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Cardiovascular System > Haemodynamic shock > Flashcards

Haemodynamic shock Flashcards

1
Q

How is mean arterial blood pressure calculated?

A

maBP = CO x TPR

maBP = diastolic pressure + 1/3 pulse pressure

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2
Q

What is another term for haemodynamic shock?

A

Circulatory shock

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3
Q

What is haemodynamic shock?

A

Acute condition
gives large drop in arterial blood pressure
inadequate blood flow throughout the body

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4
Q

What can cause haemodynamic shock?

A

Decrease in CO

Decrease in TPR

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5
Q

What are the causes of decreased CO?

A

Loss of blood volume

Heart cannot fill

Heart cannot pump

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6
Q

What is the cause of decreased TPR?

A

Excessive vasodilation

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7
Q

What are the types of shock caused by decreased CO?

A

Hypovolaemic shock

Mechanical shock

Cardiogenic shock

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8
Q

What is cardiogenic shock?

A

Ventricle fills normally

but cannot pump adequately

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9
Q

What are some of the possible causes of cardiogenic shock?

A

Myocardial infarction - damage to LV

Serious arrythmias

Acute worsening of heart failure

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10
Q

What is the CVP in cardiogenic shock? Why?

A

Normal or raised

due to backup of blood behind heart

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11
Q

What is the arterial blood pressure in cardiogenic shock? Why?

A

Dramatic decrease

due to ventricle not pumping adequately

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12
Q

What happens to the perfusion of tissues in cardiogenic shock?

A

Decreased perfusion of tissues

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13
Q

What are the effects of reduced perfusion of coronary arteries?

A

Exacerbates the situation

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14
Q

What are the effects of reduced perfusion of kidneys?

A

Oliguria - reduced urine production

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15
Q

What is cardiac arrest?

A

Heart has stopped pumping effectively

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16
Q

How does cardiac arrest present?

A

Unresponsiveness with lack of pulse

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17
Q

What are the different causes of cardiac arrest?

A

Asystole

Pulseless electrical activity

Ventricular fibrillation

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18
Q

What is asystole?

A

Lack of electrical activity in heart

gives loss of mechanical activity too

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19
Q

What is pulseless electrical activity?

A

Electrical activity present
but has been uncoupled from mechanical activity
no mechanical activity

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20
Q

What is ventricular fibrillation?

A

Uncoordinated electrical activity in ventricles

no synchronised contraction of ventricular myocytes

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21
Q

What can cause ventricular fibrillation?

A

After myocardial infarction

Electrolyte imbalance

Some arrythmias e.g. long QT syndrome

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22
Q

What is the most common form of cardiac arrest?

A

Ventricular fibrillation

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23
Q

How is cardiac arrest treated?

A

Basic life support

Advanced life support

Arenaline

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24
Q

What does basic life support involve?

A

Chest compressions

External ventilation

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25
Q

What does advanced life support involve?

A

Defibrillation

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26
Q

How does defibrillation work?

A

Delivers electric current to all cardiomyocytes
all depolarised
all in refractory period
co-ordinated electrical activity can resume

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27
Q

How does adrenaline work?

A

Increases myocardial function - heart rate, force of contraction

Increases peripheral resistance - vasoconstriction

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28
Q

What is mechanical shock?

A

Heart cannot fill properly

low EDV

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29
Q

What are some of the causes of mechanical shock?

A

Cardiac tamponade

Pulmonary embolism

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30
Q

What is cardiac tamponade?

A

Build up of fluid in pericardial space
Fibrous pericardium is non-extensible
Heart becomes compressed

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31
Q

Which side of the heart does cardiac tamponade affect?

A

Both sides

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32
Q

What is the CVP with mechanical shock? Why?

A

High

due to backup of blood before heart

33
Q

What is the arterial blood pressure with mechanical shock? Why?

A

Low

because low EDV, SV, CO

34
Q

How does a pulmonary embolism lead to mechanical shock?

A

Pulmonary embolism occludes pulmonary artery
Pulmonary artery pressure increases
RV pressure increases
CVP increases

Reduced blood flow to LA
Reduced filling of LV

35
Q

What is the LA pressure with a pulmonary embolism?

A

Low

36
Q

Where does a pulmonary embolism usually arise from?

A

Thrombus in deep vein of leg - DVT

37
Q

How does the pulmonary embolism reach the lungs?

A 
Portion of thrombus breaks off
Carried in veins
Passes through RA, RV
Enters pulmonary artery to lungs
Becomes trapped
38
Q

What do the effects of a pulmonary embolism depend on?

A

The size of the embolus

39
Q

What are the additional symptoms of a pulmonary embolism?

A

Chest pain

Dyspnea - breathlessness
due to pulmonary oedema

40
Q

What is hypovolaemic shock?

A

Significantly reduced blood volume

41
Q

What is the most common cause of hypovolaemic shock?

A

Haemorrhage

42
Q

How much blood volume has to be lost in order for hypovolaemic shock?

