Nephrologists Unite: Time to Put the 't' back in Kt/V.

Joel D. Glickman, MD


December 27, 2011

K.R. transferred to my dialysis facility, and after briefly reviewing his records, I braced myself for the inevitable argument. He had been on dialysis for about 2 years and had no residual renal function. Yet his dialysis treatment time was 3 hours. I prescribe 4-hour treatments and recommend even longer treatments. I knew exactly what K.R. was going to say: "Doc, my Kt/V is 1.4, and I don't feel well during the last hour of treatment. I have things to do, I hate being on the machine, and my last nephrologist said as long as my Kt/V was OK, 3 hours is just fine. I've been on dialysis for 2 years, I feel well, and I don't need to change." Is 3 hours "just fine" if Kt/V is at target? If not, where did this myth come from?

It all started with the NCDS published in the New England Journal of Medicine in 1981.[1] This study randomly assigned just 151 hemodialysis patients into 4 treatment groups to measure the effect of 2 variables on survival: time on dialysis (short or long) and time average urea concentration (high or low). The authors of the study concluded that morbidity was worse in the group with high blood urea nitrogen, but time on dialysis was not a significant determinant of outcomes. Patients who received longer dialysis treatments had a trend to less time to first hospitalization, but the P value was .06.

Commenting on the article, Chertow and colleagues said, "It is difficult to conclude from the NCDS that session length is not meaningful; the authors presciently stated that the study conclusions should be interpreted cautiously, given the design and limited powers of NCDS. In retrospect, one might argue that the NCDS' session length P = .06 was the most significant (important) "nonsignificant'" (statistically) effect in the history of dialysis research."[2] Regardless of the interpretation of the study results, we must recognize that the long treatment time was 4:30 + 3 minutes and the short treatment time was 3:15 + 3 minutes. The effects of shorter treatment times, such as the 3 hours K.R. was prescribed, were not studied.

Observational data supporting the benefits of longer treatment times are abundant. Data from the DOPPS demonstrate that compared with treatment time >4 hours, treatment times of 211-240 minutes and <211 minutes had a 1.19 and 1.34 relative risk for mortality, respectively.[3] Similarly, in a study of dialysis patients from New Zealand and Australia, patients receiving < 3.5 hours of dialysis per treatment had a relative risk for death of 1.75 compared with the reference group that received 4-4.4 hours of treatment. Patients receiving more than 4.5 hours of treatment had a decreased relative risk for death of about 0.7.[4] More recently, Brunelli and colleagues[5] studied a national cohort of 8552 incident hemodialysis patients. The study reported a 42% increase in mortality for dialysis patients with session lengths less than 4 hour. But there was also a dose-response relationship between session length and mortality. Patients receiving 181-239 minutes of dialysis had an approximate 35% increase in all-cause mortality, and patients whose dialysis sessions were < 180 had a 60% increase in mortality.

So, what should we do with K.R., and what is the problem? For certain, he needs more education. As medical director, I also need to educate my staff, both nurses and patient care technicians, about the hazards of shortened treatment time so that they can consistently and persistently deliver the correct message to patients and their families. Maybe I need to distribute literature so patients like K.R. can understand the benefits of 4-hour (or longer) treatments and be able to make the right decision. But the problem is not just K.R.'s survival. The problem is that any patient within earshot of him, either in the dialysis unit or waiting room, will start asking for shorter treatments, too. I am going to have a rebellion on my hands. So it is time for nephrologists to unite. Stand firm: Minimum treatment time is 4 hours. That's the rule -- no negotiating. Prescribing shorter treatments is prescribing shorter life expectancy for hemodialysis patients. Let's take the time to educate our patients and staff about the benefits of time when we prescribe the appropriate time of hemodialysis treatments.


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