WILLIAM CLARK
The clinical effects of varying prescription parameters,
such as treatment flow rates and frequency, were discussed during the “Hemodialysis Kinetics”
session chaired by William Clark, MD, Baxter Healthcare Corporation, McGaw Park, Illinois. Dr.
Clark described a recently developed two-compartment model designed to assess the effects of
variable treatment flow rates and frequency and duration on solute removal. The model employed
Casino’s equivalent renal clearance (eKR) to quantify the effective (i.e., rebound-corrected)
removal of solutes over a broad spectrum of molecular weights.
Ken Leypoldt, PhD, research biochemical engineer, VA Medical Center, Salt Lake City, Utah,
summarized some recent work from his laboratory exploring the effect of dialysate flow rate on
in vitro small solute (urea and creatinine) mass-transfer area coefficients (KoA). He reported
that a decrease in dialysate flow rate to below the standard value of 500 mL/min results in a
decrease in small solute KoA values for high efficiency dialyzers, because at low dialysate flow
not all fibers are separated and the effective surface area is decreased. These data provide
additional evidence that dialysate perfusion of dialyzer fiber bundles and, consequently, the
efficiency of dialysate mass transfer for small solutes, is directly related to dialysate flow
rate.
Marcia Keen, PhD, RN, Amgen, Inc., Thousand Oaks, California, provided a comprehensive
review of the issue of optimal dialysate sodium concentration for patients receiving various
hemodialysis regimens. She presented new data confirming prior studies that the optimal
dialysate sodium concentration is a very patient-specific parameter. Hemodialysis is better
tolerated if dialysate sodium concentration is similar to the patient’s serum sodium
concentration.
Naomi Dahl, PharmD, of the Robert Wood Johnson Medical School, New Brunswick, New Jersey,
provided an overview of the factors influencing drug dosing in different hemodialysis regimens.
The multicompartmental distribution of drugs and the importance of considering the effect of
posthemodialysis rebound on dosing were emphasized.
Finally, Professor Umberto Buoncristiani, MD, of the University of Perugia, Italy, discussed
the beneficial effects of frequent dialysis on control of metabolic acidosis. Clinical data
indicating both an improvement in overall (time-averaged) control and a reduced deviation
(“peak-and-valley effect”) of the serum bicarbonate con-centration from the time-averaged value
were presented.
Overall, the session provided a great deal of useful clinical information pertaining to
solute kinetics for different hemodialysis schedules.
