Continuous renal replacement therapy (CRRT) requires considerable involvement from the bedside nurse. Host Michael Smith, MD, is joined by Barbara McLean, MN, RN, CCNS-BC, NP-BC, CCRN, FCCM, to explore when to start CRRT, the nursing role, and other considerations and challenges. Barbara McLean is a critical care clinical nurse specialist at Grady Health System in Atlanta, Georgia, USA. This podcast is sponsored by Baxter Healthcare.
Estimated Time: 20:40 min
Michael Smith, MD (Host): Hello and welcome to the Society of Critical Care Medicine’s iCriticalCare podcast. I’m your host, Dr. Mike Smith. Today we’ll be talking about renal replacement therapy. I’m joined by Barbara McLean, a Critical Care Clinical Nurse Specialist at Grady Health System in Atlanta, Georgia. Barbara, welcome to the show.
Barbara McLean, MN, RN, CCNS-BC, NP-BC, CCRN, FCCM (Guest): Thank you so much Michael. I appreciate the invitation and I’m so excited to talk about continuous renal replacement therapy.
Host: Awesome. I’m glad to have you. So, how about a little bit of a background first in renal replacement therapy and why is it so important?
Barbara: I always remind everyone that if I have a patient with acute respiratory failure, we intubate them, we ventilate them, and we ventilate them 24 hours a day. Because we have to replace lung function. And the same idea should be applied when we’re talking about continuous renal replacement therapy. The goal of renal replacement therapy is to gently replace what it is your kidneys do and to do that as much as possible, as close as possible to 24 hours a day. Most people when they think about the kidney, they think about that it regulates the metabolic waste and it regulates fluids and electrolytes but the other really important component when we talk about kidney function is to remember that it regulates our acid base balance. And that to me, is one of the most important aspects particularly in the critically ill population.
As we know, persons who have metabolic acidosis frequently will lose their vascular response to circulating catecholamines. So, one of the aspects of continuous renal replacement therapy is to actually supply an external kidney that operates close to 24 hours a day, gently mobilizing fluid, electrolytes, metabolic acids, regulating your base and actually supplying you the more unstable you are, supplying you and benefitting you as the patient by the clearance of those acids, restoring you to a better vascular tome state.
Host: And that’s true. So, you know with these critically ill patients, many of them on ventilators; they already are very weak in their vascular response so the last thing we want to do is create an environment through ventilation where the kidneys are having to overwork, not controlling the acids; so in a sense, what we’re doing, right, and tell me if I’m wrong here is you’re giving the kidneys a break. You are allowing that external kidney to manage all of these acids which then allows for the rest of the treatments that may be you’re doing on these patients to work better.
Barbara: Well that was very nicely said. I think I would just generally organize that just a little differently. And that is, that if – when we are looking at an acute respiratory failure patient, typically we have an issue with oxygenation and the respiratory acid removal which is CO2. And if we have a patient who has competent lungs, if you have acute kidney injury, they’re going to hyperventilate to compensate for the kidney injury and the loss of metabolic acid removal. So, there are two really important components which you’re touched on and that is of course that the kidney actually regulates the metabolic acid hydrogen and it also conjugates hydrogen to carbon dioxide and therefore, producing bicarbonate. So, when we lose our kidney function, we have a double digit problem and you’re exactly right, that then that puts an extraordinary burden on the lungs. But I think my reference was really about – I wouldn’t intubate you, put you on a ventilator, say breathe for three hours and I’ll be back in two days. And I don’t want to do that with the kidney in a really critical patient. I want to replace them 24 hours a day and that’s what – that’s the beauty of CRRT is it allows us that ability to replace kidney function but also, to do it gently enough in a hemodynamically unstable patient so that we achieve some stability as you mentioned, of vascular tone and that’s vascular competence is so incredibly important in restoring normalized blood flow.
Host: So, when do you suggest that patients should be started on renal replacement therapy and specifically what’s the nurse’s role in getting that started?
Barbara: I believe that we should follow basic KDIGO guidelines that’s the Kidney Disease Improving Outcomes Group. And they talk about the RIFLE criteria which is about renal risk injury failure loss and end stage. You can always look that up anywhere on Google just make sure you say RIFLE for kidney because otherwise you just put in the word rifle, you’ll get ten billion responses. And I think one of the really important concepts for us in critical care is to recognize that when patients have increased their creatinine 100%, they may not be outside of what the normal levels are by the lab, but they’ve increased their creatinine by 100% which indicates to us that we have a kidney at risk.
