Dr. Viachaslau Barodka on Acute Kidney Injury Post Cardiac Surgery

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About Dr. Viachaslau “Slava” Barodka, MD

Dr. Viachaslau Barodka is an associate professor of anesthesiology and critical care medicine at the Johns Hopkins University School of Medicine. His area of clinical expertise is cardiac anesthesiology. An expert in both red blood cell deformability and vascular stiffness, Dr. Barodka has a strong connection to Biomedical engineering and is developing new tools for real-time assessment of renal function. He has also optimized strategies to reduce renal failure post cardiac surgery.

Dr. Barodka earned his M.D. from Belarussian State Medical Institute in Minsk, Belarus. He completed a residency in orthopaedic surgery at City Pediatric Outpatient Clinic No. 17 in Minsk and another residency in anesthesiology at Thomas Jefferson University Hospital. Dr. Barodka performed a fellowship in anesthesiology at the Johns Hopkins University School of Medicine. Dr. Barodka joined the Johns Hopkins faculty in 2009.

His research interests include vascular stiffness, blood transfusion and cardiovascular physiology.

Dr. Barodka served as the reviewer for the Journal Anesthesia and Analgesia, section on Cardiovascular Anesthesia, in May 2009. He was recognized by Jefferson Medical School with the Joseph L. Seltzer Alumni Award to the graduating resident in recognition of outstanding academic achievement and the Arthur B. Tarrow, M.D. Award for the contribution to the field of anesthesiology research. He is a member of American Society of Anesthesiologists and the American Society of Cardiovascular Anesthesiologists.

Interviewer: Omar M. Khateeb

Interviewee: Dr. Viachaslau “Slava” Barodka

Khateeb: Hi everyone, this is Omar M. Khateeb, Director of Growth over at Potrero Medical and we are at the Society of Cardiac Anesthesiology here in Chicago. I got a chance to catch up with Dr. Barodka who is a very busy guy and fortunately, we were able to grab him for a little bit today.

Thank you so much for sitting down and joining us.

Barodka: You’re welcome.

Khateeb: Wonderful. Now, Dr. Barodka, I have to ask, what’s your story? How did you get into medicine? And how did you get to the position that you’re in today?

Barodka: So I was born in eastern Europe in Belarus, and that was the time when the Soviet Union collapse was happening. I was a classmate of one very famous guy in Belarus named Victor Kislyi, he’s the founder of Wargaming app, so a very big and prominent guy.

Anyway, he asked me to join him and go into the computer science and my parents told me, “how about you choose something more realistic and go to medicine, right?” So basically that’s how I ended up in medicine.

When I finished I had an opportunity to move to the United States for training and I came to New York, did my surgical internship there, and then I recall I downgraded to the South to Philadelphia at Thomas Jefferson University. That is where I did my anesthesia training.

We had at Jefferson the Gibbon building, which is a historical building. So who is Gibbon? He is first guy in the world who developed the first cardiopulmonary bypass for cardiac surgeons. So that’s how my life in cardiac surgery started.

Then I moved, and again downgraded, to Baltimore for my fellowship in cardiac anesthesia and I stayed there as a faculty and now I’m an associate professor.

Khateeb: And now you have a lab up at Hopkins I understand?

Barodka: Yeah, we have a great interest in clinical outcomes. And one of my particular interests is acute kidney injury after cardiac surgery.

Khateeb: Very interesting. I work with a company that is also very passionate and mission-driven around the kidney. Me myself, I’ve spent time in medical education, and know that the kidney is a very complicated organ. Kidney injury specifically is a bit of a black box it seems, so why did you or what attracted you to that area of interest?

Bardoka: Well basically, it’s not that much of a black box. If you open a physiology textbook, they will list how much oxygen each organ requires. And of course, everybody is thinking about the brain, you know, you cut off oxygen and it dies. End of story.

However, if you normalize it by weight, let’s say a hundred gram of tissue. The brain needs only three milliliters of oxygen per minute versus the kidney, which requires five milliliters. It’s a physiology textbook, right? So that’s how important oxygen delivery is for the kidney.

Khateeb: Interesting. With AKI it seems that it’s one of those disease that, if you sustain an injury to your kidney, it causes a lot of other issues within the body, correct?

Barodka: Well, AKI is a specific term for acute kidney injury. In the general public, people usually develop chronic renal insufficiency, which develops, similar to hypertension and diabetes, over the years. However, AKI is a much bigger issue in hospital settings, and has a really high prevalence in people with sepsis and in people who end up in the ICU.

