Making sense of metabolic alkalosis...

AnonRNC · May 3, 2012

That's strange. I would ask the MD/NP. Definately a metabolic alkalosis - and probably some other stuff too. Typically, you would see HYPOventilation to drive the CO2 (acid) up to correct the pH. However, your patient his hyperventilating, has a HUGELY high PaO2 (on not a lot of O2) and an appropriately low-end CO2. I guess you'd call it a mixed metabolic alkalosis. But why is he doing that?

AnonRNC · May 3, 2012

Oh wait...you said that he was over-sedated and unconscious and still had that high RR? Hmmm. I'm wondering about significant infection/tissue death (maybe a necrotic infection in that hip) - no...nevermind that would cause acidosis. I'd love to hear what you find out.

MPKH, BSN, RN · May 3, 2012

The respiratory mechanism really confuses me! He does have heart problems....but no history of any respiratory diseases. He's otherwise relatively healthy. No renal issues either. So his blood gases really got me thinking!

Zookeeper3 · May 5, 2012

He may have been unconscious, but seemed to have adequate resperatory compensation. Electrolyte imbalances can cause metabolic alkalosis as well. So can eating things like tums.

On a personal experience note, I always check drawers and belongings after LOC changes. Also, never discount the helpful friends and family that sneak in their home meds to help. I love LOC changes after a family visit :banghead:

AnonRNC · May 5, 2012

Another possibility: contaminate in the sample.

Ev1987 · May 5, 2012

I'm interested in reading about the possible theories. My spring semester just ended, and VERY briefly, the topic of 'metabolic alkalosis' just came up in one of my last few A&P II chapters. According to my notes, one of the causes could be from 'repeated vomiting'.

mindlor · May 5, 2012

Hi all,
I'm not sure if this is ther right forum to post this...if not, mods please move this to its proper home.
My question concerns a patient's condition. He came in with the chief complaint of hip pain, and due to a series of human errors, he was given morphine round the clock instead of PRN. Sometime during yesterday's afternoon, he became unresponsive, and went unconscious. Blood work were drawn, and his blood gas were as follows
pH: 7.55
pCO2: 34.9
PO2: 141
HC03: 30.7
O2 sat: 99% (with 2L on rebreather)
From looking at his blood gas, I understand that the patient is experiencing uncompensated metabolic alkalosis. The elevated pH and bicarbonate are both indicative of metablic alkalosis, uncompensated as the pH is quite out of the normal range. What doesn't really make sense to me is the respiratory side of thing--why is the pCO2 so low? I thought that with a disturbance in the metabolic acid/base control, respiratory efforts will be made to try to balance the disturbance. As well, I know that with metabolic alkalosis, the body will hypoventilate to conserve CO2 to lower the pH...and the patient was hyperventilating, at a resp rate of 20-26! Is it due to the respiratory system being unable to compensate?
As well, how do you correct uncompensated acidosis/alkalosis?
Thanks!

Something seems wonky here. Are you sure these values are correct? If you went PaCo2, 34.9 is barely low...not VERY low?

mochamonster · May 5, 2012

The only thing I could come up with is perhaps they were previously compensating for an acidosis (respiratory depression from the morphine perhaps) which drove up the bicarb (which takes longer) and then started hyperventilating making them alkylotic. Does this make sense to anyone?

mindlor · May 5, 2012

The bicarb response to compensate for acidosis in my understanding takes many days.....

Admittedly we were not supplied with any sort of time frames.....

RNCEN · May 5, 2012

It is difficult to look at one ABG result to determine the state, no? I'd be interested in seeing a repeat, and then another a few hours later.

Do-over, ASN, RN · May 5, 2012

Seems doubtful to me that the morphine had anything to do with that set of gases... And, are you sure the morphine was the reason the patient was unresponsive? Just because he or she was dosed innappropriately might not mean they were overdosed, right?

I'd say, if the patient doesn't match the test results, ask for a repeat ABG.

as far as treatment, I really only have experienced with resp acidosis, and they might go on bi-pap. If they need more than that, we send them to the unit. Beyond that, the generic answer is to treat the underlying cause, if you can.