[0:00]Hello, hello. Welcome back. Today we're going to be talking about replacing electrolytes in your patients in the hospital, which is something you're going to be doing all day as an intern. And you got to get really good at this because you can save yourself a lot of time if you just know bam, bam, how to do this right away, super fast. Okay?
[0:16]So let's get straight into it. I'm going to go back to my website and we're going to be talking about electrolyte repletion. We're going to be talking about the big four: potassium, magnesium, calcium, and phosphate.
[0:26]Really, the big one is potassium. It's like every single day you got to replace those people's potassium. But really, should we really actually be replacing potassium and magnesium all the time?
[0:36]Well, actually, the evidence for this is not that great, but I think we probably still do it a lot because nurses will paid you if their potassium is like 3.6, and so we kind of just give a little bit of potassium all the time.
[0:47]The background for why we do such aggressive replacement of electrolytes is because of this 2000 practice guideline in JAMA, which said that patients at risk for cardiac arrhythmias should have their potassium replaced to greater than four and magnesium greater than two.
[1:04]However, the evidence for replacing to these goals is very poor, which I go over in some of these articles here.
[1:09]So here you can see that potassium repletion is common in patients hospitalized with heart failure exacerbations, however, the evidence for this practice is lacking.
[1:17]In a subset of patients hospitalized with acute heart failure, there was no association between low normal serum potassium values and an increased risk of adverse outcomes, whereas some patients with serum potassium levels greater than 4.5 may be at risk for poor outcomes.
[1:30]And then this is the article that they were talking about, which came out in 2019 in December, and basically, patients with mean serum potassium levels of less than 4.0 showed similar outcomes to those with mean serum potassium values of 4.0-4.5.
[1:49]Compared with mean serum potassium level of less than 4.0, mean serum levels greater than 4.5 may be associated with increased risk of poor outcomes. And the normal range that they calculated was between 3.5 and 5.0 in this study. So anyways, for potassium, you probably already learned this in medical school, but you give 10 milli equivalents for every 0.1 that you want the potassium to go up by.
[1:58]For example, if your potassium is 3.6 and you want it to be 4.0, you would give 40 milli equivalents of IV or PO potassium.
[2:07]If your potassium is 3.2 and you want it to be 4.0, then you would give 40 milli equivalents of IV potassium and 40 milli equivalents of PO potassium.
[2:14]The reason you split it up like that is because when you're giving IV potassium, you can only give 10 milli equivalents at a time through a peripheral IV.
[2:22]So in order to kind of boost up the rate at which you're giving them potassium back, you give them some oral and IV at the same time.
[2:29]And another thing to note is that if the patient is severely hypokalemic, say potassium less than 3, then they will need more than 10 milli equivalents per 0.1 increase.
[2:39]So for example, they may need 20 milli equivalents or 30 milli equivalents before you get that 0.1 increase in their potassium.
[2:43]Also key to note is that if your patient has an AKI or CKD, you need to give less potassium in order to avoid potassium.
[2:51]So if somebody's creatinine 2, 2.5, I'd probably give 50% of what I normally give.
[2:55]Your options for potassium include potassium sustained release tablets. The downside is it's kind of like a horse pill and can be very difficult for patients to swallow.
[3:04]You've got oral liquid, but reportedly it tastes very bad. Um, but some patients prefer this, especially to the large pill.
[3:10]Potassium through the IV, the biggest side effect that you're going to get from patients is a complaint of a burning sensation.
[3:17]You can try giving it with Lidocaine, or you can give it as a piggyback onto maintenance fluids to reduce this effect.
[3:22]And also, with each 10 milli equivalents, you're giving 50 milliliters of volume, which may be a lot of unwanted volume for patients with heart failure or renal kidney disease, so that's something to also be aware of.
[3:33]Another one that I've been kind of liking a little bit more recently is this K-lite effervescent tablets. Um, basically, it dissolves in their mouth, so they don't have to swallow the large horse pill.
[3:43]It doesn't have too bad of a taste. And so it's a really good option to try if the patient can't tolerate the regular tablet, and it comes in 25 milli equivalents and 50 milli equivalent forms.
[3:51]I mentioned this earlier, but peripherally you can give 10 milli equivalents an hour of potassium by IV, and if you have central access, either through a chest port or a central line, then you can give up to 20 milli equivalents per hour.
[4:02]And one other thing to watch out for is that one reason for refractory hypokalemia is a low magnesium level, so you should check their magnesium level and replace the magnesium first before giving potassium if this is happening.
[4:14]The reason this happens is because magnesium normally inhibits your potassium secreting channels in the collecting duct, so if you don't have enough magnesium, your potassium secreting channels are just going to be on all the time, and you're just going to be dumping potassium, so any replacement you give them is just going to be lost in the urine.
[4:29]What are some of the side effects of hypokalemia? They include muscle weakness, paralysis, and arrhythmias.
[4:34]All right, now let's talk about replacing magnesium, which is probably my favorite to replace because it's just fun to replace magnesium.
[4:40]When you give magnesium, each 1 gram of IV magnesium will raise the serum level by 0.1, and then a 400 gram oral dose of magnesium is equivalent to about 2 grams of IV magnesium.
[4:53]As you can see, we've got 2 grams of IV magnesium is 200 milligrams of elemental magnesium, and then 400 grams of PO magnesium is equivalent to about 240 grams of elemental magnesium.
[5:08]But again, you're going to have to watch out for how much of that is really going to be absorbed through your GI tract versus just being directly given through the IV.
[5:14]So your options for magnesium, really, is just the IV magnesium, it's the go-to method for magnesium replacement.
