Easy Framework for Hyperkalemia Workup
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Show notes:
High potassium isn't just terrifying, it's SO. COMMON.
You probably had the fear-of-potassium instilled in you as a tender nursing student like I did.
Today's video continues the Lab Interpretation Series— concise, practical videos to help manage your overflowing lab results pile.
Potassium isn't as easy as high calcium, but in this video, I've broken it down so you can feel more confident in your interpretation.
Interpreting High Potassium in Primary Care
You'll learn:
When to send someone to the ER, and when to work up outpatient
What other tests you need to look at and order
The #1 lab test that will tell you most of what you need to know
Want to Build More Confidence Interpreting Labs?
If you found this case study helpful, you'll probably enjoy the Lab Interpretation Series.
Inside the series, we take the same practical, case-based approach to interpreting common primary care labs—but go much deeper into the clinical reasoning behind them. Rather than memorizing reference ranges, you'll learn how to recognize patterns, work through differential diagnoses, and apply lab results to real patient care.
The Lab Interpretation Series includes self-paced, ANCC-accredited courses covering CBC, basic metabolic panel, renal labs, liver function tests, thyroid labs, hyperlipidemia, and more.
Learn more about the Lab Interpretation Series →
If you liked this post, also check out:
Simple Hypercalcemia Workup Case Study
Simplified Hyponatremia Workup Case Study
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Liz Rohr:
Well, hey there. It's Liz Rohr from Real World NP and you're watching NP Practice Made Simple, the weekly videos to help save you time, frustration and help you learn more, faster so you can take the best care of your patients.
So, today I want to talk to you about high potassium. Last week's video, if you didn't catch it, was about high calcium. I'm continuing on the lab interpretation series today. It's a little bit more complex than high calcium, but there are some simple frameworks you can use to think about high potassium, what it means and what to do about it.
So I'm going to again, use another case study. I was really hesitant to share this as a case study, but it's just so interesting, it's really hard not to. The reason I'm hesitant is because it's a little bit complicated, and I don't want to overwhelm you or scare you, but things like this happen, especially if you're working in a setting where patients are a little lackadaisical about their healthcare.
I'm going to keep this as brief and concise as possible. It is still going to be a little bit longer video than my other videos, because there's a lot to learn, but I'm going to keep it as straightforward without the fluff so that you can absorb it, learn it, move on, be done with worrying about high potassium. So without further ado, I'm going to share my screen with you.
This is a great case for my first year, so let's hop into it. This is George, again not his real name or his photo. He's 63, he has diabetes. He's been a patient at this clinic for several years, but he was really lost to followup for about a year so he's coming back to re-established care. Again, first visit back from one year ago. He's intermittently taking NPH insulin, 70/30, 20 units twice a day, and a sliding scale of NovoLog, five units when he feels like it. He's not checking his blood sugars. He just takes it when he doesn't feel well.
Luckily he's a non-smoker. He drinks alcohol, a few beers here and there. That's on his first visit, what he would kind of admit to, and the more I got to know him, the more he was forthcoming about, he was drinking a little bit more than that consistently. Past medical history; hypothyroidism, he has a remote history of CML leukemia, chronic leukemia in remission. He also has high blood pressure. I believe he got a STEM cell transplant from his brother in the past. I don't have full access to those records anymore, unfortunately. This is all kind of from memory.
So he has no known past surgical history or family history. His blood pressure today is 150 over 90. He is taking Synthroid 200 micrograms aside from the insulin, and his other vital signs are normal, heart rate and oxygen. He lives alone, no sexual partners. He's on disability and he's not working. So our plan today, we're going to focus on hyperkalemia for the purpose of this video, but I'll touch on the other components of holistic care at the end.
The labs we're going to check today are a CBC and a CMP. Those are for baseline liver, kidney function, any anemia, signs of infections, signs of recurrence of CML, hemoglobin A1C for managing his diabetes, urine microalbumin, which is a yearly test for early signs of kidney impairment related to the standard of care for diabetes management. We're going to check his thyroid TSH, and his cholesterol panel because of his age, high blood pressure and diabetic status.
So here are the results. Oh, they're kind of ugly. So before I get into these down here, just starting by saying the CBC is normal. His cholesterol is high as we would expect with the current diabetes, and his urine microalbumin is also high, so signs of kidney damage, but as you can see in the basic metabolic panel here, his creatinine is pretty high, 2.19. His GFR is pretty low. BUN is elevated. His glucose is super high, 572. His sodium is also low. I'm going to hold off on discussing that today. I'm going to make another video about low sodium, and his potassium, what we're talking about today is 5.8.
His chloride is also low. Carbon dioxide is normal. Calcium, protein, the liver function panels, luckily are all normal. His TSH was luckily normal, so that's great. And his hemoglobin A1C is 10%, which does not really surprise based on the glucose level, but also the fact that he hasn't been here for a year, and he's kind of not really taking his insulin as directed.
