Adequacy of peritoneal dialysis in children: consider the membrane for optimal prescription.

The peritoneal dialysis (PD) prescription should be adequate before being optimal. The peritoneal membrane is a dynamic dialyzer: the surface area and the vascular area both have recruitment capacity. At bedside, prescription is based mainly on tolerance of the prescribed fill volume, and therefore a too-small fill volume is often prescribed. A too-small fill volume may lead to a hyperpermeable exchange, with potentially enhanced morbidity-or even mortality-risks. Better understanding of the peritoneal membrane as a dynamic dialysis surface area allows for an individually adapted prescription, which is especially suitable for children on automated PD. Fill volume should be scaled for body surface area (mL/m2) and, to avoid a hyperpermeable exchange, for a not-too-small amount. Fill volume enhancement should be conducted under clinical control and is best determined by intraperitoneal pressure measurement in centimeters of H2O. In children 2 years of age and older, a peak fill volume of 1400-1500 mL/m2 can be prescribed in terms of tolerance, efficiency, and peritoneal membrane recruitment. Dwell times should be determined individually with respect to two opposing parameters: Short dwell times provide adequate small-solute clearance and maintain the crystalloid osmotic gradient (and, thereby, the ultrafiltration capacity). Long dwell times enhance phosphate clearance, but can lead to dialysate reabsorption. The new PD fluids (that is, those free of glucose degradation products, with a neutral pH, and not exclusively lactate-buffered) appear to be the best choice both in terms of membrane recruitment and of preservation of peritoneal vascular hyperperfusion.