Schneditz D, Zaluska WT, Morris AT, Fan Z, Kaufman AM, Levin
NW
Effect of ultrafiltration on peripheral urea
sequestration in hemodialysis patients
Am Soc Nephrol
J Am Soc Nephrol (abstract)
(Sep) 7:1525 1996
The rate of removal of urea during hemodialysis is partly dependent on the
rate at which urea is transferred from peripheral parts of the body into
the fistula. This inter-compartment urea transfer should be partly
dependent on blood flow and is also responsible for the post dialysis urea
rebound. In theory, ultrafiltration should reduce cardiac output and
regional blood flow. This should reduce the inter-compartment transfer
rate, causing urea to be retained in the periphery and increase the
post-dialysis rebound.
Five patients were entered into a prospective case-controlled study to
compare the rebound after dialyses with and without ultrafiltration.
Patients were studied over two consecutive hemodialysis sessions. The
first was performed conventionally with about 1 litre/hour
ultrafiltration. The second was performed without ultrafiltration.
Following the second treatment, the patient received isolated
ultrafiltration to return him to dry weight.
In the patients studied, the rebound (calculated from (Ct-Ceq)/C0) was 14%
less when the dialysis was performed without ultrafiltration.
Comment: Since only five patients were studied, any conclusions are
tentative. The inter-compartment and rebound effects reduce the mass of
urea removed during dialysis by about 12%. If the rebound is increased by
14% by ultrafiltration, this will reduce the mass of urea removed by a
further 2%. Although this will not be clinically significant, the
phenomenon does support the hypothesis that inter-compartment urea transfer
depends, at least in part, on hemodynamic factors.
(James Tattersall, M.D., United Kingdom)
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Am Soc Nephrol
Basic hemodialysis :
Adequacy, prescription, urea kinetics