Implantable Dialysis Device for Treatment of Renal Failure

Transcription

1 Implantable Dialysis Device for Treatment of Renal Failure

2 Outline Kidney function Renal Failure Dialysis overview Device Proposal Fabrication Methods Biocompatibility Conclusion

3 Function of the kidneys Kidney is a filter Removes excess waste and water from blood Create urine to be expelled from the body

4 How the kidney works Blood is brought into the kidneys through the renal arteries

5 How the kidney works The blood flows into filtering units called nephrons. Nephrons consist of the glomerulus and a tubule

6 How the kidneys work Glomerulus

7 How the kidneys work Urine is passes from the Glomerulus to the tubule In the tubule fine adjustments in chemical content are made Urine then flows from the tubule, through the ureter to the bladder where it will be expelled

8 Introduction to Renal Failure Renal failure occurs when the kidneys fail to filter blood efficiently Failure can lead to abnormal fluid levels in the body, incorrect acid levels, abnormal potassium, calcium, and phosphate levels, blood in the urine and anemia A test of the glomerular filtration rate can be used to quantify the kidney function Renal failure can be described as acute or chronic

9 Some causes of Renal failure Acute Interruption to blood supply to kidney Drug overdose Chronic Diabetes Mellitus Hypertension Polycystic kidney disease Overuse of drugs

10 Current Technology: Dialysis Dialysis is a means of replacing some body functions lost due to renal failure. Hemodialysis is most common and cleanses the blood through diffusion and ultrafiltration. More frequent / longer treatments may yield better results.

11 Nat l Stats for Hemodialysis 331,507 principal hemodialysis procedure discharges reported nationally in 2006 Average length of stay (LOS) of 5.6 days Average charges of $26,346 (both LOS and charges include secondary procedures) 77% of all patients receiving hemodialysis were in age ranges of and years (37% and 40%, respectively) Source: HCUP

12 Diffusion and Ultrafiltration Diffusion removes solutes in blood such as sodium, potassium, and calcium. Semi-permeable membrane allows solutes to pass while blood cells are retained. Ultrafiltration removes excess water from the blood.

13 Device Proposed:

14 Device Proposed: Specifications Mimic operation of natural kidneys Filter solute in similar molecular weight spectrum Continuous operation, minimal maintenance Flexible operation based on patient needs Implantable No external power source

15 Device Proposed: Challenges Perform the function of dialysis without dialysate Pressure gradient needed for diffusion Membrane selectivity Flow rate of mL/min Biocompatibility Implantable Biofouling

16 Device Proposed: Membranes G-Membrane T-Membrane

17 G-Membrane Mimics function of Glomerulus Blood Ultrafiltrate Uses convective transport to generate plasma ultrafiltrate containing solutes

18 T-Membrane Mimics function of Tubules Ultrafiltrate Waste Water/salt return to blood Uses convective transport though a smart membrane selectively reclaiming designated solutes to maintain body homeostasis

19 Membrane Fabrication Membranes will need many pores of different sizes G-membrane will have larger pores than T- membrane Ion beam milling will create holes in a silicon substrate Focused Ion Beam sputtering will be used to coat the inner surface of holes to make the diameter smaller

20 Membrane Fabrication

21 Check Valve Design Valve can be made from PDMS Flapper style Microcontact printing or micro molding used to create valve

22 Biocompatibility Considerations Blood/Implant interaction should cause minimal inflammatory response, especially for continuous operation. Biocompatibility testing should be carried out according to ISO

23 Testing Considerations Evaluation tests described by the ISO standard. Particularly relevant subparts include: Part 4, Selection of Tests for Interactions with Blood. Part 6, Tests for local effects after implantation. Long term exposure testing will also be necessary for both biocompatibility and biofouling.

24 Limitations This device will be used initially in a laboratory setting on animals. An implantable device for humans would require closed loop monitoring of blood or filtered material to determine device performance. Surface area of membrane is critical for efficiency of device.

25 Summary An implantable dialysis device would benefit patients with chronic (stage 5) renal failure Improve clinical outcome for patient Reduce trips to dialysis center Alternative to kidney transplant

26 References Dhondt, A., Vanholder, R., Glorieux, G., Waterloos, M. A., De Smet, R., Lesaffer, G., and Lameire, N. (2000). Vitamin e-bonded cellulose membrane and hemodialysis bioincompatibility: absence of an acute benefit on expression of leukocyte surface molecules. American journal of kidney diseases : the official journal of the National Kidney Foundation, 36(6): Grayson, A. C. R., Shawgo, R. S., Johnson, A. M., Flynn, N. T., Yawen, L. I., Cima, M. J., and Langer, R. (2004). A biomems review: MEMS technology for physiologically integrated devices. Proceedings of the IEEE, 92(1):6 21. Hakim, R. M. (1993). Clinical implications of hemodialysis membrane biocompatibility. Kidney Int, 44(3): Nissenson, A. R., Roncon, C., Pergamit, G., Edelstein, M., Watts, R. (2006) The Human Nephron Filter: Toward a Continuously Functioning, Implantable Artificial Nephron System. Blood Purification, 23: Saliterman, S. S. (2006). Fundamental of BioMEMS and Medical Microdevices. Bellingham, WA: SPIE Press.

27 Questions?