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In this lesson we’re going to talk about Calcium. We’ll look at what it does in the body and what happens when it’s too low or too high.
First, the normal range for Calcium is 8.4 to 10.2 mg/dL. If you’re using the labs shorthand, you’ll see it here in this spot. When we look at calcium in the body, we know that calcium is mostly stored within the bones. So if the body needs a place to put the calcium, it goes into the bones. If it needs more calcium, it will pull it out of the bones, just like pulling something out of storage. The other thing we need to know is that calcium levels are controlled by the Parathyroid gland. The parathyroid hormone, or PTH, will increase Ca levels. So they go hand-in-hand. With this same process, the parathyroid hormone also decreases phosphorus levels – so what we see is that calcium and phosphorus have an inverse relationship. That means if one goes up, the other will go down. So what does calcium actually DO in the body. Well we know it’s stored in bones, so a big job is going to be bone mineralization and keeping the bones hard. The other major place we see calcium is in neuromuscular processes. Both the nerve impulses with the calcium gated channels AND in muscle contraction where it activates the actin and myosin. We will also see calcium play a small role in coagulation processes.
So, again, we’re going to look at what happens when it’s too low and too high. Let’s start with hypocalcemia or low calcium – less than 8.4 mg/dL. Major causes are renal failure and malnutrition or malabsorption – this could be from alcohol abuse or liver disease – and the major culprit here is vitamin D deficiency. Vitamin D is required for absorption of calcium in the gut. We will also see that if the parathyroid gland isn’t working properly, we won’t have enough PTH, which will make our calcium levels drop. And, because we know there’s an inverse relationship between calcium and phosphorus – if we see a high phosphorus level, there’s a good chance our calcium will be low.
The biggest thing I want you to remember with hypocalcemia is the word “irritability”. The nerves and muscles can’t really contract like they’re supposed to. It’s like they’re sputtering or jumpy. So we start to see twitching and tetany of muscles. Little things make them twitch. The classic signs of hypocalcemia are chvostek’s sign, which is when you stroke the facial nerve and see the cheek twitches, and Trousseau’s sign, which is when the hand and wrist spasm like this after you inflate a blood pressure cuff on their arm. So that’s the neuromuscular responses. In the heart, it’s a muscle, too, right? We’re going to see inefficient contractility because of the spazzy nerves and muscles. The heart rate might go down, the blood pressure and pulse will be weak as well. And, we’re going to see a prolonged ST and QT – that means the time it takes the signal to get from the SA node to the AV node and down through the ventricles is delayed. In the gut we’ll see hyperactivity – so increased bowel sounds, cramping, diarrhea. And we may also see the bones being broken down to get more calcium – this is especially common in chronic hypocalcemia.
So, of course, our main treatment is to replace calcium. We can do that IV or PO, just know that if you replace PO you’ll want to give some Vitamin D at the same time because it helps increase absorption. We can also increase their nutritional intake with calcium rich foods like broccoli or dairy products. Then we can address some of the symptoms – we know their nerve endings are super irritable, so we want to decrease stimuli, and we can also give muscle relaxants for the twitching. So that’s hypocalcemia, remember twitching and irritability.
Hypercalcemia is when the level is greater than 10.2 mg/dL. There are two main causes that contribute to something like 90% of all cases of hypercalcemia. One is hyperparathyroidism. Again, too much PTH means that the calcium levels are going to go sky high. The other is malignancies, or cancers. A good example being multiple myeloma – because it attacks the bones and causes some calcium to be released into the bloodstream. We could also less often see hypercalcemia because of vitamin D toxicity or excessive intake of calcium-containing foods or even medications like tums, which is calcium carbonate.
The trick to remembering the symptoms of hypercalcemia is to remember the idea of muscle fatigue. We have SO much calcium that we’re trying to do SO much muscle contraction that now everything’s just exhausted. So you see muscle weakness and decreased DTR’s (or Deep Tendon Reflexes). Neurologically we see decreased LOC and drowsiness. Cardiovascularly we’re going to see the Heart Rate slow, they may even have some peripheral cyanosis or even DVT’s because of the excess clotting. The EKG may show a shortened QT segment. And the GI tract is going to have slower peristalsis – so you may see hypoactive bowel sounds, nausea and vomiting, or constipation. Everything is just kind of worn out.
Our big goals are to rehydrate the patient and lower their calcium levels. The easiest thing we can do for hypercalcemia is to give sufficient IV fluids – this helps to get the kidneys working to excrete more calcium. We can also give calcium lowering drugs – I’ve listed a few of these in your outline, but basically we either want to bind the calcium in the diet so we don’t absorb it, or we want to either PUT calcium in the bones or KEEP it there. Of course, we could also perform dialysis to filter out the excess calcium, and we always want to keep these patients on a cardiac monitor to watch for EKG changes.
Okay, so let’s recap. Normal value of calcium is 8.4 – 10.2 mg/dL. Its main functions are working in those neuromuscular processes, working for bone demineralization, and assisting with clotting. Hypocalcemia, or low calcium levels, can be caused by renal failure, malabsorption or vitamin D deficiency, or hypoparathyroidism. Remember the idea of irritability or twitching and that our goal is to replace that potassium whether through meds or diet. Hypercalcemia, or high calcium levels, are most commonly caused by malignancies like multiple myeloma or by hyperparathyroidism. Remember the idea of muscle fatigue or having so much calcium causing so much contraction that everything is just exhausted. Our goal here is to bind, restrict, or remove calcium. As always our top priority will be to treat or address the cause, and to remember that the heart and skeletal muscles are most at-risk with abnormalities in calcium levels.
That’s it for calcium, I hope this was helpful. Don’t miss all of our other electrolyte lessons and make sure you check out all the resources attached to this lesson. Now, go out and be your best selves today. And, as always, happy nursing!!