Many people become alarmed by a single lab result or a “bad” eGFR number, even though changes in kidney function often reflect only a temporary state. Medications, blood pressure–lowering drugs, dehydration, infections, and lifestyle factors can all transiently worsen lab values without indicating true kidney disease. The key question is when an abnormal result should be taken seriously—and when it should not.
This talk takes a detailed look at medications that affect kidney function, the true significance of blood pressure, the role of salt and fluid balance, and why judging health based on numbers alone can be misleading. If you want to understand what is really happening in the background and how to think about lab results and blood pressure in a personalized, level-headed way, it’s worth watching the video or reading the full transcript.
The content of the video in written form
Hello, this is Dr. Zsom.
Dear patients, well, in—during today’s presentation—we are going to touch upon two very important things: one is medication side effect as a cause for decreased kidney function, the other one is the effects of blood pressure on the kidney, and you will see that the two are really one.
Kidney filtration is a snapshot. So the lab values that you get on your—after your blood draw—they do not distinguish between these scenarios, okay. So what you need is a judgment of a nephrologist. So if your kidney function, your eGFR, okay, it decreases because you sweat a lot, or you have diarrhea and vomiting, or simply don’t eat well, okay, then that is a temporary thing which will resolve on its own. Similarly, if you take too much medications, that can cause a temporary decline in kidney function; or, of course, if you take too much for too long, then it may cause real kidney disease with chronic renal failure, okay.
Several other organs can cause either temporary or permanent damage to the kidneys; for example, you can have lung disease or heart disease or liver disease that can cause that. And you have dietary issues, okay. If you eat too many certain things or you don’t eat enough of certain things, then it can either temporarily or even permanently decrease your kidney function.
So one prominent cause for all of this, okay, it could be blood pressure medications. So different medications can influence kidney function or even make the lab results look worse, so we underestimate the kidney filtering capacity. So we really don’t have a chronic kidney disease, but it seems like that because we took a medicine that may temporarily decrease kidney function. The most prominent problem comes with blood pressure medications lowering blood pressure, especially with long-standing vascular disease. So blood vessel disease can reduce the filtering function of the kidney, though this reduction may also mean that these blood pressure medicines will then stabilize the kidney function on the long run, okay.
So what we need to understand is that sometimes it is better to have less kidney function but that kidney function will remain on the long run stable, so we never have to go on dialysis. Many doctors simply misinterpret this problem; in other words, they see a decrease in kidney function and they believe that it’s going to decrease further. Well, that may not be the case because these blood pressure medications, especially certain kidney protecting agents, may stabilize the kidney function in the long run, okay.
However, if we take too much blood pressure medications, then the kidney blood supply will be reduced. And if our blood pressure is too low—and in every single person a different value may be too low—then the kidney function may temporarily go south, go down. And if we do this for for a long time, then the kidney damage may cause a permanent decrease in kidney function and a progressive decrease in kidney function. So we need to see what is too low for that particular person, okay. And if the blood pressure is too low, then the medication dosages may need to be reduced. So “too low” may be relative to how good the blood supply to the kidney is in the first place, because, for instance, in an elderly person or somebody with already damaged blood vessels, okay, these people may be especially susceptible to too much medication with too much blood pressure lowering.
And then there are these special blood pressure medications called ACE inhibitors and ARBs, and these decrease blood pressure not only generally in blood vessels anywhere, but specifically also in the kidney. So the small blood vessels in the kidney have decreased blood pressure due to these medications. Now, this is a wonderful thing because, obviously, these prevent the kidney to exhaust itself and they prevent chronic kidney disease; and also they decrease scarring and, of course, they decrease protein in the urine, which are very good things.
However, if in a specific person too much of these kidney protective medications are given, then the blood supply will go down. And if the blood supply in the kidney is already down, then it may further increase the damage. For instance, if you have, say, diarrhea, or you have an infection, or you have any other acute illness, or you take special kinds of painkillers called non-steroid anti-inflammatory medications, then your kidney perfusion—so the blood supply—is already down. Now, if you add onto this these kind of medications which decrease the blood pressure, the blood supply in the kidney, then you might have a problem. And this is especially prevalent in vascular disease; if vascular disease is already present, which is often the case in the elderly or in diabetics, and then you can harm the kidney with this type of medications.
