Levin A, Goldstein MB
The benefits and side effects of ramped hypertonic sodium
dialysis
J Am Soc Nephrol
(Feb) 7:242-246 1996

Sodium gradient dialysis has been around for a long time, although its
benefits have not been conclusively determined by controlled studies. Levin
and Goldstein took 11 symptomatic and 5 asymptomatic patients, developed a
sodium gradient profile for each designed to minimize thirst, and then
dialyzed for 3 weeks with "ramped" sodium dialysis (basically 155-160 to 140
mM sodium) and for 3 weeks with conventional (140 mM sodium dialysis). In
some patients, number unspecified, UF was also ramped, with 50% of the
ultrafiltrate removed in the first hour. The patients and symptom assessors
were blinded as to choice of treatment.
There was no difference in blood pressures predialysis, nor differences in
intradialytic hypotensive episodes. Patients had less headache, hangover,
and cramps during ramped dialysis than during standard therapy. 81% were
more thirsty on ramped dialysis, but intradialytic weight gain was only
slightly, and not significantly, increased.
Comment: This study is interesting in that it preselected patients
with headache, hangover, and cramps. These symptoms were the major ones
improved during ramped dialysis. In my own experience, cramps certainly are
improved using this method. I find it difficult to believe that
interdialytic weight gain was not increased, although if the patients limited
their sodium intake during the interdialytic period this is possible.
Usually, any increase in the integral of the dialysate sodium concentration
predictably results in an increased interdialytic weight gain. It is almost
impossible to really blind such studies over a 3 week period. The combined
use of "ramped" UF is interesting, and use of ramped UF even in the absence
of sodium modeling may be of benefit. See also Raja and Gonzales, ASN
abstract, p. 611, J Am Soc Nephrol, September 1995, vol. 3. (John T.
Daugirdas, M.D., University of Illinois)
Further comments from one of the authors, Dr. Marc B. Goldstein,
(University of Toronto, Ontario, Canada):
The patients indeed did not gain more weight during the ramped sodium
treatments. I assume this was because of the effort made to tailor
the treatment to minimize thirst. However you are correct in the
inference that they took in less salt during the ramped sodium period.
This is evident from tables 1 and 2 in the paper. The patients go off
dialysis with a serum sodium level [Na] 4 mEq/l higher than when they
were on standard therapy. Yet they gain a similar amount of weight
and return with [Na] only 1 meq/l higher than when on standard
therapy.
Some simple calculations show that the patients must therefore have
HALVED their Na ingestion while on ramped sodium dialysis (RHDS) as
compared with when they were on standard dialysis (SD): On SD they
gained 2 kg between treatments with no change in [Na]; i.e. they
ingested the equivalent of 2 liters of normal saline. On RHSD their
[Na] fell from 140 to 137 between treatments, requiring 1 liter water
(in a 70 kg pt), in addition they gained a total of 2 kg between
treatments so they ingested the equivalent of 1 liter water and 1
liter saline between treatments; i.e., they halved their Na
ingestion.
Clearly the important question is WHY? The data are consistent and the
patients received no special instructions. Both patients and the
physician making rounds were blinded. One possibility is, that RHSD
reduces the drive to ingest Na. I would be interested in other
thoughts.