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APRIL 23, 2020 -- During a recent webinar by the American Society of Nephrology, Anitha Vijayan, MD, professor of medicine in the Division of Nephrology at Washington University School of Medicine in St. Louis gave a presentation on the Practical Aspects of RRT in Hospitalized Patients with AKI or ESKD. We asked her to share some of her insights with Medscape.
This interview was edited for length and clarity.
What are the indications for renal replacement therapy (RRT) in patients with COVID-19?
Anitha Vijayan, MD: The indications for RRT in patients with acute kidney injury (AKI) of any etiology are hyperkalemia metabolic acidosis volume overload, uremic manifestations such as uremic encephalopathy, or pericarditis. We also consider the severity of oliguria.
Are there any indications specific to COVID-19 or are they typical of ICU patients with AKI?
COVID-19 patients have a very high likelihood of respiratory failure and sometimes it's difficult to distinguish whether this is from volume overload or from pneumonia. Respiratory failure may be the driving force for initiation of renal replacement therapy in these patients, and maybe in that respect they tend to be a little different.
Do you recommend that medical management strategies be exhausted before using RRT?
If the only reason to initiate RRT is respiratory failure and fluid overload, we recommend a trial of loop diuretics first. Of course, diuretics should not be used if you suspect the patient is already hypovolemic, or if they have other indications for RRT such as uremic manifestation or severe hyperkalemia, etc.
Are you delaying RRT longer because of the shortage of machines or any clinical reasons?
I would say primarily for managing resources. Because if we start replacement therapy very early for all these patients, we will run out of machines and other supplies.
Is continuous renal replacement therapy (CRRT) the preferred modality?
CRRT is the preferred modality for any critically ill patient with AKI, especially those who have hemodynamic instability. That's the case, whether or not they have COVID-19.
Is there any preference for continuous convective clearance hemodialysis (CVVH) over continuous veno-venous hemodialysis (CVVHD)?
No. Convective clearance has not been shown to be superior to diffusive clearance, as far as patient outcomes are concerned. As I said in the webinar, you should use whatever modality is available at your institution.
What about resource-wise in terms of preserving dialysate?
In most cases the same prepackaged solutions are used either as replacement fluid (CVVH) or dialysate (CVVHD). Certain machines like the Tablo can generate their own dialysate, and can only be used for CVVHD, and not CVVH. But resource-wise, there isn't any reason to prefer one modality over the other. It all depends on whatever machines are available at your institution.
One of your recommendations is to decrease flow rates to maximize resources. Can you elaborate?
Typically for CRRT, we use an effluent flow rate of about 20-25 mL/kg/hr. That recommendation is based on the ATN and RENAL studies, published in 2008 in 2009, respectively, which compared lower flow rates to higher flow rates, and did not show any difference as far as outcomes are concerned. However, nobody has compared 20-25 mL/kg/hr to an even lower flow rate such as 15 mL/kg/hr so, 20-25 mL should serve as the standard.
What I was recommending is that once patients achieve metabolic control (stable electrolytes, acidosis under control), then you can consider lowering the flow rates to about 15 mL/kg/hr to conserve resources.
Does prolonged intermittent RRT allow you to treat more patients with one machine?
We use higher flow rates for a shorter duration with PIRRT. We do CRRT 24 hours a day, but with PIRRT you can potentially use the machine for two (10 hour treatments) to three patients (6 hour treatments) while allowing time to clean and disinfect the machine in between. To ensure they're achieving a reasonable amount of clearance, we increase the flow rate significantly to approximate a total of 20-25 mL/kg/hr for 24 hours. Essentially, you calculate the fluid requirement for 24 hours per day and divide that by the number of hours you're actually going to do.
You can do PIRRT on the same machine as CRRT and it allows one machine to be used for two or three patients but it still requires the same volume of fluids.
What about anticoagulation during RRT?
Anticoagulation is very important in COVID-19, not only in my experience but also from discussing with others across the country. Every single person told me that anticoagulation is critical in patients on RRT, otherwise the machines are clotting frequently and we're wasting filters and of course blood.
Systemic anticoagulation with heparin worked for us, but others have said that their patients were clotting despite heparin, and they've used regional citrate anticoagulation or direct thrombin inhibitors such as argatroban.
If your center is not using citrate already, I don't recommend starting it now because citrate is a complicated protocol, even in the best hands. In my opinion, implementing it hastily can be a setup for errors and patient safety issues.
What about vascular access?
