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A&P2 Spring 25’ > 23 Jan 25 Determinants of CO and BP > Flashcards

23 Jan 25 Determinants of CO and BP Flashcards

1
Q

What are the two main components that determine cardiac output?

A

Health of the heart and health of the system.

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2
Q

What should the right atrial pressure be under normal operating conditions?

A

Zero.

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3
Q

What does the delta p represent in the context of venous return?

A

The difference between the systemic pressure and the right atrial pressure.

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4
Q

What is indicated by a normal resistance to venous return on a graph?

A

A normal slope of the curve.

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5
Q

How does high resistance to venous return appear on a chart?

A

Indicated by a curve with a lower than normal slope.

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6
Q

If the right atrial pressure increases, what is expected to happen to venous return?

A

It will decrease.

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7
Q

What happens to venous return if the right atrial pressure decreases?

A

It can increase.

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8
Q

What factors can modify the characteristics of the circulatory system?

A
  • Resistance to venous return
  • Systemic filling pressure.
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9
Q

What is the effect of increased systemic filling pressure on venous return?

A

It increases venous return.

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10
Q

What happens to venous return when systemic filling pressure is reduced?

A

Venous return decreases.

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11
Q

How does the body typically enhance cardiac output during exercise?

A

By changing the systemic filling pressure.

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12
Q

What role do veins play during exercise in relation to cardiac output?

A

Veins constrict to increase blood return to the heart.

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13
Q

What is the primary obstacle to venous return during positive pressure ventilation?

A

Increased pressure in the thorax.

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14
Q

What is the primary effect of phenylephrine on the venous system?

A

It tightens the veins.

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15
Q

What is the maximum cardiac output achievable without sympathetic stimulation?

A

About 13 L/min.

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16
Q

What can sympathetic stimulation increase maximum cardiac output to?

A

About 25 L/min.

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17
Q

What effect does maximum parasympathetic stimulation have on cardiac output?

A

It reduces cardiac output.

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18
Q

What happens to the cardiac output curve in a patient with a myocardial infarction (MI)?

A

It shifts downwards, indicating reduced pumping effectiveness.

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19
Q

What happens to right atrial pressure in a hypo-effective heart?

A

It shifts to the right.

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20
Q

What happens to right atrial pressure in a hyper-effective heart?

A

It shifts to the left.

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21
Q

What determines the intersection point of the venous return curve and the cardiac output curve?

A

The actual conditions of the circulatory system.

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22
Q

What is the effect of sympathetic stimulation on cardiac output if the circulatory system remains unchanged?

A

It increases cardiac output slightly, capped at around 6 L/min.

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23
Q

In the presence of catecholamines affecting the heart, what happens to filling pressures?

A

They increase, enhancing venous return.

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24
Q

What characterizes a weak heart?

A

A weak heart is characterized by reduced cardiac output and increased right atrial pressure.

This condition may arise from issues such as myocardial infarction (MI).

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25
Q

What happens to cardiac output in the presence of a weak heart?

A

Cardiac output decreases.

The right atrial pressure increases as the heart struggles to pump blood effectively.

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26
Q

What is the relationship between central venous pressure (CVP) and heart problems?

A

CVP is almost always elevated in individuals with heart problems.

This occurs as the heart struggles to pump out returning blood.

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27
Q

What occurs in heart failure regarding right atrial pressure?

A

Right atrial pressure increases significantly, often up to 3 mmHg or higher.

This is due to the heart’s inability to maintain adequate cardiac output.

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28
Q

How does the body compensate for a failing heart?

A

The body increases filling pressures to assist the struggling heart.

This may involve increasing venous return to improve cardiac output.

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29
Q

What effect do catecholamines have on the circulatory system?

A

Catecholamines tighten blood vessels and increase water retention by the kidneys.

This response helps to maintain blood pressure and volume in acute heart issues.

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30
Q

How do anesthetics affect systemic filling pressure?

A

Anesthetics reduce systemic filling pressure by relaxing blood vessels.

This can lead to a drop in cardiac output in patients reliant on high filling pressures.

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31
Q

What is the significance of the intersection of the venous return curve and cardiac output curve?

A

The intersection indicates the balance between venous return and cardiac output.

Both sides of the heart must operate similarly to avoid fluid overload or deficiency.

