Abiodun O.

INTRODUCTION Kidneys are paired of vital organs that perform about a dozen of physiologic functions and are prone to damage. They can be found behind the abdominal cavity and some of their functions include regulation of necessary electrolytes and fluids, filtration and excretion of metabolic waste products, stimulation of red blood cell-production. Kidney routinely filtered about 100 to 140 liters of blood a day to produce 1 to 2 liters of urine, composed of wastes and excess fluid. Kidney failure occurred when there is disruption of the body's normal pH balance, slow accumulation of nitrogenous wastes, salts, water. However, this failure usually occurs over a long period of time and when the patient's renal function declines enough over the course of the disease, is commonly known as end stage renal disease (ESRD). High blood pressure and Diabetes  are known to be the most common causes of kidney failure. However, detection of kidney disease before the kidneys start to shut down is uncommon but with high blood pressure and decreased appetite being symptoms that indicate a problem. According to Johnson and Steven (2014), expert has predicted that the demand for dialysis will increase as the prevalence of diabetes increases. When there is kidney failure, hemodialysis is a method used for the removal of waste products such as urea and creatinine, as well as free water from the blood. However, machine used to clean the patient’s blood is called a dialyser (artificial kidney) and can also be referred to as dialysis machine. Peritoneal dialysis (PD) is being described as portable” or “wearable” mode of dialysis and was first introduced in 1960s. It can be used only for patients with acute renal failure, whose treatment consisted of insertion, by sharp metal trocar, of hard catheters, followed by instillation of sterile dialysate supplied in 1-L glass bottles, typically continuing for more than 24 hours. Over the decade, PD is being introduced as a treatment for chronic kidney disease, initially in a form similar to that used for treating acute renal failure, but then progressing to hospital admission thrice weekly for overnight PD treatment sessions in patients who required a new catheter insertion for each treatment. This machine is made up of a cylindrical rigid casing enclosing hollow fibers cast or extruded from a polymer or copolymer, which is usually a proprietary formulation. Moreover, research has been conducted by many groups to optimize blood and dialysate flows within the dialyser, in order to achieve efficient transfer of wastes from blood to dialysate. Automated Wearable Artificial kidney (AWAK)  AWAK is a wearable dialysis machine that a person with end-stage kidney disease could use daily or even continuously which would allow a patient to be treated twenty-four hours a day. However, this device has the potential to remove protein bound solutes and middle molecules including small molecular-weight solutes and works automatically to provide dialysis-on-the go. The AWAK system is designed to continuously regenerate dialysate, so that a single conventional glucose-based peritoneal dialysate solution may be continuously reused for up to a month or even longer. As such, this system has an additional chamber containing electrolytes, lactate, and glucose to refresh regenerated dialysate, and an ammonia sensor to monitor sorbent saturation. Around 750 ml of fresh dialysate is initially infused into the peritoneal cavity, and then recirculated in a tidal manner at 4 l/h using a battery-powered pump and any ultrafiltrate generated over an 8–10-h period drained into a separate bag attached to the module. As recycled dialysate has lower glucose and changed electrolyte composition, it must be continuously regenerated, and as such the recycled dialysate is reinfused with glucose and electrolyte solutions. However, the duration of effectiveness for any sorbent will depend markedly on individual patient characteristics in terms of dietary protein intake, physical activity, and urea generation rate, and the renewed interest in sorbent technology may well lead to the development of newer, more effective sorbents. The AWAK device is currently undergoing clinical trials, and the results are eagerly awaited. David Lee and Marty Roberts worked for many years on developing a wearable continuous peritoneal dialysis device. Fissell et al., (2013) reported that AWAK uses a standard single lumen PD catheter, then peritoneal dialysate either flows into or out from the patient and as such there has to be a chamber to store peritoneal dialysate. The AWAK is made up two modules, one designed to be changed on a daily basis and the other to be changed monthly. However, sorbents can be sub-classified into either absorb or adsorb molecules. Absorption is when molecules permeate the sorbent and are subsequentlytaken up by it while adsorption is when molecules adhere to the surface of the adsorbent. In addition, some sorbents take up molecules until they become saturated; others act primarily by exchanging one molecule for another (Davenport, 2011). However, most of the used dialysate flows through a sorbent assembly which is made up of fibrin that functions as a debris trap and a carbon filter. Also, the sorbents are engineered and designed to regenerate or reproduce both the ultrafiltrate and the proteins of the spent dialysate, in order to produce a fresh protein-containing dialysate. The enrichment motif infused potassium, calcium, magnesium and glucose to the regenerated dialysate. After that, the replenished fresh dialysate will pass through a sterilising filter and a gas removal module before being recycled back into the peritoneal cavity. According to Roberts et al., (1999), urea is cleared enzymatically in the AWAK using urease, which converts urea into ammonium carbonate, producing ammonia and carbon dioxide. As ammonia is toxic, the sorbent system has to contain compounds designed to remove ammonia. Zirconium phosphate will readily adsorb ammonium, but also potassium, calcium, magnesium and other cations and metals. However, when zirconium phosphate adsorbs these molecules they are exchanged, thereby releasing hydrogen and to a lesser extent sodium ions. As hydrogen ion release is not desirable, yet another sorbent is required to remove these hydrogen ions. Zirconium carbonate will absorb hydrogen ions, along with phosphate, fluoride and heavy metals, but once again adsorption is by exchange, so releasing bicarbonate, acetate and to a lesser extent sodium (Rosenbaum et al., 2008). A sorbent-based assembly in AWAK device which regenerates both the aqueous and the protein components (AqC and PrC) of the spent dialysate is considered as a novel, autologous protein-containing dialysate. The AWAK has capacity to regenerate AqC which have similar composition with commercially available peritoneal dialysate, but contains bicarbonate instead of lactate and has slightly higher pH value (pH: 6.5-7.0) compared to commercial dialysate (pH:5.0-5.5). For regenerated PrC, it is recycled back into the peritoneal cavity to rehabilitate or eliminate protein loss. Lee and Robert (2013) reported that the regenerated dialysate that is sterilised through the filter-sterilisation before being infused into patients has been tested and the results were negative in culture and pyrogen free.