabbing in the dark. Sodium and Chloride lower than normal ranges - so definitely compensating.

Maybe this is one of those good catch type of things by an observant/competent nurse (you)? You said they were lower than normal? If you are seeing a trend, maybe she is just starting to get a pneumonia, UTI, other infection, small PE? I would investigate further and get a CXR, UA, blood cultures etc. Is your gut feeling that something out of the ordinary is going with this patient?

[Bumex, DNP, NP]

I see plenty of severe class COPD patients with 40+ bicarb on blood chemistry. This is a compensatory mechanism.

COPD= Chronic Resp Acidosis -> body compensates by the kidneys retaining bicarb

[NewHam CRNA]

Some scattered thoughts:

I agree with everyones comments - your patient's kidneys were properly compensating for the prolonged respiratory acidosis (CO2 retention), and that number alone isn't terribly worrisome given the clinical situation. You're right to question a quick 4 meg/L bump though. Even if your patient was retaining an increased amount of CO2 overnight (which may well occur), it would be unusual for a 4-5 meg/L jump in bicarb to occur in 24 hrs from renal compensation alone.

I'd first wonder if there were any other medications administered in alkaline preparation. Additionally, some diuretics such as lasix if administered may cause whats referred to as contraction alkalosis. Cessation/holding a dose of an ACEI for example may also cause a slight HCO3 bump. Or perhaps your pt was hypophosphatemic and receive phos replacement. Just a few examples.

Of course, just because you patient already has a respiratory acidosis and compensatory metabolic alkalosis, other secondary causes of metabolic alkalosis could arise - such as vomiting, hypokalemia, hypovolemia, etc.

If none of the above are true, it's possible it's do to simple equilibration:

HCO3 + H H2CO3 H20 + CO2.

So in theory if there is a sharp increase in CO2 overnight, this reaction would favor an increase in HCO3- and H+ (rather than this occurring from renal bicarb retention). That equilibration can happen fairly quickly, and could explain part of a quick HCO3 bump.

So i'd say you're right to take note of the increase in HCO3. I would take a look at an ABG, BMP, note s/s infection and pay attention to UO/appearance.