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Wearable artificial kidney (WAK): Portable dialysis for patients with chronic kidney disease

Source agency:

ANZHSN

Date of Submission:

07/12/2009

Date of Printing:

05/02/2012

Disclaimer:

This report is work in progress and should not be used for external distribution without permission from the originating agency. Users should be aware that reports are based on information available at the time of research and often on a limited literature search.

Technology, Company & Licensing

Technology name:

Wearable artificial kidney

Technology - description:

Although the wearable artificial kidney (WAK) is designed to be used for continuous renal replacement therapy 24-hours per day, seven days per week, it would most likely to be used between 4-8 hours per day. The filtration device is worn on a belt around the waist and weighs approximately five kilograms. There are four micro-pumps which are driven by standard batteries. One pump regulates the ultra-filtration unit whilst the remaining pumps infuse heparin into the blood circuit and infuse sodium bicarbonate, magnesium and calcium acetate into the dialysate circuit. The device is attached to the patient using the standard vascular access used by normal dialysis (fistula needles or central venous access catheters). Safety measures stop the ultra-filtration pump if blood flow ceases due to disconnection of the arterial needle and the blood pump is stopped if air enters the blood circuit system (Davenport et al 2007; Ronco et al 2008).



The circuit consists of two basic sections. The blood compartment takes blood from the patient to the dialyser and then returns the blood to the patient. The dialysate compartment is where fresh dialysate enters the dialyser and then exits to a series of sorbent canisters where it is regenerated and bicarbonate is added (Davenport et al 2007). The three sorbent canisters contain urease, activated charcoal, and both hydroxyl zirconium oxide and zirconium phosphate. The dialysate is regularly tested for sterility and for ammonia to ensure that they have not become saturated (Ronco et al 2008).

Company or developer:

Xcorporeal Inc (United States) provides the wearable artificial kidney

Reason for database entry:

Innovative treatment with expected improvements in quality of life

Technology - stage in early warning process:

Assessment complete

Technology - stage of development:

Experimental - pilot or phase II

Licensing, reimbursement and other approval:

 

Technology - type(s):

Device

Technology - use(s):

Therapeutic

Patient Indication & Setting

Patient indications:

Patients with chronic kidney disease (stage 5) or end-stage renal disease (ESRD) usually receive dialysis three times per week in a specialist renal unit. More frequent haemodialysis has been demonstrated to be beneficial to ESRD patients in terms of both survival and quality of life. Benefits for patients include less hypertension, reduced cardiovascular disease, improved patient appetite and nutrition, improved serum albumin levels, improved anaemia and a decrease in the incidence of stroke. All of these factors result in a reduced morbidity and mortality in ESRD patients. Therefore, it has been proposed that a wearable dialysis unit would be of great benefit to ESRD patients (Davenport et al 2007; Gura et al 2005).

Disease description and associated mortality and morbidity:

Chronic kidney disease (CKD) is marked by long-term and usually irreversible loss of kidney function. Initial evidence of kidney damage or reduction in kidney function can be detected by routine blood or urine testing with the most common indicators of kidney damage being elevated protein levels in the urine (proteinuria or albuminuria), blood in the urine (haematuria) or raised blood levels of the waste products of protein metabolism such as urea or creatinine. Kidney function is measured by the glomerular filtration rate (GFR), a measure of the amount of blood the kidneys clear of waste products in one minute (AIHW 2005).



Chronic kidney disease is classified into five stages of disease severity based on evidence of kidney damage and the degree of kidney function reduction, classified by GFR:



• Stage 1: Kidney damage with GFR at least 90 mL/min/1.73 m2. People with stage 1 CKD have evidence of kidney damage (structural or functional abnormalities of the kidney), but without decreased GFR. There are usually no symptoms.



• Stage 2: Kidney damage with GFR 60 to 89 mL/min/1.73 m2. People with stage 2 CKD have evidence of kidney damage with some reduction in GFR. Most patients at this stage have no symptoms but may have high blood pressure and laboratory abnormalities indicating dysfunction in other organs.



