Study On Phosphate Clearance And Its Influencing Factors In Peritoneal Dialysis

Objective:To investigate peritoneal phosphate clearance in peritoneal dialysis and explore its relationship with peritoneal membrane transport characteristics, dialysis prescription and hyperphosphatemia, and analyze the influencing factors of peritoneal phosphate clearance.Methods:In this cross-sectional and observational study, we selected the maintenance peritoneal dialysis patients in the peritoneal dialysis center of the department of renal medicine of the second xiangya hospital of central south university during July2013to January2014as research objects. According to the inclusion and exclusion standard of study protocol, a total of eighty seven patients were enrolled in this study. Related clinical data of of all the patients were collected, including general data such as gender, age, renal diagnosis, dialysis age,24h urine volume and medication use; dialytic data such as dialysis modality, dialysis dose, dwell time, glucose concentration of the dialysate and ultrafiltration and finally biochemical data such as fasting serum phosphate, urea and creatinine,24-hour dialysate phosphate, urea and creatinine,24-hour urine phosphate, urea and creatinine,2h serum phosphate and creatinine,4h dialysate phosphate and creatinine. Then indicators such as the peritoneal phosphate clearance, peritoneal creatinine clearance (Ccr), peritoneal urea clearance (Kt/V), Residual GFR,4-hour dialysate/plasma (D/P) phosphate (ph) ratio and4-hour D/P creatinine (cr) ratio were calculated and related statistical analysis was made.Results:1. Peritoneal phosphate clearance and peritoneal membrane transport characteristics:4h D/Pcr positively correlated with4h D/Pph (r=0.79, P<0.001).Peritoneal phosphate clearance correlated better with4h D/Pph than with4h D/Pcr (r=0.60, P<0.001and r=0.48, P<0.001, respectively).4h D/Pph was0.55±0.12and according to this,9(10.34%) patients were high (D/Pph>0.68),28(32.18%) were high-average (0.55<D/Pph<0.67),34(39.08%) were low-average (0.43<D/Pph<0.54), and16(18.39%) were low transporters (D/Pph<0.42).The total proportion of low-average and low transporters was higher than that classified according to the criteria defined by Twardowski (57.47%vs40.23%, P<0.001).2.Peritoneal phosphate clearance and dialysis prescription: peritoneal phosphate clearance was positively correlated with CAPD(With DAPD as the reference, r=0.35, P<0.01),24h total dialysate volume (r=0.67, P<0.001), total treatment time (r=0.38, P<0.001), the glucose concentration in the dialysate (r=0.23, P<0.05), and ultrafiltration (r=0.45, P<0.001), but had nothing to do with every dwell time during the daytime (r=-0.19, P>0.05).3.Influencing factors of peritoneal phosphate clearance:4h D/Pph,24h total dialysate volume and ultrafiltration affected peritoneal phosphate clearance independently.The equation of multiple linear regression was established as follows:Y=-15.566+3.273X1+42.630X2+5.699X3(R2=0.617, P<0.05, Y represents peritoneal phosphate clearance, X1represents24h total dialysate volume, X2represents4h D/Pph. X3represents ultrafiltration).4.Peritoneal phosphate clearance and hyperphosphatemia: prevalence of hyperphosphatemia (serum phosphate>1.78mmol/L) was27.59%. Hyperphosphatemia in20.00%of patients with urine, in40.63%of anuric patients, the two prevalence was significantly different (P<0.05). In patients with urine, those with hyperphosphatemia had significantly lower residual renal phosphate clearances than patients without hyperphosphatemia[14.32(10.55-34.34)L/week/1.73m2vs22.53(17.51-48.09)L/week/1.73m2, P<0.05], whereas peritoneal phosphate clearance was similar in the two groups (32.15±15.63L/week/1.73m2vs34.60±9.71L/week/1.73m2, P>0.05). In anuric patients, those with hyperphosphatemia had significantly lower peritoneal phosphate clearance and4h D/Pph than patients without hyperphosphatemia(35.90±8.06L/week/1.73m2vs42.86±9.85L/week/1.73m2and0.52±0.07vs0.60±0.10, respectively, P<0.05), while neither peritoneal creatinine clearance nor4h D/Pcr differed between the two groups(45.21±8.32L/week/1.73m2vs50.17±7.86L/week/1.73m2and 0.66±0.04vs0.68±0.07, respectively, P>0.05).Conclusions:1.Creatinine is sufficiently inadequate surrogate marker for peritoneal membrane phosphate transport, peritoneal phosphate clearance is poorly predicted by the peritoneal membrane transport characteristics based on creatinine equilibration kinetics and is better predicted by peritoneal membrane phosphate transport characteristics.2.Dialysis dose and ultrafiltration are important factors affecting peritoneal phosphate clearance, sufficient dialysis dose and ultrafiltration are important for adequate phosphate clearance.3.Peritoneal phosphate clearance plays an important role in serum phosphate control, anuric peritoneal dialysis patients are more likely have inadequate dialytic clearance of phosphate.4.In peritoneal dialysis patients, peritoneal membrane phosphate transport characteristics should be considered and peritoneal phosphate clearance should be monitored directly when optimizing serum phosphate control.