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CPB Flashcards

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1
Q

What are common cannulation sites used for CPB?

A

Peripheral: femoral or carotid artery, femoral vein
Central: Vena cava, RA, Aorta, left carotid artery

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2
Q

Name 5 pathological effects of CPB on the body.

A
  1. Traumatizes RBCs
  2. activation inflammatory pathways
  3. activation and consumption of coagulation factors
  4. Hyperfibrinolysis
  5. Predisposition to embolism (air, plastic)

This trauma can lead to hemolysis and other complications.

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3
Q

What are the usages of cardiopulmonary bypass?

A
  1. Surgery requiring asystole
  2. augmentation of circulatory flow, temperature and blood composition

It is often used in complex cardiac surgeries.

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4
Q

What is an indication for cardiopulmonary bypass?

A

Cardiac procedure requiring blood- and motionless surgical field

Examples include MV/TV repair, ASD or VSD closure, and congenital pathology repairs.

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5
Q

What type of surgery can be performed using CPB without cardioplegia? What is the benefit of a having a beating heart during surgeries with CPB?

A

Surgery of the right side of the heart

  • Reduced risk of air emboli reaching systemic circulation

This is contingent on no intracardiac shunts being present to mitigate the risk of air embolism.

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6
Q

On what does the cannulation site depend on?

A

–> Surgical procedure:

Mitral valve repair: RA
Tricuspid valve repair: Bicaval

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7
Q

What is a complication specific to tricuspid valve repair surgery?

A

Sinoatrial node dysfunction

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8
Q

Describe the broad set-up of a CPB circuit.

A
  1. Drainage of the patient’s blood from the venous circulation –>
  2. reservoir–>
  3. heat exchanger + gaseous exchange system (often integrated units) –>
  4. returning to the patient under pressure into the arterial circulation
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9
Q

Name the 11 components of a CPB circuit.

A
  1. Venous line
  2. Venous reservoir
  3. Main pump boot
  4. Heat exchangers
  5. Oxygenator
  6. Recirculation lines
  7. Pressure transducers
  8. Arterial line
  9. suction/vent lines
  10. Hemofilter
  11. Cardioplegia circuit
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10
Q

What is the oxygenator used for during CPB?

A
  • Oxygen delivery
  • CO2 removal
  • volatile inhalant
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11
Q

What is the heat exchanger used for during CPB and what is its location within the circuit?

A

Precise temperature control

–> before oxygenator to reduce gas emboli formation

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12
Q

What are the suction/vent lines used for during CPB?

A
  • scavenges blood from the surgical field into the CPB
  • “vent” air from the heart before restoring spontaneous rhythm –> reduce risk of air emboli
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13
Q

What is the hemofilter used for during CPB?

A
  • removal of water and solutes from the perfusate via convection
  • can also perform diffusive clearance
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14
Q

What is the cardioplegia circuit used for during CPB?

A
  • variable composition of cardioplegia solution - modification possible
  • often has its own heat exchanger for regional myocardial temperature control
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15
Q

What is the arterial line used for during CPB?

A
  • connects the oxygenator to the arterial circulation
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16
Q

What is the pressure transducer used for during CPB?

A
  • pressure measurement of some lines (main arterial line pressure + cardioplegia delivery pressure)
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17
Q

What are the recirculation lines used for during CPB?

A
  • allow bypass of individual circuit components in case replacement/dysfunction occurs
  • priming + deairing of the circuit
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18
Q

What is the main pump boot used for during CPB?

A
  • connects the venous reservoir to the heat exchanger/oxygenator unit
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19
Q

What is the venous reservoir used for during CPB?

A
  • Stores venous blood
  • de-airs and de-foams the blood
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20
Q

How can blood be drained from the venous circulation into the venous reservoir of the CPB?

A
  1. gravity
  2. vacuum assisted
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21
Q

What factors determine the volume of priming solutions in CPB?

