scholarly journals Cardiac output and urea kinetics in dialysis patients: Evidence supporting the regional blood flow model

1996 ◽  
Vol 50 (4) ◽  
pp. 1273-1277 ◽  
Author(s):  
Titiola O. George ◽  
Adrian Priester-Coary ◽  
George Dunea ◽  
Daniel Schneditz ◽  
Nauman Tarif ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Flow Model ◽  
Regional Blood Flow ◽  
Dialysis Patients ◽  
Urea Kinetics ◽  
Blood Flow Model

scholarly journals A diffusion-adjusted regional blood flow model to predict solute kinetics during haemodialysis

2009 ◽  
Vol 24 (7) ◽  
pp. 2218-2224 ◽  
Author(s):  
Daniel Schneditz ◽  
Dieter Platzer ◽  
John T. Daugirdas
Keyword(s):  
Blood Flow ◽  
Flow Model ◽  
Regional Blood Flow ◽  
Blood Flow Model

A Regional Blood Flow Model for Glucose and Insulin Kinetics During Hemodialysis

ASAIO Journal ◽  
2013 ◽  
Vol 59 (6) ◽  
pp. 627-635 ◽  
Author(s):  
Daniel Schneditz ◽  
Magda Galach ◽  
Karl Thomaseth ◽  
Jacek Waniewski
Keyword(s):  
Blood Flow ◽  
Flow Model ◽  
Regional Blood Flow ◽  
Insulin Kinetics ◽  
Blood Flow Model

scholarly journals Analytical Solution of Multicompartment Solute Kinetics for Hemodialysis

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Przemysław Korohoda ◽  
Daniel Schneditz
Keyword(s):  
Blood Flow ◽  
Flow Model ◽  
Linear Models ◽  
Regional Blood Flow ◽  
Compartment Model ◽  
Practical Applications ◽  
Novel Approach ◽  
The Matrix ◽  
Creatinine Kinetics ◽  
Blood Flow Model

Objective.To provide an exact solution for variable-volume multicompartment kinetic models with linear volume change, and to apply this solution to a 4-compartment diffusion-adjusted regional blood flow model for both urea and creatinine kinetics in hemodialysis.Methods.A matrix-based approach applicable to linear models encompassing any number of compartments is presented. The procedure requires the inversion of a square matrix and the computation of its eigenvaluesλ, assuming they are all distinct. This novel approach bypasses the evaluation of the definite integral to solve the inhomogeneous ordinary differential equation.Results.For urea two out of four eigenvalues describing the changes of concentrations in time are about 105times larger than the other eigenvalues indicating that the 4-compartment model essentially reduces to the 2-compartment regional blood flow model. In case of creatinine, however, the distribution of eigenvalues is more balanced (a factor of 102between the largest and the smallest eigenvalue) indicating that all four compartments contribute to creatinine kinetics in hemodialysis.Interpretation.Apart from providing an exact analytic solution for practical applications such as the identification of relevant model and treatment parameters, the matrix-based approach reveals characteristic details on model symmetry and complexity for different solutes.

scholarly journals Is intercompartmental urea clearance during hemodialysis a perfusion term? A comparison of two pool urea kinetic models.

1995 ◽  
Vol 6 (5) ◽  
pp. 1360-1370
Author(s):  
D Schneditz ◽  
B Fariyike ◽  
R Osheroff ◽  
N W Levin
Keyword(s):  
Blood Flow ◽  
Cell Membrane ◽  
Membrane Permeability ◽  
Flow Model ◽  
Regional Blood Flow ◽  
The Body ◽  
Membrane Model ◽  
Cell Membrane Permeability ◽  
Cell Membrane Model ◽  
Blood Flow Model

Analyses of intradialytic and postdialytic urea profiles call for models that consider delayed urea transfer from different parts of the body to the blood. There are two different approaches to the problem. In the classical cell membrane model it is assumed that the two compartments refer to the serial (s) arrangement of extracellular and intracellular volumes, whereas in the regional blood flow model the two compartments are identified as parallel (p) organ systems with high or low perfusion. In the cell membrane model, delayed urea removal from peripheral body compartments is governed by intercompartmental clearance (Kc) which is a function of cell membrane permeability, whereas in the regional blood flow model delayed urea removal is related to low perfusion (QL) of the large muscle/skin/bone compartment. Both models were compared in a set of 16 high-efficiency hemodialysis treatments. Modeled volumes (Vm,s = 31.2 +/- 9.5 L; Vm,p = 30.0 +/- 8.3 L) and modeled dose of hemodialysis (Kt/Vm,s = Kt/Vm,p = 1.12 +/- 0.33) were the same for both models. However, volumes modeled by either technique were significantly lower than anthropometric volumes (V alpha = 35.0 +/- 6.4 L). These data suggest that at this point the two models are experimentally indistinguishable. Moreover, the main system parameters of both models, Kc (0.54 +/- 0.16 L/min) and QL (0.63 +/- 0.15 L/min) showed a strong linear dependence (QL = 0.921 Kc + 0.139, r2 = 0.884), whereas no relation could be found between Kc and Vm. Therefore, delayed transport that has up to now been characterized by membrane permeability may also be explained by peripheral perfusion.

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