Cardiac 4 - Cardiac Output, Blood Pressure And Shock

Front 1

Which factors determine blood flow?

Back 1

1. Pressure difference between two ends of the vessel

2. Resistance of the vessel to blood flow

Front 2

Driving force of blood flow

Back 2

Pressure difference

Front 3

Impediment to blood flow

Back 3

Resistance

Front 4

Blood flow follows the principles of?

Back 4

Ohm's Law

Front 5

Ohm's Law

Back 5

Blood Flow = Pressure difference / Resistance

Front 6

Speed of blood flow is proportional to...

Back 6

Magnitude of the pressure difference

*bigger difference = more flow

Front 7

Direction of blood flow determined by...

Back 7

Direction of pressure gradient

*high to low pressure

Front 8

Blood flow is inversely proportional to...

Back 8

Resistance

Front 9

Major mechanism for changing blood flow in CV system?

Back 9

Altering resistance in blood vessels

Front 10

Total peripheral resistance, AKA

Back 10

Systemic Vascular Resistance (SVR)

Front 11

How can we measure SVR?

Back 11

SVR = (MAP - CVP) / Cardiac Output

Front 12

MAP

Back 12

Mean Arterial Pressure

Front 13

CVP

Back 13

Central Venous Pressure

*In right atrium

Front 14

Arterial Blood Pressure (divisions)

Back 14

Systolic Arterial Pressure (SAP) = ~120mmHg

Diastolic Arterial Pressure (DAP) = ~80mmHg

Front 15

SAP

Back 15

Highest arterial pressure measured during cardiac cycle (when ventricular contraction ejects blood from the heart)

Front 16

DAP

Back 16

Lowest arterial pressure measured during a cardiac cycle (when ventricular relaxation occurs and heart fills)

Front 17

Pulse pressure equation

Back 17

Pulse pressure = SAP - DAP

Front 18

Pulse pressure affected by...

Back 18

1. Left ventricular stroke volume

2. Velocity of blood flow

3. Compliance of arterial system

Front 19

MAP

Back 19

(Mean arterial pressure)

Average pressure during a complete cardiac cycle

*driving force for blood flow in the arteries

Front 20

MAP equation

Back 20

DAP + 1/3 Pulse pressure

Front 21

In MAP calculation, why does DAP count for more than SAP?

Back 21

Diastole takes about twice as long

Front 22

CVP

Back 22

(Central Venous Pressure)

Right atrial pressure

Front 23

What affects CVP?

Back 23

Venous return

Ability of right ventricle to eject blood to pulmonary circulation

Front 24

How is CVP measured?

Back 24

Advancing catheter from a peripheral vein (jugular) to an intrathoracic location (level of tricuspid valves)

Front 25

Normal CVP range

Back 25

+5mmHg to -5mmHg

Front 26

What is CVP used for?

Back 26

Balance fluid requirements with performance of the heart

Front 27

When is CVP especially useful?

Back 27

Expanding the blood volume of a hypovolemic patient with heart failure

Front 28

CVP is low in patients with...

CVP is high in patients with...

Back 28

Decreased venous return (blood loss, vomiting, diarrhea)

Heart failure (can't pump blood forward like it should)

Front 29

Velocity equation

Back 29

Velocity = Flow / Cross-sectional area

Front 30

Why is there no detectable pulse pressure in veins?

Back 30

High compliance

*more volume does not cause more pressure

Front 31

Why is body position important?

Back 31

Due to gravity, pressure is higher in veins below the heart, than above the heart and negative pressure exists in large veins above the heart

*Air can become entrained = Air Embolus

Front 32

Blood pressure is maintained by..