A
  • number of circuit components
  • size of the tubing
  • size of the reservoir
  • size of the oxygenator

Volume can be greater than 500ml based on these factors.

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22
Q

What are the benefits of hemodilution in CPB?

A
  • improves tissue blood flow
  • improves tissue oxygen delivery
  • improves venous return

Hemodilution is considered desirable in the context of CPB.

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23
Q

What is a potential side effect of considering blood priming with pRBCs or FWB?

A

Side effect: hemolysis

pRBCs refers to packed red blood cells, and FWB refers to fresh whole blood.

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24
Q

What additives may vary from institution to institution for CPB?

A
  • FFP
  • compound sodium lactate
  • sodium bicarbonate
  • mannitol
  • calcium gluconate
  • UFH

FFP stands for fresh frozen plasma.

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25
What is necessary prior to cannula insertion during CPB?
Systemic anticoagulation ## Footnote This is essential to prevent clotting during the procedure.
26
What coagulation parameter is obtained before administering anticoagulation?
Baseline ACT ## Footnote This measurement is crucial for determining the appropriate dose of anticoagulant.
27
What is the recommended dose of UFH IV prior to CPB?
300 IU/kg UFH IV ## Footnote This dosage is commonly used to achieve adequate anticoagulation.
28
What is the safe minimum ACT during CPB?
unknown, but at RVS: >400s during CPB pump is in motion ## Footnote The exact safe minimum ACT may vary between institutions.
29
What is the antidote for heparin during CPB?
3mg/kg protamine IV over 15-60min ## Footnote This is administered following surgical repair to normalize ACT.
30
What are some severe side effects of protamine administration?
* Nonimmunologic histamine-mediated reactions * Immunologic reactions * Thromboxane A2-mediated reactions ## Footnote These reactions can lead to significant complications during recovery.
31
What is the most common nonimmunologic reaction to protamine?
Histamine-mediated reaction causing vasodilation, hypotension and decreased cardiac contractility ## Footnote This can result in vasodilation, hypotension, and reduced cardiac contractility.
32
What immunologic reactions can occur due to protamine?
Immunologic reactions include: * Antiprotamine IgE antibodies * Complement activation due to heparin-protamine complexes ## Footnote These reactions can lead to serious complications.
33
What are potential sequelae to a thromboxane A2-mediated reaction due to protamine administration?
* delayed noncardiogenic pulmonary edema *acute catastrophic pulmonary vasoconstriction ## Footnote These can lead to pulmonary vasoconstriction.
34
What is the purpose of ultrafiltration during CPB?
To alter the composition of perfusate as needed via convective clearance ## Footnote Hemofilter within circuit allows adjustments to the perfusate.
35
What is convective clearance?
A process involved in ultrafiltration during CPB ## Footnote It helps in improving fluid removal and reducing inflammatory cytokine concentration.
36
List 3 benefits of ultrafiltration during CPB.
* Resolving degree of hemodilution * Fluid removal --> improved outcome * Reduction in inflammatory cytokine concentration
37
What is cardioplegia during CPB?
A substance responsible for cessation of cardiac function ## Footnote It is essential for protecting the heart during surgery.
38
What are the 2 routes of delivery for cardioplegia?
* Antegrade: via aortic root (coronary ostia) * Retrograde: via coronary sinus
39
What effect does the cardioplegia solution have in dogs?
Induces diastolic arrest due to extracellular myocardial hyperkalemia --> prevents cardiomyocyte repolarization ## Footnote This prevents cardiomyocyte repolarization.
40
How can cardioplegia be infused?
* Infused in crystalloid * Mixed with patient's own blood prior to delivery
41
What is one benefit of mixing cardioplegia with the patient's blood?
Reduces incidence of VFib after aortic cross-clamp removal in dogs ## Footnote This enhances postoperative recovery.