• Stage 3: GFR 30 to 59 mL/min/1.73 m2. People with stage 3 CKD have a significant reduction in GFR. They may or may not show other signs of kidney damage. Blood tests will show increased levels of urea and creatinine, and there may be evidence of dysfunction in other organs. Patients may have symptoms, however they often remain asymptomatic even though their kidney function may be reduced by as much as 70 per cent.



• Stage 4: GFR 15 to 29 mL/min/1.73 m2. People with stage 4 CKD have severely reduced kidney function. Blood levels of urea and creatinine are increased, and there is greater evidence of dysfunction in other organs. Patients usually have only mild symptoms.



• Stage 5: GFR less than 15 mL/min/1.73 m2. In most cases, stage 5 CKD is marked by a range of symptoms and laboratory abnormalities in several organ systems, collectively referred to as uraemia. Patients at this stage may need to be prepared for kidney replacement therapy (dialysis or transplant), which will be required when kidney function is no longer sufficient to sustain life (AIHW 2005).

Number of Patients:

In Australia one in three people are at risk of developing CKD, with one in seven having CKD and one in 1,400 requiring dialysis or a kidney transplant. CKD is the seventh highest cause of death in Australia. The need for dialysis is increasing within the Australian population due to the increasing incidence of diabetes and the ageing population. Over the past 25 years Australian population growth has been less than 40 per cent yet the need for dialysis and kidney transplants has increased 400 per cent. In 2006 there were 9,182 dialysis patients in Australia (Kerr et al 2008). In 2005 around 13 per cent (800) of haemodialysis patients dialysed at home (KHA 2005). It is estimated that the current cost of providing dialysis for one patient for a year costs AUD$60,000. Including transplants the cost of end stage kidney disease is estimated to be at least AUD$570 million annually (KHA 2006a; KHA 2006b). In Australia during 2003-04, eleven per cent of all hospital separations were for dialysis. CKD was recorded as the underlying cause of death in 2,431 cases during 2003. In addition, CKD was recorded as an associated cause of death in an additional 9,217 cases, mostly with cardiovascular disease recorded as a comorbidity (AIHW 2005).

Incidence and prevalence rates of CKD were slightly higher in New Zealand when compared with Australian rates. In 2002, the incidence of renal replacement therapy (RRT) in New Zealand was approximately 120 per million people, compared to 95 in Australia. The prevalence was approximately 680 per million people (pmp) compared to the Australian prevalence of 640. As stated previously, the incidence rate and prevalence of CKD has been increasing steadily over time. In New Zealand the incidence of RRT has increased from approximately 75 pmp in 1995 to 120 pmp in 2002, and prevalence has increased from 350 pmp to 680 pmp over the same time period (KHA 2006a).

Technology - specialities(s):

Renal disease & urology

Technology - setting(s):

Community and primary care

Setting - further information:

 

Impact

Alternative and/or complementary technology:

Substitution technology

Current Technology:

Australia and New Zealand already have one of the highest rates of home dialysis in the world, however the majority of dialysis is still centre (hospital or clinic) based, with patients usually receiving dialysis three times per week (Agar 2008). It is increasingly recognised that centre based haemodialysis is not the optimum patient management strategy regarding both health outcomes and patient survival times (ANZDATA 2006). As previously stated, more frequent haemodialysis is beneficial to ESRD patients both in terms of survival and quality of life and has been shown to be associated with decreases in mortality and RRT associated morbidity such as cardiovascular disease (Masterson 2008).

Health Impact:

Patients with chronic kidney disease (stage 5) or end-stage renal disease (ESRD) usually receive dialysis three times per week in a specialist renal unit. More frequent haemodialysis has been demonstrated to be beneficial to ESRD patients in terms of both survival and quality of life. Benefits for patients include less hypertension, reduced cardiovascular disease, improved patient appetite and nutrition, improved serum albumin levels, improved anaemia and a decrease in the incidence of stroke. All of these factors result in a reduced morbidity and mortality in ESRD patients. Therefore, it has been proposed that a wearable dialysis unit would be of great benefit to ESRD patients (Davenport et al 2007; Gura et al 2005).

