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Haemodynamic shock Flashcards

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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
What does advanced life support involve?
Defibrillation
26
How does defibrillation work?
Delivers electric current to all cardiomyocytes all depolarised all in refractory period co-ordinated electrical activity can resume
27
How does adrenaline work?
Increases myocardial function - heart rate, force of contraction Increases peripheral resistance - vasoconstriction
28
What is mechanical shock?
Heart cannot fill properly | low EDV
29
What are some of the causes of mechanical shock?
Cardiac tamponade Pulmonary embolism
30
What is cardiac tamponade?
Build up of fluid in pericardial space Fibrous pericardium is non-extensible Heart becomes compressed
31
Which side of the heart does cardiac tamponade affect?
Both sides
32
What is the CVP with mechanical shock? Why?
High | due to backup of blood before heart
33
What is the arterial blood pressure with mechanical shock? Why?
Low | because low EDV, SV, CO
34
How does a pulmonary embolism lead to mechanical shock?
Pulmonary embolism occludes pulmonary artery Pulmonary artery pressure increases RV pressure increases CVP increases Reduced blood flow to LA Reduced filling of LV
35
What is the LA pressure with a pulmonary embolism?
Low
36
Where does a pulmonary embolism usually arise from?
Thrombus in deep vein of leg - DVT
37
How does the pulmonary embolism reach the lungs?
``` Portion of thrombus breaks off Carried in veins Passes through RA, RV Enters pulmonary artery to lungs Becomes trapped ```
38
What do the effects of a pulmonary embolism depend on?
The size of the embolus
39
What are the additional symptoms of a pulmonary embolism?
Chest pain Dyspnea - breathlessness due to pulmonary oedema
40
What is hypovolaemic shock?
Significantly reduced blood volume
41
What is the most common cause of hypovolaemic shock?
Haemorrhage
42
How much blood volume has to be lost in order for hypovolaemic shock?
20-30% loss - some signs of shock 30-40% loss - serious shock
43
The severity of hypovolaemic shock depends on...?
Amount of blood lost How fast the blood was lost
44
What is the CVP with hypovolaemic shock? Why?
Low | Due to loss of blood
45
What is the arterial blood pressure with hypovolaemic shock? Why?
Low Due to reduced filling of LV reduced EDV, SV, CO
46
What is the compensatory response with hypvolaemic shock?
Decrease in arterial blood pressure detected by baroreceptors Increase in sympathetic output to heart and blood vessels
47
What are the results of the compensatory response with hypovolaemic shock?
Tachycardia Increased force of contraction Peripheral vasoconstriction Venoconstriction
48
How is the increased force of contraction brought about?
By increasing contractility of muscle fibres
49
What effect does the compensatory response have at the capillaries?
Increase in peripheral resistance reduces capillary hydrostatic pressure net movement of fluid into capillaries
50
How does hypovolaemic shock present?
Tachycardia Weak pulse Pale skin Cold, clammy extremities
51
Why is the skin pale?
Peripheral vasoconstriction | reduced blood flow to skin surfaces
52
Why are the extremities cold and clammy?
Peripheral vasoconstriction reduced blood flow to extremities Sympathetic activation of sweat glands
53
What are some other causes of hypovolaemic shock?
Severe burns Severe vomiting and diarrhoea, loss of Na+
54
What is the danger of decompensation with hypovolaemic shock?
``` Peripheral vasoconstriction impaires tissue perfusion Tissues become ischaemic, hypoxic Tissues become damaged Tissues release chemical mediators Cause vasodilation, TPR drops ```
55
What are the consequences of decompensation?
Impaired organ perfusion Multiple organ failure Mutli system failure
56
How is hypovolaemia treated?
Fluid, electrolytes Blood transfusions
57
How is hypovolaemia normally managed by the body?
Longer term response RAAS ADH
58
How long does it take the body to restore 20% of blood volume?
Approx. 3 days | with adequate salt and water intake
59
What type of shock is caued by decreased TPR?
Distributive shock
60
What are some other terms for distributive shock? Why?
Low resistance shock - drop in TPR Normovolaemic shock - normal blood volume
61
What increases in distributive shock?
Excessive vasodilation | gives increase in volume of circulation
62
What is meant by volume of circulation?
The amount of space in blood vessels
63
What are the types of distributive shock?
Toxic shock - septic shock Anaphylactic shock
64
What causes septic shock?
Endotoxins released by bacteria cause massive inflammatory response get excessive vasodilation get increased permeability of capillaries reduced blood volume
65
What else can cause inadequate perfusion of tissues in septic shock?
Increased coagulation | blood clots form within vessels
66
What is the definition of septic shock?
Persisting hypotension despite fluid resuscitation | requires treatment to maintain blood pressure
67
What is the phsyiological response to septic shock?
Baroreceptors detect decrease in blood pressure Increased sympathetic output Gives increase in heart rate force of contraction vasoconstriction
68
Is the vasoconstriction effect maintained?
No | Overridden by chemical mediators causing vasodilation
69
How does septic shock present?
Tachycardia Warm, red extremities initially - not later!
70
Why does the patient have warm, red extremities?
Due to excessive vasodilation | increased blood flow to peripheries
71
What causes anaphylactic shock?
Severe allergic reaction
72
What happens in a severe allergic reaction?
Release of histamine and other chemical mediators | Causes excessive vasodilation
73
What is the physiological response to anaphylactic shock?
Decrease in blood pressure detected by baroreceptors increased sympathetic output Increase in heart rate Increase in force of contraction Vasoconstriction
74
Is the sympathetic response to anaphylactic shock effective?
No | can't overcome the excessive vasodilation
75
What are the symptoms of anaphylactic shock?
Tachycardia Warm, red extremities Difficulty breathing
76
Why does the patient have difficulty breathing?
Allergic reaction also causes bronchoconstriction laryngeal oedema
77
How is anaphylactic shock treated? Why?
Adrenaline Causes vasoconstriction binds to A1 receptors in blood vessels
78
What is the arterial blood pressure with distributive shock? Why?
Low | Drop in TPR
79
What happens to the perfusion of organs in distributive shock? What does this lead to?
Impaired perfusion | Gives organ damage, dysfunction, failure

Cardiovascular System (22 decks)

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