2. Concept of ultrafiltration
• To remove large volume of fluid from the
intravascular space in short duration
• Movement of water across a membrane due to
hydrostatic pressure gradient
• No dialysate required
• The fluid removed is called ultrafiltrate
3. Concept of dialysis
• It is a process in which blood is separated from
crystalloid solution by a semipermiable membrane
• A solute concentration gradient exsists b/w the blood
and dialysate
4. purpose
• Effective removal of edema fluid in over hydrarted
patients.
• In renal impairment.
• To concentrate hemodiluted blood.
• Blood conservation through preservation of platelets
and coagulation factors.
• Reduced post cpb inflamatory response.
5. Purpose contd.,
• Decreases complement activation and inflamatory
response.
• Improves pulmonary cardiac and neurologic function
• Moderates temperature elevations by removing
circulating pyrogens
6. Advantages of Hemofiltration
• Advantages of Hemofiltration:
• Removal of water.
• -Reduces tissue edema .
• - Increase Hct
• Increase Coagulation factors
• Removal of inflammatory mediators
• -(tissue necrosis factor,C3a,
interleukins –1 & 6 etc)
• Removal of any solutes < Cut off
value(60,000daltons)
7. Physiologic principles
• “Selective seperation of plasma water and low
molecular weight solutes from intravascular cellular
components and plasma protiens of blood using a
semipermiable membrane filter”
9. Efficacy of ultrafilter
• Efficacy is determined by the equation
Qf = Uc X TMP _ IP
Qf – ablity to remove fluid
Uc- Ultrafiltration coefficent
Ip- Protien oncotic pressure
10. Factors affecting the
filtration:
• Factors affecting the filtration:
• Diameter of pores(10-35A)
• Number of pores
• Thickness of membrane
• Viscocity of blood, Hct, Protein levels
• Temperature
• Absolute ultration can be increased by:
• Increasing inlet pressure
• Clamping outlet partially
• Increasing filtrate side negative pressure
• Increasing blood flow
13. Efficacy contd.,
• The efficiency of the ultrafiltration will depend on
• HB concentration
• Temperature
• Rate of blood flow
• Serum protien concentration
• Membrane structure
14. Sieving co-efficient
• The efficiency of an ultrafiltration device to remove a
soluble molecule is called sieving coefficient and is
directly related to molecular size.
• The larger the molecular size the less eficient the
ultrafiltration device
17. Effect of ultrafiltration on drugs
• Heparin
• Decreases serum level of anesthetic agents
• Decreases aprotinin level
• Removes pharmacological agents with low molecular
weight
18. Technical Aspects
• Hollow fiber construction
• Materials:-
1. Polysulfone
2. Polyacrylonitrite
3. Cellulose acetate
• Pore size 180 to 200micrometers in dia
• Pores of the microporous membrane 5 to 10 nm
• Placement in extracorporeal circuit
24. Organ effects
• Reduction in PVR, Lung water, Increase in Lung
compliance
• Reduction in HR, Increase Systolic Pressure,
• Inrease in CI
• Better renal function(secondary to removal of mediators)
• Reduced cerebral edema
• Increased cerebral oxygen delivery
25. MUF advantages
• Immediate responses:
• HCt Increase (by 60-70%)
• RA Decrease (by 50-60%)
• LA Decrease (by 25-35%)
• Tidal Volume Increase (by 20—40%)
• P A Decrease (by 30-50%)
• Contractility Improved
• Haemostasis Improved
• Heart size Reduced (to be correlated)
• Blood Sugar Levels Decreased(40-50%)
• Blood transfusion No R C required
26. MUF diaadvantages
• Disadvantages:
• Time Delay
• Temperature drift if Heat Exchanger is not
available
• Homodynamic instability in the initial period
• Air embolism
• -Proper snugger around Aortic Cannula
• -Isolate Oxygenator from MUF circuit
• Disposable Cost
29. Hemodialysis during CPB
• Membrane material is similar to ultrafilter
• The difference is dialysate is passed through the
nonblood side of membrane
• Removes diffusible solutes based on concentration
gradient by the dialysate soln
• Water and solutes are removed by convection
30. Circuit design for dialysis in
CPB
• Hemodialysis machine not used in CPB
• Dialyser positioned parallel to the ECC
• Dialysate solution - .9%NS
• Dialysate can be configured so as to achieve efficient
diffusion rate
• Dialysate flow should be 3 times the blood flow
31. Advantages
• Hemodialysis is effective in removing potassium and
small molecular wt solutes
• Small molecules like urea and electrolytes can be
removed.
• Hemofiltration is better for middle molecules .
(because of convection rather than diffusion)
32. Blood conservation Techniques
• Cardiac surgery has propensity of excess blood usage
due to
• Extensive intervention involving major vascular
structures
• Destruction of rbc and coagulation factors during
CPB resulting in increased need of blood
• Extracorporeal circuit
33. Blood conservation stratagies
1. Retropriming and reduction in priming volume
2. Autologus donation
3. Scavenging of shed blood(cell savers)