Christopher Springmann: This is an encore presentation of NephTalk from Satellite Healthcare. Our guest, Dr. Tara Chang, M.D., is a nephrologist and a Satellite Healthcare Research Grant recipient, who possesses three qualities I really admire-- curiosity, asking the big why not questions; creativity, the kind you apply to problem solving, plus she is known as a great collaborator and an inspiring partner.
Dr. Chang is an assistant professor of medicine at the Stanford University Medical Center in Palo Alto, California. Let's lead into our interview with Dr. Chang with a one-minute animated video she produced to support her successful grant proposal.
Why nephrology? I mean, there's so many 'ologies out there. There's gynecology, gastroenterology, dermatology, urology. Why? Why nephrology?
Dr. Tara Chang, M.D.: Oh, it's funny. I get that question all the time, be it from medical students and residents that I work with, or just socially, family, friends, and-- CS: Well, tell me, Dr. Chang, what is the answer that you give to the question?
TC: Kidneys, I think, are a bit of a mystery. And during medical school is when I started learning about them. And most people have some concept that they filter the blood and get rid of the things that you don't want, and that's what comes out in your urine.
But beyond that, they regulate blood pressure. They help regulate your bone health. They help to control how much fluid, and salt, and electrolytes stay in your body. They help to manage how much blood your red blood cells make. They just do so many things.
CS: And do you miss them when they're gone.
TC: Exactly, exactly.
CS: Will you please read the description of the grant that you received from Satellite Healthcare?
TC: The title of the study is "Timing of Anti-Hypertensive Medications on Key Outcomes in Dialysis," which we abbreviate as "Take Hold."
CS: How would you explain this to say, an audience of students, if you were speaking at a college or high school. And after reading that, they all looked at you and leaned forward like--
TC: What? [LAUGHS]
CS: Tell me.
TC: So most people understand the concept of blood pressure. We know that if your blood pressure is too high or too low, that's generally not good for you. Too high, you might be at risk of having a stroke, heart attack. Too low and you're not getting enough blood to your brain, so then you feel dizzy, lightheaded. Not enough blood to other parts of your organs, also bad for your organs.
So all that stuff I was saying earlier, about what your kidneys do and help to regulate, so that all goes out the window when your kidneys aren't working and you're on dialysis. So for these patients, about up to 80%, 90% of them have trouble with blood pressure regulation. And mostly, that means high blood pressure.
But what happens in a lot of these patients is that once they get onto that dialysis machine, their blood pressure plummets and drops really low.
CS: Why is that?
TC: Well, that's a $20 million question there. No one's quite sure. But one thing that people often think contributes is their blood pressure medicines that they're taking. And that's what our study is focusing on.
CS: Right, exactly.
TC: A lot of our patients get told to do things by doctors, by nurses, by the technicians in the dialysis unit. They just get this advice, kind of off the cuff. Like, hey, why didn't you do this? Why don't you do this? And one of the things our dialysis patients are often told is, oh, your blood pressure drops too low when you're on dialysis. So just don't take your blood pressure medicines before you come in. Which intuitively seems like it would make some sense. If your blood pressure is dropping too low, then taking a medicine seems like it would contribute to that.
CS: Are you suggesting that those guidelines may need to be updated, or at least revisited? TC: The trouble is that there hasn't been any new data, which is where our study comes in. And even in those guidelines, they fully admit that the level of evidence to support their-- and they don't even call it a recommendation-- to support their suggestion is very weak because there aren't any data. CS: Was that part of your inspiration for applying for the grant with Satellite Healthcare?
TC: Definitely. The lack of data to help us take care of something that's so basic-- blood pressure.
CS: Did you have an aha moment? Not when you literally slapped your forehead, but wait a minute. Why do we keep doing this when the evidence seems to be old and/or thin?
TC: It was an aha moment back then, as a first year fellow rounding in a dialysis unit, and realizing that I had no idea what I was supposed to be doing and telling my patients with regard to their blood pressure and their blood pressure medications. Really, it was just me and my mentor talking about ideas. And we were both like, yeah, we are telling these people to do this and we have no idea what it's actually doing for them, if it's helping them or hurting them.
CS: Describe the intervention to me, please.
TC: It's pretty basic, to be honest. So what we've done is we've randomly assigned these first two dialysis units into a "take" group and a "hold" group. What we're telling the participants in the "take" group is, OK, take all of your blood pressure medicines that you take once a day, take those at night. And then, on the day of your dialysis, take all of your medicines as you normally would.
So take your medicines. That's the bottom line. Take your medicines on your day of dialysis.
Some people are used to not taking their medicines on the day of dialysis. So this may be a change for them, if we tell them, you know what? Take your medicine before dialysis. So don't skip it, like you usually do.
CS: Did you tell them what to expect?
