Increased drainage volume in intermittent peritoneal dialysis using a two-bag, low hydrostatic pressure drainage system

Adequate drainage volume (DV) is a prerequisite for long-term success of intermittent peritoneal dialysis (IPD). Ultrafiltration (UF) is basically determined by the interplay of two major forces: a driving osmotic force created by a hyperosmolar dialysate solution versus an opposing force--the intraperitoneal hydrostatic pressure. Conventional drainage procedures (CS) are capable of achieving a fluid volume of 3 L per bag. We found that this intrabag volume corresponds to an intrabag hydrostatic pressure of 60 cm water. Because this drainage system is closed, the intrabag hydrostatic pressure reflects intraperitoneal hydrostatic pressure. A low-pressure system (LPS) was devised to evaluate the possible influence on DV of reducing HP. Our results show that such LPS does indeed significantly improve DV, using a decreased number of exchanges. The residual volume and its glucose concentration (in a 1.5-g/dl exchange) were measured with CS. When followed by an 4.25-g/dl exchange, an 11% reduction in glucose concentration was evident. Thus, the osmotic driving force may also be impaired by incomplete drainage. To obtain maximal DV during IPD, a LPS should be used. This could be achieved by using 2 L dialysate in 3-L bags.