Wearable artificial kidney

A wearable artificial kidney is a wearable dialysis machine that a person with end-stage renal disease could use daily or even continuously. As of November 2008, no wearable kidney is widely available, but many research teams are in the process of developing such devices (see below).

History & motivation

Chronic kidney disease (CKD) affects 26 million people in the United States, and around 550,000 of these patients have end-stage renal disease requiring dialysis or transplantation. The mortality rate for patients with end-stage renal disease is around 22% per year, and at the moment, dialysis is the only therapeutic option for these people. Dialysis therapy is usually given three times a week for four hours at a time, and it involves many risks such as bleeding, clotting, and infection. For patients and society in general, the emotional and financial costs of dialysis therapy are very high. The quality of life for patients on dialysis is often very low, and the yearly cost of treating end-stage renal disease and the yearly cost of treating end-stage renal disease exceeds $30 billion in the US alone.

The ideal wearable kidney would mimic the function of the kidneys by providing:

1. continued dialysis (to avoid the sudden electrolyte disturbances associated with timed dialysis), and
2. be effectively autonomous so that little to no patient intervention is necessary.

Methods of implementation range the same spectrum as traditional dialysis. Experiments have been carried out since the seventies, and included miniature hemofilters utilizing REDY cartridges or by drinking dialysate. The development of continuous ambulatory peritoneal dialysis was successful and significant achievement, but it requires significant patient intervention.

However this technique has failed to gain acceptance with the vast majority of the patients. In many undeveloped countries it is the preferred or at times the only dialysis modality available due to its lower cost. Some of the disadvantages of this technique are that it loads patients with large amounts of carbohydrates which may not necessarily be beneficial, it may be less effective in achieving appropriate fluid removal unless large amounts of sugar are infused into the patient and the filtration capabilities of this techniques are lost over time.

The main reason however, to pursue a wearable artificial kidney is that it would work continuously, 24 hours a day, 7 days a week, filtering the blood in a continuous mode very much like our natural kidneys do. Furthermore, hundreds of scientific papers, including randomized controlled trials, extol the advantages of more frequent dialysis for much longer periods of times, preferably daily.

On the other hand there are numerous logistic and economic barriers that render daily dialysis impractical and unaffordable. Also, dialysis patients do not particularly enjoy the perspective of spending many hours of their life tied to a machine that impedes their ability to work or perform other activities.

In contrast, a wearable artificial kidney small and light that does not impede walking, working of performing any activity of daily light will greatly contribute to improve patient’s quality of life. In addition, the continuous removal of excess water, salt and toxins would allow patients to be free to enjoy any diet and fluid intake of their choice, without fear of poisoning themselves to death or landing in the hospital. Also it would greatly reduce the burden of having to swallow large amounts of pills. Also, significant cost reductions would be expected from implementing such technical advances. Thus, the hopes are high, that the Wearable Artificial Kidney (WAK) will greatly improve the quality of life dialysis patients, reduce their mortality and save a great deal of money.

Technology

Today’s dialysis machines are far from perfect. Their efficiency is only around 10% of that of a functioning kidney, and when used three times per week, they are incapable of controlling unhealthy fluctuations in the concentrations of metabolites such as urea in the blood. Many researchers are seeking to design an artificial, wearable kidney that would make dialysis a more effective therapy.

Nanotechnology offers enticing possibilities in this area. Thin nanomembranes would be more permeable to solutes in the blood than thicker conventional membranes, and these nanomembranes could be carefully engineered to contain highly selective pores, instead of the randomly sized pores present in membranes used today. Particular pores, for example, could be designed to selectively filter middle-sized molecules from the blood. Some middle-sized molecules, such as beta-microglobulin, can cause debilitating health problems when they accumulate in the body, and traditional dialysis machines do a poor job of filtering these molecules from the blood. Eventually, researchers hope to create a library of engineered pores that would allow nephrologists to come up with customized dialysis regimens specifically tailored to their individual patients. No data are available bench, animal or human trials.

Devices in development

Researchers in Italy have developed a semi-autonomous system called the Vicenza Wearable Artificial Kidney for Peritoneal Dialysis (ViWAK PD). The ViWAK PD is a fully electronic system with a belt and waterproof chamber that houses the replaceable sorbent tubes. Patients replace the sorbent cartridges a couple times a day on a schedule in conjunction with overnight peritoneal dialysis. Patients can monitor and control their therapy wirelessly via a handheld remote or a computer.

In 1997, researchers at UCLA detailed a peritoneal-based AWAK that can provide continuous filtration, mimicking the functions of the normal kidneys. The system would never need patient intervention except during cartridge replacement every 8 or 12 hours. This device is able to regenerate and reuse fluid, and protein components in the spent dialysate - the fluid that has extracted toxins from the patient through the peritoneal cavity, and which is discarded in current, traditional dialysis protocols. The regenerated dialysate is pumped into the patient for the next cycle of dialysis. As such, protein loss is minimized or eliminated and minimum amount of dialysate is required, making a wearable kidney possible. The technology has been licensed for production.

A WAK designed by Dr. Victor Gura,an Associated Clinical Professor from the David Geffen School of Medicine at the University of California in Los Angeles working at Cedars Sinai Hospital has been built and successfully tried in laboratory and animal experiments at Cedars Sinai Hospital.

This device underwent two successful human trials in dialysis patients, one in Vicenza, Italy in cooperation with Dr. Claudio Ronco and the other one in the Royal Free Hospital, University of London College, in association with Dr. Andrew Davenport. All laboratory, animal and human trials were reported in peer reviewed scientific journals and numerous prestigious scientific meeting such as the world Congress of Nephrology, the American Society of Nephrology, the European Dialysis and Transplantation Association, the International Society of Hemodialysis and the International Society of Hemodialysis, the International Society of Blood Purification, the Annual Dialysis Conference and many others. The initial prototype of this device weights approximately 5 kg, is worn as a belt and works on batteries. In addition it is the only device that affords water quality equal to that used for intravenous fluids, while currently used devices use water with some bacterial and endotoxins content. The device is now ready for clinical trials in order to obtain regulatory approval and made available to the public.

Conference references

• CIMIT Forum. January 15, 2007.

Video references

• Impact of Chronic Kidney Disease Joseph Bonventre, MD, PhD, Harvard Medical School
• an Artificial Kidney Theodore I. Steinman, MD, Harvard Medical School
• a Wearable Kidney to Market Greg Erman, MBA, former president and CEO of Renalworks Medical Corporation
• an Artificial Kidney Jeffrey Borenstein, PhD, Drapers Labs

Additional video references

• Panel Discussion on Wearable Kidney CIMIT

External links

• CIMIT Center for Integration of Medicine and Innovative Technology