Optimal number of dialysate exchanges in automated peritoneal dialysis

Means of enhancing the efficiency of dialysis in automated peritoneal dialysis (APD) should be sought. Optimum cycles of exchange in APD were studied using a simple urea kinetic model. The amount of dialysis urea was expressed as the total amount removed divided by the initial plasma level (M/CB). A highly significant correlation between calculated and measured M/CB levels (r = 0.902, p < 0.001) was observed. The kinetic study indicated an increase in cycles to greatly enhance M/CB for high membrane transporter patients, in contrast to low transporters. Maximum M/CB for 8 hours was obtained by 5 cycles at D/P (120 minutes) of 0.4, 6 cycles at D/P of 0.7, and 9 at D/P of 0.9 when 2 L were infused. An increase in infusion volume from 2--3 L augmented M/CB by only 7% at D/P of 0.4, while M/CB was augmented by 14% at D/P of 0.9. The optimum number of cycles may thus be concluded to depend on peritoneal membrane permeability. A high transporter patient requires frequent exchanges for increasing dialysis efficiency, whereas a low transporter patient does not.