On Pump vs Off Pump Flashcards
(97 cards)
1
Q
Surgical techniques for cardiac operations
A
- On pump with an arrested heart
- On pump with a beating heart
- Off pump
- Endovascular (for valve repair/replacement)
2
Q
Steps prior to incision
A
- Cardiac induction
- BOBCAT
- Leg incision to harvest the saphenous vein (for CABG)
3
Q
What is common cardiac induction?
A
- Higher versed (up to 5mg) and fentanyl (up to 250mcg) dosing
- Etomidate
- Smaller propofol dose followed by inhalational induction with bag mask ventilation
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
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
6
Q
When is Amicar dosed?
A
After central line placement
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
8
Q
Most common antifibrinolytic drug for CPB
A
Amicar
9
Q
What can be used as an alternate to Amicar?
A
Tranexamic acid
10
Q
The earliest and most sensitive sign of myocardial ischemia
A
Regional Wall Motion Abnormalities with TEE (RWMA)
11
Q
Considerations for sternal incision/sternotomy
A
- Avoid hypertension
- Turn off ventilator and remove breathing bag from circuit to keep lungs from expanding
12
Q
How do you prevent hypertension during sternotomy?
A
With fentanyl or nitroglycerin
13
Q
What is the intrathoracic pressure after sternal retraction?
A
Atmospheric
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
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
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
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
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
19
Q
Why do surgeons not close the pericardium at the end of the operation?
A
Due to a higher chance of cardiac tamponade
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
21
Q
When must heparin be administered?
A
Prior to aortic cannulation
22
Q
When is the ACT checked?
A
Roughly 3 minutes after heparin is given
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
24
Q
What are considerations for aortic cannulation?
A
-Cannulation can lead to possible aortic dissection
25
How can you decrease the risk of dissection in aortic cannulation?
You should lower the SBP to 90-100 mmHg prior to cannulation
26
Where does venous cannulation typically occur?
Right atrial appendage
27
When is the patient "on pump"
Once the venous reservoir is opened
28
What should you do at the onset of bypass?
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
29
What is the most important step at the onset of bypass and why?
Empty the foley at the onset so the perfusionist knows how much urine is produced on pump
30
What is the optimal MAP during bypass?
78 mmHg
31
How is antegrade cardioplegia usually administered?
Via the aortic root
32
Why is strain on the heart minimized with aortic cross clamp placement?
The heart is empty
33
How is cardioplegia given?
Intermittent every 20-30 min, but may be given continuously
34
What happens when the CABG/valve repair is performed by the surgeon?
The pt is typically cooled to some degree
35
What is an indication that the surgeon is almost done repairing the heart?
Rewarming
36
What increases the risk of awareness?
Rewarming bc hypothermia has anesthetic effects
37
What are possible drugs to dose in the rewarming phase?
1. Versed
2. Antiarrhythmics (magnesium, amiodarone, lidocaine)
3. Calcium
38
How does the perfusionist refill the heart with blood?
By partially closing the venous reservoir
39
When is looking for air bubbles especially indicated?
For operations where the myocardium or aorta was opened
40
When is the aortic cross clamp removed?
After all the air bubbles are removed
41
What happens when the aortic cross clamp is removed?
All the blood from the arterial cannula rushes into the heart and flushes out the cardioplegia, allowing the heart to start beating again
42
As soon as the CP washes out, the heart goes into:
Either bradycardia or vtach/vfib
43
What does the surgeon do if the heart goes into vfib/vtach?
Apply a 10-20J shock directly to the heart
44
What can you do to re-establish an effective sinus rhythm
1. Give inotropic drugs (calcium, epi, milrinone, etc)
| 2. Have the surgeon place temporary pacing wires
45
What is recommended to keep O2 demand low while allowing the heart to recover?
Have the heart beat in an empty state for 20-30 minutes prior to filling the heart with blood again
46
What are the external pacemaker (pulse generator) settings?
- Energy (20mA)
| - Rate (80-100 bpm)
47
What are the final steps of coming off pump?
1. Anesthetist turns on the ventilator and isoflurane
2. The venous reservoir is completely closed
3. The venous and aortic cannulas are removed
48
Options for reversal of anticoagulation
1. Protamine is the PRIMARY agent
| 2. DDAVP (desmopressin)
49
When should heparin reversal occur, and why?
Prior to chest closure because the surgeon won't close the chest unless the bleeding is controlled
50
When should DDAVP be administered?
If the pt is bleeding more than expected after protamine administration
51
What does DDAVP do?
It can cause clotting factor release and promote coagulation
52
Why is cell saver given after protamine?
It takes time for the blood to be centrifuged
53
Options for sedation during transport
1. Propofol (20-50 mcg/kg/min)
| 2. Precedex
54
When is the sedation drip for transport started?
Before closure because the infusion runs at a slow rate
55
What should be brought with you to the ICU during transport?
