Peritoneal dialysis prescription: the "Clearance Peak" model

Creatinine clearance (CRCL) was studied in 20 patients on CAPD in relation to the dwell times (DT), in order to establish a personalised dialysis schedule with the best clearance (CL) results, while respecting the patient's life-style. By calculating the CRCL from the two exchanges with dwell-times of 4 and 8 hours (2 I, 2.27%), curves (2nd degree polynomial regression) were plotted with three points (0h, 4h, 8h) for CRCL and the ultrafiltration rate (UF) as a function of the DT. The DT corresponding to the CRCL peak (CLPeak-time) was calculated for each subject with the first derivative of the function. On the basis of the CRCL obtained with the three most common DT (4h, 6h, 8h), we divided the patients into three categories (CLPeak-time < 5h: "fast", 5-7h: "normal"; > 7h: "slow") for the best CRCL correspondence of the 4h, 6h or 8h exchanges respectively. Also the 8h/4h ratio was used to determine CLPeak-time. For each of the three categories there is a corresponding dialysis schedule for the best CRCL and UF results of the exchanges with DT of 4, 6 and 8 hours, plus the theoretical calculation of the daily CRCL obtainable ("fast": APD; "normal": CAPD 4 exchanges/DAPD 4 exchanges; "slow": CAPD 4 exchanges). The "CLPeak" dialysis prescription model therefore identifies the most advantageous DT for each patient by using the CRCL values of two 2.27% exchanges of 4 and 8h respectively. Functional classification into three categories may give a rational orientation to dialysis prescription in order to reach the maximum CRCL possible with the individual peritoneal transport rates.