Diffusion:

The wearable artificial kidney is not available in Australia or New Zealand.

Cost, infrastructure and economic consequences:

The authors of the included study were contacted for pricing information regarding the WAK device and consumables, however no response was received by the evaluators.

Ethical, social, legal, political and cultural impact:

 

Evidence & Policy

Clinical evidence and safety:

Initial testing of a smaller WAK device (2.27 kg) was conducted on 12 pigs with ligated ureters, divided into two groups based on weight: group 1 (74.9 +/- 1.2 kg) with a blood flow of 44 ml/min and group 2 (47.9 +/- 1.7 kg) with a blood flow of 75 ml/min. The animals were dialysed for eight hours with an average dialysate flow of 73 and 85 ml/min in group one and two, respectively. No adverse events were recorded on any of the animals and effective removal of solutes and excess fluid from the uremic animals was achieved (see web link for Table 1). Similar clearance rates were reported in both groups despite differences in initial weight.



The only published study using the WAK device is a small, proof-of-concept case series of eight patients with ESRD (level IV intervention evidence). All patients were currently being treated with conventional haemodialysis three times per week and had been receiving RTT for an average of 17.9 years (range 4-29 years). The average age of the group was 51.7 +/- 13.8 years (range 26-67 years). The cause of CKD was glomerulonephritis (n=4), polycystic kidney disease (n=3) and obstructive uropathy (n=1). Due to the experimental nature of the study, the ethics committee required that all patients still underwent conventional intermittent haemodialysis. Patients were weighed before and after treatment and their blood oxygen and cardiac measures were monitored continuously. Ethics required that initially only a maximum of four patients could be treated for four hours. After the successful implementation of this phase, treatment could be extended up to a maximum of eight hours (Davenport et al 2007).

All patients reported on the device favourably with no complaints and would recommend it as a treatment option. Five patients attempted to sleep whilst wearing the device and reported no difficulties. Dialysis outcomes are summarised in Table 2. Concentrations of serum electrolytes and cardiac parameters remained stable and unchanged throughout dialysis. Several times bubbles of carbon dioxide accumulated in the dialysate circuit, creating difficulty with the dialysate flow, but this did not result in the cessation of treatment. One patient experienced clotting of the central venous access catheter when partial thromboplastin time fell to 45 seconds (normal 26-36 seconds) and treatment was discontinued after seven hours. Clotting also occurred in another patient, however this patient was scheduled to terminate treatment at four hours and the partial thromboplastin time had been allowed to fall to ensure that bleeding did not occur upon removal of dialysis needles. Another patient experienced a temporary disconnection when a fistula needle dislodged. This was detected by the WAK’s safety mechanism with the needle reinserted and treatment continued.



Further dialysis outcomes were reported in a later paper by Gura et al (2009) and are summarised in the lower section of Table 2(see web link). In patients on long-term dialysis, B2-microglobulin, a serum protein, is unable to cross the dialysis filter and can aggregate into amyloid fibres which can deposit into joint spaces. Conventional thrice-weekly haemodialysis cannot clear the amount of B2-microglobulin generated and it has been suggested that more frequent dialysis would reduce the plasma concentration of this molecule. It has been suggested that improved clearance of B2-microglobulin is important for increased patient survival. The average rate of +/-2-microglobulin removal was 15.59 +/- 9.86 mg/ hour. Similarly, serum phosphate concentrations increase due to the dietary requirements placed on CKD patients. Phosphate is effectively removed with the average rate of removal of 69.56 +/- 50.92 mg/ hour (Gura et al 2009a). The clearance rates of these so-called “middle molecules” appear to be more efficient with WAK than conventional haemodialysis probably due to differences in pump design, with the WAK pump providing simultaneous pulsatile flow of both blood and dialysate compared to the high amplitude and pulse frequency of the conventional roller pumps (Gura et al 2009b; Ronco et al 2008).



The same authors have reported on the development of the Vicenza wearable artificial kidney (ViWAK) for continuous peritoneal dialysis for CKD patients (Lee & Roberts 2008; Ronco et al 2008; Ronco & Fecondini 2007). To date, patient studies using the ViWAK have not commenced.

