Topic 14 Flashcards
Hemoconcentration=
an increase in the number of red blood cells resulting from a decrease in plasma volume.
–Increases Hct
Conventional Ultrafiltration (CUF)=
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)=
technique utilizing an hemoconcentrator to maintain a controlled EQUALIZED INPUT and OUTPUT
–IN = OUT
Slow Continuous Ultrafiltration (SCUF)=
a technique utilizing a slow, steady ultrafiltration during the CPB pump run
Modified Ultrafiltration (MUF)=
ultrafiltration occurring AFTER THE SEPARATION FROM CPB
how is Ultrafiltration 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
Hollow Fiber Hemoconcentrators:
Blood flow path is ____ the fibers
Effluent path is ____ the fibers
Blood flow path is inside the fibers
Effluent path is outside the fibers
Hemoconcentration involves letting the pressure gradient “push” body water to the effluent side, can be used with or without a?
vacuum
Dialysis will use a dialysate solution on the _____ side to control precise solute excretion
effluent
HOW DO ULTRAFILTERS WORK?
diffusion
–Exchange of things dissolved in fluid (solutes) across a membrane due to differences in amount of the solutes on the two sides (concentration gradient)
If a higher concentration of a given solute is on one side, then diffusion will try to do what?
make the concentrations across the membrane the same
fluid flow through the membrane, forced by a difference in _____ on two sides of the membrane
pressure
–referred to as convection
Osmosis=
the NET MOVEMENT OF WATER across a selectively permeable membrane
Osmosis is driven by what?
a difference in the amounts of solute on the two sides of the membrane.
In dialysis, this refers not to water movement across the hemodialyzer membrane, but across…
cell membranes
Achieving filtration across a membrane requires what 2 things?
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 what?
the molecular weight compared to the pore size of the filter (SIEVING coefficient)
The rate of solute removal through the membrane depends on what?
the flow rate and transmembrane pressure (TMP)
A dalton quanitates mass, defined as 1/12 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
Removing body water will allow an elevation in the Hct without doing what?
transfusion
–This is what you can do when you have extra volume in your reservoir
Sieving Coefficient=
Ratio of blood solute concentration to plasma concentration. Ranges from 0 to 1.0
Sieving Coefficient of 1=
the solute concentrations equilibrate on both sides of the membrane
Sieving Coefficient of 0=
no solute passed the membrane (large molecular weight/size)
Sieving Coefficient of Ca++
0.55 (so it will dilute systemic calcium)
Sieving Coefficient of K+
1
Sieving Coefficient of Mg++
1
Sieving Coefficient of Aprotinin
1
Sieving Coefficient of Heparin
0.20 (so it will decrease your ACT)
Sieving Coefficient of furosemide
0.05
Sieving Coefficient of digoxin
0.75
how do you find net pressure gradient of membrane
add positive and negative pressures
what does pink effluent mean
red cells are being lysed so decrease occlusion or vacuum pressure
Diffusion in dialysis=
movement of solutes from a area in which they are in high concentration to one of a lower concentration – along an electrochemical gradient
Diffusion in dialysis:
An electrolyte solution runs _____ to blood flowing on the other side of the membrane. Small molecules such as ___ move along the into the dialysate fluid. Larger molecules are ____ removed by this process. Solute removal is _____ proportional to the dialysate flow rate
countercurrent
urea
poorly
directly
describe the process known as solvent drag
Convection / ultrafiltration – solute is carried (in solution) across a semipermeable membrane in response to a transmembrane pressure gradient
Ultrafiltration: This is very effective in removal of ___ and ___, which are thought to cause ___. Moreover, most of the ____ involved in ____ are “middle molecules”
fluid and middle-sized molecules
uremia
cytokines
sepsis
Transmembrane Pressure=
the pressure across the filter capillary tubes
Pore Size=
the molecular weight cut off the filter is designed for (in Daltons)
Transmembrane pressure is NOT
pressure drop
transmembrane pressure (TMP)= [formula]
[ (Filter P(in) + Return P(out)) / 2] + Vacuum
*Treat vacuum as an absolute number (so just drop the negative sign and treat as a positive number)
membrane surface area ranges
0.09-1.3m2
max transmembrane pressure
500 mmHg
what ultrafiltration method will improve potential for increasing adequate oxygen delivery to tissue (increases Hct)
Conventional Ultrafiltration (CUF)
what ultrafiltration method will Draws in extravascular fluid
Conventional Ultrafiltration (CUF) --Your level in the venous reservoir will drop
what ultrafiltration method has a Slow rate over longer time
Slow Continuous Ultrafiltration (SCUF)
what ultrafiltration method may utilize the existing cannulas and allows concentration of the circuit contents to be hemoconcentrated (allows post-op reduction in total body water)
Modified Ultrafiltration (MUF)
what ultrafiltration method is Considered a “standard of care” in pediatrics
Modified Ultrafiltration (MUF)
PRACTICE DRAWING THE DIFFERENT CIRCUITS
NOW :)
with ULTRAFILTRATION 3 main parameters are critical to monitor?
Flow
Pressure
Volume
The blood flow through the ultrafilter should be monitored, it will be easier to control when?
a roller pump is used exclusively for the ultrafilter
When the blood to the ultrafilter is removed directly from the arterial line, flow depends on the characteristics of the ultrafilter and may be reduced by doing what?
partially clamping the inlet
The mean pressure on the inside of the fibers depends on what?
the pressure drop through the ultrafilter.
We can vary the TMP by varying what?
the negative pressure applied. In general, negative pressures (vacuum) of 100 to 200 mmHg may be applied
The effluent flow can be augmented by regulating what?
the vacuum source
More vacuum equals what?
more H2O removal
increased resistance (clamping) with increase effluent flow- this relationship is _____ proportional
directly
greater ultrafiltration can be achieved by what 3 things?
- increasing the TMP
- partially clamping the outlet line of the ultrafilter
- increasing in vacuum applied to the external surface of the membranes
CPB causes increased capillary permeability, including the systemic inflammatory reaction–>Capillary permeability increases total body water–>This increase of the extravascular fluid affects the functions of what?
the major organs
ultrafiltration effects on the lungs=
Pulmonary edema may reduce the efficiency of gas exchange and pulmonary complacency
ultrafiltration effects on the heart=
Myocardial edema may affect ventricular function making (diastolic filling difficult and reducing the efficiency of systole)
ultrafiltration effects on the brain=
Cerebral edema may have serious consequences
ultrafiltration effects on the kidney=
Renal function may also be impaired and the renal immaturity may make elimination of liquids more difficult
The most severe systemic inflammatory response may manifest as what?
multiple system organ failure (MSOF)
CPB activates the leucocytes and several proteic systems of the plasma. Activation results in the production of a large number of what 3 things?
cytokines, complement fractions and vasoactive substances
The main pro-inflammatory cytokines are? (4)
tumor necrosis alpha factor
IL-1 beta
IL-6
IL-8
The residues of the activation of complement system is the activation of what?
C3a and C5a
–These substances with the vascular endothelium and neutrophils produce a set of alterations that result in a systemic inflammatory reaction of the organism
When you filter you are losing volume- so make sure to…
watch your level
Pink effluent is often a result of what?
too high TMP
Vacuum will increase effluent and increase hemolysis but…
more is not necessarily better
Hemoconcentration is usually a SHUNT… so you need to
turn it off when the pump is off (compensate for it)