[5:20]Just consider how much fluid you're going to be giving with each dose. Um, you can also give the magnesium oxide tablets, but the biggest side effect of this is diarrhea, which is a frequent side effect and the main reason why it's not preferred.
[5:30]Common doses you can try are 400 milligrams times 1, 400 milligrams daily for 2 days, or 400 milligrams twice a day for 2 days, etcetera.
[5:39]So again, try and just spread it out over the course of a few days if you can, just to reduce the amount of diarrhea that your patients will have.
[5:47]And the side effects of hypomagnesemia include muscle cramps, such as Charley horses, numbness and tingling, arrhythmias, hypokalemia, and hypocalcemia due to resistance to PTH.
[5:58]Now we're going to talk about calcium, which is an important electrolyte to replace, especially in ICU level patients, I feel like is when we tend to replace calcium the most.
[6:07]First of all, remember to check that the patient is actually hypocalcemic or not by correcting for the albumin, so the corrected calcium is equivalent to 4 minus the albumin, and then that result times 0.8, and then you add that to the serum calcium levels.
[6:20]And then also, you can check the serum ionized calcium levels, which bypasses the need for doing this correction equation entirely.
[6:27]Your options for replacement include calcium chloride, calcium gluconate, calcium carbonate oral, and calcium citrate oral.
[6:35]Calcium chloride is preferred in patients with cardiac arrest. It's got a higher concentration, three times more than calcium gluconate, but the downside of it is that it's got a higher risk of tissue necrosis if the fluid extravasates somehow.
[6:48]And calcium gluconate is preferred in your non-cardiac arrest patients, there's a lower risk of tissue necrosis, and in general, most studies actually show that calcium gluconate raises the serum calcium the same as calcium chloride, and that there's really not that big of a difference between the two of them.
[7:05]So typically you would give 1 to 2 grams of this. So I'd say your go-to is probably going to be calcium gluconate most of the time.
[7:11]If you want to give oral calcium, then you do Tums, calcium carbonate. Um, you can do 500 milligrams to 4 grams total a day in one to three divided doses until their calcium starts to get better.
[7:22]And then also another option is calcium citrate, which is 200 milligrams to 1 gram a day in single or divided doses.
[7:28]There's a nice algorithm for treatment on UpToDate. Basically, the key point is if they're severely hypocalcemic, like less than 7.5 of calcium or ionized less than 3, then give IV calcium.
[7:40]And if it's only mild or moderate hypocalcemia, then you can start with oral calcium and vitamin D supplementation.
[7:46]One reason for refractory hypocalcemia, again, is that low magnesium, so make sure their magnesium levels are normal.
[7:53]And side effects of hypocalcemia include perioral numbness, which is the first sign of hypocalcemia.
[7:58]Then you've got Trousseau's sign, which is the involuntary hand and arm contraction with checking blood pressure, Chvostek's sign, which is facial twitching with light touch on the facial nerve, bronchospasm, so if somebody's complaining of hiccups or diaphragm issues, that may be one of the reasons, it may be a low calcium level, muscle numbness, spasms, tingling, seizures, altered mental status, and arrhythmias, especially prolonged QT common.
[8:21]And finally, let's go to our last friend, which is phosphate. So, LOL, I wrote, I don't actually know how to replace phosphorus that well. I don't really have to do it that much.
[8:34]For this one, we use millimoles instead of milliequivalents to calculate how much to give.
[8:41]You know, this happens a lot in the chronic kidney disease patients, but this one, you have to use millimoles instead of milliequivalents to calculate how much to give, so it's kind of a weird thing that I don't have to do as often. It's a little bit different than the other ones.
[8:44]But we can take a look at how we would approach this if this were to happen to us while we are on service.
[8:47]So the normal range at UC Davis is 2.4 to 5 milligrams per deciliter, and your options are potassium and sodium phosphate tablets, otherwise known as K-phos, and this I would just use if they have mild hypophosphatemia, so if their phosphate was greater than 2.0.
[9:01]One of the side effects is diarrhea if you use too much, so if you need higher doses, then you'd probably just give IV.
[9:07]What I tend to do is I do one or two tablets, three times a day with meals for like one or two days, and just basically follow their phosphate.
[9:13]You know, it's not critical if their phosphate is like 1.8 or 2.2, it's not going to be like a huge deal.
[9:21]So you have a couple days to follow to make sure their potassium, their phosphate is getting better. The next two options you can give are sodium phosphate and potassium phosphate.
[9:27]Um, I'd probably lean more towards using the sodium phosphate because you don't have any potassium in the sodium phosphate one, so you're not going to have to accidentally correct for giving too much potassium.
[9:40]The potassium phosphate one has 21 milliequivalents of potassium per 15 millimoles of phosphate. This is a tip that I found on Reddit, instead of doing what UpToDate says, which is weight-based dosing for all of this.
[9:52]So if their phosphate is less than 2, you can do 15 millimoles of sodium phosphate over 4 hours. Less than 1.5, you can try 30 millimoles over 6 hours, and less than 1, you can try 45 millimoles of sodium phosphate over 8 hours.
[10:05]And then the side effects of hypophosphatemia is basically all the same stuff as above, muscle weakness and cramps, bone pain.
[10:11]And that's it. That's my approach to electrolyte repletion in the hospital.
[10:16]I hope this was helpful for you, and if it was, please like, comment, and subscribe. Leave any suggestions or questions in the comments if you have any of them. And in the next video, we are going to be talking about insulin regimens in the hospital, so click on this video right here.
[10:28]I know it's not exciting, but everybody's got to learn how to do insulin regimens, how we can give people a good basal bolus insulin regimen, and convert their outpatient dosing into inpatient dosing.
[10:40]So click on that video. You'll like it. It'll still learn something. All right. See you in that one. Peace.