Back 32

Changes in cardiac output and systemic vascular resistance

Front 33

Moment-to-moment regulation of blood pressure

Back 33

Autonomic Nervous System

Baroreceptors

*sympathetic

Front 34

Long term regulation of blood pressure

Back 34

Control of fluid balance by kidneys

Adrenal cortex

CNS

*Maintains constant blood volume

Front 35

Frank-Starling Law of the Heart

Back 35

The volume of blood ejected by the ventricle depends on the volume present in the ventricle at the end of diastole

Cardiac Output = Venous Return

Front 36

In order to maintain oxygen delivery, we need to...

Back 36

Support and maintain venous return

Front 37

Driving force for blood flow?

What must it be maintained at?

Back 37

MAP

~100mmHg

Front 38

Cardiac Output and its equation

Back 38

Volume of blood that is pumped by the heart over a period of time

Cardiac Output = Stroke Volume x Heart Rate

Front 39

Organ blood flow is under... (what control)

Back 39

Local control

Front 40

Stroke Volume

Back 40

Amount of blood that is ejected by each ventricular contraction

Front 41

Stroke Volume affected by?

Back 41

1. Preload (amount of blood returning to heart)

2. Contractility (how hard heart is contracting)

3. Afterload (resistance the heart must pump against)

Front 42

Preload, contractility and afterload of the left ventricle...

Back 42

P: End-Diastolic volume (venous return)

C: Ejection fraction (~50%)

A: Aortic Pressure

Front 43

Cardiac Work equation

Back 43

Work = Cardiac Output x Aortic Pressure

*Aortic pressure = afterload

Front 44

For the left ventricle,

Cardiac output represents...

Aortic Pressure represents...

Back 44

Volume work

Pressure work

Front 45

Which is more costly: pressure work or volume work?

Back 45

Pressure work!

It is harder for heart to pump against a pressure, than it is to move a volume of blood

Front 46

Myocardial hypertrophy

What does it result from and give example?

Back 46

Results when the ventricles need to pump against an increased force

Ex. Aortic stenosis causing left heart enlargement

Front 47

Blood Pressure Equation

Back 47

Blood Pressure = Resistance x Cardiac Output

Front 48

For blood pressure to be maintained, it needs

Back 48

Vascular tone

Heart rate

Venous return

Contractility

Front 49

2 Systems monitoring blood pressure

Back 49

Neurally-mediated

Hormonally-mediated

Front 50

Neurally Mediated

What it does and example

Back 50

Restores blood pressure values to normal within seconds

Ex. Baroreceptors

Front 51

Hormonally mediated

What it does and example

Back 51

Regulates blood pressure more slowly by affecting blood volume

Ex. Renin-Angiotensin-Aldosterone system

Front 52

Neurally-mediated system involves nervous system responses such as..

Back 52

1. Baroreceptor reflexes

2. Chemoreceptor reflexes

3. Atrial reflexes

4. CNS ischemia reflexes

Front 53

Baroreceptor reflex pressure sensor locations

Back 53

Carotid Sinus

Aortic Arch

Front 54

Carotid Sinus responds to... and uses...

Back 54

Increases and decreases in pressures

Uses CN IX (glossopharyngeal nerve)

Front 55

Aortic Arch responds to..

Back 55

Increases in pressure

Uses CN X (vagus nerve)

Front 56

Both baroreceptor reflex locations relay information to the..

Back 56

Brain stem, where responses are immediately initiated to correct the abnormality

Front 57

How do baroreceptors work?

Back 57

Changes in MAP results in stretching/relaxation of baroreceptor nerve endings

Front 58

Baroreceptor nerve endings are sensitive to?

Back 58

Absolute pressure

Changes in pressure

Rate of change

Front 59

Baroreceptor nerve endings sends impulses to..

Back 59

Vasomotor center in medulla and pons to elicit changes in output of the sympathetic and parasympathetic systems

Front 60

Changes in the output from the sympathetic and parasympathetic systems to heart and blood vessels will alter...

Back 60

Heart rate, vascular tone, cardiac contractility and Blood Pressure

Front 61

Sympathetic stimulation can maintain near-normal CV function when as much as....

