Embolic Events

Question 0

Greatest periods of risk for emboli during surgery

Answer 0

1. Insertion of arterial cannula
2. Initiation if bypass (hypotension, most circuit “junk”)
3. XC on/off (manipulation of aorta, trauma to aorta can lead to brain infarcts for up to a month)
4. Use of centrifugal pump (anytime decreasing blood flow because could lead to retrograde flow)

Question 1

Different types of emboli, and their main target

Answer 1

Biologic (bloodborne)
Foreign material (circuit, manufacturing)
Gaseous

Main target: micro vessels, 3-500um in diameter

Question 2

Examples of Biologic emboli

Answer 2

Fibrin/fibrinogen microthrombi
Fats or lipids
Protein
Cold-reacting antibodies
Calcium fragments
Platelet aggregates
Bone and muscle fragments
Neutrophil aggregates
RBC aggregates

Question 3

Increased storage time has what affect in homologous transfused blood?

Answer 3

Increased formation of Biologic emboli

Question 4

Formation of Biologic emboli: inadequate anticoagulation

Answer 4

Contact with foreign surface area
Areas at risk: minimal flow, stagnant areas, turbulence, cavitation, rough surfaces
Areas of the circuit: connectors, bubble oxygenators, ALF, cardiotomy reservoir, intraluminal projections

Question 5

Formation of Biologic emboli: trauma to fat cells of epicardium and tissue of surgical wound

Answer 5

Fat emboli can be produced by median sternotomy or thoracotomy (not necessarily bypass)
2/3 of fat emboli comes from cardiotomy suction
Large particles: 4-200um
Found in organs past bypass: kidney, lungs, heart, brain, liver, spleen

Question 6

Formation of Biologic emboli: complement activation

Answer 6

Caused by surface contact

Question 7

Immune response on bypass

Answer 7

Platelet count drops 30-50% with initiation of bypass
Number of functional platelets drop
Platelets: postop bleeding, neurologic dysfunction, histamine release (membrane permeability), serotonin and Thromboxane release (vasoconstriction)
Neutrophils: aggregation, interact with endothelial cells, change permeability

Question 8

Examples of foreign particle emboli

Answer 8

Cotton fibers
Plastic particles
Filter material
Tubing fragments (spallation)
Metal
Talc
Bone wax
Micro fibrillate collagen
Silicone anti foam

Question 9

4 sources of gaseous microemboli

Answer 9

Bubble oxygenator (mainly oxygen, 35-45um bubbles lead to M&M)
Temperature gradients
Surgical air
Pump/circuit problems

Question 10

Sources of surgical air

Answer 10

Heart contracts before chambers deaired
Surgeon cuts into chamber of beating heart
Placement of arterial, venous,mor LV vent cannula

Air present in heart 30-40min post bypass
86% of bubbles gone within 1 minute if flush with CO2

Question 11

Most common causes of pump air

Answer 11

Inattention to reservoir level (37%)
Aortic root air during CPS administration (29%)
Unexpected heart beat (10%)
Reversed LV vent line (9%)
Pressurized cardiotomy (5%)
Ruptured arterial pumphead tubing (5%)
Pump creep (5%)

Question 12

Two largest perfusion introduction of air into circuit

Answer 12

Administration of drugs

Taking blood samples

Question 13

Blood/bubble interactions

Answer 13

Adsorption/denaturation of plasma proteins, phospholipids, and fibrinogen
Complement activation
Clumping RBCs
Leukocyte activation
Lipid peroxidation
Microthrombi production
Platelet activation
Thrombin activation
Phospholipase activation
Endothelial wall damage

Question 14

Safety devices

Answer 14

Low level alarm
Air bubble detector
ALF/cardiotomy filter
One way Purge line
One way valve in vent line
One way valve In arterial line
Clear communication 
Protocols, policies,mad procedures
Per bypass checklists

Question 15

Ways to minimize Biologic emboli formation

Answer 15

Transfusion filters
Adequate anticoagulation
Design of circuit components 
Minimize surface area of circuit
Use membrane oxygenator
Minimize complement/immune activation
Minimize platelet activation
Minimize neutrophil activation

Question 16

Ways to minimize introduction of foreign particle emboli

Answer 16

Component design and manufacturing
Circulate crystalloid throughout entire circuit
Flush circuit with crystalloid in conjunction with pure bypass filter in AV loop
Use medical grade tubing rather than silicone

Question 17

Ways to minimize formation of gaseous micro emboli

Answer 17

Check equipment for proper operation
Ensure all connections are secure
CO2 flush
Warm prime, then let it cool
Check circuit alignment 
Check tubing placement in raceway
Proper use of safety devices 
Use purge line
Use pressure relief valve when using VAVD
Test vent line prior to attachment to catheter
Continually scan circuit while on bypass
Always ensure forward flow with centrifugal pump
Avoid air in venous line