Hemodialysis Kinetics 101

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Basics

The Absolute Basics

We conduct DIALYSIS to remove ‘uremic solutes/toxins’ from blood in a patient with kidney failure.

Urea is one of the many uremic toxins (>100 identified). It is considered a low molecular weight toxin (molecular weight: 60 Daltons) that is water soluble. Its volume of distribution is the total body water. It is produced by the liver and is also the end product of protein catabolism.
It is only mildly toxic by itself. However it is considered an easily measurable surrogate for other small molecular weight uremic toxins.
We frequently measure ‘success’ of dialysis in terms of how effectively we clear the patients blood of urea.
This is also called urea clearance.

Blood is cleared of urea by its movement across the dialysis filter membrane into the dialysate.

This occurs via both diffusion (diffusive clearance) and convection (convective clearance)

Hemodialysis removal of urea (urea clearance) during a dialysis session is measured numerically as Kt/V

Yale University School of Medicine
Veterans Affairs Medical Center
2017