Back 61

25% of the blood volume has been lost

Front 62

Chemosensitive cells located in

Back 62

Carotid bodies

Aortic body

Front 63

When are chemoreceptors stimulated?

Back 63

Whenever blood pressure and blood flow decrease below a critical level (Decrease availability of oxygen and accumulation of CO2 and H+)

Front 64

Cemoreceptors stimulate activity in.. and do what/

Back 64

Vasomotor centre to increase sysmpathetic tone to return BP back to a normal level

Front 65

Chemoreceptor reflexes more important in the _______________ system than the ___________ system

Back 65

Respiratory

Cardiovascular

Front 66

Atrial Reflexes

Back 66

Atria contain low-pressure stretch receptors similar to baroreceptors in large arteries

Front 67

Atrial reflexes are important for...

Back 67

Both short-term and long-term control of blood pressure

Front 68

CNS ischemic reflex occurs when..

Back 68

Blood flow to the medullary vasomotor centre is decreased, causing ischemia or hypoxia

*Intense outpouring of sympathetic NS activity, resulting in profound increases in BP

Front 69

CNS ischemic reflex becomes active when.. and reaches max activity when..

Back 69

MAP <50mmHg

MAP is 15-20mmHg

Front 70

Basically, the CNS ischemic reflex is a...

Back 70

Last ditch effort to improve BP before death

Front 71

Moderate-term control of BP, relies on..

Back 71

Hormonal responses (not neural)

-Catecholamine-induced vasoconstriction

-Renin-angiotensin induced vasoconstriction

-ADH-induced vasoconstriction

Front 72

Moderate-term control of BP, attempts to increase BP by....

Back 72

Increased vascular resistance

Front 73

Long-term control of BP by...

Back 73

Kidneys that regulate Na+ and water to adjust blood volume

Changes in blood volume leads to alterations in cardiac output and BP

Front 74

Long-term control of BP relies on...

Back 74

Renin-Angiotensis-Aldosterone system

Front 75

Autoregulation

Back 75

Local control

or

Neural or Hormonal control

*Independent of systemic arterial pressure

Front 76

Changes in blood flow of an organ are achieved by..

Back 76

Altering arteriolar resistance

Front 77

Local control

Back 77

Primary mechanism for matching blood flow to metabolic needs of a tissue

Front 78

Local control exerted through...

Back 78

Accumulated vasodilator metabolites induce vasodilation of arterioles, decrease resistance, and increase flow to meet the increased oxygen demands of the tissue

Front 79

Local control allows for..

Back 79

An organ or tissue to maintain relatively constant blood flow over a wide range of systemic arterial blood pressures

Front 80

Neural control of blood flow

Back 80

Sympathetic NS is most important

Conveys the ability to regulate blood flow to certain tissues at expense of others

Front 81

Sympathetic system and blood flow (impulses)

Back 81

Impulses transmitted to all vessels in the body to maintain partial vasoconstriction

Impulses sent to adrenal gland to stimulate release of Epinephrine and NE

Front 82

Epinephrine and NE act on...

Back 82

Adrenergic receptors in vascular smooth muscle

Stimulates alpha1 receptors to induce vasoconstriction of small arterioles, affecting resistance to blood flow through all tissues

Front 83

Hormonal constrictors of blood flow

Back 83

Epinephrine

Norepinephrine

Angiotensin

ADH

Front 84

Hormonal dilators of blood flow

Back 84

Bradykinin

Serotonin

Histamine

Prostaglandins

H+

K+

CO2

Front 85

Circulatory shock..

And equation

Back 85

Inadequate oxygen delivery to cells, resulting in generalized deterioration of organ function

Delivery of O2 = CO x CaO2

Front 86

Shock can be due to..

Back 86

Hemorrhagic, hypovolemic, neurogenic and septic reasons for inadequate tissue blood flow

Front 87

Stages of Shock

Back 87

Compensated (normal BP)

Uncompensated (low BP)

Terminal (Patient about to die)