1. Filtration, Venting, Suction
Cooper University Hospital: School of Perfusion 2014
Michael F. Hancock

2. Filtration Things that need to be Filtered: Gaseous Emboli Blood Field
Microemboli- < 40 micron
Macroemboli- > 40 micron
Gases- O2, CO2, nitrous oxide, N
Blood
Clots
Fibrin formation
Platelet activation
Complement activation
Agglutination of damaged RBCs
Field
Fat or bone particulate
Foam
Heart-Lung Machine
Tubing pieces due to spallination of roller pump
CPB air

3. Emboli and Thrombus Thrombus- stationary clot Emboli- mobile clot
Coronary artery plaque
Emboli- mobile clot
Air embolus
Broken off pieces of a thrombus
Travels upstream and occludes vessels
Particulate matter traveling through vessels
Bone or fat pieces

4. Air Emboli Surgical Air- CPB Air- Cannula sites
Open atrium or ventricle
CPB Air-
Emptying or Vortexing of resevoir
Excessive VAVD (vacuum assist venous drainage)
Rapid rewarming
Roller Pump tubing rupture
Roller Pump off, cardioplegia pump on
Draw air across the oxygenator
Injection of air through drug syringes

5. Air Emboli Air Emboli seen on CPB: Brain Right Coronary Artery
Carotid Arteries at the Aortic Arch
Air rises to these vessels and causes stroke
Trendelenburg position used to put the “head down” to prevent any air emboli from reaching the head
Right Coronary Artery
Right Coronary Ostia is located on the upper portion of the aorta making it susceptible to air rising into the vessel causing an obstruction

6. CPB Filters
Filters are placed at various spots in the CPB circuit to protect the patient against embolus during surgery
Designed to trap air and any substance that could cause obstruction in the patient’s vasculature
Must allow adequate blood flow and certain components through
> 20 microns to allow adequate blood flow without excessive back pressures
RBCs are 5-7 microns, must allow them to pass through
Platelets are 2-3 microns
Leukocytes are 7-21 microns

7. Types of Filters Depth Filters- Made of packed fibers of Dacron Wool
Work by Impaction and Absorption
No defined pore size
Lose efficiency as time goes on
More hemolysis
Less air trapping capability
More platelet activation and destruction

8. Types of Filters Screen Filters- Made of woven polyester mesh or Nylon
Work by interception
Specific pore size
Useful for trapping air and particulate matter without impeding flow or causing much hemolysis and platelet dysfunction

9. Filter Locations Arterial Line Cardiotomy Resevoir Pre-Bypass Pack
Cardioplegia System
Gas Line
Transfusion Line

10. Arterial Line Filter Arterial Filter-
Located after oxygenator and before patient
Air enters the side, swirls and around and exits the bottom, which allows air to rise and be purged out of a line with a one-way valve leading to the cardiotomy resevoir
Last point of defense before returning to the patient
Can be integrated with the oxygenator
Newer oxygenators

11. Ideal Arterial Filter 20-40 microns Small priming volume
Trap emboli and allow adequate flow
40 micron preferred
Small priming volume
~ 100cc
Easy to de-air
Made of polyester
NOT Nylon
Causes complement activation and hemolysis
Have bypass line in case filter clots

12. Cardiotomy Resevoir Cardiotomy Resevoir
Filters all blood returning to CPB circuit
From Vents and Suckers
Most aggregates caused by suckers
Filters venous blood
Filters drugs injected into CPB circuit manifold
Uses combination of Depth and Screen filters
100 microns

13. Pre-Bypass Filter
Located in sterile tubing pack or before venous resevoir
Removes particulate matter generated by manufactoring or priming
Spallination, Plastic debris
5 micron size
Must remove before CPB
Will trap RBCs (5-7 microns)
3/8” Line going in
½” Line going out

14. Cardioplegia Filter
Some places use micron filter on their cardioplegia system
Cooper does NOT

15. Gas Line Must filter out bacteria and particulate debris
0.2 micron filter will filter 99% of bacteria
Used for O2, CO2, and Nitrous Oxide
Hydrophobic membrane removes particulate
Bi-directional filter
¼” Lines

