KT/V AND PROTEIN CATABOLIC RATE DETERMINATION FROM SERIAL UREA MEASUREMENT IN THE DIALYSATE EFFLUENT STREAM

A bloodless technique of evaluating protein catabolic rate (PCR) and KT/V (K, clearance; T, dialysis time; V, urea distribution volume) in hemodialysis patients is presented based on serial measurement of urea in the dialysate effluent stream. PCR follows from equating urea generation and urea removal over a 7 day cycle, changes in body stores being comparatively negligible: PCR = 0.026 [U1 + U2 + U3]/BW(dry) + 0.17, where U(i) is the amount of urea in mmol appearing in the dialysate for each session in the 7 day period. KT/V is obtained from the slope of the natural logarithm of spent dialysate urea concentration-time plot: KT/V = [- slope . T + 3 - DELTA-BW/BW(dry)]/[1 - 0.01786 . T(hr)], where DELTA-BW - amount ultrafiltered in liters. The dialysate-based approach was validated and compared with conventional urea kinetic modeling (UKM) for 17 patients studied for three consecutive dialyses. The dialysate-based and UKM values of PCR agreed well when in vivo clearance values based on total dialysate collection were used for UKM. KT/V values agreed poorly on a session-by-session basis but were nearly equivalent when averaged for the three dialyses of the week. These findings lay the foundation for UKM automation with a urea sensor in the effluent dialysate stream.