What is Dialysis?

The-Merck-Home-Manual-of-Medical-Information-Dialysis
Flickr CC Amber Case The-Merck-Home-Manual-of-Medical-Information-Dialysis taken May 28, 2009

Blog post by written by Joanna Manero, BS Research Assistant,
Master’s Degree Student University of Illinois at Urbana-Champaign Food Science and Human Nutrition.

Please join us on June 29th at 11AM ET for an informative webinar on diet and exercise in the Kidney Disease population.  Dr. Kenneth Wilund from the University of Illinois at Urbana-Champaign will share with us his expertise on the subject.  To register, visit the event page.  Dietitians earn 1.0 CPEU.  If you can’t attend you can view the video posted after the webinar and still earn CPEU.

In anticipation for Dr. Wilund’s webinar, I started thinking about how incredible hemodialysis technology is.  To have a machine be able to strip a person’s blood of waste material and reduce fluid in place of the kidneys is really quite remarkable.  Let’s take a quick look at just how this machine works.  

In hemodialysis, a dialyzer is used to filter the blood.  A dialyzer is an external filter that uses a semipermeable membrane and a liquid solution called dialysate to filter accumulated waste in the bloodstream due to loss of kidney function.  The blood flows in one direction while the dialysate flows in the opposite direction and into a waste tub.  Dialysate is a fluid that is mostly made up of electrolytes and water.  It acts as a filtrating fluid by attracting waste material found in the blood at high concentrations (urea, potassium, phosphorus) to itself by osmosis.  Because of this, dialysate is renewed continuously during the dialysis process to ensure that concentration levels of waste materials remain low.  Fluid is removed from the bloodstream by increasing hydrostatic pressure across the dialyzer membrane.  This causes the separation of fluid from the blood stream which is then adhered to the dialysate.  Once the blood is clean, it is reinserted into the patient.  This whole process takes around 4 hours and must be done several times a week.  

Now let’s take a look at how this technology came to be.

Bulb dialyzer used by Graham (from Ref. 2) Image by: Philosophical Transactions
Bulb dialyzer used by Graham (from Ref. 2) Image by: Philosophical Transactions


In 1854, Thomas Graham, a chemist, created the device that we see above.  Distilled water was placed below the bell-shaped container.  Urine was placed inside the bell-shaped container.  At the opening of the bell-shaped container, Graham used a semi-permeable membrane made from ox bladder.  After some time, the bell-shaped container was removed and the distilled water in the larger container was boiled dry.  After boiling, Graham showed that the residue was composed of sodium chloride and urea.  These are components from the urine that had passed through his semi-permeable membrane (ox bladder). Graham termed this process as dialysis.  

We have come a long way from using ox bladder as a semi-permeable membrane. Sometimes looking back at how a concept originated puts into perspective how far it has come.  We hope that you will tune in on June 29th at 11am EDT to learn about kidney disease.  

References:

Advanced Renal Education Program (2015) History of Hemodialysis. Available at: http://advancedrenaleducation.com/content/history-hemodialysis (Accessed: 13 June 2016).

Graham, T. (1861) ‘Liquid Diffusion Applied to Analysis’, Philosophical Transactions, 151, pp. 183–224.

McMorran, J., Crowther, D., McMorran, S., Youngmin, S., Wacogne, I., Pleat, J. and Prince, C. (no date) Composition of dialysate fluid – general practice notebook. Available at: http://www.gpnotebook.co.uk/simplepage.cfm?ID=1644560429 (Accessed: 13 June 2016).

This blog is posted by Robin Allen, a member of the Military Families Learning Network (MFLN) Nutrition and Wellness team that aims to support the development of professionals working with military families.  Find out more about the MFLN Nutrition and Wellness concentration on our website, on Facebook, on Twitter, and LinkedIn.

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