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Perf Tech II (exam 2) > Topic: Myocardial Protection (11A?) > Flashcards

Topic: Myocardial Protection (11A?) Flashcards

1
Q

Qb stands for what?

A

Coronary Blood Flow

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2
Q

Coronary Blood Flow is determined by what?

A

is determined by hemodynamic factors such as perfusion pressure (P) and coronary vascular resistance (R)

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3
Q

The delivery of oxygen (DO2) to the myocardium (oxygen supply) is determined by two factors:

A
  • coronary blood flow (CBF)

* oxygen content of blood(CaO2).

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4
Q

O2 delivery equation

A

O2 Delivery = CBF × CaO2

where CBF = ml/min and CaO2= ml O2/ml blood

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5
Q

The two terms are often used interchangeably although they are not equivalent

A

Oxygen Consumption and Oxygen Demand

Demand =Need
Consumption= Actual amount of oxygen consumed per minute.

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6
Q

Oxygen consumption will: (2)

A

•regenerate ATP used by membrane
transport (Na+/K+-ATPase pump) and by
•Myocyte contraction and relaxation (myosin ATPase)

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7
Q
  • MVO2 (ml O2/min per 100gram)

Cardiac State:Arrested heart

A

2

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8
Q
  • MVO2 (ml O2/min per 100gram)

Cardiac State: Resting Beating Heart

A

8

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9
Q
  • MVO2 (ml O2/min per 100gram)

Cardiac State:Heavy Exercise

A

70

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10
Q

Fick Principle

A

MVO2= CBF×(CaO2− CvO2)

CBF= coronary blood flow (ml/min), and (CaO2–CvO2) is the arterial-venous oxygen content difference (ml O2/ml blood)

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11
Q

The unique relationship between MVO2, coronary blood flow (CBF), and the extraction of oxygen from the blood (A-V O2 difference) is

A

The Fick Principle

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12
Q

2 points during cardiopulmonary bypass the heart is prone to fibrillate?

A
  • Cooling

* Post cross clamp (post ischemic episodes)

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13
Q

What are the dangers during the cooling or post cross clamp periods during CPB?

A
  • Distension/Overfilling
  • Muscular/cellular damage
  • Starlings Curve
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14
Q

When is cardiac oxygen consumption (MVO2) at its Lowest level

A

•When heart is arrested

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15
Q

When is cardiac oxygen consumption (MVO2) at its Highest level

A

•Shortly after weaning from bypass–Heart is repaying oxygen debt
(catch up period-the heart needs time)

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16
Q

An imbalance of oxygen delivery and demand leads to what?

A

ANAEROBIC metabolism and the production of lactic acid

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17
Q

Decreased intracellular pH decreases the stability of what membranes?

A

cellular and mitochondrial membranes

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18
Q

Decreased intracellular pH also impairs what influx and overload?

A

Na-> K ATPase leading to calcium influx and calcium overload

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19
Q

ATP generated from AEROBIC metabolism is used preferentially for

A

myocardial contraction

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20
Q

anaerobically produced ATP is used for

A

cell survival and repair

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21
Q

% of O2 Cardiac muscle extracts

A

> 70%

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22
Q

True Coronary Perfusion Pressure

CoPP=

A

DBP–LVEDP

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23
Q

Coronary blood flow is dependent on what gradient?

A

the transmural gradient

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24
Q

increased myocardial oxygen demand is met primarily by ?

A

an increase in coronary blood flow

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25
Q

A diastolic aortic pressure of 80 and a

LVEDP pressure of 14 would get what value?

A

CPP of 66 (normal 60-80mmHg)

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26
Q

During cardiac arrest, CPP is one of the most important variables in achieving what?

A

the return of spontaneous circulation

which is why CPR compressions are important > respiration

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27
Q

A pressure gradient of what may be necessary for survival ? (mmHg)

A

15 mmHg at a minimum

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28
Q

Pre-Ischemic Intervention

A

Minimize on-going ischemia (i.e. NTG)
•Prevent ventricular distension
•Wall tension increases MVO2 and increases LVEDP
•Vent !