A

20-30% loss - some signs of shock

30-40% loss - serious shock

43
Q

The severity of hypovolaemic shock depends on…?

A

Amount of blood lost

How fast the blood was lost

44
Q

What is the CVP with hypovolaemic shock? Why?

A

Low

Due to loss of blood

45
Q

What is the arterial blood pressure with hypovolaemic shock? Why?

A

Low
Due to reduced filling of LV
reduced EDV, SV, CO

46
Q

What is the compensatory response with hypvolaemic shock?

A

Decrease in arterial blood pressure detected by baroreceptors
Increase in sympathetic output to heart and blood vessels

47
Q

What are the results of the compensatory response with hypovolaemic shock?

A

Tachycardia
Increased force of contraction
Peripheral vasoconstriction
Venoconstriction

48
Q

How is the increased force of contraction brought about?

A

By increasing contractility of muscle fibres

49
Q

What effect does the compensatory response have at the capillaries?

A

Increase in peripheral resistance
reduces capillary hydrostatic pressure
net movement of fluid into capillaries

50
Q

How does hypovolaemic shock present?

A

Tachycardia
Weak pulse
Pale skin
Cold, clammy extremities

51
Q

Why is the skin pale?

A

Peripheral vasoconstriction

reduced blood flow to skin surfaces

52
Q

Why are the extremities cold and clammy?

A

Peripheral vasoconstriction
reduced blood flow to extremities

Sympathetic activation of sweat glands

53
Q

What are some other causes of hypovolaemic shock?

A

Severe burns

Severe vomiting and diarrhoea, loss of Na+

54
Q

What is the danger of decompensation with hypovolaemic shock?

A 
Peripheral vasoconstriction impaires tissue perfusion
Tissues become ischaemic, hypoxic
Tissues become damaged
Tissues release chemical mediators
Cause vasodilation, TPR drops
55
Q

What are the consequences of decompensation?

A

Impaired organ perfusion
Multiple organ failure
Mutli system failure

56
Q

How is hypovolaemia treated?

A

Fluid, electrolytes

Blood transfusions

57
Q

How is hypovolaemia normally managed by the body?

A

Longer term response
RAAS
ADH

58
Q

How long does it take the body to restore 20% of blood volume?

A

Approx. 3 days

with adequate salt and water intake

59
Q

What type of shock is caued by decreased TPR?

A

Distributive shock

60
Q

What are some other terms for distributive shock? Why?

A

Low resistance shock - drop in TPR

Normovolaemic shock - normal blood volume

61
Q

What increases in distributive shock?

A

Excessive vasodilation

gives increase in volume of circulation

62
Q

What is meant by volume of circulation?

A

The amount of space in blood vessels

63
Q

What are the types of distributive shock?

A

Toxic shock - septic shock

Anaphylactic shock

64
Q

What causes septic shock?

A

Endotoxins released by bacteria
cause massive inflammatory response
get excessive vasodilation

get increased permeability of capillaries
reduced blood volume

65
Q

What else can cause inadequate perfusion of tissues in septic shock?

A

Increased coagulation

blood clots form within vessels

66
Q

What is the definition of septic shock?

A

Persisting hypotension despite fluid resuscitation

requires treatment to maintain blood pressure

67
Q

What is the phsyiological response to septic shock?

A

Baroreceptors detect decrease in blood pressure
Increased sympathetic output

Gives increase in heart rate
force of contraction
vasoconstriction

68
Q

Is the vasoconstriction effect maintained?

A

No

Overridden by chemical mediators causing vasodilation

69
Q

How does septic shock present?

A

Tachycardia

Warm, red extremities initially - not later!

70
Q

Why does the patient have warm, red extremities?

A

Due to excessive vasodilation

increased blood flow to peripheries

71
Q

What causes anaphylactic shock?

A

Severe allergic reaction

72
Q

What happens in a severe allergic reaction?

A

Release of histamine and other chemical mediators

Causes excessive vasodilation

73
Q

What is the physiological response to anaphylactic shock?

A

Decrease in blood pressure detected by baroreceptors
increased sympathetic output

Increase in heart rate
Increase in force of contraction
Vasoconstriction

74
Q

Is the sympathetic response to anaphylactic shock effective?

A

No

can’t overcome the excessive vasodilation

75
Q

What are the symptoms of anaphylactic shock?

A

Tachycardia

Warm, red extremities

Difficulty breathing

76
Q

Why does the patient have difficulty breathing?

A

Allergic reaction also causes
bronchoconstriction
laryngeal oedema

77
Q

How is anaphylactic shock treated? Why?

A

Adrenaline

Causes vasoconstriction
binds to A1 receptors in blood vessels

78
Q

What is the arterial blood pressure with distributive shock? Why?

A

Low

Drop in TPR

79
Q

What happens to the perfusion of organs in distributive shock? What does this lead to?

A

Impaired perfusion

Gives organ damage, dysfunction, failure

Cardiovascular System (22 decks)

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