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32
Q

How does metabolic rate influence cardiac output?

A

Cardiac output increases with higher metabolic rates due to vasodilation in active tissues.

Conversely, lower metabolic rates allow for lower cardiac output.

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33
Q

What happens to cardiac output in hypothyroidism?

A

Cardiac output decreases due to lower metabolic rates and increased vascular resistance.

Thyroid hormone plays a crucial role in regulating metabolic rates.

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34
Q

What is the effect of hyperthyroidism on cardiac output?

A

Hyperthyroidism increases metabolic rate, leading to increased cardiac output.

This is due to lower vascular resistance in tissues requiring more blood.

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35
Q

What is BeriBeri, and how does it affect cardiac output?

A

BeriBeri is a vitamin B1 deficiency that increases the need for energy delivery, thus raising cardiac output.

It results in cells being less efficient in energy utilization.

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36
Q

How do AV shunts affect cardiac output?

A

AV shunts lower vascular resistance, thus increasing cardiac output.

An extra connection in the circulatory system allows more pathways for blood flow.

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37
Q

What is the relationship between oxygen consumption and cardiac output?

A

Increases in oxygen consumption typically correlate with increases in cardiac output.

Both parameters adjust to meet metabolic demands.

38
Q

What happens to cardiac output when dinitrophenol is administered?

A

Dinitrophenol increases metabolic rate and subsequently cardiac output, provided the nervous system is functioning.

Without sympathetic nervous system support, cardiac output may not increase effectively.

39
Q

True or False: The body can compensate for heart failure by decreasing blood volume.

A

False. The body compensates by increasing blood volume to support cardiac output.

40
Q

Fill in the blank: If the metabolic rate is low, the cardiac output can be _______.

A

lower.

41
Q

What happens to blood pressure when the sympathetic nervous system is removed?

A

Blood pressure crashes

The sympathetic nervous system is crucial for maintaining stable blood pressure.

42
Q

What is the primary responsibility of the heart regarding cardiac output?

A

To handle tissue metabolism

The heart cooperates with the circulatory system to maintain adequate cardiac output.

43
Q

How is cardiac index calculated?

A

Cardiac output divided by surface area of the body (L/min/m^2)

Typical surface area for a 70 kg adult is 1.7 m².

44
Q

What factors can affect cardiac index?

A
  • Gender
  • Pregnancy
  • Age

Cardiac index can vary based on several physiological factors.

45
Q

At what age does cardiac index typically max out?

A

Around age 10

Cardiac index increases rapidly from birth to age 10.

46
Q

What happens to cardiac index as we age?

A

It decreases

A healthy 80-year-old has a cardiac index of about 2.4.

47
Q

What is the typical pressure in the right atrium?

A

0 mmHg

The left atrial pressure is typically around 2 mmHg.

48
Q

How do central venous pressure (CVP) and right atrial pressure correlate?

A

They usually move in tandem

CVP is influenced by the distance from the heart where it is measured.

49
Q

What effect does sympathetic stimulation have on mean circulatory filling pressure?

A

It increases the pressure

Conversely, a reduction in sympathetic tone decreases the pressure.

50
Q

What is a common consequence of progressive hemorrhagic shock?

A

The heart becomes a weaker pump

Insufficient blood volume leads to inadequate perfusion of the heart.

51
Q

What happens to cardiac output during inspiration?

A

It typically increases

Negative pressure in the thorax helps suck blood into the heart.

52
Q

What is the normal intrapleural pressure?

A

-4 mmHg

This negative pressure aids in respiration and venous return.

53
Q

Fill in the blank: The cardiac index is typically around ______ for a healthy 20-year-old patient.

A

3.0

This is based on a normal cardiac output for a 70 kg individual.

54
Q

True or False: The left side of the heart works harder than the right side.

A

True

The left side pumps against higher resistance.

55
Q

What is the relationship between filling pressure and cardiac output?

A

Higher filling pressure typically leads to higher cardiac output

This is crucial for maintaining blood circulation.

56
Q

What happens to venous return resistance in cases such as an AV fistula?

A

Resistance to venous return decreases

This can lead to increased cardiac output despite normal filling pressure.

57
Q

What is mean circulatory filling pressure approximately equal to?

A

Mean systemic filling pressure

Both pressures are about 7 mmHg.

