Exam 5 - Filters & Arterial Cannulas Flashcards
1
Q
What is floating around in system?
A
- Fat aggregates
- Platelets
- Microbubbles
2
Q
Why do we use filters
A
- GME
- Other microparticles
- Can cause transient to detectable microembolic events
3
Q
ECC post-op dysfunction
A
- Alter blood components
- Platelet aggregation and compliment activation - Alter efficiency of the body systems
4
Q
Sources of emboli
A
- Platelet / Leukocyte (MAJOR source)
- Denatured proteins
- Particulates from ECC manufacturing
- Fat microemboli
- Microbubbles
- Fibrin
5
Q
Causes of GME
A
- Repositioning / Insertion of cannula (can’t control)
- Adding volume to reservoir
- Rapid bonus injection
- Excessive venous line negative pressure
- can control last 3
6
Q
Sources of Platelet / Leukocyte Aggregates
A
- Blood trauma
- Bank blood
- Rxn between donor / patient blood
- Hypotension / Trauma
- Contact with foreign surface
7
Q
Screen filters
A
- made of woven mesh (polyester)
- filters via direct interception
- mesh pore size determines what can filter
- pressure drop depends on:
- fluid viscosity, flow, and filter design
8
Q
Bubble Point Pressure
A
- Ease at which bubble can pass through filter
- If BPP is exceeded by pressure gradient, bubble will pass through
9
Q
Depth filters
A
- Made of packed filter material (poly foam, nylon, glass wool)
- Filtration depends on adsorption of emboli
- Particle removal depends on:
- amount of surface available and pathway traveled in filter
10
Q
Pre-CBP filter
A
- placed before reservoir inlet
- 0.2 microns
- Used during priming / recirculation of crystalloid
- Cut out after recirculation BEFORE adding blood
- NEVER leave in with blood products
11
Q
Venous reservoir / cardiotomy filter
A
- Removes aggregates picked up from suction trauma
- Low resistance (cannot impede gravity drainage)
- 20 - 40 microns
- Filter integrated into reservoir
- Can have both screen and depth filters (depth then screen) - Source of emboli due to suction
12
Q
Arterial line filter (ALF)
A
- located in arterial line
- 20-40 microns
- Must be able to:
- easy prime, high flow rate, continuous pressure monitoring, purge trapped air, add bypass line, low prime volume
- In 2013, AmSECT made it standard to use in ECC
- Great big bubble traps (need purge line w/ one way valve to remove micro bubbles)
13
Q
ALF disadvantages
A
- add to cost
- can obstruct flow
- possible source of GME….hard to de-air
- can cause hemolysis and compliment activation
14
Q
Self-venting ALF
A
- Have hydrophobic membrane on top
- can vent micro bubbles w/o purge line
- still recommended to use a purge line with them
15
Q
Integrated ALF / membrane oxygenator
A
- no external filter
- reduces prime volume
- easier set up and priming
16
Q
Leukocyte Depleting filters (LD)
A
- Located in ALF or cardioplegia line
- 40 microns
- drops leukocyte levels
- non-woven polyester fibers w/ polysaccharide surface
- selectively grabs leukocyte and leaves other blood components
17
Q
Why do we remove Leukocytes from ECC
A
- Release cytokines when activated
- cytokines contribute to SIRS and other organ injury
18
Q
LD disadvantages
A
- Effects line pressure
- high resistance as filter becomes saturated
- less effective over time
- WBC selective
- studies of efficacy show mixed results
19
Q
LD for ECC vs Bank blood
A
- Should be used on Bank blood due to patient condition or surgeon request
- ECC and bank LD filters look different….pay attention
20
Q
Cardioplegia Filters
A
- located in Cardioplegia line system
- blood = >40 microns
- crystalloid = 0.2 microns
- removes particulates, endotoxins, bacteria
21
Q
Gas line filter
A
- located between gas source (blender) and oxygenator
- 0.2 microns
- removes 99.999% of bacteria
- minimizes cross contamination between equipment and patient
22
Q
Blood transfusion filters
A
- use when transfusing blood into pump
- use when administering processed, washed RBC
- lots of microaggregates in bank blood
- AABB recommends use of lipid filter too when transfusing blood
23
Q
3 Common cannulation sites
A
- Ascending Aorta
- Femoral artery
- Axillary / subclavian artery
24
Q
Cannulation site determination
A
- surgeon preference
- operation planned
- type of cannula used
- quality of aorta
- previous conditions
25
Arterial cannula
- made of plastic (can be wire reinforced)
- various tip formations (want thin tip....best ID:OD ratio)
- narrowest part of ECC
- keep pressure gradient less than 100 mmHg
26
Cannula size
- usually measured in French (Fr)
- adults are 20 and above
- can be measured with external diameter
27
Reynolds number
- determines if flow is laminar or not
- >2500 flow is turbulent
- <2000 flow is laminar
28
Jetting effects
- velocity of blood leaving cannula tip
- jetting velocities can be 5-10x more than systolic velocity
- can change jetting velocities with different tips
- too high jet effect causes:
- sandblasting, aortic dissection, hemolysis, protein denature
29
Diagnosis of cannula tip in head vessel
- High arterial line pressure of ECC
- High radial pressure
- Asymmetric cooling of neck
- Unilateral hyperemia, edema, and petechia
- Petechia = little blood spots under skin due to hemorrhage
30
Diagnosis of aortic dissection
- Sudden decrease in venous return and arterial pressure
- excessive loss of perfusate
- increased circuit arterial line pressure
- decreased organ perfusion
- blue color in aortic root due to adventitial hematoma
31
Special purpose arterial cannulas
- Embol-X : has extra filter to capture particulates
| - Triumph : soft occlusion aortic cannula (instead of x-clamp)
32
Aortic arch vs. Femoral artery
Accessibility: easy of AA....hard for FA
Direction: AA is antegrade....FA is retrograde
Leg ischemia: AA is not possible....FA is possible
33
Femoral artery advantages
- allows peripheral cannulation
- allows cannulation for high risk patients
- may be only option
34
Femoral artery disadvantages
- limited flow due to size
- FA trauma (dissections most serious)
- bleeding
- leg ischemia
- infection
35
Axillary/Subclavian cannulation
- Can be direct or via 8mm graft
- Right axillary favored
- allows selective antegrade cerebral perfusion
- less malperfusion during aortic dissection surgery
- less risk of cerebral atheroembolism
36
Axillary cannulation complications
- Axillary injury
- brachial plexus injury
- limp ischemia in arm
37
4 types of integrated filters
- Terumo FX
- Sorin synthesis
- Medtronic Affinity Fusion
- Quadrox-I
