Topic 7: Embolic events

Question 1

Incidence of clinically obvious strokes post CPB is what %?

• % MRI suggests could be new cerebral infarcts in those same patients?

Answer 1

~1-5%

~30%

Question 2

% of CABG patients experienced cerebral infarct prior to surgery

Answer 2

~50%

Question 3

Types of emboli (4)

Answer 3

• Biologic (bloodborne)
• Foreign material (Circuit, Manufacturing)
• Gaseous
• Micro vessels main target -3 to 500m in diameter

Question 4

greatest period of risk of emboli during CPB

Answer 4

• 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

Question 5

Biological Emboli

Answer 5

• Fibrin / fibrinogen microthrombi
• Fat or lipids
• Protein
• Cold-reacting antibodies
• Calcium fragments
• Bone fragments
• Muscle fragments
• Platelet aggregates
• Neutrophil aggregates
• RBC aggregates

Question 6

Homologous transfused blood emboli chance increases with what?

Answer 6

Increase with the storage time

Question 7

Areas at Risk of Inadequate anticoagulation (5)

Answer 7

• Minimal flow
• Stagnant areas
• Turbulence
• Cavitation
• Rough Surfaces

Question 8

Areas of the Circuit where inadequate anticoagulation is a problem (5)

Answer 8

• Connectors
• Bubble Oxygenators
• Arterial line filters
• Cardiotomy (venous) reservoir
• Intraluminal projections

Question 9

Do you need bypass to produce fat emboli?

Answer 9

Do not need bypass to produce fat emboli
Median sternotomy
Thoracotomy

Question 10

2/3 fat/lipid emboli within a circuit come from

Answer 10

cardiotomy suction

Question 11

Large particles are what size range?

Answer 11

4-200 microns

Question 12

Formation of Biologic Emboli how?

Answer 12

•Trauma to fat cells of epicardium and trauma to tissue of the surgical wound

Question 13

Platelet count drops what % with initiation of bypass?

Answer 13

30-50%

Question 14

Drop in Platelets causes what?

Answer 14

Post op bleeding, neurologic dysfunction, release of histamine (membrane permeability), release of serotonin/thromboxane (vasoconstriction)

Question 15

Increased Neutrophils does what?

Answer 15

aggregation, interaction with endothelial cells, change permeability

Question 16

Foreign Particulate Emboli examples

Answer 16

• Cotton fibers
• Plastic particles
• Filter material
• Tubing fragments (spallation)
• Metal
• Talc
• Thread
• Bone wax
• Microfibrillar collagen
• Silicone antifoam

Question 17

Bubble oxygenator

•bubbles of what size are associated with CPB mortality and morbidity?

Answer 17

in 35 to 40m
•Mainly oxygen
•Transitioned to membrane oxygenators

Question 18

Air emboli formed what ways?

Answer 18

Bubble oxygenator
Temperature gradients
Surgical air
Pump / Circuit problems

Question 19

Surgical Air caused by what?

Answer 19

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

Question 20

2 Biggest causes of air contamination?

gray round graph

Answer 20

Inattention to reservoir level -37%

Aortic Root Air during CPG delivery - 29%

Question 21

Blood blubble interactions - adsorption of what?

Answer 21

Adsorption / denaturation plasma proteins
Adsorption phospholipids
Adsorption fibrinogen
Endothelial wall damage

Question 22

Blood blubble interactions - activation and production of what?

Answer 22

• Complement activation
• Clumping red blood cells
• Leukocyte activation / adherence
• Lipid peroxidation
• Microthrombi production
• Platelet activation / adherence
• Thrombin activation
• Phospholipase activation

Question 23

Safety devices?

Answer 23

• 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

Question 24

How Do You Minimize Biologic Emboli
Formation?
use what? 2
minimize what? 4

Answer 24

• 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

Question 25

How Do You Minimize Introduction of Foreign | Particle Emboli? (4)

Answer 25

•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

Question 26

How Do You Minimize Formation of Gaseous | Microemboli ?

Answer 26

* 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

Question 27

How Do You Minimize Formation of Gaseous | Microemboli temps?

Answer 27

•Warm prime–then let it cool