The Vicenza Wearable Artificial Kidney for Peritoneal Dialysis (ViWAK PD)

BACKGROUND: The study describes the structure and operational characteristics of a new wearable system for continuous ambulatory peritoneal dialysis (CAPD) for chronic kidney disease patients. METHODS: We designed a wearable system consisting of: (1) a double lumen peritoneal catheter; (2) a dialysate outflow line; (3) a miniaturized rotary pump; (4) a circuit for dialysate regeneration featuring a waterproof container with 4 cartridges in parallel with a mixture of activated carbon and polystyrenic resins; (5) a filter for deaeration and microbiological safety; (6) a dialysate inflow line, and (7) a handheld computer as a remote control. The system has been tested circulating 12 liters of exhausted PD solution through the experimental adsorption unit at a rate of 20 ml/min. Creatinine, beta2-microglobulin (beta2-MG) and angiogenin were measured before and after the adsorption unit at baseline, and after 4 and 10 h of use. RESULTS: The cartridges containing polystyrenic resin completely removed beta2-MG and angiogenin from the fluid batch. Those with the activated carbon removed completely urea and creatinine. The final result was 11.2 liters of net solute clearance. The system is designed to be used as follows: The peritoneal cavity is loaded in the morning with 2 liters of fresh PD solution. After 2 h, when dialysate/plasma equilibration at approximately 50% has occurred, recirculation is activated for 10 h at a rate of 20 ml/min. After this period, recirculation stops and glucose is optionally added to the peritoneal cavity to achieve ultrafiltration if needed. After 2 h the fluid is drained and a 2-liter icodextrin exchange is performed overnight to achieve further ultrafiltration. The clearance provided by the minicycler is further increased by the 2-liter exchange and the overnight exchange. Therefore, the system operates 24 h/day and provides creatinine and beta2-MG clearance in the range of 15-16 liters/day, corresponding to a weekly clearance of 100-110 liters. The patient reduces the number of exchanges compared to CAPD and uses less fluid than in automated peritoneal dialysis (APD). Furthermore, the handheld computer allows for prescription and assessment of the therapy providing information on cartridge saturation, flow and pressure conditions and offering the possibility of remote wireless control of operations. Some problems still remain to be solved in the present configuration including the addition of an injection system for glucose and bicarbonate when needed, a system to reduce fibrin delivery to the sorbent and finally a more complex mixture of sorbents to make sure a complete removal of small molecules including urea is achieved. CONCLUSION: The wearable PD system may become a possible alternative to APD or CAPD reducing the time dedicated to perform exchanges and improving peritoneal dialysis adequacy and patient's rehabilitation.