So for hyperkalemia workup, I want to make this as simple as possible. There's a lot more causes than hypercalcemia, if you listened and watched my last video, but I want to break it down and make it really easy. So these are the first kind of three steps. So number one, is a truly high? So same thing as calcium. So this is a really important point I want to make, so kind of keep this in your mind. Potassium is normally stored in the cells or it's excreted in the urine, also stool but mostly urine. So those are the main places you're going to find potassium in your body and that's relevant because it helps you understand what the reasons are for high potassium in the first place.
So we need to repeat this test with a basic metabolic panel or a heparinized potassium if available, because we need to make sure that it is not a false high or a artifact, which I'll talk to you about in a second, so just stick with me. So is it truly high? You're going to want to recheck it and verify it, and how high is it? And again, same thing as calcium. This is really 1A and 1B, less than a step one and two, because we need to think about it at the same time.
So the normal range depends on your lab, of course, but my lab is 3.5 to 5.3, and first step here is greater than 6.5 with symptoms. They need to go to the ER and or with symptoms, honestly. If it's 6.5 or above, I'm sending somebody to the ER, even if they have no symptoms, because the symptoms here are muscle weakness, paralysis, and cardiac conduction abnormalities. So those are a little bit vague, and then when you see a patient, you're going to get the results the next day, and you want to get that work up done quickly if they have a potassium greater than 6.5. And so, you're going to want to do an EKG right then. So they're going to have peaked T-waves or widened QRS complex, and that's kind of a simplified version, but those are kind of the first two signs you'll see on the EKG in terms of abnormalities.
So is it truly high? How high is it? And then there are unfortunately not two diagnoses like high calcium, but two main categories of etiology, and understanding the categories really helps you figure out, and remember instead of memorization, where this is possibly coming from.
So number one increase release of potassium from cells. Remember how I said, the majority of potassium in your body is inside of cells and excreted in urine. Number two is decreased excretion from the kidney. So either there's more potassium getting into your bloodstream from the cells, or your kidneys aren't able to excrete it, as they normally would. A quick note here I want to make is that, it is extremely uncommon for an increased amount of potassium in your diet to cause an increased potassium, if you have a normal kidney, because your kidneys are extraordinarily good at getting rid of potassium, when they're healthy, and will adapt to anything you eat in your diet to get rid of the appropriate amount. So unless you have kidney disease, abnormal kidneys, then dietary potassium is not a cause for hyperkalemia.
So kind of bucket number one, increased potassium release from cell, so venipuncture artifact. So unfortunately when you use a tourniquet, when you pump your fist, when the blood components coagulate in your blood samples, then you can get higher potassium than it's true. So that's one of the reasons why you want to re-check it. Hyperglycemia, hyperosmolality, lack of insulin, so when you have a lot of glucose in your bloodstream, it's going to increase the concentration osmolality, and then the lack of insulin additionally, is going to prevent you from getting the glucose into the cells.
So when, when glucose is high and there's not enough insulin, insulin and glucose are the things that kind of open the door to your muscles and your liver to be able to absorb the glucose and the potassium. So, when you don't have that, that's going to increase the amount of potassium in your serum. So drugs, there's a whole list. I'm going to hold off on those for one second.
Other less common causes, but I just want you to know that this exists, transiently can go up with exercise. It should improve over time with better conditioning, physical conditioning. GI bleed, typically like massive GI bleeds, tumor lysis syndrome if somebody is undergoing chemo radiation therapy, but that's typically not seen in primary care, burn accident, blood transfusions, and this crazy diagnosis here, hyperkalemic periodic paralysis. Number one, this is outside of the scope of primary care because they should be seen in the ER, aside from exercise of course, and hyperkalemic this is something genetic, that is as a specialty diagnosis. So if you're getting there, then you've done your job as a PCP, and it's time to hand off to a specialty care.
So decreased potassium excretion from kidneys. Number one, as you probably guessed is kidney disease. So chronic kidney disease and end stage renal disease. Drugs as well, but hold on for a second and we'll go through those. And then states of reduced blood flow to the kidneys. So if your kidneys are not getting sufficient blood flow to function the way that they're supposed to, they're not going to work as well. So they're not going to get rid of potassium as much as they should. So this happens in heart failure and cirrhosis, in which could also be on top of CKD, but those states, in and of themselves can cause a reduced functioning of the kidneys.
This is another kind of remote cause, hypoaldosteronism. This is a state that's typically caused by chronic kidney disease itself, as well as certain drugs. I'm going to cover in one second, but it can be from adrenal insufficiency, congenital cause, et cetera. But again, if you're getting to this stage and you've ruled out the CKD and the drugs, then this is time to seek care with a specialist.
