Hi there. My name’s Abby and I’m with nursing.com. In this lesson, we’re ionized calcium. It’s one of my favorite lab values. We’ll talk about normal values, when it might be increased or decreased, and its value to us in clinical. Let’s get started! 

To measure ionized calcium is to evaluate the effective disease disorders and medications on calcium levels. Now, calcium is so super plentiful. It’s an integral electrolyte in our bodies and 99% of it is bound up in our bones and teeth. Whereas, only 1% is actually in the blood, and the part of that that we care about, is the free calcium, that’s ionized calcium. That means that it’s not bound to protein, so it’s bioavailable for our cells to actually be able to use, and it’s massively, massively needed in the body. Look at this list. It’s needed for muscle contraction, like we know in our cardiovascular system, as well as in our muscles, it’s a major part of self signaling, hormone secretion, glycogen metabolism, blood clotting, and membrane integrity of our cells. So, have I stressed enough how important it is now? 

What are some clinical indications of when we might draw this lab? Well, it could be used for diagnostics like hyperparathyroidism, or hypercalcemia, especially when there’s a malignancy present. Now, in monitoring treatment, it’s especially valuable if a patient is on CRRT. In a CRRT machine, there are these bags, in my institution we call them baths, that clean the blood for those patients that aren’t able to. So, the clean blood goes out and the patient’s blood comes in, and it goes through these baths to get cleaned, and then we get the urine at the end. Well, in these baths, one of them can be citrate and be used as an anticoagulant. And, what we find is that citrate, the preservative in blood bags, binds in ionized calcium, so that can really drive down our levels, and we need calcium for so many things, like we just talked about, and so we would draw that lab value often on patients that we’re on CRRT, and especially those that have had massive blood transfusions because of all the citrate. Now, medications can also reduce the levels or affect the levels. We talk about corticosteroids constantly when we talk about calcium, right? Because it really influences the GI system to absorb calcium, and can really cause problems with the levels. Massive amounts of Tums or Rolaids can also affect our I calcium level, and, if a patient is taking bisphosphonates for osteoporosis, or it might even be part of a cancer treatment, that can also affect, as well as kidney disease, of course the kidneys, always responsible for excretion, right? And in thyroid disease and in malnutrition, we would draw this lap. 

Normal therapeutic values are between 1.1, one and 1.3 millimoles per liter. It’s collected in a serum separator tube. I often collected it in an ABG tube and it was written with all of those values that we see on a blood gas. Lab values will be increased in the face of hyperthyroidism. PTH, parathyroid hormone draws calcium out of the bones and into the blood, so of course you would see an increased level. It’s also evident in lung disease, in sarcoidosis, tuberculosis, and even cancer of the lungs. Kidney failure, we just talked about some excretion, as well as breast cancer and other blood cancers can really affect ionized calcium. It’s also evident in hyperparathyroidism and multiple myeloma. It will be decreased when we have the face of citrate, so massive transfusion, or CRRT, when it’s used for anticoagulation. It can also be decreased with a vitamin D deficiency, hypomagnesemia, remember how magnesium and calcium kinda hang out together, and in pancreatitis as well as conditions of mal-absorption like that of celiac or irritable bowel disease. And then, it will be decreased in the face of hyperphosphatemia, because calcium and phos have an inverse relationship. 

The linchpins for this lesson are that ionized calcium is the free calcium in circulation. It’s actually bioavailable to the tissues, because it’s not attached to protein. It’s measured to evaluate the effects of disease disorders and medications on calcium levels. Normal values are between 1.1 and 1.3 millimoles per liter. We’ll see it increase in the times of too much parathyroid hormone, certain cancers, and kidney failure, and then it will be decreased if it’s bound by citrate, a vitamin D deficiency, or hyperphosphatemia. This wraps it up on ionized calcium. You all did great. We love you now, go out, be your best self today and as always, happy nursing.

References:

• https://jasn.asnjournals.org/content/19/7/1257
• https://my.clevelandclinic.org/health/diagnostics/22021-calcium-blood-test
• https://medlineplus.gov/lab-tests/calcium-blood-test/
• https://www.uptodate.com/contents/relation-between-total-and-ionized-serum-calcium-concentrations?search=ionized%20calcium&source=search_result&selectedTitle=1~137&usage_type=default&display_rank=1
• https://ltd.aruplab.com/Tests/Pub/0020135