42
What is the significance of temperature in cardioplegia?
Temperature can be altered independently to systemic temperature --> regional myocardial warming/cooling ## Footnote This allows for regional myocardial warming/cooling.
43
What temperature is commonly used for cardioplegia? What is one benefit and one adverse effect thereof?
4°C + in combination with chemically induced diastolic arrest --> reduces myocardial oxygen requirements by 97% - worsens postoperative cardiac function ## Footnote This, in combination with chemically induced diastolic arrest, reduces myocardial oxygen requirements by 97%.
44
What is a side effect of using cold cardioplegia?
Worsens postoperative cardiac function ## Footnote Caution is required to balance benefits and potential harms.
45
What happens if excessive delivery pressure is used during cardioplegia?
Causes myocardial edema, leading to worse postoperative cardiac function ## Footnote Proper pressure is critical for effective myocardial protection.
46
What occurs with insufficient pressure during cardioplegia delivery?
Leads to heterogeneous delivery and inadequate myocardial protection ## Footnote This can compromise the effectiveness of the procedure.
47
What are 3 beneficial effect of therapeutic hypothermia on metabolic rate? Give the brain as example.
1. Reduces metabolic rate for tissues --> cerebral metabolic rate decreases by 6%–7% for every 1°C reduction in brain temperature --> reducing risk of ischemia --> slower circulatory flow rates during CPB possible 2. Suppression of proapoptotic genes 3. Expression of "cold shock" proteins --> aid in cell survival ## Footnote Cerebral metabolic rate decreases by 6%–7% for every 1°C reduction in brain temperature, reducing risk of ischemia.
48
What are 12 risks associated with therapeutic hypothermia?
1. Acid-base alterations 2. Cold induced diuresis 3. Coagulopathy 4. Heterogenous organ blood flow 5. Intracellular Na+ accumulation 6. Hormonal alterations 7. Reduced RBC deformation 8. Arrhythmias 9. Myocardial ischemia 10. Immunodysfunction 11. Impaired oxygen unloading from hemoglobin 12. Pharmacodynamic and pharmacokinetic alteration ## Footnote These risks can affect patient outcomes during and after cardiac procedures.
49
What does the Alpha Stat strategy involve during CPB? What are its proposed benefits and downsides?
Results are not corrected to patient's temperature --> PCO2 and pH are maintained at normal levels for 37°C (Maintains a normal [OH-]:[H1] ratio) +: 1. preserved intracellular function 2. avoids increased risk of cerebral embolic events (seen with pH stat management) -: 1. may lead to reduced cerebral perfusion ## Footnote This approach may lead to reduced cerebral perfusion but avoids increased risk of cerebral embolic events.
50
What is a key feature of the pH Stat strategy during CPB? What are its proposed benefits and downsides?
Correcting results to the patient's systemic temperature --> yields alkalemia + reduced pCO2 --> Exogenous CO2 is added to the perufsate to normalize pCO2 and therefore pH + 1. Causes cerebral vasodilation --> improves cerebral blood flow + cerebral cooling -: 1. Increases risk of cerebral embolism ## Footnote This yields alkalemia and reduced pCO2, with the addition of exogenous CO2 to normalize pCO2 and pH.
51
What is the definition of deep hypothermic circulatory arrest?
Circulatory arrest at temperatures <18°C followed by stopping CPB pump ## Footnote This technique has shown improvement in outcomes for human neonates and pediatric patients when using pH stat during cooling and Alpha stat during rewarming.
52
What coagulational changes occur during therpapeutic hypothermia?
* Thrombocytopathia * Platelet sequestration * reduced serine protease function
53
What is the primary concern in the first 24 hours post CPB?
Deranged physiology and behavior of the heart following cardioplegia requires a different approach than usual. ## Footnote This period is critical for monitoring and management as most abnormal physiologic aberrations have not yet resolved.
54
What is the goal of fluid balance and routine transfusions post CPB?
