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Methods of Anesthesia > On Pump vs Off Pump > Flashcards

On Pump vs Off Pump Flashcards

1
Q

Surgical techniques for cardiac operations

A
  1. On pump with an arrested heart
  2. On pump with a beating heart
  3. Off pump
  4. Endovascular (for valve repair/replacement)
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2
Q

Steps prior to incision

A
  1. Cardiac induction
  2. BOBCAT
  3. Leg incision to harvest the saphenous vein (for CABG)
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3
Q

What is common cardiac induction?

A
  1. Higher versed (up to 5mg) and fentanyl (up to 250mcg) dosing
  2. Etomidate
  3. Smaller propofol dose followed by inhalational induction with bag mask ventilation
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4
Q

What should you do during cardiac induction?

A

Give the drugs more slowly and use the A-line pressure as a guide for when to intubate

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5
Q

What does BOBCAT stand for?

A 
Baseline labs/ACT
OG insertion/removal
BIS monitor placement
Central line placement
Amicar bolus followed by 1g/hr infusion
TEE monitoring
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6
Q

When is Amicar dosed?

A

After central line placement

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7
Q

What is the purpose of Amicar?

A

An antifibrinolytic to counteract the damaging effects of the bypass machine in the blood, and reduce bleeding post CPB by inhibiting fibrinolysis

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8
Q

Most common antifibrinolytic drug for CPB

A

Amicar

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9
Q

What can be used as an alternate to Amicar?

A

Tranexamic acid

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10
Q

The earliest and most sensitive sign of myocardial ischemia

A

Regional Wall Motion Abnormalities with TEE (RWMA)

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11
Q

Considerations for sternal incision/sternotomy

A
  • Avoid hypertension

- Turn off ventilator and remove breathing bag from circuit to keep lungs from expanding

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12
Q

How do you prevent hypertension during sternotomy?

A

With fentanyl or nitroglycerin

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13
Q

What is the intrathoracic pressure after sternal retraction?

A

Atmospheric

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14
Q

What is significant about the intrathoracic pressure being atmospheric after sternal retraction?

A

The “increase” in intrathoracic pressure should cause a decrease in venous return and cardiac output

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15
Q

What should be noted about sternal retraction regarding arterial line readings?

A

The retractor can cause compression of the subclavian artery, which may cause R arterial line readings to show a falsely low number

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16
Q

What are considerations for harvesting the LIMA?

A
  • only applicable for CABGs
  • Less stimulation
  • Lung expansion can get in the way
  • L sided radial A-lines may not function during LIMA dissection due to compression of subclavian
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17
Q

How do you keep the lungs out of the surgeon’s view when harvesting the LIMA?

A
  • Decrease the tidal volume

- May need to increase the RR to keep minute ventilation normal

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18
Q

What can happen when the pericardium opens, and why?

A

A possible vagal response bc the nerves innervating the pericardium are derived from the vagus and phrenic nerves

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19
Q

Why do surgeons not close the pericardium at the end of the operation?

A

Due to a higher chance of cardiac tamponade

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20
Q

Is LIMA harvested before or after the pericardium is opened, and why?

A

LIMA is harvested before so the pericardium is not in the way when it is sewn to the chest wall

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21
Q

When must heparin be administered?

A

Prior to aortic cannulation

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22
Q

When is the ACT checked?

A

Roughly 3 minutes after heparin is given

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23
Q

How do you know if the pt is adequately heparinized?

A

Draw 1ml blood from the arterial line to check if ACT is >450 seconds

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24
Q

What are considerations for aortic cannulation?

A

-Cannulation can lead to possible aortic dissection

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25
Q

How can you decrease the risk of dissection in aortic cannulation?

A

You should lower the SBP to 90-100 mmHg prior to cannulation

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26
Q

Where does venous cannulation typically occur?

A

Right atrial appendage

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27
Q

When is the patient “on pump”

A

Once the venous reservoir is opened

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28
Q

What should you do at the onset of bypass?

A
  1. Turn the ventilator and vaporizer off (for full bypass)
  2. Measure pre-bypass urine output
  3. Put the monitor in “bypass mode”
  4. Put vasoactive infusions in standby, but keep amicar and insulin going
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29
Q

What is the most important step at the onset of bypass and why?

A

Empty the foley at the onset so the perfusionist knows how much urine is produced on pump

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30
Q

What is the optimal MAP during bypass?

A

78 mmHg

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31
Q

How is antegrade cardioplegia usually administered?

A

Via the aortic root

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32
Q

Why is strain on the heart minimized with aortic cross clamp placement?

A

The heart is empty

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33
Q

How is cardioplegia given?

A

Intermittent every 20-30 min, but may be given continuously

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34
Q

What happens when the CABG/valve repair is performed by the surgeon?

A

The pt is typically cooled to some degree

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35
Q

What is an indication that the surgeon is almost done repairing the heart?