It's important that the right length of the catheter be chosen for the right vein, and our preferred order for vascular access is the right internal jugular (IJ) vein, the femoral veins, and then the left IJ.
One of your recommendations was a cheat sheet for people who might not be used to placing these catheters, right?
Yes, we made a cheat sheet that we discussed with our critical care colleagues during our daily rounds and made sure it was available for them in the ICU.
Preferred Catheter Length (cm)
Right internal jugular
Left internal jugular
Do you recommend multidisciplinary rounds?
Yes, the multidisciplinary rounds have been extremely useful for collaborating with the critical care physicians taking care of these patients. We do them every morning, mostly with the critical care physicians from pulmonary or anesthesia.
What would you advise hospitals preparing for a surge — should they be purchasing/borrowing machines or stockpiling dialysate?
Nobody would recommend stockpiling dialysate because that means there's less availability for folks who really need it. I think the best approach is to talk to your hospital leadership to get projections of patient volumes for your institution, and try to prepare for that.
We were blindsided by the amount of acute kidney injury and the need for RRT because we did not get a lot of early reports about this from other countries. Initially all the talk was about ventilators. The incidence in the US of critically ill patients with AKI needing RRT appears to be about 25%. You could prepare for that volume at your institution.
Should centers be cross-training other specialties on how to set up and monitor RRT equipment?
I think cross-training is important. We are cross-training nurses in monitoring dialysis patients so that the dialysis nurses can take care of more patients. At our institution, we planned for that ahead of time, and addressed it in our planning documents.
You also showed some MacGyvering tricks for the machines.
I tweeted two photos. One was with a patient who happened to be on ECMO [extracorporeal membrane oxygenation], and the tubing of the ECMO is long enough to keep the Prisma-Flex machine outside the door.
The Prisma-Flex has an effluent bag that needs to be changed every 2 hours. One of our nurses took that bag and hung it up on an IV pole and let it drain by gravity back into the toilet inside the room instead of him having to stand by the sink and
I would caution that patient safety always has to come first. When blood tubing extensions are added, patients are at risk for hypothermia and blood loss. Patient safety always trumps any of these maneuvers.
Is there any concern about renal toxicity of the treatments for COVID-19?
I'm not aware of direct toxicity from these medications at this time, but, like most medications, whenever patients have acute kidney injury, the doses have to be adjusted to prevent other kinds of toxicity from medication accumulation.
Some of these patients will still need dialysis after discharge. Any concerns about that?
That's a very important point which we're seeing in New York. Even before COVID-19, I always told my critically ill patients and their families that the kidneys are the last organ to come back.
The need for dialysis always lasts longer than the need for a ventilator. These patients require dialysis after they leave the ICU, and sometimes after they leave the hospital. Transitioning them to outpatient hemodialysis facilities has been difficult in some situations, unless they're proven to be COVID negative. Facilities will accept them for treatment provided they have repeat testing to prove that they're negative for COVID.
Does that requirement mean you have to keep them in hospital longer than you would normally?
Yes. We may have to keep them longer to make sure that we have a facility who will accept them.
Another nephrologist suggested that kidney injury may be one of the top long term sequelae from COVID-19. Would you agree?
Possibly. Patients who suffer from AKI have long-term consequences, especially if they have severe AKI. So they may be left with chronic kidney disease. They will definitely need long-term nephrology care and close follow-up.
What about somebody who already has some renal dysfunction pre-COVID-19?
Any time you have underlying CKD and you have AKI on top of that, your prognosis is worse than if you had just AKI.
The other population that we didn't discuss much is the end-stage kidney disease population — these patients are already vulnerable to infections, as they tend to be older, and to have a weaker immune system. They are also more exposed because they're sitting in a facility with other patients three times a week for dialysis.
We've had patients with end-stage kidney disease contract COVID-19. As far as their outcomes, I don't think we have enough data to say how they fare compared to patients with COVID and acute kidney injury.
Is there anything else you would like to tell our readers?
I would say that managing kidney disease in COVID patients has been extremely challenging for everyone across the US partly because we were not prepared. It is somewhat surprising to me that we didn't hear more about the nephrology aspects from other countries who were hit before the United States. And we still need to learn more about the exact pathophysiology of the AKI from COVID-19 and its long-term sequelae.
Anitha Vijayan MD is on the Scientific Advisory Board for NxStage Fresenius Medical Care.
Tricia Ward is an executive editor at Medscape who primarily covers cardiology and nephrology. She is based in New York City and you can follow her on Twitter @_triciaward