Re: how to model blood volume change during and after hemodialysis?
Hello,
In terms of how long it takes to restore blood volume, i think it should be
immediate because they usually give fluids during the dialysis to replace lost
blood volume. Otherwise, there will be a significant drop in BP. You may have
the volumes of fluid given in the patient charts if you have that.
In terms of changing volume you can do that in two ways:
1. If you have serial measurements of patient body weight, you can link that to
volume as a covariate and it will change with change in weight (time-varying
covariate). But this needs hourly or even more frequent weight measurements.
2. You can model the change in volume with time using a simple linear slope
model where volume decreases with time during dialysis and increases with time
after dialysis and estimate the slope for each process. However, i think this
will be difficult to estimate separate from changes in clearance and the slope
estimates you get will just be arbitrary. If you have samples from dialysate,
it might be better.
I hope this helps.
Quoted reply history
----- Original Message -----
From: "Nele Kaessner" <[email protected]>
To: [email protected]
Sent: Friday, January 18, 2013 8:24:05 AM
Subject: [NMusers] how to model blood volume change during and after
hemodialysis?
Dear nmusers,
I would like to model PK profiles of a compounds which mostly distributes in
blood volume. The subjects which were investigated underwent hemodialysis for
approx. the first three hours after infusion start, and the compound was given
over a time period of ~5-10 min.
It is well known that during hemodialysis, blood volume changes. Therefore, I
would like to add a dynamic component to the central volume parameter, allowing
it to decrease during hemodialysis and then to reincrease after dialysis has
ended. I have all information about start and end time of both dosing and
dialysis. Individual times between subjects differed. Unfortunately, I have not
been creative enough to come up with a NONMEM code that can do this. Could any
of you help out?
Also, I probably do not have late enough time points to estimate when exactly
blood volume would be restored. Does anyone know how much time the body needs
after dialysis has ended until it is back to the original blood volume?
Thanks for your help and best
Nele
______________________________________________________________
Dr. Nele Käßner
Principal Scientist Modeling and Simulation
Global Pharmacometrics
Experimental Medicine
Takeda Pharmaceuticals International GmbH
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8152 Glattpark-Opfikon (Zürich)
Switzerland
Visitor address:
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