A

Rewarming

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36
Q

What increases the risk of awareness?

A

Rewarming bc hypothermia has anesthetic effects

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37
Q

What are possible drugs to dose in the rewarming phase?

A
  1. Versed
  2. Antiarrhythmics (magnesium, amiodarone, lidocaine)
  3. Calcium
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38
Q

How does the perfusionist refill the heart with blood?

A

By partially closing the venous reservoir

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39
Q

When is looking for air bubbles especially indicated?

A

For operations where the myocardium or aorta was opened

40
Q

When is the aortic cross clamp removed?

A

After all the air bubbles are removed

41
Q

What happens when the aortic cross clamp is removed?

A

All the blood from the arterial cannula rushes into the heart and flushes out the cardioplegia, allowing the heart to start beating again

42
Q

As soon as the CP washes out, the heart goes into:

A

Either bradycardia or vtach/vfib

43
Q

What does the surgeon do if the heart goes into vfib/vtach?

A

Apply a 10-20J shock directly to the heart

44
Q

What can you do to re-establish an effective sinus rhythm

A
  1. Give inotropic drugs (calcium, epi, milrinone, etc)

2. Have the surgeon place temporary pacing wires

45
Q

What is recommended to keep O2 demand low while allowing the heart to recover?

A

Have the heart beat in an empty state for 20-30 minutes prior to filling the heart with blood again

46
Q

What are the external pacemaker (pulse generator) settings?

A
  • Energy (20mA)

- Rate (80-100 bpm)

47
Q

What are the final steps of coming off pump?

A
  1. Anesthetist turns on the ventilator and isoflurane
  2. The venous reservoir is completely closed
  3. The venous and aortic cannulas are removed
48
Q

Options for reversal of anticoagulation

A
  1. Protamine is the PRIMARY agent

2. DDAVP (desmopressin)

49
Q

When should heparin reversal occur, and why?

A

Prior to chest closure because the surgeon won’t close the chest unless the bleeding is controlled

50
Q

When should DDAVP be administered?

A

If the pt is bleeding more than expected after protamine administration

51
Q

What does DDAVP do?

A

It can cause clotting factor release and promote coagulation

52
Q

Why is cell saver given after protamine?

A

It takes time for the blood to be centrifuged

53
Q

Options for sedation during transport

A
  1. Propofol (20-50 mcg/kg/min)

2. Precedex

54
Q

When is the sedation drip for transport started?

A

Before closure because the infusion runs at a slow rate

55
Q

What should be brought with you to the ICU during transport?

A

A transport monitor, laryngoscope and vasoactive meds

56
Q

Summary of pump steps (29)

A
  1. Cardiac induction
  2. BOBCAT
  3. Leg incision to harvest saphenous
  4. Sternal incision and sternotomy
  5. Sternal retraction
  6. Harvesting the LIMA
    7/8. Opening the pericardium
    7/8. Heparin administration
  7. Aortic cannulation
  8. Venous cannulation & opening of venous reservoir
  9. Cardioplegia catheter insertion
  10. Aortic cross clamp placement
  11. Heart is arrested with cardioplegia
  12. The CABG and/or valve repair is performed by the surgeon
  13. Rewarming phase (if pt was cooled)
  14. The perfusionist partially closes the venous reservoir to fill the heart with blood
  15. The surgeon removes air from the heart
  16. The aortic clamp is removed
  17. The heart comes out of asystole and resumes electrical activity
  18. Defibrillation (if applicable)
  19. Re-establishment of sinus rhythm
  20. Turn on ventilator and isoflurane
  21. Venous reservoir is completely closed
  22. The venous and aortic cannulas are removed
  23. Reversal of anticoagulation
    26/27. Cell saver blood given (if applicable)
  24. Chest closed/chest drainage tube placed
  25. Transport to ICU with monitor
57
Q

What is the problem with a redo sternotomy?

A

The heart structures develop postop adhesions with the back of the sternum, posing a risk of uncontrollable hemorrhage

58
Q

How do you manage a redo sternotomy?

A
  1. Have blood and blood tubing available
  2. Have defibrillator pads placed prior to induction
  3. Ventilation is necessary, often gentle hand ventilation to prevent lungs from inflating too much
59
Q

% of pts that will require surgical re-exploration

A

2-4%

60
Q

Normal blood output from chest tube after cardiac surgery

A

0.5-1 ml/kg/hr

61
Q

Blood output that prompts immediate surgical intervention

A

8-10 ml/kg/hr

62
Q

Reperfusion occurs when:

A
  1. Occluded artery being opened up

2. Re-establishment of perfusion after being weaned from bypass

63
Q

Significance of reperfusion

A

There is a chance that further injury can occur to the heart

64
Q

Causes of reperfusion injury

A
  1. Accumulation of intracellular calcium

2. Prolonged ischemia period

65
Q

Why is nitrous oxide avoided during bypass surgery?

