Core Topic 1: Cardiopulmonary Bypass, Myocardial Protection, Thoracic Aortic Injury, Thoracic Trauma Flashcards

1
Q

What are the general goals that CPB achieves?

A

maintain CO and organ perfusion, blood oxygenation, CO2 elimination, temperature control; bloodless field and ability to manipulate the heart

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2
Q

How is CO2 production affected by temperature (in the setting of CPB)?

A

CO2 production decreases as temperature decreases, so less ventilation is required through the oxygenator with a cooler patient.

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3
Q

In the context of CPB, how does reducing body temp affect the body’s metabolism? What is the range of this temperature?

A
Reduces metabolism (ie oxygen consumption) to allow the body to tolerate lower CO or even total circulatory arrest.
16-28 C.
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4
Q

What are the components of the CPB circuit?

A

venous drainage cannula, reservoir, blood pump, oxygenator, heat exchanger, arterial filter, and arterial return cannula

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5
Q

What is Poiseuille’s Law as it relates to the CPB circuit?

A

Resistance is directly related to the length of a tube and indirectly related to the internal radius to the 4th power.

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6
Q

What are the advantages of vac assisted venous drainage (VAVD)?
What are the risks?

A

permits use of dry venous drainage lines, smaller drainage cannulas, minimizes air lock

risks - can draw air into venous lines if misplaced

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7
Q

In terms of drainage, what is a disadvantage of the single/dual stage cannulation of the RA?

A

poor drainage from the vena cava, e.g. if the heart is rotated to expose a coronary target, the superior cavoatrial jct can kink, leading to obstructed cerebral drainage

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8
Q

What is the preferred femoral vein for CPB?

A

R femoral vein - straighter trajectory to the heart

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9
Q

What would be some typical indications for femoral venous cannulation?

A

Minimally invasive cardiac surgery, redo sternotomy, descending aortic surgery

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10
Q

If atriocaval kinking is anticipated (ie rotation of the heart for an extended period of time), what cannulation strategy should be employed?

A

Bicaval

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11
Q

What are the typical surgeries that utilize bicaval cannulation?

A

mitral valve, tricuspid valve, intracardiac surgery to remove blood from the field; surgeries that cause kinking to improve drainage (particularly from SVC)

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12
Q

Which arterial cannulation location has the best coronary perfusion?

A

Ascending aorta

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13
Q

In an ascending aorta cannulation strategy for CPB, what must be evaluated on imaging to minimize dissection and stroke risk?

A

calcified aorta

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14
Q

What is the best option for emergency arterial cannulation?

A

femoral artery

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15
Q

What are some of the hemodynamic limitations of femoral arterial cannulation in CPB?

A

when heart is beating, there is competitive flow in the descending aorta; increased LV afterload

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16
Q

What is the ideal site for aortic cannulation?

A

opposite of the innominate artery in the inner curve of the aorta, which provides a thicker wall to hold sutures; avoid plaque by palpating

17
Q

What are some options for aortic cannulation in ascending aorta aneurysm/dissection, heavy atherosclerotic burden in ascending?

A

Innominate, axillary, subclavian arteries.
If no other options, and the patient needs the surgery, may need circ arrest.

18
Q

What are the advantages and disadvantages of soft-bag vs hard-shell venous reservoirs in CPB?

A

heard-shell - open to air, allowing release of air from venous line, used for VAVD; large air-blood surface, which can lead to activation of blood elements

soft-bag reservoirs - no air-blood interface; work best with centrifugal pumps; can’t use VAVD

19
Q

What are the three mechanisms used to protect the heart during cardiac surgery?

A

hypothermia, chemical arrest, decompression

20
Q

How does temperature management in CPB affect the myocardium and the systemic temperature differently?

A

myocardium and systemic temp are uncoupled - systemic hypothermia ranges from mild (>28), moderate (20-28), and deep (<20), myocardial temp goal is 10-14 C

21
Q

What pressure do you expect in the aortic root when deliver cardioplegia in an adult? Child?
When delivering cardioplegia, when should you expect arrest?

A

180-220 mmHg in adults and 110 in neonates

30-60 seconds

22
Q

What pressure do you expect to deliver through a retrograde cardioplegia strategy? Why is it so much lower than via the aorta?

A

30-50 mmHg. Any higher can injure the coronary sinus. Arrest in 2-4 minutes.

23
Q

What is a standard UFH dose for CPB?

What ACT are you looking for?

A

400 u/kg IV

480 ACT

24
Q

How do you treat heparin resistance?

A

FFP or AT III

25
Q

What is the generally accepted flow in adults during CPB?

A

2.2-2.4 L/min/m2

26
Q

Weaning from CPB requires what?

A
warm and remove cross-clamp (end of coronary ischemia)
ventilation
good contractility
stable rhythm
adequate de-airing
balanced electrolytes
-> start wean -> inc CO and dec CPB until venous line completely clamped
-> turn off vent
27
Q

How do you calculate VO2 (ie Fick equation)?

A

VO2 = Q x 1.34 x Hgb x (SaO2 - SvO2) x 10

28
Q

What organ is particularly vulnerable to congestion in the setting of CPB?

A

liver - 75% of hepatic blood flow occurs by venous pressure through the portal vein

29
Q

What parameters are measured during CPB as surrogates to VO2 (ie outside of this than this require higher flow)?

A

SVO2 >75%, base deficit > -5, lactate <4

30
Q

What is a shortfall of measuring the Fick?

A

systemic measurement, so does not detect regional hypoperfusion (brain, coronary system, kidney, gut)

31
Q

What is the risk if DHCA (18-20 C) is extended longer than 40 mins?

A

brain injury risk increases; at 60 mins, the majority of patients will suffer brain injury; longer periods are tolerated in neonates and children

32
Q

What does elevated venous pressure during CPB do to effective perfusion pressure in an organ?

A

reduces it; ie if the MAP is 60 during CPB, and venous pressures start to rise, perfusion pressure decreases even though MAP may be maintained; the back pressure also increases transudation/congestion

33
Q

What venous drainage strategy for CPB has the best LV unloading efficiency?

A

BiCaval cannula (SVC/IVC)