So remember Ohm’s law. That means that if you have an electric current, okay, and you have high resistance in that electric current, then you need a high voltage so that you guarantee a flow of the current, okay. So the similar situation in the circulation: so if you have a lot of resistance because of plaques, okay, in your arteries, then you need a higher pressure, okay. So if in these patients the blood pressure is lowered a little bit too much, then that’s gonna mean that you are going to have a decreased flow; for the same blood pressure, because of high resistance, you are going to have a decreased flow and your organ—in this case the kidney—doesn’t get enough oxygen. So that’s not good.
Therefore, blood pressure medications may need to be halted or reduced, okay, if anything is present that may decrease blood supply of the tissues, for example: dehydration—and dehydration always means not only loss of water, but loss of salt through diarrhea, for example—acute illness for instance infections, blood loss, a heat wave, or too much diuretics are taken and therefore too much loss of water and salt is the case. In this case, blood pressure medications may need to be lowered because, if the same blood pressure medications are taken as in normal conditions, then in these conditions they work much stronger, reduce the blood supply to the organ—in this case the kidney—and that means that your kidney function is going to go down acutely and abruptly. So kidney protecting medications, for example ACE inhibitors, are very useful in the long run but may be risky in acute illness, potentially causing acute kidney failure and or high potassium. Why is that? Because these decrease the pressure especially in the small arteries of the kidney, okay. And so if you have a decreased blood supply because of an acute illness, then these medications may cause further decrease in the blood supply, the kidney cannot compensate, and then you end up with severe kidney failure with a high potassium. In the elderly this might be even more prominent, since they have atherosclerosis with blockages in blood vessels, among them in blood vessels inside the kidney, okay. So then the nephrologist should be consulted anytime, okay, you have a change in your condition because these medications may need to be reduced in dosage or paused, in other words, held for a few days, okay, until the illness subsides.
This risk is almost always higher with anti-inflammatory medications, okay, because if you take these medications you have an acute decrease in blood supply and then this will be aggravated by by the use of ACE inhibitors and other kidney protective medications; diuretics the same thing.
So let’s talk about diuretics a little bit more, because diuretics are often a subject to a whole lot of errors and misconceptions. So diuretics are only useful if there’s too much salt and water in the body. That’s it, okay. If there’s too much salt and water in the body, then diuretics work by removing the excess salt and water. So far, so good. Diuretics may increase urine volume, but more urine does not equal better kidneys, okay. So many people believe that “the more urine I have, the better kidneys I have.” This is wrong, okay. Salt and water removal or reabsorption is a different function than filtering function, and the two correlate only in extreme cases, okay. So more urine does not mean better kidneys.
The diuretics may not be always be the best, okay, to treat leg swelling. It depends on the situation. For instance, if you have leg swelling because of a local problem—for example you have varicose veins, in other words a local vein problem, okay—then diuretics are not going to help that and they may harm the kidney, okay. If you have a urine blockage, you should not treat that with diuretics, okay, because that may also harm the kidney, okay. Too much salt and water are removed and the blood pressure drops and the blood supply is damaged to the kidney, okay. So that is not a good idea in this situation.
Diuretics should always follow dietary changes. Okay. So diuretic dose should depend on salt and water intake. Increase or reduction in dosage may be necessary to avoid heart and kidney failure. Remember that heart and the kidney need a special amount and salt and of salt and water in the body and the and the ratio between salt and water, okay. So that means that if you eat a huge salt load, you are going to be very thirsty, okay. So the salt and water content of your body are gonna go up. In this case you need a lot of diuretics, okay, to get rid of this salt and water, because if you have a heart or kidney failure then you are not able to fully compensate to a great salt and water load, okay. So in these situations diuretics may be very helpful.
Now let’s see this situation, okay: you sweat a lot and maybe your appetite goes down because there is a heat wave, okay, then the diuretics dose should be less that particular day because the heart and the kidney need blood supply. And if you don’t give them enough salt and water, okay, then your blood pressure is going to go down and the blood supply is going to decrease. Lack of appetite means less diuretics; pizza means more diuretics. Now it is best to have relatively stable intake of salt and water, okay, so you have an even diet, right. Actually if you have an even diet, then an even dose of diuretics is going to be good for you, okay.
