19: Cardiovascular responses to shock

Question 1

What is shock?

Answer 1

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

Question 2

Outline the steps leading from shock to cellular failure.

Answer 2

Shock

Inadequate tissue perfusion

Inadequate tissue oxygenation

Anaerobic metabolism

Accumulation of metabolic waste products

Cellular failure

Question 3

What two factors does adequate tissue perfusion depend on?

Answer 3

1. Adequate blood pressure
2. Adequate cardiac output

Question 4

What is hypovolaemic shock?

Answer 4

Shock caused by loss of blood volume

Question 5

Outline the steps of hypovolaemic shock between loss of volume and inadequate tissue perfusion.

Answer 5

1. Loss of blood volume
2. Decreased venous return
3. Decreased end diastolic volume
4. Decreased stroke volume
5. Decreased cardiac output and blood pressure
6. Inadequate tissue perfusion

Question 6

Briefly summarise the Frank-Starling Law of the heart.

Answer 6

Increased/decreased EDV = increased/decreased stroke volume –> cardiac output

Question 7

What is cardiogenic shock?

Answer 7

Sustained hypotension caused by decreased cardiac contractility

Question 8

Outline the steps of cardiogenic shock.

Answer 8

Decreased cardiac contractility

Decreased stroke volume

Decreased cardiac output and blood pressure

Inadequate tissue perfusion

Question 9

Give an example of a condition which may cause obstructive shock.

Answer 9

Tension pneumothorax

Question 10

Imagine a patient has presented with a tension pneumothorax. Outline the steps of obstructive shock which lead to inadequate tissue perfusion.

Answer 10

Increased intrathoracic pressure

Decreased venous return

Decreased end diastolic volume

Decreased stroke volume

Decreased CO and BP

Inadequate tissue perfusion

Question 11

Give an example of an injury which may trigger neurogenic shock.

Answer 11

Spinal cord injury

Question 12

Outline the steps of neurogenic shock following an event like a spinal cord injury.

Answer 12

Loss of sympathetic tone

Massive venous and arterial vasodilatation

Decreased venous return and TPR

Decreased CO and BP

Inadequate tissue perfusion

Question 13

Outline the steps of vasoactive shock.

Answer 13

Release of vasoactive mediators

Massive venous & arterial vasodilation

Decreased venous return and TPR

Decreased CO and BP

Inadequate tissue perfusion

Question 14

Which mnemonic should be the first thing you think of when someone presents with shock?

Answer 14

ABCDE

Question 15

Apart from ABCDE, which other general treatments are given for shock?

Answer 15

High flow O₂

Volume replacement

Question 16

What is a treatment which can be given for cardiogenic shock?

Answer 16

Positive inotropes (e.g Digoxin)

Question 17

Say someone had obstructive shock due to a tension pneumothorax - what is an immediate treatment?

Answer 17

Immediate chest drain

Question 18

What immediate treatment is given for anaphylactic shock?

Answer 18

Adrenaline

Question 19

What type of drug would you give to someone suffering septic shock?

Answer 19

Vasopressors (which cause vasoconstriction

Question 20

Name a cause of hypovolaemic shock.

Answer 20

Haemorrhage

Vomiting

Diarrhoea

Excessive sweating

Question 21

Compensatory mechanisms can maintain blood pressure until which percentage of total blood volume is lost?

Answer 21

> 30%