AUGMENTING SOLUTE CLEARANCE IN PERITONEAL-DIALYSIS

Background. The removal of low molecular weight solutes by peritoneal dialysis is less than by hemodialysis. The targets for Kt/V-urea and c reatinine clearance formulated in the Dialysis Outcome Quality Initiat ive are unlikely to be achieved in a substantial portion of peritoneal dialysis patients. Possibilities to increase small solute clearances have therefore been subject to many investigations. Methods. A review of the literature and of recent new data on determinants of solute rem oval, such as residual renal function, the role of drained dialysate v olume and manipulation of the diffusive capacity of the peritoneum are presented. Results. The contribution of residual GFR is more importan t for the clearance of creatinine than for Kt/V-urea. It is even more important for the removal of organic acids that are removed from the b ody by tubular secretion. High dosages of furosemide increase the urin ary volume and the fractional Na+ excretion, but have no effect on the magnitude of residual GFR, renal creatinine clearance, renal urea cle arance, and peritoneal transport characteristics. The drained dialysat e volume per day is the main determinant of the peritoneal removal of urea. Its effect decreases the higher the molecular weight of a solute . It can be augmented by using large instillation volumes, by the appl ication of more exchanges, and by increasing peritoneal ultrafiltratio n. A large exchange volume is especially effective in patients with an average transport state, but: in those with high solute transport rat es, Kt/V-urea is especially influenced by the number of exchanges. Pos sibilities to increase ultrafiltration are discussed. The diffusive ca pacity of the peritoneum can be augmented by using low dosages of intr aperitoneally administered nitroprusside. This increases solute transp ort most markedly when it is applied in combination with icodextrin as osmotic agent. Conclusions. Small solutes clearances cannot be increa sed by furosemide. Increasing the instilled volume of dialysis fluid a nd the number of exchanges both affect solute clearance. Studies are n ecessary on long-term effects of manipulation of the peritoneal membra ne with nitroprusside.