A transport monitor, laryngoscope and vasoactive meds
56
Summary of pump steps (29)
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
9. Aortic cannulation
10. Venous cannulation & opening of venous reservoir
11. Cardioplegia catheter insertion
12. Aortic cross clamp placement
13. Heart is arrested with cardioplegia
14. The CABG and/or valve repair is performed by the surgeon
15. Rewarming phase (if pt was cooled)
16. The perfusionist partially closes the venous reservoir to fill the heart with blood
17. The surgeon removes air from the heart
18. The aortic clamp is removed
19. The heart comes out of asystole and resumes electrical activity
20. Defibrillation (if applicable)
21. Re-establishment of sinus rhythm
22. Turn on ventilator and isoflurane
23. Venous reservoir is completely closed
24. The venous and aortic cannulas are removed
25. Reversal of anticoagulation
26/27. Cell saver blood given (if applicable)
28. Chest closed/chest drainage tube placed
29. Transport to ICU with monitor
57
What is the problem with a redo sternotomy?
The heart structures develop postop adhesions with the back of the sternum, posing a risk of uncontrollable hemorrhage
58
How do you manage a redo sternotomy?
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
% of pts that will require surgical re-exploration
2-4%
60
Normal blood output from chest tube after cardiac surgery
0.5-1 ml/kg/hr
61
Blood output that prompts immediate surgical intervention
8-10 ml/kg/hr
62
Reperfusion occurs when:
1. Occluded artery being opened up
| 2. Re-establishment of perfusion after being weaned from bypass
63
Significance of reperfusion
There is a chance that further injury can occur to the heart
64
Causes of reperfusion injury
1. Accumulation of intracellular calcium
| 2. Prolonged ischemia period
65
Why is nitrous oxide avoided during bypass surgery?
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
When are off pump procedures NOT an option?
1. When the heart needs arrested
| 2. When the heart needs to be drained of blood
67
Why must the surgeon intermittently lift the heart in off pump CABG?
To get to the coronary arteries
68
What does lifting the heart cause?
1. Arrhythmias
2. Profound decrease in ejection fraction and cardiac output
3. Hypotension
69
Advantages to off pump
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
Disadvantages of off pump CABG
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
Most common procedures where an off pump technique is used
1. CABG
2. Transmyocardial laser revascularization (TMR)
3. Endovascular valve repair
72
What arteries are more likely to have collateral flow?
Severely stenosed arteries
73
Results in severe myocardial ischemia with adverse hemodynamic consequences
Vessels that are proximally diseased or less severely stenosed with less extensive collaterals
74
How do you know which vessels to expect the most hypotension with?
Read the cath report
75
Better collateral circulation (more or less stenotic)
More stenotic vessels
76
Less hypotension is expected when surgeon lifts the heart (more or less stenotic)
More stenotic
77
Underdeveloped collateral circulation (more or less stenotic)
Less stenotic
78
More hypotension expected when the surgeon lifts the heart (more or less stenotic)
Less stenotic
79
When are proximal anastamosis sewn in?
After the distal
80
What should the SBP be when sewing the proximal anastomosis, and why?
Below 100 mmHg to prevent aortic dissection
81
When does the surgeon apply suction to the heart?
During sewing of distal anastomosis
82
What is required for BP in distal anastomosis?
- Vasopressors and inotropes are usually required
| - MAP should be 90-100 mmHg for normotension to maintain coronary perfusion
83
What should you do prior to the surgeon lifting the heart?
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
What is the purpose of fluids prior to lifting the heart?
To prevent hypotension
85
What is the purpose of amiodarone and magnesium prior to lifting the heart?
To decrease the chance of the pt going into arrhythmias
86
What is the purpose of caclium prior to the surgeon lifting the heart?
Inotropic support and prevent hypotension
87
What is the optimal BP for distal anastomosis?
Normal, MAP of 90-100 mmHg
88
What is the optimal BP for proximal anastomosis?
SBP less than 90 mmHg
89
How can you combat hypotension when the heart is lifted?
Vasopressors and/or inotropes
90
On ___ bypass, the lungs don't need to be ventilated
Full
91
On ____ bypass, the lungs need to be ventilated
Partial
92
When is myocardial oxygen delivery greater?
When blood is allowed to pump through the heart into the coronary arteries as opposed to the arterial cannula
93
Benefits of pump assisted beating heart surgery over off pump
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
Advantages to arresting the heart
1. Lower oxygen demand
| 2. Technically easier for surgeon
95
Disadvantages to arresting the heart
1 . Aortic clamp is placed
2. Worse perfusion (higher risk of reperfusion injury, modest hypothermia)
3. Heart must be restarted, longer CPB times
96
Advantages to beating heart cardiac surgery
1. Perfusion is better
2. Less neurologic risk
3. Heart does not need restarted
97
Disadvantages to beating heart cardiac surgery
1. The heart has higher oxygen demand
2. Higher risk of air and debris embolization
3. Can be more challenging