Economic evaluation:

 

Ongoing research:

 

Ongoing or planned HTA:

Based on the low-level, preliminary evidence the WAK device appears to be promising for the frequent treatment of chronic kidney disease patients. This device may have a great clinical impact in terms of reduced mortality and morbidity of CKD patients, and therefore may also represent savings in the health system. However this technology may be several years away from being a commercially viable proposition, therefore HealthPACT has recommended it be monitored for further information in 24-months time.

Web link:

http://www.horizonscanning.gov.au/

References and sources:

Agar, J. W. M. (2008). 'Home hemodialysis in Australia and New Zealand: Practical problems and solutions', Hemodialysis International, 12 (SUPPL. 1), S26-S32.

AIHW (2005). Chronic kidney disease in Australia, Australian Institute of Health and Welfare, Canberra. Available from: http://www.aihw.gov.au/publications/phe/ckda05/ckda05.pdf

ANZDATA (2006). Australian and New Zealand dialysis and transplant registry ANZDATA registry report 2005, Australian and New Zealand dialysis and transplant registry Available from: http://www.anzdata.org.au/v1/reports_2005.html

Arcaro, S. (2009). Wearable Artificial Kidney [Internet]. Ubergizmo. Available from: http://www.ubergizmo.com/15/archives/2009/08/wearable_artificial_kidney.html [Accessed 24th September].

Davenport, A., Gura, V. et al (2007). 'A wearable haemodialysis device for patients with end-stage renal failure: a pilot study', Lancet, 370 (9604), 2005-2010.

Gura, V., Beizai, M. et al (2005). 'Continuous renal replacement therapy for end-stage renal disease. The wearable artificial kidney (WAK)', Contrib Nephrol, 149, 325-333.

Gura, V., Davenport, A. et al (2009a). 'Beta2-microglobulin and phosphate clearances using a wearable artificial kidney: a pilot study', Am J Kidney Dis, 54 (1), 104-111.

Gura, V., Macy, A. S. et al (2009b). 'Technical breakthroughs in the wearable artificial kidney (WAK)', Clin J Am Soc Nephrol, 4 (9), 1441-1448.

Kerr, P. G., Polkinghorne, K. R. & McDonald, S. P. (2008). 'Home hemodialysis in Australia: Current perspective', Hemodialysis International, 12 (SUPPL. 1), S6-S10.

KHA (2005). Home haemodialysis: a treatment option [Internet]. Kidney Health Australia. Available from: http://www.kidney.org.au/LinkClick.aspx?fileticket=EWealRHD26U%3d&tabid=609&mid=882 [Accessed 15th October].

KHA (2006a). The Economic Impact of End-Stage Kidney Disease in Australia, Kidney Health Australia. Available from: http://www.kidney.org.au/assets/documents/Economic%20Impact%20of%20ESKD%20in%20Australia%20Published%202006.pdf

KHA (2006b). National chronic kidney disease strategy, Kidney Health Australia. Available from: http://www.kidney.org.au/LinkClick.aspx?fileticket=Q96sqCSVqzQ%3d&tabid=635&mid=1590

Lee, D. B. & Roberts, M. (2008). 'A peritoneal-based automated wearable artificial kidney', Clin Exp Nephrol, 12 (3), 171-180.

Masterson, R. (2008). 'The advantages and disadvantages of home hemodialysis', Hemodialysis International, 12 (SUPPL. 1), S16-S20.

medGadget (2007). Wearable Artificial Kidney [Internet]. Available from: http://medgadget.com/archives/2007/12/wearable_artificial_kidney_wak.html [Accessed 24th September].

Ronco, C., Davenport, A. & Gura, V. (2008). 'Toward the wearable artificial kidney', Hemodial Int, 12 Suppl 1, S40-47.

Ronco, C. & Fecondini, L. (2007). 'The Vicenza wearable artificial kidney for peritoneal dialysis (ViWAK PD)', Blood Purif, 25 (4), 383-388.

Notes: