Topic 7: Embolic events Flashcards
Incidence of clinically obvious strokes post CPB is what %?
• % MRI suggests could be new cerebral infarcts in those same patients?
~1-5%
~30%
% of CABG patients experienced cerebral infarct prior to surgery
~50%
Types of emboli (4)
- Biologic (bloodborne)
- Foreign material (Circuit, Manufacturing)
- Gaseous
- Micro vessels main target -3 to 500m in diameter
greatest period of risk of emboli during CPB
- Insertion arterial cannula
- Initiation of bypass
* Hypotension
* Most circuit “junk” - Cross-clamp application / removal
* Manipulation of aorta
* Trauma to aorta can contribute to brain infarctions for up to 1 month - Use of centrifugal pump
* Any time you have to decrease BF
Biological Emboli
- Fibrin / fibrinogen microthrombi
- Fat or lipids
- Protein
- Cold-reacting antibodies
- Calcium fragments
- Bone fragments
- Muscle fragments
- Platelet aggregates
- Neutrophil aggregates
- RBC aggregates
Homologous transfused blood emboli chance increases with what?
Increase with the storage time
Areas at Risk of Inadequate anticoagulation (5)
- Minimal flow
- Stagnant areas
- Turbulence
- Cavitation
- Rough Surfaces
Areas of the Circuit where inadequate anticoagulation is a problem (5)
- Connectors
- Bubble Oxygenators
- Arterial line filters
- Cardiotomy (venous) reservoir
- Intraluminal projections
Do you need bypass to produce fat emboli?
Do not need bypass to produce fat emboli
Median sternotomy
Thoracotomy
2/3 fat/lipid emboli within a circuit come from
cardiotomy suction
Large particles are what size range?
4-200 microns
Formation of Biologic Emboli how?
•Trauma to fat cells of epicardium and trauma to tissue of the surgical wound
Platelet count drops what % with initiation of bypass?
30-50%
Drop in Platelets causes what?
Post op bleeding, neurologic dysfunction, release of histamine (membrane permeability), release of serotonin/thromboxane (vasoconstriction)
Increased Neutrophils does what?
aggregation, interaction with endothelial cells, change permeability
Foreign Particulate Emboli examples
- Cotton fibers
- Plastic particles
- Filter material
- Tubing fragments (spallation)
- Metal
- Talc
- Thread
- Bone wax
- Microfibrillar collagen
- Silicone antifoam
Bubble oxygenator
•bubbles of what size are associated with CPB mortality and morbidity?
in 35 to 40m
•Mainly oxygen
•Transitioned to membrane oxygenators
Air emboli formed what ways?
Bubble oxygenator
Temperature gradients
Surgical air
Pump / Circuit problems
Surgical Air caused by what?
Heart contracts before chambers completely de-aired
•Surgeon cuts into chamber of beating heart
•Placement of arterial, venous or LV vent
cannulae
•Air present in heart 30 to 40 minutes post bypass
•Flush with CO2–86% bubbles gone within 1 minute
2 Biggest causes of air contamination?
gray round graph
Inattention to reservoir level -37%
Aortic Root Air during CPG delivery - 29%
Blood blubble interactions - adsorption of what?
Adsorption / denaturation plasma proteins
Adsorption phospholipids
Adsorption fibrinogen
Endothelial wall damage
Blood blubble interactions - activation and production of what?
- Complement activation
- Clumping red blood cells
- Leukocyte activation / adherence
- Lipid peroxidation
- Microthrombi production
- Platelet activation / adherence
- Thrombin activation
- Phospholipase activation
Safety devices?
- Low level alarm
- Air bubble detector
- Arterial line filter
- cardiotomy filter
- One-way purge line from arterial line filter to cardiotomy reservoir
- One-way valve in vent line
- One-way valve in arterial line
- Clear lines of communication
- Use of protocols, policies and procedures
- Use of prebypass checklist
How Do You Minimize Biologic Emboli
Formation?
use what? 2
minimize what? 4
- Use of transfusion filters
- Use membrane oxygenator
- Adequate anticoagulation
- Design of circuit components
- Minimize surface area of circuit
- Minimize complement / immune activation
- Minimize platelet activation
- Minimize neutrophil activation
How Do You Minimize Introduction of Foreign
Particle Emboli? (4)
•Component design and manufacturing
•Circulate crystalloid solution through entire circuit
•Flush circuit with crystalloid solution in
conjunction with a pre-bypass filter in AV loop
•Don’t use silicone tubing in arterial pump head
•Use medical grade tubing
How Do You Minimize Formation of Gaseous
Microemboli ?
- Check all equipment for proper operation
- Ensure all tubing / component connections are secure
- Flush circuit with CO2 prior to priming
- Careful priming of arterial filter
- Check circuit for proper alignment of tubing and components
- Check proper placement of tubing in roller pump raceway
- Proper use of all safety devices
- Open one-way purge line from arterial filter to cardiotomy reservoir
- Use of pressure relief valve on venous reservoir when using VAVD
- Test vent line prior to attachment to vent catheter
- Continual circuit scan while on bypass
- Continual monitoring of centrifugal pump flow and RPM–ensure forward flow at all times
- Avoid air in venous line
How Do You Minimize Formation of Gaseous
Microemboli temps?
•Warm prime–then let it cool
