Just a little clarification of my point on stKt/V as a unit of measure for NxStage and in center clearances. Not to defend the noted inadequacies of Kt/V in the least, but when we are looking at why some people including myself did not feel well on the standard starting dosage recommend by NxStage, I did find the stKt/V of use in comparing tow very different dialysis modalities. I suspect that Alaskagirl doing 5 hours 3 times a week, she is actually getting a higher clearance than her current 2.5 hours at 6 days a week and that may indeed be a measure she can take to her dialysis team as an objective measure that may have a correlation with her symptoms in addition to the fact that she is actually getting fewer hours of dialysis as well.
In my case, I had an incenter spKt/V of about 1.4 on most measures. On 20L of NxStage, my spKt/V for about 2.5 hours of dialysis was 0.5 and I felt TERRIBLE just as Alaskagirl has noted. In this instance, my stKt/V was less with NxStage and the daily frequency did not make up for the excellent clearances I was getting incenter. I took a look at the science of low flow solute removal with NxStage and hypothesized for myself that although time on dialysis is absolutely an important factor, but with the significantly lower clearances on NxStage, we are looking at different therapeutic curves that frankly have not been defined in the public medical literature available on NxStage. I thus hypothesized that I could improve my clearances to see if there was a clinical effect by increasing the dosage of dialysate beyond the standard recommended doses as well as increasing the dialysate FF to 45% which kept me below the theoretical 200 ml/min limit noted in NxStage literature for high dialysate efficiency.
I increased first to 30L at FF of 35% but still did not feel I had even returned to how well I felt in center on most days at nearly a 4 hour run, 5 times/week. I then went to 40L at 45% FF and only at that level of clearance did I feel better clinically than incenter. Had my unit not allowed me to increase my dosage to 40L, I would have absolutely quite NxStage especially on the days when I had no choice but to go two days without dialysis. I believe that what Alaskagirl is experiencing is related to the unique characteristics of NxStage which is unlike all other dialysis machines used to date which operate at much higher dialysate flow rates since I went through the exact same symptoms as she has related in her posts.
One of the most important markers of my treatments that I followed when starting on NxStage was PO4 levels which I had been able to maintain at an average of 3.5 without any binders while incenter conventional dialysis. My PO4 levels on the same diet jumped by nearly 30% even with 30L of dialysate and I could only duplicate my prior results when I went to the 40L at the same exact time factor of hours/week as I had on 30L. A recent article documents that NxStage has much lower levels of solute removal for each individual session that is made up by higher frequency, but it does not match the solute clearances of other home dialysis machines such as the Baby K:
The weekly treatment time for the patients averaged 17.4 h/wk, a figure higher than the average weekly treatment time embraced by many US in-center dialysis units where a thrice-weekly regimen is practiced. The removal rates and clearance values in the present study should therefore be interpreted in the context of increased weekly dialysis time. While the low dialysate flow rate reduces urea removal, the increase in the frequency of the treatments improves it. In the case of phosphorus and β2M, increased dialysis time is more critical for their removal and compensates for the low dialysate volume.
http://www3.interscience.wiley.com/cgi-bin/fulltext/122599527/PDFSTART?CRETRY=1&SRETRY=0
My continued use of the NxStage is that I have been able to improve most, but not all of my symptoms with the more frequent treatments which are now 5.5 times/week on average for a total of 23 hours. Time is an absolutely critical component of the NxStaqe equation and I was not in any manner trying to imply otherwise. An interesting aside is how the Scribner Dialysis Product with includes factors for duration of treatment and frequency squared has a linear correlation to the stKt/V which measure urea kinetics on a weekly basis and is the only way to compare urea Kinetics among differing dialysis schedules. Dr.John Daugirdas kindly pointed this out to me from his own calculations of both the stKt/'V and the dialysis product from the same data sets.
http://ureakinetics.org/files/hdp_vs_stdktv.pdf
So noting that the stKt/V does have a component of treatment duration and frequency within its calculations which correlate to the dialysis product, I do find it of a limited but very useful measurement to compare to my incenter treatments.
