All right, you guys, welcome back to another video lesson from ICU Advantage. If this is your first time to the channel, welcome. If not, welcome back. And for those of you who don't know me, my name is Eddie Watson.
Alright, so this is going to be a continuation on the series here talking about CRRT and really explaining what this therapy is. In the second lesson here, what we're going to talk about is what exactly CRRT is. I'm going to explain what the therapy is, why it is that we use it, and give you some basic info really about the therapy and the setup of everything. Over the next few lessons, we're going to dive deeper into the principles and the type of therapy that we really can offer these patients, so make sure and follow along and stay tuned.
So on that note... I really started Icy Advantage to try and create some of the the best online free critical care education content that was out there. So if you'd be interested in getting more of this content, please make sure and subscribe to the channel down below.
If you do though, make sure you hit that bell icon that way you'll never miss out on whenever I release a new lesson. All right, and so let's go ahead and get started here. And let's start off talking about what exactly is CRRT. So CRRT stands for continuous renal replacement therapy. And so CRT is a therapy that really is in the same class as our intermittent hemodialysis IHD or our peritoneal dialysis PD.
And so what CRT is designed for is for the critically ill patient who oftentimes is unable to tolerate the rapid short iterations and the accompanying fluid and electrolyte shifts that we typically will see with intermittent hemodialysis. And so as its name suggests, instead of the typical three to four hour runtimes that we see with normal dialysis, CRT is running continuously 24 hours a day. And so this is going to be better tolerated by our unstable patients. And so just as with regular dialysis, the goal of CRT is to remove toxins, excess fluid, and really balance our electrolytes. And our goal is to mimic the job of the failing kidneys.
It does this by reproducing the various functions that we saw in the nephron that I talked about in that first lesson. If you haven't watched that lesson, I'm going to link to it up above here, so make sure you check that one out to really have a good understanding of some of the stuff that we're going to talk about here. Now it is important to know though that not all facilities offer CRT. Oftentimes in these cases when we have these critically ill unstable patients is we're going to offer them a different type of therapy that we call SLED, which stands for slow low efficient dialysis, and these are runs that last anywhere from six to eight hours and are oftentimes done every single day for these patients. So as you can see, that'd be a pretty resource and time-heavy commitment for these patients, but in facilities where you just don't have a CRT available to you, this is a really good option for these unstable patients.
Now, in order to operate the CRT machine, as well as to take care of the patient that's receiving the therapy, it really requires specialized nurses who have been trained in this therapy, as well as the physiological impact that this therapy is going to have on the patient. Now, these patients are often very sick and, to be honest, quite time-consuming. And in many facilities, these patients who are on CRT are staffed as one-to-ones. And so the next question we want to ask is, why is it that we use CRT? And so I really hit on some of this already, but we're going to use CRT in the critically ill unstable patient who have AKI or acute kidney injury and are in acute kidney failure, or in patients who are end-stage renal patients who receive dialysis who are also too unstable to receive normal IHD.
And then just to list out some of the main indications for renal replacement therapy, which would also include CRT in those critically ill and stable patients, are going to be things like elevated toxins, so our creatinine and BUN, fluid volume overload, severe electrolyte imbalances, and some acid-base imbalances. Now those are the primary indications, but we also find that we can use CRT for patients in sepsis to aid with the cytokine clearance, patients who have rhabdomyolysis. CHF, and even post open heart surgery. And then given that these patients are pretty sick, typically these patients are going to be hemodynamically unstable and they're going to be requiring pressors to maintain an adequate blood pressure. And one of the really nice things about CRT is that because it's continuously running, we can make changes to the therapy at any time.
And so we can adapt to really rapidly changing situations that are being presented with these critically ill patients. So that's kind of the quick down and dirty on what really CRRT is and why it is that we're going to use it. And so then let's move on and talk about really the basics of the machine and the circuit setup for running these patients on CRRT. So what we're going to do is we're going to talk about the arrangement of the machine and the circuit and really how it is that we run the therapy through here.
There are different types of therapy, which use some or all. the parts that I'm going to talk about here. And I am going to discuss those in the next lesson, but for now let's just review the entire setup. Now there's really three main machines that are used most often.