So here are the drugs. I wanted to make a separate slide because there were just so many and they're so common. Beta blockers, not atenolol, so it's the beta two is what helps the potassium go into the cell. So if you have a beta blocker, it's going to block the potassium from getting into the cells. Whereas atenolol is just the beta one, the cardioselective one. So that's not an issue there, it's something to think about. Digoxin, not that common, but happens. NSAIDs, super crazy, but this one can definitely cause a decreased filtering of the potassium. ACE-inhibitors are up too, you've probably seen them before. Spirinolactone, eplerenone and triamterene, these are potassium sparing diuretics and aren't that common, but I figured I'd mentioned them because I see them fairly enough in primary care.
I'm probably not going to say this right, but I've heard it pronounced multiple ways, tacrolimus. Anyway, however, it's pronounced these two kind of rejection medications, anti-rejection medications are such as. One that I forgot to write down that I just remembered, this always happens when I try to treat a UTI with bactrim and somebody is on an ace-inhibitor. Bactrim can kind of also, I think it's the trimethoprim component of bactrim, trimethoprim-sulfamethoxazol, trim-sulfa, can cause high potassium. I don't know if inherently it does or if it's just a combination of the two, but anyway, that's a common one. Heparin, not that common, but one to think about.
So two steps to potassium management. If you've gone through three steps of, is it really high, how high is it and thinking about these two kind of buckets of categories to work up, the two main steps to potassium management is number one, is this safe to do outpatient or is it not? Do they need to do the ER or can we work on an outpatient? And number two is identifying the causes. So the true treatment of hyperkalemia, in the ER hospital setting, there's a whole algorithm for treating pure hyperkalemia. When you're doing outpatient management, you're really working on identifying the underlying cause and managing that, because you're not going to be doing things like giving insulin and D50, and giving albuterol and giving Kayexalate.
You're not going to necessarily be doing, I mean, you really shouldn't be doing any of that stuff in primary care and that's how they manage it in the hospital. So your job in primary care is to identify the underlying cause, so that you can treat that in a safe way. And if it's not safe to do it that way, then they need to go in the ER. So those are your kind of two framing ideas.
So this is an algorithm of the workup, and these kinds of four boxes here, they really kind of need to be done around the same time in terms of thinking about it, but just stick with me for a second. So step one again, you're going to confirm hyperkalemia. If it's greater than 6.5 and they're symptomatic and/or they're symptomatic, they need to go to the ER. So we've covered that.
So if it's still greater than 5.5 and they're not symptomatic, you can go outpatient management, the first thing you're going to look at is the BUN and the creatinine and the GFR looking at their renal function. So if you see a high potassium, the first thing you need to think of aside from, let's recheck and make sure it's not an artifact, and it's not super high, is let's look at the kidney function, because impaired kidney is going to be the main reason you have high potassium.
You also want to look at their glucose. So typically when you find hyperkalemia and you're not necessarily expecting it, you're just kind of doing screening labs for somebody, you're going to order a basic metabolic panel. So you'll be able to see the glucose and the BUN, creatinine, and GFR. So if somebody has impaired renal function, that's going to be number one. Number two is going to be ... High glucose is going to cause that high potassium to be also hanging out in the bloodstream.
So if this patient does have impaired renal function and they have ongoing potassium release causes, these are things that you're not really going to see in primary care. But if someone has an extensive burn or hypothermia or GI bleed, or something that's causing active release from their cells of potassium, some kind of trauma or traumatic thing, you're definitely going to send them, even if it's not that 6.5, even if it's just about 5.5, because you don't want that to get worse and worse and worse.
So the next thing, textbook says that if you have a high potassium, you want to do an EKG. So I'm going to say a real-world note about that in just a second, but those are one of the signs and symptoms of high potassium, is the muscle weakness, paralysis, and then the cardiac conduction abnormalities, but just sit tight with that for one second. So you're also going to look at the med list, to look at all those drugs. So let's kind of bring this together.
So for him, it's safe to do an outpatient workup because his potassium is less than 6.5 on the first check. He has no symptoms. We don't have any EKG results, but just sit tight for one second. So these are his labs again. This glucose is super high. His renal function also not great, and his potassium is 5.8. But in terms of like the real world management of this patient, I'm kind of much more concerned about the glucose and the renal function right now than I am with the potassium. I'm definitely concerned about the potassium, but looking back to this algorithm, high glucose is going to be one of those main causes, that's going to make the potassium and be that high in the first place.
