1. ULTRAFILTRATION

2. Capillary Permeability
Why Ultrafiltration
Inflammatory Response
Increased
Hemodilution
Interstitial
Organs
Extravascular fluid
EDEMA
CPB
SIRS
Capillary Permeability

3. ULTRAFILTRATION AND CPB
Operational charecteristics of Ultrafilters
Impact of hemoconcentration on circulating durgs and ions
Use of hemoconcentration before, during and after CPB

4. ULTRAFILTRATION History: 1928 concept developed
clinical application
1970 first use w/OHS
1979 use w/CPB becomes general practice
1991 MUF

5. ULTRAFILTRATION Basic Physiologic Principle:
Selective separation of plasma water and low-molecular-weight solutes from the intravascular cellular components and plasma proteins of blood, using a semipermeable membrane filter.
The driving force for ultrafiltration is provided by hydrostatic pressure differential across membrane.

6. ULTRAFILTRATION Physiologic Priciple: Relationship between pressures:
Trans Mebrane Pressure (TMP)
TMP = (Pa + Pv)/2 + V
Pa – arterial or inlet pressure
Pv – venous or outlet pressure
V – negative pressure at effluent site
A-V Pressure Difference is ̴̴̴ 100 mm Hg
Due to resistance of fibers and also effected by
Viscosity, temperature, rate of flow

7. ULTRAFILTRATION Physiologic principles: Device related issues:
Flow – Pressure - Resistance
Viscocity ↑with ↓in temperature.
Device related issues:
Diameter of pores
Total number of pores (membrane surface area)
Length of pores (membrane thickness)

8. ULTRAFILTRATION Device comparison: Efficacy of device
Compare using concept of “Ultrafiltration coefficient” (intrinsic to each device)
Ultrafiltration coefficient (Kuf) is directly related to the efficiency of the device’s ability to remove fluid

9. ULTRAFILTRATION Factors Affecting Rate of Removal:
Physiologic Principle
ULTRAFILTRATION
Factors Affecting Rate of Removal:
Ultrafiltration coefficient (Kuf)
TMP
Membrane pore size(membrane surface area)
Hematocrit
Rate of flow
Negative pressure on effluent side (V)

10. How to select Hemoconcentrators

11. Molecular Cut Off Device acts as a sieve
Solutes (molecules) dissolved in plasma are either retained or removed according to their size (molecular Wt. MW)
MW cut off 65,000 Daltons
Electrolytes Daltons
Therapeutic drugs 6,000-20,0000 daltons

12. ULTRAFILTRATION
Some Heparin will be filtered (possibly due to negative charge ‘binding’ it to plasma proteins)
Heparin concentrations should be closely monitored during ultrafiltration
Serum levels of anaesthetic agents may be filtered – monitoring is necessary
Electrolytes should also be monitored

13. ULTRAFILTRATION
Small molecules < 10,000 Daltons such as sodium, potassium, chloride, urea, creatinine and glucose have a sieving coefficient of 1
This means they are filtered at a rate equal to their concentration in plasma
Larger molecules such as albumin (69,000 Da), hemoglobin (68,000 Da) and fibrinogen (341,000 Da) and cellular components of blood cannot traverse the pores, and therefore remain in blood
This results in higher blood concentration of non-filtered elements (sieving coefficient of 0)

14. Sieving Coefficient
SC - The ratio of the amount of a given solute in the UF to that amount in the Blood.
Ex 1. Sodium
amount in UF is 135 mEq/L and amount in the blood is 135 mEq/L the Sieving Coef. is 1.0.
Ex 2. Albumin
Serum = 5 gm/dl (Blood Albumin) UF=0 gm/dl Sieving Coef - 0

17. Clinical considerations

18. ULTRAFILTRATION Set – up:
Technical Concerns
Set – up:
Prior to CPB, connect inflow to Arterial source and outflow to Venous Line/reservoir
Effluent side connected to collection system (vaccum assist is possible)
No independent control of flow as to arterial flow and device flow (shunting)
Contact surface area (priming volume)
Fiber rupture (TMP > 600 mm Hg)

19. ULTRAFILTRATION Free water removal during CPB
Indications
Free water removal during CPB
Useful for patients with renal failure
Preservation of Hemostatic Elements
Clotting factors/proteins preserved
Alteration of Immune Function
Removal of proinflammatory mediators
(Complements - C3a, C4a, cytokines - IL1, IL6, IL8)

20. ULTRAFILTRATION Contraindications: None at present
Research available does not support any damage to red cells, releasing free hemoglobin into blood stream