There is a very specific subgroup, the second largest subgroup of all AKI, which is cardiac surgery related. It is literally called cardiac surgery-associated acute kidney injury and it has been known for years. Patients come in for cardiac surgery because they have heart problems that they want to get fixed, and nobody’s coming in thinking I fixed my heart but I end up on dialysis, right? So that’s a big problem.

Khateeb: And so how do you fix a problem like that? Where does it start?

Barodka: Well, the way it starts is prevention and also knowing what are the causes of acute kidney injury. Specifically in cardiac surgery, where a patient might come in with normal renal function. So this is multifactorial as with many other problems.

Specifically our interest at Hopkins and our focus was related to cardiopulmonary bypass, because the cardiopulmonary bypass is what set cardiac surgery apart from any other surgery. And again, if we look at all surgeries the highest rates of AKI is after cardiac surgery, right?

Khateeb: So why is it after cardiac surgery specifically?

Barodka: So again, we think it’s related to the cardiopulmonary bypass because all your normal physiology and blood flow is disrupted. You go on this machine, you lose your pulsatile flow, there is a hemodilution because the bypass machine decreases your hemoglobin count, you have to be on pressors.

Then you have to come off and there is reperfusion injury. It’s very very complex. You know, it’s a sophisticated machine that made cardiac surgery pretty safe today, but still with an inherent risk.

Khateeb: Interesting. Now, you mentioned something earlier that I wanted to see if you could dig a little deeper into. You mentioned the disruption of pulsatile flow: can you explain the pulsatile flow to the kidney, why that’s important, and how that’s disruptive in cardiac surgery?

Barodka: So the kidney specifically needs flow. Not just blood pressure, but the flow. When we think about the flow in medical literature, normal cardiac output is 5 liters a minute. A lay person thinks about 5 liters a minute as if, you know, it’s going out of your holes.

In reality, the heart doesn’t work like that, right? It’s pulsatile. It’s intermittent. You have a contraction of the heart, it sends a stroke volume and then you multiply by heart rate and that’s your cardiac output, right?

This is a very complex process. So when the stroke volume hits the central vasculature, and kidneys connect right to the central vasculature through the abdominal aorta, there is no compliance resistance. This is what is called the Windkessel effect, where their central arteries and aorta store the energy with a heart contraction. Then during diastole when the heart is not pumping blood into the fuel system, that energy and blood are going backwards.

That’s why in people who smoke and who have stiff arteries, or  arteriosclerosis, they have a really high incidence of chronic kidney injury because you lose this mechanism. The kidney requires flow and they see this pulsatility.

When you go on bypass, the major issues related to kidney injury is not just the fact that you lose pulsatility as long as you maintain adequate flow. The problem is that we don’t have any monitors which can detect how much of cardiac output is the proportion going to the kidney. We know in a normal healthy person that it’s basically like 25%, right?

So when you go on bypass you lose this pulsatility, because it’s continuous flow. We now have no clue how much out of the same five liters of flow the patient has that will actually go to the kidney or to the brain.

That’s part of the challenge. There are no technologies which can assess continuously and in real time the renal perfusion or perfusion of the kidneys. They are just non-existent.

Khateeb: I guess this problem becomes even more complicated because you’re administering different drugs in the surgery and also doing hemodialysis. So the amount of fluid that is being fluctuated through the vasculature is going to change, and all these factors make it more difficult, correct?

Barodka: Dialysis is for patients who develop renal failure, so we don’t do dialysis to begin with and we hope to avoid it. But going back to cardiopulmonary bypass, part of our research is to focus on adequate oxygen delivery on cardiopulmonary bypass.

There is a group in Italy who just finished a multicenter, randomized control trial on the topic. They calculated in real time the oxygen delivery on bypass, which depends on the flow and also on hemoglobin concentration. And if you do this kind of goal-directed, then there was a reduction in acute kidney injury.

We did basically the same study at Hopkins five years ago retrospectively, also developing a specific protocol with focus on oxygen delivery. So, if you pay attention to this very simple physiological parameter, we had a reduction of AKI by basically three times.

But not all cases of AKI are equal. Now the current standard for assessing kidney injury is called the KDIGO criteria, which basically stages AKI as a guide from stage 1, 2, and 3. AKI stage 1 is a mild one, patients would go through the surgery and they wouldn’t even know that their kidney were affected. They wouldn’t be on dialysis and they would go home and do everything else as normal.

