Hey everyone, Abby here with nursing.com. Today, we’re going to learn about a lab for carbon dioxide, or total carbon dioxide. Let’s get started

This lab value accounts for CO2, not in its gaseous form, but actually in its liquid form. This is called total CO2 and it’s part of an electrolyte panel. And what it’s really evaluating just to confuse you a little more is bicarbonate. We wanna know what that serum bicarbonate is and in a regular lab that we, or a lab, that we often see rather like a CMP or a BMP, the CO2 is reported and can give us early clues of whether or not there’s an acid base imbalance. Remember, this is not going to be interchangeable with the gases form of CO2. It’s actually the liquid form. If we wanted the gaseous value, we would go for an ABG. Now, if you briefly look at this little interchange here, you can see that CO2 and H2O can eventually dissociate and become hydrogen and by carbon via carbonic acid.

So just recall that carbon dioxide and bicarbonate have this interchangeable relationship, depending on the number of ions. Now, when do you think we would worry about carbon dioxide or bicarbonate balance? You’re right. This would be in times of acidosis. Now again, because we’re looking at bicarbonate, not CO2 in its gas form with this value, we’re looking at metabolic imbalances, not respiratory. So this would be the case in diseases or conditions affecting acid-base balance. And what does that, the lungs and the kidneys, right? And this is part of our routine chemistry, our CMP or BMP. Now take a look at all these signs and symptoms. They’re pretty general. That means that this could be indicative or indicated rather for a number of reasons. And it’s a really good way to evaluate what’s happening in the body with an acid base. A normal value is between 23 and 30 mEq per liter.

This is our liquid form of CO2. This lab is collected at a mint top and run with the electrolyte panel. An increased serum CO2 shows us that there’s an increase in bicarbonate or metabolic alkalosis present. It can also happen in times of compensated respiratory acidosis, lung diseases, hormonal disorders, kidney diseases, even Cushing syndrome, all affect electrolyte balance and acid-based balance. Now remember these lab skeletons, where we write out our values on our patients and report them well, lab skeletons can either be written as the CO2 value or the BI card value. Since that’s what we’re actually looking. A decreased serum, CO2 value indicates metabolic acidosis. This would be someone’s case in Addison’s disease, diabetic ketoacidosis, shock presentation, kidney disease, or with an aspirin overdose. Now remember these signs and symptoms can be a little generic. So it’s always about that full clinical picture. The linchpins for this lesson. The thing that I’ve probably hit over the head enough is that this is total serum, total serum CO2, and it’s evaluating first and foremost bicarbonate. Normal value between 23 and 30 mEq. And if we see an increased value, we’re going to see metabolic alkalosis because the bicarbonate is increased. Decreased values in the total CO2 would be metabolic acidosis, meaning that the bicarb is decreased.

Everyone did a great job on this lesson. Now go out and be your best self today and as always happy nursing.

References:

• https://www.uptodate.com/contents/laboratory-test-reference-ranges-in-adults?search=carbon%20dioxide%20lab%20plasma%20separator&source=search_result&selectedTitle=9~150&usage_type=default&display_rank=9#H596382261
• https://www.ncbi.nlm.nih.gov/books/NBK308/
• https://pubmed.ncbi.nlm.nih.gov/28232934/
• https://medlineplus.gov/ency/article/003469.htm
• https://www.uptodate.com/contents/simple-and-mixed-acid-base-disorders?
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4725444/
• https://medlineplus.gov/lab-tests/carbon-dioxide-co2-in-blood/