In conjunction with that, of course, as the urine output decreases, and we use the basic KDIGO guidelines in six hours we’re less than 0.5 mls per kilogram per hour after a six hour urine collection; those are times that we start being wary and we’re really now observing our patient. But I think the other aspect is in conjunction with the basic KDIGO guidelines and the basic RIFLE criteria that has been put forth by them; is to also recognize especially if we’re talking about patients in our current crisis with COVID-19, patients who have severe sepsis, to also recognize that in conjunction with the diminishing urine output, a diminishing glomerular filtration rate, an increasing creatinine, that we have to think about refractory metabolic acidosis. So, if I have metabolic acidosis that I am not explaining by ketosis, I’m not explaining by hyperchloremia and in the critical care unit then the other two obvious options are acute kidney injury and lactic acidosis. I think it’s really important to evaluate patients with refractory metabolic acidosis who are spiraling hemodynamically to consider the role of continuous renal replacement therapy early. And I think we need to consider that earlier than we do in general.
The bedside nurse’s responsibility and it’s a really extraordinary one is that from the time that renal replacement therapy has been order and the time that the vas cath gets placed, we should be operationalizing that as soon as possible. And one of the things that I talk about with the nurses is the more unstable your patient, the more that patient needs their renal replacement therapy. Because as bedside nurses, frequently when patients are unstable, we say we’re going to stop the renal replacement therapy, we’re mobilizing too much fluid, we’ve made the patient worse. The thing that’s so wonderful about continuous renal replacement therapy is you don’t necessarily have to pull fluid immediately with an unstable patient, but you absolutely need to normalize their electrolytes, their waste products, and most importantly, normalize their acidosis.
So, for bedside nurses, what I always encourage them to recognize is first and foremost, the more unstable the patient who has been ordered for CRRT, the sooner you need to get that going and the bigger the commitment you make to maintain it. and maintaining it also means that we understand the effects of clotting, clotting in the filter, clogging the filter with large mediators that are typically are inflammatory mediators and then our vas cath pressures which are both access and return. And a lot of what I talk about with the nurses and physicians is really tracking what’s occurring for your patient so you can intervene before they actually have clotted their filter and now you can’t return blood and now you have a whole lot of extra effort to get them back on CRRT and keeping patients on CRRT as close as possible to 24 hours a day is our standard goal.
Host: Yeah. so, you mentioned right there, some of the challenges faced, I guess what you might call some of therapy troubleshooting that has to go on with continuous renal replacement therapy, but I want to go into that a little bit more. Here you have a critically ill patient, there’s a lot of things going on, a lot of therapies being administered; what are some of the other challenges that you would like to bring up in this conversation besides say that the blood clotting aspect?
Barbara: Well the number one challenge and it’s one that we all face all the time, the most important challenge is maintaining good catheter, vas cath. And so I don’t want to use the word access, because access is the pathway that I use to remove the blood from the patient and then I bring the blood back to the patient. On either side of my catheter, so the removal or the return side of the catheter; I can have a clot, I can have a kink, I can have a position problem; but the most common issue is that it’s not a good catheter. It wasn’t placed in the right vessel; it may not have been the right diameter and it might not be the right length. And if you have a circuit issue with the catheter, with the vas cath, you’re going to have problematic CRRT and it’s going to alarm all the time. The blood pumps are going to stop. You’re going to have stasis of blood in the filter and now you’ve got to remove the filter, but you can’t return the blood. And we don’t want that to happen.
So, number one is catheter issues. And we know there’s a catheter issue because the display on whatever monitor we are using doesn’t matter, the display will tell us that we have access or return issues with high pressures. So, everyone at the bedside needs to pay attention to those pressures to assure that they’re not extraordinarily negative on the removal side or extraordinarily positive on the return side because that is telling you that you have a catheter problem. Now sometimes it’s just the patient’s position in the bed. It might be a clot in the catheter. It could be a kink in the catheter. And sometimes the catheter gets bent. And especially being a bedside nurse I know we really like our patients to be neat and we’re going to smooth out the catheter but many of our vas caths actually are meant to be bent over.