16. Transfusion Filter
All blood added to CPB circuit or to the patient should be transfused through a filter
Pall Filter
Reduction in leukocytes, fat globules, C3a, and microaggregates
40 micron filter

17. Bubble Point Pressure
The pressure required for an undissolved air bubble to be pushed across a filter pore
Determines when a bubble will get through your filter
Calculation-
BBP= (4)(surface tension)(cos. Wetting angle)
Diameter

18. CO2 Flushing Rid the circuit of O2 and N
CO2 is 20x more soluble than O2
We would rather have CO2 in our circuit because any remaining air bubbles would have a greater chance to dissolve in blood
Most important to CO2 flush the arterial filter

19. Ultrafiltration (Hemoconcentration)
Ultrafiltration- the process of removing plasma free water and solutes from the blood
Uses:
Hemoconcentration- remove plasma free water and raise the hemoglobin
Remove excess fluid in lieu of diuretics
Zero-Balance Ultrafiltration- used to reduce high Potassium levels (Hyperkalemia)
Pull off plasma water and solutes, such as K+, then replacing the fluid taken off with 0.9% normal saline

20. Hemoconcentrator Semi-permeable hollow fiber device
Inflow line comes from the arterial port out of the oxygenator
Outflow line goes into a port on the cardiotomy resevoir
Water and solute extraction occurs through a separate port

21. Hemoconcentrator
Flow through a hemoconcetrator can be as great as 500 cc/min
Fluid removal can go up to a rate of 180 cc/min but is usually cc/min
Suction may be applied to water extraction line to facilitate water takeoff
Transmembrane pressure can be increased by partially clamping hemoconcentrator outflow line
Increases the amount of solute and water extracted
Flow remains the same
Max. transmembrane pressure is 500 mm Hg
Can increase flow to hemoconcentrator by increasing pump flow

22. Hemoconcentrator Filter size is 15,000-55,000 daltons Solutes removed:
Some Heparin will be removed
Heparin mean molecular mass is 15,000 daltons
Solutes removed:
K (39 da)
Na (22 da)
Cl (23 da)
Insulin (~6,000 da)
Glucose (180 da)
Urea (60 da)
Creatinine (113 da) like dialysis?
Bicarbonate (84 da)

23. Hemoconcentrator Potential Problems
Generation of Plasma free Hemoglobin due to hemolysis
Can precipitate iron and cause renal artery vasoconstriction

24. Venting the Heart on CPB
Cardiac Vents-
Allow for continuous venting of the heart
Maintains an empty heart
Prevents fluid distension in the heart
Starling’s Law
Prevents pooling of warm blood in the LV
Could get into coronaries and interrupt asystole
Prevents ejection of air
Vent Tubing- placed in a roller head to direct blood into cardiotomy resevoir
LV Vent should always contain a One-Way valve to prevent pumping air into the LV

25. Causes of LV Distension
Inadequate drainage of venous cannulas
Bronchial and Thebessian vein return
Bronchial veins drain into the pulmonary veins which drain into the Left Atrium
Aortic insufficiency
Congenital or aquired heart defects
ASD, VSD, PDA

26. Vent Sites Left Ventricle Aortic Root Pulmonary Artery Apex- direct
Right Superior Pulmonary Vein- most common
Aortic Root
Attached to an antegrade cardioplegia cannula through a Y
Commonly used in CABG cases to vent the heart
Cardioplegia delivery must be interrupted if LV distension occurs
Separate Root vent for de-airing before left heart is closed during valve surgery
Pulmonary Artery

27. RSPV Vent Insertion Incision made in the RSPV Vent inserted
Must have volume in the heart to insert vent….WHY?

28. RSPV Vent Insertion
Fingers checking correct position of LV Vent

29. RSPV Vent Insertion
LV vent inserted and advanced across the Mitral Valve
Vent sits in the LV

30. Vent Types A- B- C- D- 1- 2-

31. Suckers
Sucker cannulas are used at the field to suck back any blood in or around the chest cavity
Primary source of particulate entering the CPB circuit
Blood/air interface causes hemolysis
Excessive suction pressure causes hemolysis
Be aware of sucker occlusion at the field
Will see collapse and chugging of your sucker tubing