Now, if you have a lot of sweating, diarrhea, vomiting, or low blood pressure for any reason, okay, then for a few days stop these medications, okay. Stop diuretics, because if you don’t stop you’re going to get dehydrated. Dehydration here means too little amount of salt and water in your body.
So, non-steroid anti-inflammatory medications are very good in treating your joint aches; however, they may be very harmful reducing blood supply even acutely. So if you take diuretics and kidney protective medications, then the blood supply may go down even more, okay. So acute kidney failure risk is that much higher. So be very careful with anti-inflammatory medications if you take blood pressure medications, kidney protective medications, or diuretics, okay. Antibiotics may sometimes also cause kidney disease, okay, though this often subsides after antibiotics are stopped. Nevertheless, they can cause harm in various mechanisms, one of which is they may cause a disbalance, loss of balance in the gut flora, or there could be also an allergic reaction.
Summary: better tell your nephrologist all medication changes, because the nephrologist knows how these medications may may change the kidney function and therefore medication side effects may be best avoided if the nephrologist, you know, will supervise these medications, okay.
Now, we were talking about all kinds of medications but mostly blood pressure medications. And high blood pressure, also called hypertension, is extremely important in chronic kidney disease and therefore let’s talk a little bit about hypertension. So again, high blood pressure disease or hypertension is a misnomer; high blood pressure is a symptom of chronic vascular disease, blood vessel disease. So what happens here is that if there is certain harmful event and that event keeps on coming back, okay, then you have an inflammation—a chronic inflammation in your body that damages the inner layer of your blood vessel wall, and that causes hypertension and many other things. And so, since blood pressure is easy to measure, we call this whole disease process “high blood pressure disease” because it is blood pressure that we can measure, okay. But the basis, the root cause of this disease, is really inflammation due to chronic repetitive damage, okay.
And so then you have calcium and phosphorus deposition and in your blood vessels and you call that atherosclerosis, which is especially prominent in kidney disease. But what is the cause of this vascular inflammation? Okay. Well, one of the most common causes of vascular inflammation—so blood vessel wall inflammation—is excessive salt intake, okay. And some of the other things that can cause this is whatever causes a disbalance in the gut flora. In other words, the good bacteria versus not-so-useful bacteria in the gut flora will change because of certain dietary and other issues, okay, and antibiotics.
So what could be these dietary issues? Well, first let’s talk about salt because that may be the most common of these dietary problems. Let’s remember that salt is one of the most ancient preservatives, so it is the foundation of food industry and trade. So there cannot be food trade without salt, okay. Salt is also a seasoning that one can get easily used to, so it becomes a luxury item, one of the oldest luxury items. So it used to be also used as currency in the old times because it was a luxury item which was very important actually.
So what happens if there is a sudden change from a low salt, high exercise, high sweat environment to a high salt, low exercise, low sweat environment? Okay. So what did we expect? Well, you got it: vascular inflammation. Because you sweat less, you eat more salt, the kidney will try to handle this and it can handle it for a few years, but after that you’re going to have vascular inflammation and chronic kidney damage from that inflammation, okay.
So then here’s what happens: sooner or later vascular inflammation is going to happen because salt induces the immune system. You add to that changes in the microbiome, so the bacteria gut flora. And so what then happens is that certain bacteria are overgrowing, okay, and they produce certain materials which, going into the circulation, further increase this—the activity of the immune system, okay. And so also what happens is that if you have too much salt and water you may have got a wall, bowel wall problems, so that you have here a damaged gut wall and that’s—means that—certain toxic materials derived from these bacteria will enter the circulation and damage the blood vessels by causing inflammation, okay. And so you have vascular and renal inflammation; obviously the kidney is very sensitive to any vascular changes because it it is full of blood vessels, okay. And so you have hypertension, high blood pressure, and chronic kidney disease, all right.
So from salt to chronic kidney disease there is a relatively straight line. Salt intake again changes the composition of the gut flora. So subtle substances are released from abnormal gut flora, okay, that cause inflammation, okay. So these good bacteria go down, there is a compensatory increase in other bacteria, and then you activate your immune system and you have inflammation, okay.
