Shock

Question 1

What is shock?

Answer 1

An abnormality of the circulatory system resulting in inadequate tissue perfusion and oxygenation

Question 2

Steps in how shock leads to cellular failure

Answer 2

Shock → inadequate tissue perfusion → inadequate tissue oxygenation → anaerobic metabolism → accumulation of metabolic waste products that are toxic to the cell → cellular failure

Question 3

What does adequate tissue perfusion depend on?

Answer 3

Adequate blood pressure and adequate cardiac output

Question 4

What does stroke volume depend on?

Answer 4

Preload, myocardial contractility, afterload

Question 5

Afterload

Answer 5

The resistance against which the heart is pumping

Question 6

Myocardial contractility

Answer 6

How well the heart can contract

Question 7

Hypovolaemic shock

Answer 7

Loss of blood volume

Question 8

How can hypovolaemic shock lead to inadequate tissue perfusion?

Answer 8

Loss of blood volume → decreased blood volume → decreased venous return → decreased end diastolic volume → decreased stroke volume → decreased CO and BP → inadequate tissue perfusion

Question 9

Cardiogenic shock

Answer 9

Sustained hypotension caused by decreased cardiac contractility

Question 10

Example on when cardiogenic shock can occur

Answer 10

When the heart is severely damaged e.g. after a myocardial infarction

Question 11

How can cardiogenic shock lead to inadequate tissue perfusion?

Answer 11

Decreased cardiac contractility → decreased stroke volume → decreased CO and BP → inadequate tissue perfusion

Question 12

Obstructive shock

Answer 12

Increased intrathoracic pressure

Question 13

What can cause obstructive shock?

Answer 13

Tension pneumothorax

Question 14

How can obstructive shock lead to inadequate tissue perfusion?

Answer 14

Increased intrathoracic pressure → decreased venous return → decreased end diastolic volume → decreased stroke volume → decreased CO and BP → inadequate tissue perfusion

Question 15

Why does increased intrathoracic pressure cause decreased venous return?

Answer 15

Venous return depends on the pressure gradient outside and inside the chest

Question 16

Neurogenic shock

Answer 16

Loss of sympathetic tone to blood vessels and heart

Question 17

What can cause neurogenic shock?

Answer 17

Spinal cord injury

Question 18

How can neurogenic shock lead to inadequate tissue perfusion?

Answer 18

Loss of sympathetic tone to blood vessels and heart → massive venous and arterial vasodilation causing effect on heart rate → decreased venous return and decreased SVR leads to decreased heart rate → decreased CO and BP → inadequate tissue perfusion

Question 19

What is different in how neurogenic shock leads to inadequate tissue perfusion compared to other types of shock?

Answer 19

Heart rate decreases

Question 20

Vasoactive shock

Answer 20

Release of vasoactive mediators

Question 21

Examples of vasoactive shock

Answer 21

Septic shock, anaphylactic shock

Question 22

How can vasoactive shock lead to inadequate tissue perfusion?

Answer 22

Release of vasoactive mediators → massive venous and arterial vasodilation and increased capillary permeability (vessels become leaky) → decreased venous return and decreased SVR → decreased CO and BP → inadequate tissue perfusion

Question 23

Treatment of shock

Answer 23

• ABCDE approach
• High flow oxygen
• Volume replacement
• Call for help early
• Treat the cause as appropriate

Question 24

For which type of shock would you not give volume replacement as treatment?

Answer 24

Cardiogenic shock

Question 25

Additional treatment for cardiogenic shock

Answer 25

Inotropes

Question 26

Treatment for tension pneumothorax

Answer 26

Immediate chest drain

Question 27

Treatment for anaphylactic shock

Answer 27

Adrenaline

Question 28

Treatment for septic shock

Answer 28

Vasopressors

Question 29

Causes of hypovolaemic shock

Answer 29

Haemorrhage e.g. trauma, surgery, GI haemorrhage | Vomiting, diarrhoea, excessive sweating

Question 30

How can vomiting lead to circulatory shock?

Answer 30

Vomiting leads to decreased extracellular fluid volume → decrease in blood volume → decrease in CO → circulatory shock and decreased MAP

Question 31

Until what stage in haemorrhagic shock can compensatory mechanisms maintain blood pressure?

Answer 31

Until greater than 30% of blood volume is lost

Question 32

Compensatory mechanisms to maintain blood pressure in haemorrhagic shock

Answer 32

Increased heart rate, decreased stroke volume → cardiac output may be decreased Increased systemic vascular resistance

Question 33

Class I haemorrhagic shock: - Blood loss (mL and % blood volume) - Pulse rate - Blood pressure - Pulse pressure - Resp rate - Urine output - Central nervous system/mental status

Answer 33

- Up to 750ml, up to 15% blood volume - <100 - Normal - Normal or increased - 14-20 per minute - >30 ml/hour - Slightly anxious

Question 34

Class II haemorrhagic shock: - Blood loss (mL and % blood volume) - Pulse rate - Blood pressure - Pulse pressure - Resp rate - Urine output - Central nervous system/mental status

Answer 34

- 750-1500ml, 15-30% blood volume - 100-120 - Normal - Decreased - 20-30 per minute - 20-30 ml/hour - Mildly anxious

Question 35

Class III haemorrhagic shock: - Blood loss (mL and % blood volume) - Pulse rate - Blood pressure - Pulse pressure - Resp rate - Urine output - Central nervous system/mental status

Answer 35

- 1500-2000ml, 30-40% blood volume - 120-140 - Decreased - Decreased - 30-40 per minute - 5-15 ml/hour - Anxious/confused

Question 36

Class IV haemorrhagic shock: - Blood loss (mL and % blood volume) - Pulse rate - Blood pressure - Pulse pressure - Resp rate - Urine output - Central nervous system/mental status

Answer 36

- >2000ml, >40% - >140 - Decreased - Decreased - >35 per minute - Negligible - Confused/lethargic