Designing dialysis prescriptions

Our objective was to determine the adequacy of dialysis in our patients currently on home peritoneal dialysis and develop a program of surveillance aimed at maintaining tKt/V (Kt/V calculated from peritoneal clearance and residual renal function) greater than 2.0 as recommended by the CANUSA study. Eighty-nine patients were entered into our study between September, 1993 and September, 1995. Initial dialysate volumes used during the training period were determined by using a patient-specific protocol. Two weeks after discharge a standard peritoneal equilibration test was performed to determine total Kt/V using a computer program, and dialysis prescriptions were changed to achieve a tKt/V > 2.0 in those patients who had tKt/V < 2.0, and those with tKt/V > 2.0 were followed without further intervention. Of the patients who had initial assessments, 33.7% had tKt/V of 1.65 and 66.3% had tKt/V of 2.46, and the difference was mainly due to residual renal function. Forty-four patients were started on continuous ambulatory peritoneal dialysis (CAPD), of whom 34% had tKt/V < 2.0 and 66% had tKt/V > 2.0, and of the 36 patients on continuous cycling peritoneal dialysis (CCPD), 30.5% had tKt/V < 2.0 and 69.5% had tKt/V > 2.0. The cost of changing dialysis prescriptions is less with CCPD than with CAPD, and a 0.8-1.0 L increase in dialysate volume will increase peritoneal Kt/V (dKt/V) by 0.1 on average. Patients weighing less than 53 kg can achieve a dKt/V > 2.0 even in the absence of residual renal function, but as body weight increases there is greater dependence on residual renal function to achieve adequate dialysis. We have been able to maintain patients on adequate dialysis (tKt/V > 2.0) by checking peritoneal clearance and residual renal function initially and on a regular basis. Whether a tKt/V > 2.0 will be sufficient to maintain health and well-being of our patients will require a longer period of observation.