HDCN Article Review/Hyperlink

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.