TC: In the process of consenting them, and describing it, yes. We said, these are the things that we are going to watch for. Namely, is your blood pressure going to drop?
And in dialysis, honestly, they do this all the time anyway. They're watching for blood pressure dropping, for people complaining of dizziness or light headedness, any kind of symptoms associated with your blood pressure being too low.
CS: That could be a problem, for example, after four hours they leave the center and hop in their car, and--
TC: But we do check it during the dialysis session itself. And then of course, at the end, they check it with them sitting down. They stand up, they check it again, make sure that it seems stable. But then they let them go. Yeah, that's true.
So that's for the folks in the "take" group. And then, in the "hold" group, we essentially tell them to not take their blood pressure medicine on the day of dialysis, before their dialysis session. In a sense, a simple intervention, if you will, or a somewhat simple study. But I think will help shed a lot of light, in terms of is this advice that our patients are getting, to skip their blood pressure medicines, is this actually even preventing what we wanted to provide, which is preventing the drop in dialysis?
CS: Has anyone said to you, Dr. Chang, I can save you a lot of money and a lot of time. I know exactly what's going to happen.
TC: Oh, yeah. We have some patients who are like, oh, I can't-- I know what will happen if I either take all my medicines, or if I don't take all my medicines. And they are very firm in making up their mind. And for those folks, they didn't really want to do this because they were like, well, I don't want to be randomly assigned because I feel like I already tried that experiment on my own before. But that was probably a minority of patients, I would say. CS: Tell me, doctor, just between the two of us and several million listeners--
--what do you think might happen?
TC: I personally-- my hypothesis is that we're not going to see any difference in the rates of blood pressure dropping too low between the two groups. Because I don't think it's the blood pressure medicine that's the main driver of whether or not someone is prone to having their blood pressure drop too low on dialysis.
CS: So where do you go from there? If that is indeed what happens, what's the next step?
TC: So that's the main outcome that we're looking at. That said, we are going to be investigating some other important things, namely for a subset of patients who agree, we're going to hook them up to this nifty-- I say nifty in jest. It a pretty cumbersome device. It measures your blood pressure for 44 hours. It goes off every 30 minutes. It's called an ambulatory blood pressure monitor.
But in the subset of people who will allow us to do this to them, we want to see what happens to their blood pressure in between their dialysis sessions. And that's where I think we might see that in the group of patients that we tell to skip their blood pressure medicines, that potentially we're doing them a disservice in terms of their blood pressure control overall.
CS: Is that what you're ultimately seeking to find?
TC: Ultimately, we want to be able to give them advice to say, if you take your medicines as prescribed, without skipping them, that number one, you're not going to trigger these drops in your blood pressure during dialysis. And number two, you will have better blood pressure control in between your dialysis sessions. That's what I would like to see.
CS: In other words, you might be, in essence, rewriting the guidelines, updating the guidelines.
TC: Or at least giving some evidence to help them rewrite the guidelines. I think ultimately, this study-- we're doing it in 10 units. I think ultimately it will need to be replicated in a larger study with more people, and in different settings.
CS: How does Satellite Healthcare benefit from what you learn from this grant? They're obviously very curious about this, too.
TC: We know that the vast majority of our patients who are on dialysis will die from cardiovascular disease. We know that high blood pressure is one of the main risk factors for cardiovascular disease. But there's also been a lot of studies showing that low blood pressure is associated with cardiovascular disease.
So if we can help provide some evidence that will help us better manage blood pressure, and by extension, hopefully, better manage cardiovascular disease in these patients-- I mean, that's something that all of us who take care of patients on dialysis would want.
CS: You could potentially reduce mortality rates.
TC: That would be the big goal, yes. We won't be able to look at those hard outcomes. But it's a step. I see it as a step on the road towards getting to that goal.
As I've told my research coordinator, regardless of how it works out in terms of our stated aims and our hypotheses, we will learn something valuable. CS: There is an old cliche in business that a desk is a dangerous place from which to view the world.
TC: [LAUGHS] Yes.
CS: And have you rediscovered that simple truth? TC: Well, that's one of the reasons why I never want to stop seeing patients. CS: Oh, absolutely.
TC: You've got to be out there. You've got to be interacting with patients and hearing their stories. And like I said, most patients are very open. But there are some that have really challenged us and questioned us when we've gone to talk to them. And it's been really useful. CS: You really enjoy this, don't you?
TC: I love it, yeah. It's a lot of work, don't get me wrong. Especially because essentially, it's a two-woman show right now. It's really rewarding. So I enjoy it.
CS: Dr. Chang, thank you so much for joining us today on Neph Talk.
TC: Thank you for having me.
CS: You're listening to NephTalk, a podcast series created with nephrologists in mind, from Satellite Healthcare, a not for profit dialysis provider and clinical researcher with a special focus on home, as the industry's home dialysis leader. I'm Christopher Springmann.