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29
Q

Myocardial preconditioning can be achieved by (2)

A
  • Ischemia
  • Drugs
    • Bradykinin, nitric oxide, phenylephrine (neosynephrine), endotoxin, adenosine, Sevoflurane, desflurane, isoflurane
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30
Q

Myocardial preconditioning can be achieved by what drugs?

A 
Bradykinin
nitric oxide
phenylephrine (neosynephrine) endotoxin
adenosine
Sevoflurane
desflurane
isoflurane
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31
Q

What may be the “best” preconditioning tool and override ischemia and drugs?

A

Cardiopulmonary bypass

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32
Q

Why give cardiplegia?

A
  • Cardiac quiescence
  • Bloodless field
  • Preservation of myocardial function
  • Induces myocardial hypothermia
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33
Q

Four Main Objectives of Hypothermic Cardioplegia (4)

KNOW!

A
  • Immediate/sustained electromechanical arrest
  • Rapid/sustained homogenous myocardial cooling
  • Maintenance of therapeutic additives in effective concentrations
  • Periodic washout of metabolic inhibitors
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34
Q

advocated the use of high potassium solutions to induce cardiac quiescence. Caused permanent myocardial injury

A

Melrose 1955

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35
Q

Buckberg & Follette

A

introduced 4:1 blood cardioplegia

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36
Q

Without cardioplegic arrest, irreversible ischemic injury to the myocardium would occur within how many minutes?

A

20 minutes

37
Q

When myocardial protection strategies are

used, irreversible ischemic injury can be prolonged for how long without irreversible damage?

A

4-5 hours

38
Q

Cardiac Action Potential Phase 0 ?

A

0–Na+influx

39
Q

Cardiac Action Potential Phase 1?

A

1-Transient K+efflux

40
Q

Cardiac Action Potential Phase 2?

A

2–Ca++influx

41
Q

Cardiac Action Potential Phase 3?

A

3–K+efflux

42
Q

Cardiac Action Potential Phase 4?

A

4–Na/K ATPase

43
Q

Mechanism of Depolarizing Potassium Arrest

A

Disrupt Phase 3–K+efflux

44
Q

(Mechanism of Depolarizing Potassium Arrest)

sodium gates_____

A

sodium gates do not reset:

45
Q

(Mechanism of Depolarizing Potassium Arrest)

fast-gates _____

A

fast-gates remain open;

46
Q

(Mechanism of Depolarizing Potassium Arrest)

slow gates _____

A

slow gates remain closed

47
Q

sodium gates ____: fast-gates ____;
slow gates _____
(Mechanism of Depolarizing Potassium Arrest)

A

sodium gates do not reset:
fast-gates remain open;
slow gates remain closed

48
Q

(Mechanism of Depolarizing Potassium Arrest)

Because the extracellular potassium is so high
the cell cannot what?

A

cannot repolarize and the sodium remains inside the cell.

49
Q

Mechanism of Sodium Arrest

A

Low sodium environment

Disrupts Na+ gates and influx

50
Q

(Mechanism of Sodium Arrest)

•sodium gates ___

A

– sodium gates disrupted –

Because the extracellular sodium is low the cell cannot depolarize.

51
Q

Mechanism of Sodium Arrest - which phase is disrupted ?

A

Phase 0

52
Q

Gauge and size are related how?

A

inversely

53
Q

Smaller Gauge= ___ diameter

A

greater

54
Q

French size and diameter are related how?

A

directly;

55
Q

Larger French= ___ diameter

A

larger

56
Q

French= to determine diameter size (mm)

A

divide by 3

57
Q

Gauge= to determine diameter size (mm)

A

1/gauge

58
Q

Antegrade Delivery initial dose adults

A

Initial dose = ~10-15 mL/kg

Keep in mind that if blood cardioplegia is used, a 1000mL dose would only be 200mL of crystalloid at a ratio of 4:1

59
Q

Antegrade Delivery in pediatrics initial dose

A

Up to 30mL/kg in pediatric patients.

60
Q

Antegrade Flow generally?

ml/min and in ml/min/m2

A

Flow is generally 250-400mL/min

•150 ml/minute/m2

61
Q

Antegrade Flow the goal is to maintain root pressure of what?

