Ultrafiltration Flashcards
Conventional Ultrafiltration (CUF)
is a technique that removes plasma water and low molecular weight solutes by a convective process using hydrostatic pressure forces across a semipermeable membrane.
Zero Balance Ultrafiltration (ZBUF)
is a technique utilizing an hemoconcentrator to maintain a controlled EQUALIZED input and output over the CPB pump run
Slow Continuous Ultrafiltration (SCUF)
s a technique utilizing a slow, steady ultrafiltration during the CPB pump run
Modified Ultrafiltration (MUF)
is ultrafiltration occurring after the separation from CPB.
the Effluent path first concepts related to the use of ultrafiltration in hospital practice, date from
1928
Ultrafiltration is achieved
(using a hemoconcentrator) in the CPB circuit and allows the filtration of body water across a semi-permeable membrane utilizing a hydrostatic pressure gradient
Blood flow path is
inside the fibers. (higher pressure)
Effluent path
is outside the fibers
uses pressure gradient to
push crap from blood to effluent side. is outside the fibers
Dialysis will use a dialysate solution on the
effluent side to control precise solute excretion
HOW DO ULTRAFILTERS WORK?
Diffusion (change in concentration)
Ultrafiltration (change in pressure)
referred to as convection, is fluid flow through the membrane, forced by a difference in pressure on two sides of the membrane
osmosis in dialysis
this refers not to water movement across the hemodialyzer membrane, but across cell membranes
Achieving filtration across a membrane requires
blood flow and hydrostatic (pressure gradient)
Pressure /flow and resistance is key
The ability of a solute to be filtered through the membrane depends on
the molecular weight compared to the pore size of the filter (sieving coefficient)
he rate of solute removal through the membrane depends
on the flow rate and transmembrane pressure (TMP)
A dalton quanitates mass, defined as
/12 the mass of a carbon-12 nucleus. It’s also called the atomic mass unit, abbreviated as either “amu” or “u”. You can convert kg into u using this conversion factor:
1 u = 1.6605655(86) × 10-27 kg
BOTTOM LINE: very, very small
Removing body water will allow
an elevation in the Hct without transfusion
This is what you can do when you have extra volume in your reservoir. Can be combined with other procedures and will become CUF, SCUF, Z-BUF, MUF.
Sieving Coefficient
Ratio of blood solute concentration to plasma concentration
Ranges from 0 to 1.0 A coefficient of 1 means the solute concentrations
equilibrate on both sides of the membrane
A coefficient of 0 means no solute passed the membrane (large molecular weight/size)
ca Sieving Coefficient
.55
k Sieving Coefficient
1.0
mg Sieving Coefficient
1.0