58
Q

What happens to cardiac output if the pressure surrounding the pump is more negative?

A

Higher output

This is reflected by the cardiac output curve shifting to the left.

59
Q

What occurs during forceful expiration?

A

Increased thoracic pressure

This typically involves contraction of the abdomen to push air out quickly.

60
Q

What is expected if there is a sustained increase in thoracic pressure?

A

Drop in cardiac output

61
Q

What happens to cardiac output during normal inspiration?

A

Cardiac output increases

62
Q

What effect does a sustained positive pressure surrounding the heart have on cardiac output?

A

Shifts the curve to the right, leading to lower cardiac output

63
Q

What is one example that could cause sustained positive pressure around the heart?

A

Mechanical ventilation

64
Q

What happens to cardiac output when the chest is opened to the outside environment?

A

Cardiac output decreases

65
Q

How can the body compensate for high pressure surrounding the heart?

A

Increase filling pressure or add volume to the system

66
Q

What happens if there is fluid surrounding the heart?

A

May shift the curve to the right and depress the slope of the cardiac output curves

67
Q

What is the expected outcome if the heart can’t fill adequately due to extra fluid?

A

Low cardiac output

68
Q

What is a hypo-effective heart characterized by?

A

Lower plateau phase of the cardiac output curve

69
Q

What effect does a hyper-effective heart have on the cardiac output curve?

A

Increases the plateau phase

70
Q

What is systemic vascular resistance primarily governed by?

A

Arterioles

71
Q

What happens when arterial-specific vasodilators are used?

A

Easier blood flow from left heart to right heart

72
Q

What is an example of an arterial-specific vasodilator?

A

ACE inhibitor

73
Q

What effect do venular-specific vasodilators have on filling pressure?

A

Reduce filling pressure

74
Q

What is an example of a venular-specific vasodilator?

A

Nitroglycerin

75
Q

What is a mixed vasodilator expected to change?

A

Both filling pressure and resistance to venous return

76
Q

What is the impact of venodilation on filling pressure?

A

It reduces filling pressure

77
Q

What happens to cardiac output if filling pressure is low?

A

Cardiac output will be much lower

78
Q

What can happen if the heart is stimulated to pump harder while blood return is low?

A

Not much help

79
Q

What is the main factor that influences cardiac output when both filling pressure and resistance to venous return change?

A

Filling pressure

The reduction in filling pressure outweighs the reduction in resistance to venous return.

80
Q

What happens to cardiac output when filling pressure decreases?

A

It drops

The net result of decreased filling pressure and reduced resistance to venous return is a drop in cardiac output.

81
Q

What are the two variables that affect the return of blood to the heart?

A

Filling pressure and resistance to venous return

Both variables can oppose each other, but filling pressure is more influential.

82
Q

How can filling pressure be increased?

A

By constricting veins or adding volume

Both actions increase filling pressure without changing the path blood takes back to the heart.

83
Q

What does venous compliance measure?

A

How stretchy the walls of the vein are

High compliance means low pressure; low compliance means higher pressure.

84
Q

What effect does a reduction in venous compliance have on filling pressure?

A

It increases filling pressure

Tighter walls of veins lead to higher filling pressure.

85
Q

What happens to cardiac output if volume is lost or veins dilate?

A

It decreases

Lower volume or increased venous compliance results in lower expected filling pressure.

86
Q

What is the relationship between systemic vascular resistance (SVR) and arterial constriction?

A

Arterial constriction increases SVR

Increased SVR makes it harder for blood to flow from the left heart to the right heart.

87
Q

True or False: Relaxing the choke point changes the average pressure in the system.

A

False

Average pressure should remain about the same if nothing else is changing.

88
Q

What happens to venous compliance during heart problems?

A

It decreases

This tightening increases filling pressure to help drive cardiac output.

89
Q

What compensatory mechanism occurs during a heart attack?

A

Venous and arterial constriction

The body constricts blood vessels to redirect blood where it’s most needed.

90
Q

What long-term change occurs if a heart problem is persistent?

A

Expansion of blood volume

The kidneys help to expand blood volume instead of relying on constant constriction.

91
Q

Fill in the blank: The body typically backs off the squeeze of blood vessels by _______.

A

filling them up

This reduces the need for constant sympathetic activation.

A&P2 Spring 25’ (6 decks)

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