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 â1 & 6 etc)
⢠Removal of any solutes < Cut off
value(60,000daltons)
7. Physiologic principles
⢠âSelective seperation of plasma water and low
molecular weight solutes from intravascular cellular
components and plasma protiens of blood using a
semipermiable membrane filterâ
9. Efficacy of ultrafilter
⢠Efficacy is determined by the equation
Qf = Uc X TMP _ IP
Qf â 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 20â40%)
⢠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)