Archives of Hellenic Medicine

Last update:

08-Jul-2004

Arch Hellen Med, 20(1), January-February 2003, 42-48

ORIGINAL PAPER

Estimation of hemodialysis adequacy based
on blood urea measurement at various time intervals
during the dialysis session

P. KALOCHERETIS, A. DROUZAS, H. VLAMIS, I. MAKRYNIOTOU,
S. ZERBALA, N. ARVANITIS, E. POIRAZLAR, Ch. IATROU
"G. Papadakis” Nephrology Center, “Agios Panteleimon” Nikea’s General Hospital, Pireaus, Greece

OBJECTIVE The main hemodialysis (HD) adequacy index is Kt/V, depending, to a large extent, on the measurement of blood urea at the end of the dialysis session, which overestimates dialysis efficacy in proportion to the degree of urea rebound. In this study Kt/V values, based on blood urea measurements, were compared 30 min before the end, at the end and 30 min after the end of the HD session, in order to investigate the possibility of substitution of the routinely used method for dialysis efficacy estimation.

METHOD The study population comprised 42 chronic HD patients (24 male, 18 female), with a mean age of 51.88±16.5 years who had been on HD for 61.6±55 months. All patients had a well-functioning permanent vascular access (arteriovenous fistula or arteriovenous graft). They were informed about the aim and the method of the study and they participated voluntarily. The length of all the dialysis sessions was four hours and all dialyzers consisted of cellulosic membranes and had a low ultrafiltration coefficient (low-flux). Just before the beginning of dialysis a venous catheter was inserted in the arm without the dialysis access. Blood samples were drawn at the beginning (time 0 min), 30 min before the end of dialysis, at the end, and 30 min after the end of the dialysis session, from the arterial line and from the peripheral vein, simultaneously, in order to determine urea concentration. Kt/V was estimated by using the formula: Kt/V=-ln(R–0.008 x t) + (4–3.5R) x UF/BF.

RESULTS The average Kt/V at the end of the HD session was 11% greater than at 30 min after the end of the session, which, in turn, was less than Kt/V 30 min before the end of dialysis by only 3%. The differences were not statistically significant.

CONCLUSIONS Despite the fact that Kt/V determination based on urea measurement at the end of the HD session overestimates dialysis adequacy, there was no convincing evidence for its substitution by Kt/V based on urea assessment at other time intervals of the HD session.

Key words: Dialysis adequacy, Kt/V, PRU.