Although I recognize that being misunderstood is an unavoidable side effect of joining chat rooms, it makes me sad to be accused of underhanded motives. I honestly have no ax to grind. I work for neither NxStage nor Aksys. Since I read here that some of you were soliciting opinions from dialysis professionals, I am simply trying to contribute. Nevertheless, I understand why there may be concerns and will try to address some of them.
While my last posting definitely contained opinions, it did not contain any statements that were deliberately false or misleading. They were all based on information reported in the scientific literature. I did not cite many of these points because I did not think the patients who read this board wanted it turned into a scientific journal.
The information I provided regarding the expected nutritional outcomes is based on a validated computer model that uses the equations that are generally accepted by the renal community. I based my figures on the standard hyopthetical “average sized male”. It is fairly well known that certain patients actually reach a higher weekly standard Kt/V than predicted - but that is usually due to the fact that (at least in the USA) heavier people usually are heavier because they have a higher than average amount of body fat, in which urea is not well distributed. In other words, their actual V (volume of distribution of urea) is lower than the value used in standard Kt/V equations, which base V on lean body weight.
Since Dr. Hull brought up the HEMO Study and the Kt/V targets published by K-DOQI, I would like to briefly discuss these topics.
The first thing you should understand about the K-DOQI target for dose of dialysis is that it is a floor, not a ceiling. The target is a value below which there is a reasonable likelihood that you would start to show symptoms of under-dialysis. So when someone tells you that you are receiving an “adequate” dose of dialysis as defined by DOQI, you might want to ask why you cannot have an “optimal” dose, i.e. that dose above which no further clinical improvement would be expected.
The second thing you should know about this dose target and Kt/V in general is that it only applies to urea - a small molecule easily removed by dialysis. Studies long ago showed that urea is not particularly toxic and that when infused into normal people in high doses, does not cause uremic symptoms. It did, however, in the same study cause normal people to reduce their protein intake. Thus, there is some question as to just how relevant urea is as a marker of uremia.
The HEMO Study was a major, multi-center, randomized clinical trial aimed at identifying what difference in martality would result when one large group of patients was dialyzed at the prevailing target Kt/V and another group of patients was dialyzed at a somewhat higher dose. The result was - there was absolutely no difference. The most plausible explanation that I’ve heard at scientific meetings as to why there was no improvement with “more” dialysis is that when you’re receiving thrice weekly dialysis (as all HEMO Study patients were), increasing the Kt/V in the range that was selected should not have been expected to result in much of a change in significant clinical outcomes (like mortality). Since the advent of daily dialysis, we now know we should be comparing modalities on the basis of a newer parameter called “weekly standard Kt/V”. If one looks at the difference in that measurement between the experimental and control groups of the HEMO Study, one sees that there is a miniscule difference. On the other hand, if one were to switch patients from 3 to 6 days of dialysis per week while keeping the number of total hours of dialysis per week constant, the increase in weekly standard Kt/V would be much larger. This is because the largest amount of wastes are cleared in the first hour of dialysis - and 6 first hours are more valuable than 3.
This is why the NxStage patients in their clinical trial reported feeling better and eating better. Switching to any form of daily dialysis from thrice weekly dialysis will result in major positive clinical outcomes. Thrice weekly dialysis is a subsistence treatment; it is not designed to return you to a level of health and energy that will enable a near normal life and return to work. It was originally designed as a holding therapy until the person could receive a transplant; then Government funding came along and froze the pattern.
That daily dialysis at very low dialysate volumes results in significant clinical improvement has been known for over twenty years. One of the pioneers of daily dialysis, Dr. Buoncristiani in Italy, dialyzed 22 patients from 1982 to 1988 on a daily basis (7 days per week, 90 minutes per day, weekly Kt/V=1.5-1.7). He did this by cobbling up a homemade dialysis machine that stored 25 liters of dialysate in a plastic jug. In his published results, he reported significant improvements in a long list of clinical parameters.
As interesting as that experience was, it may be of equal interest that he later converted all of those same patients to 2 hour dialysis sessions using conventional single pass machines which allowed him to increase the weekly Kt/V to 3.0-3.5. The results were further dramatic improvements in all of the previously measured parameters plus improvement in several additional areas, such as bone disease. The point is that daily dialysis - even using a very low dialysate volume - is a big improvement over thrice weekly treatments.
However, it is a fundamental law of nature that you can’t remove as much nitrogenous waste product from the blood using 19 liters of dialysate flowing through the dialyzer at 100 ml/min as you can with 50-150 liters of dialysate flowing at 500-800 ml/min, such as you get with the Aksys PHD or any other hemodialysis machine like the Fresenius Baby K or the B Braun or the Baxter Arena system. It is also a matter of chemistry that if you remove less nitrogenous waste products from the blood on a daily basis (as you would for example if you switched from daily treatments with the Fresenius Baby K to a NxStage System One), one of two things has to happen: either the level of nitrogenous wastes in your blood has to go up or you have to eat less protein to keep them low.
One additional point: Dr. Hull did agree with the emphasis I placed on solution purity and biocompatibility. He pointed out that there are multiple approaches to this issue and that NxStage had chosen to use bags of heat sterilized dialysate. Sterile dialysate is a good thing but heat sterilized dialysate is less good than cold filtration sterilization because it results in a lot of heat-induced byproducts of both the dialysate itself and of the plasticizers that keep the bags transparent and flexible. Most of the conventional dialysis machines manufactured in recent years have taken the cold filtration route by placing a depyrogenation filter in the dialysate line just prior to the dialyzer. This creates “ultrapure” dialysate. Aksys has taken that one step further and produces “injectable quality” dialysate.
I could go on but this message is, once again, too long. Sorry! But I hope it is helpful to at least a few of you. I want to help disseminate as much information to you as possible so that you can make the most informed decision possible. I can see why some of you may have viewed my previous contribution as being biased. If I am biased, I would like to think that it’s because I have considered the information available in the medical literature, at nephrology symposia and from personal experience and drawn conclusionas as to how I would dialyze myself if I contracted chronic kidney failure (my father’s mother and sister died of polycystic disease).
I would like to give you one more piece of advice regarding the dialysis professionals whose advice you are soliciting. Do as they do, not as they say. In other words, look at the dialysis professionals who do end up with kidney failure and see how they have elected to dialyze. At this moment, I am aware of three nephrologists who have had to go on dialysis in the past three years and they chose to use the PHD. I am also aware of one pediatrician using the system. There may be nephrologists using NxStage or Fresenius systems but I am not aware of them. As for me, I would not leave my nephrologist’s office without asking this question: if it were you, what would you choose?