It’s almost the same problem as hypertension. If you don’t measure it people don’t even know that they have high blood pressure, and down the road it has very negative consequences. So it is the same story with cardiac surgery and mild AKI; we measure creatinine and we know it happened. We know that it has negative consequences down the line in the patient’s life, but the patient doesn’t know.

Khateeb: How many them follow up with a nephrologist after that? Because I don’t think there’s much of a discussion around this.

Barodka: Right. So currently, if you look at the literature over the last forty years, the problem of cardiac surgery-associated acute kidney injury still exists. The rates of AKI in the literature ranged from 20 to 40 %, depending on different definitions, and didn’t change in the last 40 years despite multiple different medication interventions.

So thus far, everything is failing. Now I think I see the light at the end of the tunnel and that’s what we speak about at our society, new interventions specific to cardiac surgery. Things like oxygen delivery systems, or not using very aggressive ultra-filtration and removing extra fluid from the patient, which deprives the kidney of fluids.

And universally, the society is moving towards using balanced crystalloid IV fluids which were used during the surgery and are used exclusively now. This was not the case even two to three years ago, and it looks like a small thing, but altogether you put them in a bundle intervention and that’s how you decrease the rates of AKI.

Khateeb: Interesting. Now you had a workshop here at SCA specifically on fluid management, but also I believe in prevention of AKI. Can you you share some of the pearls from that for those who unfortunately were unable to attend the meeting?

Barodka: Yeah. So basically we’re talking about the goal-directed perfusion.

There are several items which I already elucidated, such as paying attention to hemoglobin and flow, calculating oxygen delivery, and that the threshold for this is between 280 and 300 milliliters of oxygen per minute per meter squared. We have to calculate this from height and weight and body surface area. You have to talk as a team and work with a perfusionist to set the goal.

Within the last year, there was a randomized control trial done on transfusion in cardiac surgery which basically showed that restrictive transfusion strategy, having the hemoglobin threshold of seven grams per deciliter, is safe and has the same outcomes as a liberal transfusion. If anything, it actually decreases your complications.

So now we live in this renal bypass where you have hemodilution, you have low hemoglobin, and you cannot transfuse because if anything that leads to harm. This basically leaves you with only one option to prevent AKI, which is by increasing the flow on bypass.

Khateeb: Interesting. Now, one question I had while educating myself about AKI and the management of it was about urine output. What’s the role that urine output plays for you as a cardiac anesthesiologist in the OR?

Barodka: So again, it’s unfortunate that we live in the 21st century and we don’t have anything better than urine output as a monitor for kidney function. Period. There is growing interest in biomarkers, but still nothing better than just a creatinine check.

So the problem with markers like creatinine is that it’s raised only 24 to 48 hours after the injury occurred, right? The damage has already been done. We know patients come in with normal kidney function we can detect two days after the cardiac surgery that it’s no longer normal. But we can’t say when it happened.

Did it happen before the bypass? Was it actually the bypass that is affecting the kidneys? Or is it our management, our drugs and vasopressors, which we give before the bypass and in the ICU.

So this is the current clinical challenge and that again leaves us with the only option of urine output. And in a criteria to diagnose kidney injury, it’s not just a rise in creatinine that gives you stages of AKI, but there is an alternative one based on urine output.

So what we do in cardiac surgery is eyeball the foley and just look at the urine drop by drop by drop, and when we see that we get kind of happy. Whenever the kidney is getting perfusion, you don’t see urine coming out during bypass and you start to worry.

As you can see it’s a more qualitative assessment not quantitative assessment and that’s a problem.

Khateeb: It sounds like the inability to monitor it not only accurately but continuously is an issue. Because right now, you’re having to eyeball it among the hundreds of other things that you have to look at in the ICU. Is it ever an issue where perhaps urine output doesn’t seem to be good, but in reality the catheter may be bent or perhaps the patient is in a position where the bladder isn’t draining very well? Is that a possibility?

Barodka: Well, absolutely. So there are problems with eyeballing, and there were several papers published about it. They recorded what the nurse in the ICU or anesthesia team perceived as a urine output and then they exactly measured it. The error rate with eyeballing is as large as 30 to 40% – its enormous, right?

Think about this: somebody measures your heart rate or blood pressure and they record an error of 40%. It’s nonsense considering we are in the 21st century.

Khateeb: Why has it existed for this long? What do you think?

