By Bill Peckham
The videos are no longer available at the links in this post,
instead all the videos are embedded and can be watched at the CIMIT
blog in this post. The five videos are embedded in the same order as they were presented in 2008. My review of the videos are all listed in the Future of Dialysis Category on DSEN.
On Saturday I wrote The future of dialysis: T and G membranes about CIMIT's forum: Quest for a Wearable Kidney: Will Nanotechnology Make a Difference? . The forum is broken up into five video segments; I thought this week I would review one video segment a day. On Monday I wrote CKD overview video: Dr. Bonvertre about the first video segment of the forum. This second video is about 45 minutes long and features Theodore I. Steinman, MD, Clinical Professor of Medicine, Harvard Medical School; Beth Israel Deaconess Medical Center.
Dr. Steinman gives a fascinating talk picking up the story where Dr. Bonvertre left it. Dr. Steinman looks to what the future of dialysis may hold as work proceeds on "developing a new type of functioning artificial nephron". At one point in the video he gives a tour of the human nephron but for the most part this video segment covers nanotechnology and the sort of impact nanotechnology is expected to make on the provision of dialysis.
Dr. Steinman goes over some of the common clinical impacts of standard dialysis; he suspects that chronic inflammation may be at the heart of the cardiovascular problems associated with dialysis. He makes the point that "advances at the margin" in the provision of dialysis do not address some of the major problems that we need to address to improve the quality of patients lives.
Dr. Steinman gives some nanotechnology background. Which for the most part I feel hopeful when he talks about manipulating pore size of the semipermeable membrane to make a better dialyzer but when he talks about microscopic nano-robots, nano drug delivery devices and multipurpose nano particles ... well I wonder if society is prepared for injectable nano particles, let alone nano-robots. Thankfully that is not an issue dialyzors will have to pioneer. The nanotechnology that will revolutionize dialysis has to do with a nano-engineered dialysis membrane with specially devised nanoscale pores.
As a dialysis geek or wonk I have to say, I was in heaven when he started talking about membrane pores. This is where dialysis actually happens. Right there at the semi permeable membrane a molecule moves across from the blood space into the dialysate. That moment is the key, repeated many times. Here Dr. Steinman talks about unselective pores v highly selective pores and his plan to selectively filter and then selectively reabsorb just the molecules we want, he describes a pore library that will offer just the right membrane pore for each component of plasma, good and bad.
He lists the faults of today's modern dialyzers:
unselective transport; wide distribution of pore sizes leads to statistical filtration
relatively thick, often low flux
no opportunity for precise atomic placement
long pore pathways
tortuous path
Thats an interesting concept "statistical filtration". Today dialysis is based on the concept that it's bound to work. That the size and shape of the membrane pores vary enough that statistically you're bound have some proportion of pores that are suitable. heh
If that wasn't enough for one video he then comes to the meat of his talk on the Continuous Functioning Artificial Nephron (CFAN). This is the device that uses the G and T membranes to create a highly efficient dialyzer. G stands for glomerulus, T stands for tubular together the mimic the human nephron. Dialysis using this new technology (and running 12 hours a day 7 days a week) could provide a GFR equivalent to 30 - that's barely stage 4 CKD. Someday the technology could provide a GFR equivalent of 60 - barely stage 3.
So the G membrane would take stuff out, the T membrane would allow stuff back. What each membrane would do exactly would depend on which pores you incorporate into the membrane - the membranes would be customized based on prescription. Fluid removal based on pores chosen. This could work on a standard machine but the technology opens up many possibilities in design because it doesn't use dialysate. Solute transport occurs by convection - passive transport.
With no dialysate an implantable device looks more practical and certainly a wearable kidney is easier to create. However a wearable kidney again brings cannulation into play and about five slide from the end Dr. Steinman shows what a double lumen needle and immobilization device looks like. Double lumen so you use one needle for venous and arterial duties but how can it be immobilize? It looks to be a tape based contraption with a portal in the tape that presumable is centered on a buttonhole. Then once the needle is in, it looks like a cap disengages from the tape to snap over the needle "locking" it to the tape? Maybe. And then there might be a tab of sur-seal material in a circle that covers the cannulation site on ex-cannulation. It would be helpful to see this system demonstrated. I'm good at making stuff up. Still not sure about wearing it for 12 hours a day. Maybe.
So many things come to mind but for one thing they're imagining a waste bag taped to the thigh. Clearly the better way would be to wear it like a shoulder holster and run the drain line down to the zipper. I hope that highly efficient, engineered membranes are coming; the next video segment touches on the business side of the equation. One problem Dr. Steinman mentions is coagulation and how to keep it from clotting up. I guess that is where the nano-robots come in or maybe nano heparin dispensers. Unless cost is prohibitive we should be seeing nano-engineered membranes someday. Maybe they can be reused if they are expensive. Cleaned between treatments by nano pore cleaners. Endless possibilities. All very hopeful.
Comments