21. ULTRAFILTRATION CUF – Conventional Ultrafiltration
TYPES
CUF – Conventional Ultrafiltration
PUF – Prebypass Ultrafiltration
Z-BUF – Zero balance Ultrafiltration
MUF – Modified Ultrafiltration

22. PUF Prebypass Ultrafiltration can be done while priming
Following addition of blood to CPB circuit, ultrafiltrate removal is initiated, and volume replacement with a balanced electrolyte solution
Reduce bradykinin, FXIII, prekallikrein
Eliminate initial drop in blood pressure commonly seen with initiation of CPB
Reduces Hyperkalemia

23. CUF
Conventional ultrafiltration during CPB was initiated when the volume of blood in the cardiotomy reservoir made it possible
CUF is performed throughout CPB
Conventional ultrafiltration usually commenced during rewarming phase
Applied in Adults with huge reservoir volume and pre-op Renal Dysfunction.

24. CUF circuit
NO PUMP

25. CUF Advantages: Disadvantages: It does not delay surgical times
It removes UF during highest mediator production phase
Disadvantages:
It might quickly empty reservoire volume

26. Z-BUF
Zero-balanced ultrafiltration is a method of filtration in which the filtered fluid is replaced with an equal volume of a balanced crystalloid solution
Water soluble inflammatory mediators are removed from circulation during ZBUF.
It has been shown that Z-BUF is capable of removing pro-inflammatory mediators such as tumor necrosis factor alpha, interleukin-6 and complement factors C3a and C5a
PrismaSol® solution used for continuous renal replacement therapy - CRRT ’

27. 10 liters of zero-balance ultrafiltration over 60 minutes
10 liters of zero-balance ultrafiltration over 60 minutes. The patient was extubated 5 hours postoperatively and discharged from the intensive unit on postoperative day 3. antegrade cerebral perfusion. used a Hemocor HPH® PrismaSATE® BK0/3.5 solution, a zero-potassium, bicarbonate-based continuous renal replacement fluid

28. MUF
Modified ultrafiltration is performed after coming off CPB and before the reversal of heparin, with negative suction applied to the ultrafiltrate
MUF started using the aortic cannula as inflow onto the oxygenator and the haemofilter, whilst the arterial filter was clamped, it was returned to the patient through the venous cannula towards the right atrium

29. MUF - Considerations Pressure in Arterial inlet – never below 0
Rate of Blood Flow – 10 to 20 ml/kg/min
Steal
Fluid removal – According to Hb, Volume
Negative suction ( -80 mm Hg)
Time period
Desired Hematocrit
Learning Curve

30. MUF - Circuits
BCD
DIFFERENT CIRCUITS

31. Postfiltration Rollerpump Oxygenator Reservoir Hemofilter Air Trap
HExr
36 °C
Air Trap
Rollerpump
Oxygenator
Reservoir

32. Beneficial Effects of MUF
Decreased tissue edema
Reversal of Hemodilution
Remove systemic inflammatory mediators & vasoactive substances

33. Potential Clinical Benefits of MUF
Reduce accumulation of total body water
Improved cardiac function, pulmonary function
Decreased bleeding & blood product requirements
Decreased pleural effusions following Fontan operation
Decrease postoperative blood loss
Decrease in PVR with unchanged SVR
decreased total body water, decreased duration of postoperative inotropic support, improved oxygenation, better pulmonary compliance, decreased duration of ventilator support, higher postoperative hematocrit value, and lower requirement for blood transfusion

34. Disadvantages of MUF Delay of approximately 10 - 15 minutes
Potential for hemodynamic instability
Entrainment of air from Aortic cannula
Obstructive cannula in small aorta(Neonates)
Not Using Modified Ultrafiltration
Surgeon’s impatience
2. Some bad experience
3. Increased complexity
4. Doubts about cost-effectiveness

35. ULTRAFILTRATION Allows patients with renal failure to undrego CPB
Method for concentrating hemodiluted blood
Method for blood conservation
Applications include removal of inflammatory mediators
Reduction of post-CPB inflammatory response and immunological activation
↓ complement activation resulting in:
Improved post-CPB cardiac and pulmonary function

36. CONCLUSION
MUF can effectively reduce total body water accumulation and induce hemoconcentration, but its contributions to removing inflammatory mediators are still controversial
The efficacy of ZBUF to remove inflammatory mediators has been proven, but it is inefficient in increasing the patient’s haematocrit because of its basic fluid balance principal
Ultrafiltration is safe and proven in reducing intravascular volume, preserving postoperative hemostasis, and improving postoperative end-organ function.