A

the goal is to maintain root pressure 50-100mmHg

62
Q

Antegrade Delivery Benefits (5)

A 
•Easy
•Physiological flow pattern
•Quick arrest
•Appropriate distribution to the right and
left heart.
•Root is tolerant of higher pressures
63
Q

Antegrade Delivery Disadvantages (3)

A
  • Requires competent aortic valve
  • Poor distal perfusion in diseased arteries
  • Poor subendocardial perfusion (especially in LVH)
64
Q

Retrograde Cardioplegia delivery flow? ml/min

A

Flow is ~ 150-200 mL/min

65
Q

Retrograde Cardioplegia flow should be titrated to maintain coronary sinus pressure of what?

A

Flow should be titrated to maintain a coronary sinus pressure 40 mmHg

66
Q

Retrograde Delivery Benefits (5)

A
  • Ideal for aortic valve regurgitation
  • Good distal perfusion of obstructed arteries
  • Good subendocardial perfusion
  • Retrograde flushing of emboli–augments de-airing
  • Does not impede conduct of case-can run continuously (ie, warm)
67
Q

Which cardioplegia delivery is ideal for aortic valve regurgitation?

A

Retrograde delivery

68
Q

Retrograde Delivery Disadvantages (6)

A
  • Catheter placement can be difficult
  • Impaired right heart protection
  • Right coronary veins drain into the right atrium
  • Surgical skill required for placement of cannula
  • Distracting to perfusionist
  • Possible coronary sinus rupture
69
Q

Which cardioplegia delivery method does not impede conduct of case-can run continuously (ie, warm)?

A

Retrograde Delivery

70
Q

Cardioplegia delivery that gives Appropriate distribution to the right and left heart?

A

Antegrade Delivery

71
Q

Which cardioplegia delivery method:

  • Requires competent aortic valve
  • Can interrupt and delay surgery
A

Antegrade Delivery

72
Q

Which is the most complex of the Cardioplegia Delivery methods?

A

Integrated Delivery

73
Q

CPG delivery method that you cannot use if patient has advanced CAD?

A

Antegrade

74
Q

Direct Ostial Delivery

A

Hand-held cannula directly perfuse ostia

Not as common as other methods

75
Q

Direct Ostial Delivery circuit pressure required?

A

Approximately 250 mmHg required (circuit pressure)

•high pressures due to small cannula orifice

76
Q

Direct Ostial Delivery Normal Flow? mL/min

A

50-150 mL/min flow seen on delivery
•Variable with disease and technique
•Normal perfusion is 5-8% of cardiac output

77
Q

Doing distal anastamosis first allows what type of cardioplegia to be given?

A

allows Vein Graft cardioplegia to be given

78
Q

Delivery through vein graft infusion pressure of what?

A

•Infusion pressure of 50 mmHg

79
Q

Delivery through vein graft flow rate range of what? mL/min

A

Flow rate of 50-100 mL/min

80
Q

Delivery through vein graft allows the surgeon to check what?

A

allows the surgeon to check the anastomosis and adequacy of flow, and also allows flow to previously underperfused areas

81
Q

Delivery Through Grafts Benefits (3)

A
  • Allows antegrade protection of areas of coronary artery disease
  • Obviates limitations from aortic insufficiency and coronary artery disease
  • Allows delivery without need to pressurize aortic root or interrupt surgery
82
Q

Delivery Through Grafts Disadvantages (3)

A
  • Requires graft placement
  • Complexity
  • Distribution only to those areas perfused by graft
83
Q

Cardioplegia method that obviates limitations from aortic insufficiency and coronary artery disease?

A

Cardioplegia delivery through vein graft

84
Q

Integrated Cardioplegia Delivery Doses?

A

It is common to give a large arresting dose of
antegrade cardioplegia 1-1.5 L, followed by a
smaller dose of retrograde cardioplegia 0.5 L.

85
Q

Pressure Drop and CArdioplegia Delivery main determinant

A

The main determinant: velocity and viscosity

86
Q

Pressure drop _______ to shear forces

A

increases proportionally

87
Q

High flow velocities and fluid viscosities result in what kind of pressure drop during cpg delivery ?

A

in a larger pressure drop

88
Q

A lower pressure drop across a cpg cannula results from what?

A

a low velocity of CPG

Perf Tech II (exam 2) (6 decks)

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