To reduce unnecessary crystalloid administration and thus reduce mortality. ## Footnote A reduced fluid load is crucial for patient recovery.
55
Name 5 causes of a high UOP post CPB surgery?
1. Cold induced diuresis 2. Mannitol in prime fluid 3. Altered cortisol levels 4. Altered catecholamine levels 5. Renal tubular dysfunction ## Footnote These factors contribute to increased urine production following surgery.
56
What are potential consequences of hypokalemia post CPB?
* Respiratory muscle weakness * Arrhythmias ## Footnote These complications can significantly impact patient recovery.
57
Name X causes of hypernatraemia post CPB surgery. What is the treatment when levels > 165 mmol/L?
1. marked UOP 2. reduced IVRT 3. reduced oral water intake (sedation) --> Treat with 0.45% saline or D5W. ## Footnote This helps to restore normal sodium levels.
58
What does perioperative hyperglycemia indicate in terms of patient outcomes in people?
Reduced survival ## Footnote Managing blood sugar levels is essential for recovery.
59
What are consequences of hypocalcemia and hypercalcaemia post CPB?
Hypocalcaemia: * Ongoing bleeding * affects myocardial electrical activity Hypercalcaemia: * worsening of ischemia-reperfusion injury ## Footnote This condition can lead to serious cardiac complications.
60
What are the effects of acute post-operative pain?
* Worsens myocardial ischemia * Reduces UOP * Causes myriad pulmonary effects (hypoventilation, reduced vital capacity, increased risk of pulmonary infections) ## Footnote Effective pain management is crucial for recovery.
61
When should antiplatelet therapy be initiated post CPB in people in order to reduce mortality?
Within 48 hours post OP ## Footnote This therapy is critical for preventing thromboembolic complications.
62
What causes coronary dysfunction post CPB? What are signs on ECG?
ligation, obstruction, and spasm of the main coronary artery ECG: * Regional myocardial dyskinesia * ST segment alterations * Arrhythmias ## Footnote Coronary dysfunction is uncommon.
63
What indicates acute failure of the surgical repair?
* Reversion to heart failure * movement of intracardiac prosthesis seen on echocardiography ## Footnote Treatment involves revision surgery.
64
What is the relationship between peripheral and central arterial pressure post CPB?
Peripheral arterial pressure has reduced correlation with central arterial pressure --> peripheral < central --> may persist for up to 24hr ## Footnote This may persist for up to 24 hours.
65
What are potential causes of hypotension post CPB?
1. Absolute hypovolemia (UOP, CTO, aggressive rewarming) 2. Relative hypovolemia (low SVR, Vasoplegic syndrome) 3. Electrolyte abnormalities 4. Myocardial stunning 5. Tachycardia ## Footnote Each cause has specific treatment considerations.
66
What are the effects of CPB on coagulation?
* Thrombocytopenia * Thrombocytopathia * Hypofibrinogenemia * Hyperfibrinolysis * Consumption of coagulation factors * Endothelial dysfunction * Hemodilution ## Footnote These effects lead to increased risk of hemorrhage during and after surgery.
67
What surgical factors associated with postopreative hemorrahge after CPB surgery?
* Incision in myocardium + great vessels * Surgical trauma from thoracotomy ## Footnote These factors can contribute to increased bleeding during surgery.
68
Name 5 broad causes of postoperative hemrorhage after MVR utilizing CPB?
1. CPB effects on coagulation 2. Surgical factors (cardiac incisions, thoracotomy, inadequate hemostasis) 3. Inadequate protamine administration 4. Markedly elevated SBP --> hemorrhage from aortic cannulation site 5. Markedly elevated CVP --> hemorrhage from RA cannulation site ## Footnote These issues can complicate recovery and increase the risk of bleeding.
69
Are perioperative antifibrinolytics recommended in people? What is the downside?
Yes, they are routinely recommended cons = thrombotic events ## Footnote The use of antifibrinolytics may vary based on species, particularly in dogs and cats.
70
What is the percentage reduction in FRC post CPB?
Up to 50% reduction in FRC
71