Barodka: There were several companies on the market from Europe, and I think one of them was BARD, who basically try to automate the process. Basically, they will measure the urine output minute by minute and provide a way of taking these subjective nursing measurements away.

We had them at Hopkins, we played with them and we used them in the study and we were very happy. And then, I don’t know the reason why exactly, but it was withdrawn from the market. It was probably related to technical problems: how accurately it measures output, how user-friendly it is, and if nurses are required to spend more time setting up the equipment versus charting.

So we still need a real-time, continuous, and non-invasive or minimally invasive monitor for kidney function, whether it’s based on urine output or something else.

It’s critical that it will not be cost-prohibitive, be user-friendly, and be integrated into the electronic health record. And it’s also very important to be clinically validated.

Khateeb: Now, we want to be mindful of your time. When you say user-friendly this is definitely a big problem across medicine, which is known for very non-user friendly devices. If you look at the critical care unit from 1917 compared to a picture now, not much has changed in the pictures I’ve seen.

So when you say user-friendly what do you mean by that specifically?

Barodka: User-friendly meaning it takes very minimal time from the provider to set it up and it automates as much as possible. I’ll give you one example of a great device on the market right now that is user-friendly, continuous, real-time, and non-invasive. It’s called pulse oximeter.

It’s one sticker that is placed on the finger. You can activate it before the surgery and you don’t touch it again. It’s automatically on your monitor non-stop and it automatically will go to the electronic health record. That’s it.

Khateeb: And it doesn’t alert you unless something is wrong?

Barodka: Exactly. It’s the same thing with the EKG. I still remember when I was in medical school, if you wanted to get an EKG you had to go to a special bed. It was almost like an execution, with lots of electrical wires, and they strap your arms and legs with the wires. The patient wouldn’t even breathe right for about 12 seconds.

Khateeb: And somehow you’re supposed to get a normal heart rate. I guess if it’s elevated you have to guess if it’s physiological or is it because of the chair, right? [laughing]

Barodka: Exactly. But again, you just put the stickers on the patient away from the surgical field, and you can activate it and then forget it. It’s automatic. If something happens, it gives you an alarm.

This is the kind of technology we need for different organ systems. Whatever the sophisticated technology, it’s extremely user friendly. Again, you put two stickers that are non-invasive and cause no harm to the patient. No needle sticks and you’re done. I just use it through the whole case, right?

So this is something it would be nice to use for kidney function. You put couple of stickers or whatever it is, it could be a Foley, and then you forget it. You don’t have to bend or empty the Foley, you don’t have to remember “has it been one hour since I emptied the Foley?” Let’s see, what is the urine output now? Like you hear my point, right? You can connect it at the beginning of the case and you can forget about it because it’s automatic.

Khateeb: I think this is really the future of medical technology for Physicians. We sat in a couple of lectures with Dr. Perry out of University of Minnesota, who talked about automation and intuition, and we had a discussion yesterday where we agreed that the future is really to have technology that automates things that the physicians don’t want to do.

For instance, recording urine output every hour and then once it’s there, you forget about it. You don’t have to deal with it ever again. And so all these pieces of technology are hooked up and out of the way. This way, the physician can go back to bedside and spend more time directly interacting with the patient versus dealing with the technology.

Do you feel that a lot of physician burnout these days is because of having to deal with so much technology and putting stuff into the EMR?

Barodka: The electronic health record was a big step right? Because we used to paper chart, and it was even in the United State’s leading institutions until like 10 years ago.

So that’s the history, and we feel that difference where you are actually paying attention to the monitor and to the patient and not just charting them. I think the same is coming with monitoring technology: artificial intelligence, automatic alarms, there is clearly a lot of fatigue.

We have to be very useful in how we set them up and use them, but this is where technology is going. Activate it somewhere in the background and have it constantly monitoring, if something goes wrong you get the alarm and it drives all of your attention to the patient. That will be the future.

Khateeb: Versus right now, where it’s just too much. You’re having to look at so many different data points and eyeball certain things, right?

Barodka: If I know what the normal urine output is and my device knows it, then I don’t even need to be updated every hour. If it’s the same cerebral oximetry or the same pulse oximetry? I want it to alarm me only if something is wrong. If something is good, I shouldn’t be focusing on it. I can’t refocus my attention on the normal things, I have to focus on what is important.

Khateeb: Right. Well doctor, this has been very enlightening and helpful. Thank you so much for spending some time with us.

Barodka: Yeah, you’re very welcome. That’s what we’re doing at Hopkins, bringing new evidence and spreading knowledge for all.

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