What are biocompatible Peritoneal Dialysis solutions, and what is their clinical impact?
PD solutions whose composition more closely mirrors physiologic conditions in terms of pH, osmolality, osmotic agent, manufacturing-induced breakdown products of osmotic agents, and buffer are generally considered “biocompatible” PD solutions. The intent of “biocompatibility” is “to leave the anatomical and physiological characteristics of the peritoneum unchanged in time.” Conventional PD solutions are considered “bioincompatible” because they are glucose-containing, hyperosmolar, lactate-buffered, and generally below physiologic pH. They also contain glucose degradation products (GDPs) that develop as consequence of heat sterilization of the glucose contained in the PD solutions. Fibrotic and microvascular changes are observed to occur in the peritoneal membrane over the time of chronic exposure to these solutions. The association has led to the conclusion of their presumed culpability for these histologic changes, which are linked to increased small solute permeability, reduced UF, and attenuated technique success. Relevant to this discussion is the fact that UF failure accounts for less than 10% of PD technique failure at 2 to 3 years.
Production of more “biocompatible” PD solutions employing alternative osmotic agents (e.g., icodextrin, amino acids), buffers (e.g., lactate/bicarbonate or pure bicarbonate), and dual-chambered containers to reduce GDP content has therefore ensued. The composition of the latter includes a low pH, calcium/magnesium, and glucose-containing compartment. GDP production is minimized during heat sterilization of glucose at low pH. The adjacent buffer-containing compartment contains either bicarbonate/lactate or bicarbonate alone. Precipitation of calcium or magnesium with these buffers is prevented by their separation until just prior to peritoneal infusion, at which time the seal between the two adjacent chambers is broken.
The clinical impact of neutral-pH, low-GDP PD solutions in comparison to conventional PD solutions was assessed in a recent systematic Cochrane review. No significant effects were seen on peritonitis, technique survival, and patient survival, nor were harms identified with their use. In addition, while extended time to anuria and greater urine output was noted in several studies, this effect may have been influenced by diminished UF capacity of some of the neutral-pH, low-GDP solutions. Reduced UF could result in expanded effective arterial volume, augmenting urine output. Studies examining the potential benefit of “biocompatible” solutions on preservation of peritoneal membrane solute transport and UF capacity are ongoing.