Ultrafiltration coefficient

Dialysis, kidney, 15 844-845 Dialysis membrane, hydraulic permeability/ultrafiltration coefficient of, 26 818-819 Dialyzer model, 26 817 Dialyzers... 

Hydraulic permeability/ultrafiltration coefficient, of a dialysis membrane, 26 818-819... 

Many classification schemes for hemodialysis membranes exist. Water permeability through the porous membranes is frequently used.14 Water permeability for a dialyzer is defined by the ultrafiltration coefficient for the particular device (KUF, mL/ h/mmHg). The KUF of any individual fiber will be related to the pore size and has an... 

If we consider a membrane having the same solute concentration on both sides, we have All 0 However, a hydrostatic pressure difference AP exists between the two sides, and we have a flow Jv that is a linear function of AP. The term Lp is called the mechanical filtration coefficient, which represents the velocity of the fluid per unit pressure difference between the two sides of the membrane. The cross-phenomenological coefficient Ldp is called the ultrafiltration coefficient, which is related to the coupled diffusion induced by a mechanical pressure of the solute with respect to the solvent. Osmotic pressure difference produces a diffusion flow characterized by the permeability coefficient, which indicates the movement of the solute with respect to the solvent due to the inequality of concentrations on both sides of the membrane. 

Dog Uranyl nitrate 5-10 mg/kg Backleak of filtrate Decreased ultrafiltration coefficient S3 segment of proximal tubule [194,195]... 

Rat Gentamycin 40-120 mg/kg/day Decreased ultrafiltration coefficient Tubular obstruction Proximal convoluted tubule [197-199]... 

Infusions of AmB, intravenously or into the renal artery, induce short-term reduction in renal blood flow (RBF) and GFR, and an increase in renal vascular resistance, in both rats and dogs [83-85]. The effects of short term infusions of AmB on the renal microcirculation in rats revealed that the single nephron GFR was decreased by 2 mechanisms (Table 1) 1) a decrease in single nephron plasma flow, due to vasoconstriction of the afferent and efferent arterioles, and 2) a reduction in the glomerular capillary ultrafiltration coefficient (Kf), an effect probably mediated by mesangial cell contraction [86]. Previous micropuncture studies demonstrated a similar vasoconstriction of the afferent arteriole but also an increased permeability of the tubular epithelium to inulin [75]. Thus, the reduction in GFR after acute AmB infusions can be attributed to contraction of afferent smooth muscle cells, efferent smooth muscle cells and glomerular mesangial cells, as well as increased tubular permeability with back-leak... 

In an in vivo animal study, at doses not causing crystalluria or tissue crystal deposition, short term exposure to acyclovir caused increased renal vasoconstriction and an associated fall in renal blood flow and single nephron plasma flow [22]. Longer-term treatment resulted in a fall in glomerular ultrafiltration coefficient. Thus, it is not clear whether the pathogenesis of acyclovir-induced AKI in humans reflects an obstructive nephropathy from intratubular precipitation of acyclovir, a hemodynamic response, or a type of toxic, immunologic, or hypersensitivity reaction. It is also possible that more than one process may be involved. 

There are several potential mechanisms of PG involvement in the pathogenesis of acute renal failure (ARF). Vascular factors are pre-eminent in the initiation and maintenance of acute renal failure. These include control of RBF, autoregulation, tubuloglomerular feedback, the glomerular capillary ultrafiltration coefficient (Kf), the no-reflow phenomenon (which is secondary to capillary endothelial injury and swelling), the renin-angiotensin system and endogenous vasoconstrictors (e.g. catecholamines). 

The terminology for characterizing dialysis membranes is somewhat unique to the dialysis field. Instead of being characterized in terms of hydrauhc penneabUity, diffusive membrane permeabihties, and solute rejection coefficients, dialyzers arc generally characterized in terms of an ultrafiltration coefficient (Kuf), solute clearances, and the product of the mass transfer coefficient times the surface area (KoA). 

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