So, we always have to just be very knowledgeable about our catheter, catheter access and reminding ourself that unfortunately, for anyone who is cannulating patients for any reason; that the best place to put your vas cath, is in the right IJ which also tends to be the place that everyone wants to place a central line because it’s a direct path right to the right atrium or to the vena cava junction. And so, trying to preserve that right sided IJ, which is the number one preferred place for catheter access can be difficult. So, that’s I can tell you, that’s the number one challenge.
And the number two challenge is reminding ourselves that whether we are using citrate or heparin, that we need to anticoagulated right before the filter in order to maintain filter life and to reduce clotting. And that’s extraordinary that we have to do that, and we’ve changed very significantly in my hospital kind of our idea of anticoagulation with renal replacement therapy. And we use low intensity or high intensity heparin prefilter. We monitor it and we adjust it as appropriate. But we found that that has helped prolong our filter life. Except in extraordinary circumstance with people who are hypercoagulable such as patients in septic shock and patients in COVID-19 and then we have a much bigger battle trying to maintain their filter life.
Host: Yeah. You had said earlier that you really wish, hope that hospitals would be putting patients on continuous renal replacement therapy earlier. So, I want to touch on that just for a little bit. Is there a plan to teach ICU nurses and doctors that this should be done earlier? What’s your thoughts on that?
Barbara: One thing that we have learned with COVID-19 is we need to introduce patients to CRRT much earlier. And we have really made steps to doing a much earlier integration of CRRT into our therapeutic plan. And I hope that that will carry forward as we move beyond this pandemic, when we move beyond it that lesson will stay with us. I think that there’s oftentimes a lot of resistance to CRRT because it’s a significant intensity burden. It changes the nurses workflow. It’s significantly extra work and nurses extraordinarily and always want to do what’s right for patients. So, I – my impression overall would be with both nurses and physicians is to totally appreciate what the benefits of CRRT are, which I think most of the time folks think about it as fluid, waste, and electrolytes. But maybe not always appreciating how we can decompress the heart, how we can decompress the arteries, we can decompress the abdomen and the lungs by utilizing CRRT early to achieve a euvolemic state and to return patients to a more normal physiology.
I think that that’s a huge paradigm shift. It’s a paradigm shift in terms of work. It’s a paradigm shift in terms of understanding the philosophy of CRRT and appreciating CRRT just like you would appreciate a really organized mechanical ventilator. So, I think there should be a plan and should be a worldwide plan and I think that the KDIGO group with incredible persons like John Kellum and Runco, the thought leaders of nephron intensivists. I think they feel quite strongly that we should be looking at this sooner, but I think even within the nephrology group, we’re not 100% there yet.
Host: Well it sounds like you touched on the plan a little bit, right Barbara, that just the education side of it, teaching the nurses and the doctors that the continuous renal replacement therapy is – it goes beyond just removing waste as an example. It actually plays a major role in hemodynamic, vascular restoration. I mean I think maybe that’s that shift and that’s maybe that’s the plan. So, Barbara maybe you should come up with some education stuff. I think you’d be great at it. I can tell.
Barbara: Well thank you so much. I do a lot of discussion about renal replacement and it’s funny because I’m really – I think it all ties together, I’m really a self-proclaimed hemodynamacist. That’s really my area of interest and I have this burgeoning love affair now with the kidney and with CRRT especially as it relates to hemodynamic stabilization. And I think frequently, we start way too late, our creatinine’s are greater than four and our patient now has a base deficit of negative 17 and we have a lot of damage already because of alterations in vascular tone and blood flow, coagulation. I mean it’s not simple. It’s very complex. But I think that is my number one message is that renal replacement therapy should be introduced as soon as you see that you have refractory metabolic acidosis that’s not explained by ketosis or hyperchloremia. And not explained my some of the extraordinary things that can cause it but that are really related to both acute kidney injury and lactic acidosis. And that goes along with all our normal aspects as well.
Host: In summary, what would you like the audience to know about continuous renal replacement therapy in just a nice short couple of sentence statement? Go.
Barbara: I would like for all providers to be able to experience the ability to return blood to normal earlier, sooner to protect our patients, to bring them back to euvolemia and as much as possible, to a normal metabolic state, to actually significantly improve and impact outcomes long term.
Host: So, this concludes another edition of the iCriticalCare podcast. For the iCriticalCare podcast, I’m Dr. Mike. Thanks for listening.