Four if you want to count the the most recent upgrade to one of them. And honestly there there may be others, but these are the three that I've seen. Now the first and most popular of these is actually going to be by a company called Baxter.
And this is going to be the more common and older machine, which is the Prismaflex, as well as their new Prismax. Then we have the Edwards LifeScience Aquarius. And I believe this machine and its business was actually purchased by Baxter some years ago. So these might be just eventually working their way out into the newer Baxter machines.
And then the other one is going to be something called Next Stage. Now each facility that I've worked at has used the Baxter Prismaflex. And then now we're starting to get in some of the new Prismax machines. The Aquarius is actually very similar in the machine configuration to the Prismaflex Prismax. Now I did spend a little bit of time moonlighting at a facility that used NextAge.
I didn't get to the point to where I was actually doing this therapy on those patients there, but this machine seemed simpler to use and required less work from the ICU nurse from what I saw. Now the operation of the NextAge was slightly different than what I was used to with the PrismaFlex, but really the basics I'm going to talk about here and the principles discussed in this lesson, as well as the next couple lessons, are still going to apply to nurses who are running therapy through that machine. Now with all that said, I'm going to base my example here on the Baxter machine.
And honestly part of this is because of the simplicity and really just the availability and the wide use of this machine, as well as just my personal experience and knowing this machine much better. Now again, each of these machines essentially has the same parts or really functions in much the same way. Alright, so when we talk about CRT therapy, the first thing that we have to talk about is our access.
In order to operate, we need to be able to remove blood from the patient, run it through our CRT machine, and then return that filtered blood back to the patient. Now, most patients that are going to be running with this are going to be newly placed temporary catheters. And these are typically 12 or 14 gauge double lumen catheters. And these catheters are going to be placed in a vein, most commonly in either the internal jugular, subclavian, or femoral veins. Now these can be either tunneled or non-tunneled, but again typically most are not going to be.
And so for our example here I'm going to have a right IJ double lumen HD line. Now on this catheter there is going to be an access and a return line on the catheter, and typically these are going to be color-coded red for access and blue for return. And so for this catheter we really want to make sure that we're using the proper ports that are going to our circuit.
And to really help better illustrate this let me draw a quick example of what the catheter is like internally. And so what happens is we have the return lumen that's exiting at the distal part of this catheter and then the access line is going to draw from more proximal ports. And the reason that this is is that we're trying to minimize drawing any already filtered blood back into the system, which if we do that is really just going to reduce the efficiency of what our run is able to do. All right so now that we have the talk about access out of the way, the first part of the machine that I actually want to talk about is going to be the blood pump.
And so this pump here is a roller pump. and this is going to create negative pressure on the patient side to draw blood from the patient and then positive pressure on the machine side to drive that blood through the filter and then return it to the patient. Now for the blood pump typically we're going to see blood flow rates that are anywhere from 150 to 300 milliliters per minute but we can actually have much higher flow rates that that can be achieved with this although we typically aren't going to run the therapy this way.
Alright, so next thing along on the machine that I want to talk about is going to be our actual filter. And this filter is actually going to be very similar to a typical dialysis filter. And for these, there are different types that have slightly different purposes.
But the one thing that they have in common is they're actually filled with thousands of hollow fiber membrane tubes. And I'm going to put up a picture here to hopefully show you kind of what that actually looks like. And if you really look at it up close, it really looks like thousands of tiny hairs.
And so what we get is the blood flows up from the bottom to top inside of those tiny fibers. And it's here in this filter where all the magic is going to be taking place. All right, and so now we're going to have filtered blood that's now coming out of our filter here. And the next stop is to go through some sort of air removal, or in the case of the Baxter, this deaeration chamber.
It's going to continue on from there and then it's going to reach the safety clamp. And the safety clamp is really going to be the the last stop. if it detects air or some other critical issue that's really going to stop the machine and stop the blood flowing to the patient. Now one thing to note real quick is I did draw this with red and blue, which typically we see when we're talking about circulation in the body denoting oxygenated and deoxygenated blood, but that's not the case here. We're going to have the same oxygen content of the blood that's coming out of the filter as what first went into it, but these are the the color schemes that these machines use to really identify which is your access line and which is your return line.
