An Integrated Membrane/Sorbent PD Approach to a Wearable Artificial Kidney

Abstract

A wearable artificial kidney has been the dream of patients, physicians, and scientists for many years. Most systems developed to date incorporate some combination of membranes, sorbents, enzymes, and/or cells, which are used to mimic the filtration and metabolic aspects of the kidney. These systems aim to provide equivalent or better treatment than traditional dialysis while allowing more freedom and better quality of life to patients. Nevertheless, many challenges have yet to be solved in creating a dialysis device that is small, lightweight, ergonomic, effective, and safe.

Wearable systems based on peritoneal dialysis avoid the risk of sepsis inherent in repeatedly accessing the bloodstream and use the peritoneal cavity as a built-in dialysate reservoir. Continuous-flow PD systems offer the advantage of improved peritoneal transport due to better mixing and reduced boundary layer thickness. The use of sorbents to regenerate PD fluid may enable dialysate solution to be used for an extended period of time, but currently available sorbent dialysis systems are too large and heavy for use in a wearable system.

A new approach to a PD-based wearable artificial kidney entails the use of specialized membranes in combination with sorbents. Placement of sorbents in the shell side of hollow fiber device has a number of advantages. This configuration reduces the power requirement by reducing the effective “column height” of the sorbent particles. Membranes protect the peritoneal cavity from particulates and eliminate the need for alumina to retain urease. Ion-rejecting membranes prevent excessive adsorption of Ca and Mg by the ammonia sorbent, and improve the sorbent capacity for ammonia by retaining ions that would otherwise compete for binding sites. When combined with improvements in sorbent capacity, miniaturized pumps, and batteries, the membrane/sorbent system offers the potential for a truly wearable system.