So high salt and therefore high water intake in the heart and kidney leads to hypervolemia—too much water and too much salt retained. So here’s here’s what happens: if you have high salt intake, okay, then you overburden your heart with too much salt and water, okay. So you are going to develop heart disease. And of course the heart is also working against higher resistance because you have blood vessel disease also increasing the resistance to the heart. And so what happens then is that heart failure will also cause more gut wall problems; more of these inflammatory mediators come into the circulation causing even more blood vessel inflammation, okay.
And the kidney, okay, very much depends on the heart. Why? Because it is the heart that supplies the blood and the oxygen that the kidney needs. So therefore, if you have high salt, there are multiple mechanisms by which heart and blood vessel problems cause kidney failure. So true kidney disease due to a low oxygen environment, okay. So you have leg swelling, abdominal fluid, you have bowel wall swelling, okay, and the barrier to bacterial toxins goes down and therefore you have more blood vessel inflammation. And the same mechanism can be also observed in chronic stress; in other words, you also have gut flora the changes and you have a lot less inflammation, okay.
So what do we understand from all of this? It is that high salt intake is not a good idea because it can damage your blood vessels, your kidney and heart, okay; and by multiple mechanisms it can cause chronic kidney disease.
So committees—medical committees—always debate what is “normal” blood pressure, what should be their target blood pressure, because they look at a whole community of patients, okay, a large population of patients. So they don’t care about you; they care about a population of patients, so they have generalizations, okay. And so they standardize targets, okay. And so so what happens is that they don’t take into account you, of your situation, and they establish a general target for it—for anyone.
So why is this? Because blood pressure is readily quantifiable; you can have a lot of measurements and a lot of patients, okay. And since science is really a game of numbers, you then begin to worship numbers and they say, “Okay, I know best what is the real target for an ideal person.” But you fall out of the equation, okay. No! What is the—what is good blood pressure for you? Whatever a blood pressure is the lowest possible without causing you symptoms. Okay. So if you are dizzy the whole day and you fell unconscious, that means that that blood pressure—whatever the number was—was too low for you in that situation, okay. So we need to understand the situation so that we can determine in in your particular condition what is the best blood pressure for you, okay.
It should bring about a decrease in protein concentration in the urine without drastically reducing filtering function. So we also judge how good your blood pressure is for your kidneys by looking at what—how much protein you have in your urine. Obviously, if you have zero protein in your urine, then there is a chance that that blood pressure is not very harmful for you. There are exceptions, but this is an important—it’s an important factor, okay, that we should consider.
And your blood pressure has to be maintained relatively stable without wide swings up and down, okay. So blood pressure should always be a pattern recognition from either a 24-hour monitoring or multiple home blood pressure measurements when you are at rest, when you are not stressed out like this, okay, or stressed out for any reason, okay. It—so what causes problems, okay, is and what is the marker of blood vessel inflammation is sustained high blood pressure at rest, okay. So it’s—it’s—if if you are nervous, then of course your blood pressure is going to go up, but that is not to be treated by blood pressure medications; that should be treated by calming down, okay.
Stress, exercise can increase blood pressure normally, okay. So so these—natural increase—blood pressure while sleeping should decrease your blood pressure. There are exceptions: if you have chronic blood vessel inflammation or you have too much salt and water in your body, then sleep will not decrease your blood pressure, okay; and that needs to be treated, okay. So therefore we need a blood pressure diary soon, because it’s a pattern recognition; we need to see how your blood pressure generally is. So if you have three high numbers, it may be because you were, you know, very nervous, you know, and and that may not be a sustained high blood pressure—and it is not because most of your blood pressure is really good, right? Should bring in your blood pressure diary; let’s discuss it, let’s, you know, control your blood pressure in a special way for you.
The first number when you get blood pressure measurements: the first number is systolic blood pressure, okay, and it may be high with old age or hypervolemia. So if you have too much salt and water in your body, that first number is often very high and there are special medications—diuretic here and certain type of blood pressure medications with old age that are especially useful. The second number is diastolic, okay, generally goes with with the systolic blood pressure number, okay. But you know, if your systolic blood pressure is high yet your second number, the diastolic number, is below 55, that may mean that your organ perfusion—so the blood supply to your organs: brain, heart or kidney—is maybe too low. So it’s often not a good idea to go below 55, okay. Your third number is the pulse, okay; generally should be over 55 and less than 100, because if if it’s too low then it can cause problems, if it’s too high it can cause problems. And there are special medications that specifically target the pulse rate, okay.