So if we go back to the labs ... Sorry, one second. So if we go back to the labs, it's 572 on the glucose. When you lower this glucose, you're going to lower this potassium. So I mean that, we're not necessarily going to change the creatinine, unless this is an acute kidney injury. It's most likely going to be chronic, because he has the high blood sugar, uncontrolled diabetes, high blood pressure. I mean topic for another time, but we can certainly talk about that. But in terms of management, you get these lab results, step one.
Step number two, is you're going to reconcile the meds with the patient. You're going to give a call to the patient on the phone and say, "Hey, are you having any symptoms? Are you feeling okay? Just to confirm these are the medications you're taking, correct? You're not taking a ton of NSAIDS. You're not taking any extra medications that you forgot to tell me about." And then your step number one, even before you recheck the potassium on that algorithm, you're going to want to lower the glucose and kind of fix the insulin situation first, because more than likely, that's going to bring your potassium back down to normal in this case.
So step number three is going to repeat the potassium. So over the phone, I advised him to recheck his blood sugar more consistently. I advised him of the danger of the situation that, risk of death, that this is a really serious situation. He really has to think about stepping up in terms of his management and if he's willing to do that or not. And if he's not, then he might not have to go to the ER. He might have to be hospitalized.
So over the phone, he agreed to consistently take his dose of the NPH, consistently check his blood sugar. We decided on a sliding scale that he had used a year ago, as needed with his meals, the NovoLog five units, and kind of use that as he appropriately should instead of kind of willy-nilly. Then also working on decreasing his intake of those blood sugar raising foods, and alcohol, things like that. So this is moment one, as soon as you get the Lab results. I want to repeat the potassium either the next day or the day after that, make sure that it's ... See if it's still high or if it's come down at all with our glucose management.
At that point, you can consider to do an EKG. So 5.8 is high, but you know what, because he has all these other reasons. So if he didn't have this and he just had the creatinine, I'd be a lot more concerned. So when he came back in for the potassium in two or three days, what you could do is, you could do a visit with you to do an EKG and do a lab at the same time. Or you could wait and see if his blood sugar went down, repeat the potassium in another day or two, see if it went down and if it didn't, then you could put an appointment for an EKG or do another visit.
It's a lot of visits to do, but I think that the trade off here is that you're risking somebody having to go to the hospital, be admitted versus taking time out of his day to kind of come in. And his transportation was reliable enough and that he was also on disability, so his schedule was a little bit more flexible. He didn't have like a nine to five job that he was trying to get time away from.
Then the next thing after that, if his potassium went down, if it was trending on its way down, so I check it two days later, it's 5.6. I'll recheck it in another week. We'll keep working on the glucose, things like that, and then we'll kind of take it from there.
So let's head back to George. So I was able to get his potassium down with his management of his glucose. He needs long-term diabetes management to get that A1C down from 10. And I can definitely make a video about diabetes management, but that's kind of a multi-pronged process here. So step one, continuing his Synthroid, so his TSH was normal. That's awesome, Continued the 200 micrograms. I'm going to work on lowering his blood pressure for his renal protection, also MI and stroke and things like that. I'm going to avoid ACE and ARBs right now because his potassium has been high, but I'm going to consider adding that back on, because that is helpful for renal protection specifically, even though it raises potassium.
I did a nephrology referral for him because most likely his impaired kidney function is related to his high blood pressure and his diabetes, but there are other causes and I'm not going to do those kinds of fancy tests for further workup for that. But I also don't want to leave that open and just kind of assume that that's the cause, in case there's anything else going on with him. And also it's kind of further reinforcement in terms of, "Hey, look, let's take this really seriously, because here's what dialysis means, and you could head towards dialysis. And if we don't manage it, here's what's going to happen." And it can also be really helpful in terms of management of high blood pressure, in terms of making medication suggestions and giving me that reinforcement of feeling comfortable, adding an ACE back on for him, even though he had a history of hyperkalemia in the past, because that is like I said, really helpful for renal protection in particular.
Then I did a follow-up with me. I did a couple of visits. I did the labs in two days and then a labs a week later, and then I had him come back for a visit with me in a month. Then you can either manage somebody like that every month. You have to kind of get buy-in from him, right, because if he hasn't been there in a year, and if you're telling him he needs to come in every week or every month and all that, he might go again.
So it's kind of a discussion about, it's recommended at least in my clinic, our protocol is that, if your A1C is greater than nine, we recommend coming in once a month to kind of do for their counseling and medication management, even if you're not necessarily checking the A1C every month that they're there. And definitely see an endocrinologist, who take over for me, check every three months. And they are not necessarily seeing somebody every month because that's kind of like bread and butter for them. And for whatever reason, the A1C is not necessarily going to show any change within three months anyway, but that's kind of up to your discretion.
So that's it. I'd love to hear from you. Is there anything from this video that is going to change your practice? Also, of course anytime, please leave me a comment below, if there's any topics in particular that you want to hear about, especially that came out of this case study.
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