As previously reported, I had a Dialysis Team meeting this past Friday. All team members were present – my Renal Doctor, Social Worker, Dietician and Nurse. Before the meeting started, my Dialysis Nurse Cindy mentioned Fresenius had a program to calculate the optimum dialysis solution amount and dwell time but she could not run it because it only ran on Windows 7 which they no longer had access to. Subsequently I volunteered to provide a Windows 7 notebook but have not heard back as of this writing.
This got my thinking, if an algorithm had been developed in the past, it should be available to port to newer systems. So I did a Google search on “Peritoneal Dialysis Algorithms” and came up with what I thought I needed. In a 2020 article in Sage by Chang Yin Chionh et all (link), the graphic above and the following equations were extracted. This article provides the equations we need to calculate both the volume of fluid to use given a target adequacy target (Kt/V) and/or Dwell time.
The top portion of the lead graphic portrays the interconnection between the measurement of how well PD is working, that is Kt/V, and the variables that influence this value incorporated in the prescription, that is # of cycles, dwell volume, and dwell time. These values “influence” Urea which in turn feed into the calculation of Kt/V, which we want to keep at or above 2.0 in my case.
The following screenshot is from the section of the cited article wherein equations are presented to calculate dialysis volume and/or time given a target Kt/V.
Interestingly, at the end of the linked article there is a downloadable Excel spreadsheet that accomplishes their calculations very well. However, there is one big problem that precludes using this article for my particular case. In the fine print it states that their model, or algorithm if you will, is only valid for cycle times of 1 to 4 hours (I am on 2 hours per cycle so we’re OK here) and 6-24 cycles (I am on 4 cycles so the model restrictions fail here.)
Neglecting failure of the cycle restrictions, I ran my numbers anyway, and came up with I should be using 1.17 liters of fluid in 12 cycles to obtain a Kt/V of 2.0, the lower bound. I am currently using 2.0 liters of fluid in 4 cycles and have a Kt/V of 1.67.
Stay with me, we’ll figure this out. I’ll search for more algorithms that accommodate my particular situation and seek to optimize my prescription. Nobody said it would be easy I did learn that there is an entire publication, Peritoneal Dialysis International devoted to peer reviewed research into the subject so all is not naught!
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