The bottom line is that Northwest Kidney Center among others already uses higher dialysate dosages and higher spKt/V goals for their NxStage program above and beyond the standard NxStage dosage recommendations. I simply took their approach and maxed out what I could do in a single “short daily” dialysis session of around 4 hours and I did have significant subjective and objective clinical benefits. The low flow dialysate strategies have a very scant body of literature and no long term clinical studies on how well they work. For me, the low dose recommended starting dialysate dosage of 20L left me feeling completely terrible compared to my incenter regimen and I very seriously considered quitting NxStage and returning incenter. However, I am pleased that I was able to increase both the time and intensity of my treatments to improve upon my incenter treatments. Northwest Kidney Centers employs this same strategy with excellent results. For the specific instance of NxStage, only looking at the time element does not tell the entire story since it has such reduced solute clearances compared to incenter single day clearances. It is my opinion and others that this will be found clinically significant in future studies.
The other issues mentioned by Dr. Agar on frequency and duration of total weekly dialysis treatments I strongly advocated for myself and the intentions of my first post were not to contradict that aspect what-so-ever. It is my personal opinion that the NxStage low flow dialysate standard doses are too low by at least a factor of 50% or more. In my case, I did not gain clinical benefit from NxStage until I increased my clearances by a factor of 86% when I compared how I felt with incenter. It is my opinion that NxStage should increase its standard recommended dosages especially in people such as myself over 90 kgs in weight.
As far as Blood Flow Rates, I have been able to reduce mine to 370 ml/min which gives me an arterial presurre of 120-140 and a venous pressure of 140-155 which is significantly lower than my incenter readings. I strongly disagree with the trend in NxStage programs to crank up the BFR to get the time on dialysis as short as possible. I was able to keep my time on dialysis near 4 hours each session by increasing the FF beyond standard recommendations with the permission of my nephrologist. I am a strong advocate of longer, slower and gentler dialysis and practice that philosophy with my own treatments.
As far as nocturnal dialysis, it is not something that I have completely ruled out in the future, but at present it has been quite stretch for my wife to be able to feel comfortable without undo stress even doing dialysis at home at all. One of the most important aspects of home dialysis is how it impacts the care partner. My wife simply feels uncomfortable with the idea of strapping me to a machine and going to sleep. She would simply stay awake all night checking on me and I respect her level of comfort for what it is. She is a very helpful and competent care partner, but I am sure that many care partners feel out of their element just having these machines in our house. If I did not respect her level of comfort, I am quite sure that she would quickly burn out and I would not be able to continue at home. I readily understand this issue since I did surgeries in my medical training but I didn’t have the comfort level that would be required to make that a daily practice. My forte was the problem solving involved in internal medicine. Understanding our care partners strengths and weaknesses is a critical aspect of home dialysis and it has been my goal to mitigate the burdens of dialysis on my wife as much as possible. I cherish her sleep and comfort as much as my own. She is simply not a candidate for a nocturnal dialysis care partner at present.
I would much rather be able to discuss clinical findings of NxStage dialysate dosages published in the medical literature, but they simply do not exist. The clinical relationship between very low urea clearances and mortality is well established with conventional dialysis and is the key factor on the minimum goals of 1.2 by Medicare which showed a significant survival benefit over a spKt/V of 0.9 which was the prior minimum goal in the past. Without the clinical studies to define the optimal NxStage dosage, we are stuck with surrogate markers among which I did find the stKt/V useful for my own treatment parameters. Once again, Dr. John Daugirdas has shown the linear correlation between stKt/V and the dialysis product. I did not reflect that known relationship in my prior post which may have inadvertantly implied my support of urea kinetics over treatment duration and frequency, but that is not and has not been my position for quite some time.
I apologize for not making my position more readily clear in the prior post.
With the upmost kind reqard,
Peter Laird