A
  1. Because of its potential to expand air bubbles
  2. It can increase pulmonary vascular resistance and elevate PA pressures
  3. Many pts require higher FiO2 during this period
66
Q

When are off pump procedures NOT an option?

A
  1. When the heart needs arrested

2. When the heart needs to be drained of blood

67
Q

Why must the surgeon intermittently lift the heart in off pump CABG?

A

To get to the coronary arteries

68
Q

What does lifting the heart cause?

A
  1. Arrhythmias
  2. Profound decrease in ejection fraction and cardiac output
  3. Hypotension
69
Q

Advantages to off pump

A
  1. Pts may experience faster recovery and shorter hospital stay
  2. Post-op neuro deficiencies appear to be decreased
  3. Better renal, pulmonary and myocardial protection when compared to conventional bypass
  4. Physiologic cardiac perfusion is maintained
70
Q

Disadvantages of off pump CABG

A
  1. Higher degree of hemodynamic instability throughout the procedure
  2. Distal anastomosis may not be as good as those performed on pump
  3. The total number of grafts being performed may be less on these patients, resulting in under vascularization
  4. There is a steep learning curve
71
Q

Most common procedures where an off pump technique is used

A
  1. CABG
  2. Transmyocardial laser revascularization (TMR)
  3. Endovascular valve repair
72
Q

What arteries are more likely to have collateral flow?

A

Severely stenosed arteries

73
Q

Results in severe myocardial ischemia with adverse hemodynamic consequences

A

Vessels that are proximally diseased or less severely stenosed with less extensive collaterals

74
Q

How do you know which vessels to expect the most hypotension with?

A

Read the cath report

75
Q

Better collateral circulation (more or less stenotic)

A

More stenotic vessels

76
Q

Less hypotension is expected when surgeon lifts the heart (more or less stenotic)

A

More stenotic

77
Q

Underdeveloped collateral circulation (more or less stenotic)

A

Less stenotic

78
Q

More hypotension expected when the surgeon lifts the heart (more or less stenotic)

A

Less stenotic

79
Q

When are proximal anastamosis sewn in?

A

After the distal

80
Q

What should the SBP be when sewing the proximal anastomosis, and why?

A

Below 100 mmHg to prevent aortic dissection

81
Q

When does the surgeon apply suction to the heart?

A

During sewing of distal anastomosis

82
Q

What is required for BP in distal anastomosis?

A
  • Vasopressors and inotropes are usually required

- MAP should be 90-100 mmHg for normotension to maintain coronary perfusion

83
Q

What should you do prior to the surgeon lifting the heart?

A
  1. Administer a fluid bolus of up to 2L crystalloid and 500 mL 5% Albumin
  2. Dose amiodarone (150mg) and magnesium (1-2g)
  3. Dose caclium (1g)
  4. Maintain BP in correct range depending on distal or proximal anastomosis
  5. Amicar
  6. Heparin
84
Q

What is the purpose of fluids prior to lifting the heart?

A

To prevent hypotension

85
Q

What is the purpose of amiodarone and magnesium prior to lifting the heart?

A

To decrease the chance of the pt going into arrhythmias

86
Q

What is the purpose of caclium prior to the surgeon lifting the heart?

A

Inotropic support and prevent hypotension

87
Q

What is the optimal BP for distal anastomosis?

A

Normal, MAP of 90-100 mmHg

88
Q

What is the optimal BP for proximal anastomosis?

A

SBP less than 90 mmHg

89
Q

How can you combat hypotension when the heart is lifted?

A

Vasopressors and/or inotropes

90
Q

On ___ bypass, the lungs don’t need to be ventilated

A

Full

91
Q

On ____ bypass, the lungs need to be ventilated

A

Partial

92
Q

When is myocardial oxygen delivery greater?

A

When blood is allowed to pump through the heart into the coronary arteries as opposed to the arterial cannula

93
Q

Benefits of pump assisted beating heart surgery over off pump

A
  1. Hypotension is less likely

2. Offers better myocardial protection because there is less O2 demand when the heart beats in an empty state

94
Q

Advantages to arresting the heart

A
  1. Lower oxygen demand

2. Technically easier for surgeon

95
Q

Disadvantages to arresting the heart

A

1 . Aortic clamp is placed

  1. Worse perfusion (higher risk of reperfusion injury, modest hypothermia)
  2. Heart must be restarted, longer CPB times
96
Q

Advantages to beating heart cardiac surgery

A
  1. Perfusion is better
  2. Less neurologic risk
  3. Heart does not need restarted
97
Q

Disadvantages to beating heart cardiac surgery

A
  1. The heart has higher oxygen demand
  2. Higher risk of air and debris embolization
  3. Can be more challenging

Methods of Anesthesia (20 decks)

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