So like I said the access is going to be red and that return is going to be blue. So now let's actually talk about some of the different fluids that we use and the pumps that help to drive all this. Now on this system there's three different types of fluids that we can use and each is going to have its own dedicated pump.
And I'm going to color coordinate these with the same colors that we see again on the the PrismaFlex machine. First we have our pre-blood pump. which is our pre-replacement solution. Then we have our dialysate and then we have our post-filter replacement fluid. So first let's talk about the dialysate here.
So this is going to flow with the help of our pump to the top of the filter and this is going to flow top to bottom in the filter on the outside of those hollow fibers carrying the blood. And then this now filtered dialysate is going to exit the bottom of the filter in what we call the effluent line. Now this effluent drainage is actually going to be controlled by another pump, what we call the effluent pump.
And it's really this pump that is going to be responsible for pulling the plasma water out of the patient's blood across that filter membrane. Again, this is going to be something I'm going to talk more in depth into the next coming lessons here. But so the effluent is going to move past the effluent pump and then make its way to the effluent drainage bag.
All right, so now let's go on and talk about the pre-blood pump or the pre-replacement fluid. And this one's actually going to travel a long way. The pump is going to move it along and it's going to connect with the access line just after we draw the blood from the patient. And therefore, we're going to be infusing this fluid before it gets to the filter. And then finally, we have our post-filter replacement.
And so again, we're going to have the pump that's going to move this fluid along and it's going to meet up in the case here right at the point which the blood is going into the deaeration chamber. And so then this means that this fluid is being mixed with the blood. after the filter and just prior to going to the patient.
Now when we talk about these different replacement fluids and the dialysate, there's many different types of solution that we can use for these fluids. Now we do have pre-made solutions for this that actually have like particular balances of electrolytes and bicarb or your pharmacy can mix up special bags or even you can use some various standard fluids in certain cases. So again I'm going to discuss some of those differences on when and why you would use them in the later lessons in this series.
Now one last bit of solution or fluid that we really could include in this system is going to be our anticoagulation. And this is actually going to be a topic that I'm going to dedicate an entire lesson to. But know that there is an option to use a heparin syringe or some other form of anticoagulation to be given to the blood prior to entering the filter.
And typically this is If we're using the syringe pump, it's going to be just prior to the filter. Or in other cases, we actually put a Y connector up on the access line and infuse it way back there. All right, the next important part of this whole circuit in this setup is actually going to be our pressure monitoring. So we monitor the pressure at various points in the system.
And there's really four main pressures that we're monitoring. First, we have our access pressure. And this is going to be the pressure required to pull the blood from the patient.
And this one's... always going to be negative. Next we have our pre-filter pressure and this is going to be the pressure required to move the blood up through those hollow membrane fibers.
This one's always going to be positive. And then we have our return pressure and then this one's monitoring the pressure required to return the blood back to the patient. And again this one's always going to be positive. And then finally we have our affluent pressure and this is going to be the pressure required to pull the plasma water from the blood. Typically this one is going to be negative but From time to time it can be slightly positive.
Not usually though, and in most cases you're going to have a negative value here. And so this here is the the basic overall setup of our CRT machine and our circuit, what different parts and fluids we have coming in and where they're going in, and kind of what's happening at various points along the way within this machine. Now I know it looks kind of crazy on here, a lot of things going on, but as we go through the next few lessons here I'm really going to be talking about the different types of therapies and the way that we run the machine.
You'll have a good understanding of why it is we would do certain things at certain points to really help and aid in the process of filtering our patient's blood. So hopefully this lesson, though, at least gave you a good understanding of, again, what exactly CRT is, the indications and why we're using it, and then give you a good overview of how this circuit is set up so that as we talk through some of these next steps, you'll have an understanding of where this stuff is taking place. Alright, and so as always I really hope that you guys found this lesson useful. If you did, please go down below the video, hit that like button, it really helps this channel out in terms of the YouTube algorithm.
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We'll see you in the next lesson.