Now that remember, we are using pattern recognition here, okay. So that means that we don’t average out numbers, but we look at all numbers and we always compare your numbers to previous numbers; that’s what we call auto control. So we—we—use your numbers in the last few months and compared to your numbers the previous few months, okay. So we are targeting your situation and we are seeing which way you are going, okay. So this whole thing needs to be individually tailored for your situation. So the—you know—these big shots, they are telling you that your your target should be 130 over 80 and “I’m sure of that, I am science.” The other company says, “No, it should be 140 over 90, especially if you are are diabetic or an old person it should be this or that number.” Well, okay, we should not generalize; one patient may be different from the next, okay.
So you should always consult your nephrologist, because if your blood pressure is 130 over 80, okay, but you fall down unconscious on the floor, that’s not good. And remember that depending on how much atherosclerosis you have, this might happen, yeah, in a given person and it may not happen in another person, okay.
In other words, you need to be comparing your blood pressure values to your previous blood pressure values—number one. Number two: we need to understand what symptoms or or side effects you might have because of a certain set of of blood pressure measurements, okay.
So let’s go back a little bit and and let’s talk about one thing more. So we also look at the protein in the urine. Why? Because if your protein in the urine is high, that might mean that you need either more blood pressure control or you need diuretics to get out the salt and water in your body, okay, that is excessive—that is too much. Or, if your proteinuria is zero, that might mean that that blood pressure is pretty good for you, okay. So you should not generalize; you—you—really need to factor in the protein in the urine in a specific person and the symptoms that a certain a set of blood pressure measurements may be associated with.
So now let’s talk about a little bit of what determines the blood pressure. Well, two things: blood vessel wall tension and heart work are both very important in determining what your blood pressure is going to be. So if your heart, okay, is working very hard, okay, then your blood pressure may be higher than if you have heart failure. Heart failure patients very often have a low blood pressure, okay, and that may also be dependent on what resistance you have in your heart. So for example, if you have atherosclerotic hardening of the arteries, okay, then your heart work needs to be that much harder.
Or if you have blood vessel wall tension because of too much salt and water—remember, here’s a hose, okay, and this here, okay, is—is—and the wall of this hose and the tension in that wall, like the tension in the blood vessel wall, okay, is going to be determined by how much pressure you have because of the fluid inside the blood vessel or the hose, okay. So therefore if you have too much salt and water in your body, then you’re gonna have a high blood pressure, and that high blood pressure is going to be maintained day and night, even when you sleep. And normally your blood pressure should fall here; it’s not gonna fall because you have permanently too much salt and water creating a lot of wall tension, okay. So if you have this type of a blood pressure, that’s different than if you have a lot of hard hard work and a lot of resistance to the heart, okay. And you need to reduce salt and water in your body first before you do anything else.
So that brings us to fluid status, okay. And in the next presentation we are going to talk about what fluid status you need so that you avoid this type of high blood pressure.
So let’s summarize that we learned this far: we are gonna say that your lab values are a snapshot, okay, and they depend on a lot of things. One of these things is your blood pressure and your medication side effects, okay. We also always should review your medications so that we understand how we should adjust these medications depending on your condition, okay; and that includes changing your blood pressure medications and kidney protecting medication dosages under certain situations.
Also we need to understand that high blood pressure is a problem, but it is a problem that is really a symptom of blood vessel wall disease, and the blood vessel wall disease is caused by chronic inflammation which can be then influenced by dietary factors. What I didn’t say was—and I’m saying it now—that dietary factors also include, in addition to salt, other issues. For example, excessive animal protein intake—we’re going to talk about that—certain carbohydrates can cause it—we already talked about it in in the carbohydrate presentation, okay—and certain preservatives and food additives can also cause it.
So a fresh food is always a good idea, yeah, but one of the main important factors in your blood pressure is going to be fluid status, which is determined by salt and water content of your body, okay. And we will detail that issue in the next presentation. Until then, thank you for your attention and goodbye for now.
