Future Research in Peritoneal Dialysis Fluids

Solutions for APD: special considerations

Automated peritoneal dialysis (APD) has become the fastest growing dialysis modality in Europe and the United States in recent years. Freedom from daytime exchanges, flexibility of prescription, performance in recumbent position leading to enhanced treatment efficacy, and a decreased incidence of peritonitis are the main advantages of APD over CAPD. Studies on new developments of glucose-based PD fluids were performed predominantly in CAPD patients. High volumes and frequent APD cycles in patients may aggravate the adverse effects of standard CAPD fluids on the peritoneal membrane with increasing time on PD. New, glucose-based PD fluids with neutral pH, very low concentrations of glucose degradation products (GDPs), containing either lactate or bicarbonate as buffering substances have been introduced into clinical use recently. With these new fluids, various in vitro, ex vivo, and in vivo studies could demonstrate a better preservation of peritoneal cell viability and growth, less inhibited secretory cell functions, a significant reduction in the formation of advanced glycation end products (AGEs), and clinical signs for an improved preservation of peritoneal mesothelial cells indicated by an increase in effluent CA125. One has to be aware, however, that uremia per se prior to initiation of PD, as well as during PD treatment itself, directly impacts on peritoneal membrane structural changes so that new, more biocompatible PD fluids may not be completely sufficient to prevent morphologic and functional changes of the membrane. Due to a strong sodium sieving during APD, PD fluids with sodium concentrations of 125-130 mmol/L may be beneficial. Systematic calcium kinetic studies have not yet been performed in APD patients. APD fluids should offer a calcium concentration range of 1.0-1.75 mmol/L in order to enable an individualized APD prescription. For long-term APD treatment, better knowledge of peritoneal membrane physiology and PD kinetics should promote individualization of prescriptions. New, pH-neutral PD solutions with minimized amounts of GDPs may be a significant step forward to improved membrane preservation during long-term APD treatment.

Continuous flow peritoneal dialysis: is there a need for it?

Automated peritoneal dialysis (APD) is the fastest growing technique of peritoneal dialysis. However, recently APD has displayed some limitations imposed by the characteristics of the technique and by the characteristics of the peritoneal membrane of some patients. In general, the advent of a new technique such as continuous flow peritoneal dialysis (CFPD) should be seen as a benefit for several patients based on different considerations: CFPD is a high-efficiency technique which could overcome some of the limitations imposed by other techniques in terms of adequacy targets and performance. CFPD may become a useful tool to keep patients on PD who would otherwise be transferred to hemodialysis. CFPD may present advantages in terms of biocompatibility and also in terms of the possible modulation of the peritoneal solution to patient needs. Recent developments in technology seem to have made CFPD easily feasible and well tolerated. A new era of PD is probably beginning and CFPD will definitely represent one of the key issues in the future of PD.