References & Formulas

Estimated as a function of blood flow (Qb), dialysate flow (Qd) and membrane permeability area coefficient (koA) using the proposed model by Michales and modified by Depner et al.

Michaels AS. Operating parameters and performance criteria for  hemodialyzers and other membrane-separation devices. Trans Am Soc Artif  Intern Organs. 1966;12:387-92. 

PMID: 5960730.

Depner TA, et al.  Dialyzer performance in the HEMO Study: in vivo K0A and true blood flow  determined from a model of cross-dialyzer urea extraction. ASAIO J. 2004;50(1):85-93.

PMID: 14763497.

The product of estimated urea clearance (K) and therapy time divided by the estimated urea volume of distribution (V). The urea V is the total body water calculated with the Watson formula. 

Watson PE, Watson ID, Batt RD. Total body water volumes for adult males  and females estimated from simple anthropometric measurements. Am J Clin Nutr. 1980;33(1):27-39. 

PMID: 6986753.

Solved from the previous estimated Kt/V as:  URR = 1- (eKt/V) 

Daugirdas JT, Leypoldt JK, Akonur A, Greene T, Depner TA; FHN Trial  Group. Improved equation for estimating single-pool Kt/V at higher  dialysis frequencies. Nephrol Dial Transplant. 2013 Aug;28(8):2156-60.

PMID: 22561585

BUN, sodium and potassium have similar mass transfer during hemodialysis, so when considering a one compartment model the new concentration is:  Pre therapy solute - [(Solute blood - Solute dialysate) * URR]

For the 2-pool post-therapy K:   a  1.6 liters/kg  of body weight was used  as  volume of distribution to predict  a 5-hour post-dialysis potassium levels, accounting for a two-compartment kinetic model.  

Feig, P. U., Shook, A., & Sterns, R. H. (1981). Effect of potassium removal during hemodialysis on the plasma potassium concentration. Nephron, 27(1), 25–30.

PMID: 7219633

These results have been validated in a prospective cohort pending publication