Phosphate kinetics during different dialysis modalities.
BACKGROUND
An abnormal serum phosphate concentration is common in acute renal failure patients, with a reported incidence of 65-80%. Phosphate removal and kinetics during intermittent hemodialysis (IHD) have been investigated, but there is no information on its kinetics during slow low-efficiency dialysis (SLED) and continuous renal replacement therapy (CRRT).


METHODS
Eight IHD, 8 SLED, and 10 continuous venovenous hemofiltration (CVVH) patients with a residual renal clearance of <4.0 ml/min were studied during a single treatment to evaluate phosphate removal and kinetics. CVVH was studied the first 24 h after initiation. Dialysis/replacement fluid contained no phosphate. Kt/V, clearance of urea (Ku), inorganic phosphate (Kp) and solute removal was determined by direct dialysate quantification (DDQ).


RESULTS
Kp recorded with the three techniques were: IHD, 126.9 +/- 18.4 ml/min; SLED, 58.0 +/- 15.8 ml/min, and CVVH, 31.5 +/- 6.0 ml/min. However, in shorter dialysis treatment the total removal of phosphate was significantly lower than in longer dialysis (IHD, 29.9 +/- 7.7 mmol; SLED, 37.6 +/- 9.6 mmol; CVVH, 66.7 +/- 18.9 mmol, p = 0.001). The duration of treatment is the only factor determining phosphate removal (r = 0.7, p < 0.0001 by linear correlation model). Like IHD, phosphate kinetics during SLED could not be explained by the two-pool kinetic model, and the rebound of phosphate extended beyond 1 h after dialysis. Rebound, however, is less marked than in short dialysis.


CONCLUSIONS
These results are reliable evidence about amount of phosphate removal and behavior of intradialytic phosphate kinetics in renal failure patients undergoing different dialysis modalities. These data will help clinicians plan phosphate supplementation and treatment intensity.
Ratanarat
Ranistha
R
Department of Nephrology, Dialysis and Transplantation, St Bortolo Hospital, Vicenza, Italy.
Brendolan
Alessandra
A
Volker
Gopel
G
Bonello
Monica
M
Salvatori
Gabriella
G
Andrikos
Emilio
E
Yavuz
Asuman
A
Crepaldi
Carlo
C
Ronco
Claudio
C
D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010710:Phosphates / Q000097:blood / Q000493:pharmacokinetics*; D011446:Prospective Studies; D006435:Renal Dialysis / Q000295:instrumentation / Q000379:methods*; D017582:Renal Replacement Therapy / Q000295:instrumentation / Q000379:methods*; D013997:Time Factors; D014508:Urea / Q000097:blood / Q000378:metabolism
D010710:Phosphates; D014508:Urea