Intra-abdominal pressure, peritoneal dialysis exchange volume, and tolerance in APD.

Automated peritoneal dialysis (APD) is increasingly popular compared to continuous ambulatory peritoneal dialysis (CAPD). It not only can provide more solute clearance and ultrafiltration than its CAPD counterpart, but it is conducive to a more convenient lifestyle as well. Using relatively smaller-volume daytime dwells, with the use of larger-volume exchanges while the patient is recumbent during the night, is an attractive approach. Advantages of supine exchanges include greater small molecule clearances for equivalent flow rates and decreased intra-abdominal pressure per volume of dialysate (as intraperitoneal pressure parallels intraperitoneal volume). Urea nitrogen clearance can be optimally increased on APD by increasing both the exchange volume and the frequency of exchanges at night. This is even true for anuric low transporters. This approach allows daytime exchanges and volumes to be minimized. Historic studies in peritoneal dialysis including flow rate analysis, clearance and adequacy studies, as well as tolerance have primarily involved CAPD. As a result, there is a paucity of investigations involving APD. More research is required in APD related to these subjects.