OPTIMIZATION OF DIALYSATE FLOW AND MASS-TRANSFER DURING AUTOMATED PERITONEAL-DIALYSIS

The purpose of this study was to evaluate the effect of patient positi on on the mass transfer area coefficient (KoA) and to characterize dra in/fill profiles in an effort to enhance efficiency of automated perit oneal dialysis. Over 100 exchanges were performed in 38 stable periton eal dialysis patients to either determine the small solute KoA in the supine versus upright position or to characterize fill/drain profiles. The KoA for all salutes tested was significantly greater in the supin e position compared with the upright position (P < 0.05). Fill profile s revealed the fill rate to be a function of fill height (P < 0.001) a nd patient position (supine > upright [P < 0.001]). Analysis of drain flow rate versus time revealed an initial segment of high outflow (350 +/- 89 mL/min) followed by an abrupt transition to a segment characte rized by slow drainage (36 +/- 21 mL/min). The first segment of drain only took 5.6 +/- 23 minutes (42% of the total drain time); in that ti me, 83% +/- 10% of the dialysate was drained. The transition volume (v olume of dialysate remaining at the time the transition occurs, exclud ing residual volume) correlated with body surface area (R = 0.52, P < 0.01). In conclusion, automated peritoneal dialysis treatment (includi ng intermittent peritoneal dialysis, which may be done in the upright position) should be done in the supine position to optimize the KoA, a nd shortening drain time to include only the initial segment of high o utflow will improve the efficiency and convenience of therapy. (C) 199 5 by the National Kidney Foundation, Inc.