List 6 causes of pulmonary injury post CPB.
1. Pleural space disease (pneumothorax, hemothorax) 2. Thoracic wall pain 3. Altered pulmonary blood flow 4. Interstitial edema 5. Cytokine mediated alterations 6. Atelectasis 7. Neutrophil activation + trapping 8. Complement mediated bronchospasm
72
What is a significant cause of atelectasis during CPB?
Absence of MV during CPB due to membrane oxygenation
73
What has been proven to reduce atelectasis and improve post-operative pulmonary function?
* FiO2 <50% + CPAP (5-7.5 cmH2O) * low frequency MV
74
What are some effects of neutrophil activation post CPB possibly causing pulmonary injury?
Neutrophil trapping and pulmonary endothelial dysfunction --> can last for several days post-operative
75
What is the primary treatment for pulmonary injury post CPB?
* Supplemental oxygen * monitoring of ventilation * thoracic drainage * analgesia
76
Which route of oxygen delivery should be avoided due to the risk of hemorrhage?
Mechanisms that can lead to self-trauma, such as nasal cannulae
77
What are oxygen delivery methods that can be used post CPB?
* O2 cage * Nasal prongs * HFNO
78
What percentage of dogs develop AKI after CPB?
28% ## Footnote Acute kidney injury is a significant concern in this population.
79
What percentage of people develop AKI following thoracic aortic surgery?
> 50% ## Footnote This indicates a high risk associated with this type of surgery.
80
Name 4 causes of AKI after CPB (multifactorial)?
1. CPB-mediated systemic inflammatory response syndrome 2. Emboli 3. Altered renal blood flow 4. Changes in vasomotor tone ## Footnote Each of these factors can contribute to kidney injury during and after surgery.
81
How does therapeutic hypothermia contribute to AKI?
It increases renal vascular resistance + reduces renal blood flow ## Footnote While it lowers metabolic rate and risk of renal ischemia, these benefits can be offset by the adverse effects.
82
What is the treatment for dogs with AKI following CPB?
1. Optimizing vascular volume 2. Fluid balance 3. Limiting further renal insults (e.g., nephrotoxic drugs, hypotension) selected cases: indication for hemodialysis ## Footnote Close monitoring for progression is also recommended.
83
When should arrhythmias be treated aggressively?
If they cause low CO ## Footnote Treatment involves eliminating extracardiac causes and administering pharmacologic therapy.
84
Name 3 factors contributing to postoperative arrhythmias?
1. Structural heart disease 2. surgical trauma 3. myocardial ischemia ## Footnote Myocardial ischemia may be due to electrolyte abnormalities, hypoxemia, and elevated catecholamines.
85
Which dogs are at highest risk for arrhythmias?
* preoperative rhythm disturbances * intracardiac suturing near pacemaker or conducting tissue * myocardial infarction * certain cannulation techniques
86
What may cause pacemaker dysfunction and conduction disturbances?
* Surgical trauma * ischemia ## Footnote These may be transient, allowing time for recovery before placing a permanent pacemaker.
87
Name 4 gastrointestinal complications that occur postoperatively?
1. Pancreatitis 2. Intestinal ischemia 3. Cholecystitis 4. Gastrointestinal ulceration
88
What is the incidence range of gastrointestinal complications?
0.3%–5.5% ## Footnote The incidence depends on diagnostic criteria.
89
What are potential etiologies for gastrointestinal complications?
* Ischemia–reperfusion injury * Emboli * Hypoxemia * Inflammation-mediated alterations in microvascular blood flow
90
What immunological changes occur due to CPB?
* Altered complement and immunoglobulin levels * Decreased number and function of natural killer cells * Decreased T lymphocyte subsets
91
What infection risk does intracardiac surgery pose?
Risk of direct bacterial load to the heart ## Footnote This increases infection risk following surgery.
92
Why is there a high risk of infection following CPB?
Due to numerous invasive in-dwelling devices + altered pharmacokinetics of antimicrobials ## Footnote Strict barrier nursing must be performed to minimize infection risk.

Cardiovascular (21 decks)

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