Physiology: Cardiovascular Response to Shock

Question 1

Define shock

Answer 1

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

Question 2

How does shock cause cell damage?

Answer 2

Shock (inadequate perfusion)
-->
Inadequate oxygenation
-->
Anaerobic metabolism in cells
-->
Anaerobic metabolic waste products accumulate
-->
Cell failure

Question 3

On what does adequate tissue perfusion depend

Answer 3

• Adequate blood pressure

- Adequate cardiac output

Question 4

Can patients have different forms of shock at the same time?

Answer 4

Yes

Question 5

List the different types of shock

Answer 5

• Hypovolemic shock (haemorrhagic, non-haemorrhagic)
• Cardiogenic shock
• Obstructive
• Distributive (Neurogenic, Vasoactive)

Question 6

Define hypovolaemic shock

Answer 6

Shock do to a loss of blood volume

Question 7

Describe how loss of blood volume causes hypovolaemic shock

Answer 7

Loss of blood volume
-->
Blood volume decreases
-->
Decreased venous return
-->
Decreased end diastolic volume
-->
Cardiac output and Bp decrease
-->
Inadequate tissue perfusion

Question 8

By what mechanism does the decrease in end diastolic volume in hypovolaemic shock cause a decrease in stroke volume

Answer 8

The Frank-Starling mechanism

Question 9

Define cardiogenic shock

Answer 9

Shock due to sustained hypotension caused by decreased cardiac contractility

Question 10

How does decreased cardiac contractility cause cardiogenic shock?

Answer 10

Decreased cardiac contractility
-->
Decreased stroke volume
-->
Decreased cardiac output and Bp
-->
Inadequate perfusion

Question 11

Describe the effect of decreased cardiac contractility on the end diastolic volume in the left ventricle

Answer 11

Decreased contractility = EDV increase

increased contractility = EDV decrease

Question 12

Define obstructive shock

Answer 12

Shock due to obstruction of the heart or its great vessels

Question 13

List causes of obstructive shock

Answer 13

• tension pneumothorax
• cardiac tamponade
• pulmonary embolism (big)
• severe aortic stenosis

Question 14

Describe how a tension pneumothorax causes obstructive shock

Answer 14

Increased intrathoracic pressure
-->
decreased venous return
-->
Decreased end diastolic volume
-->
Decreased stroke volume
-->
Decreased cardiac output and Bp
-->
Inadequate perfusion

Question 15

List the 2 types of distributive shock

Answer 15

• Neurogenic shock

- Vasoactive shock

Question 16

Describe the mechanism of neurogenic shock

Answer 16

loss of sympathetic tone to the heart and blood vessels
–>
Venous and arterial vasodilation, -ve chronotropic effect
–>
Decreased venous return, decreased SVR, decreased heart rate
–>
Decreased cardiac output and Bp
–>
Inadequate perfusion

Question 17

Define neurogenic shock

Answer 17

Shock due to a loss of sympathetic tone to the heart and blood vessels

Question 18

Which is the only type of shock to reduce heart rate?

Answer 18

neurogenic shock

due to the loss of sympathetic tone in the heart

Question 19

Define vasoactive shock

Answer 19

Shock due to the release of vasoactive mediators

Question 20

How does the release of vasoactive mediators cause vasoactive shock

Answer 20

Release of vasoactive mediators
-->
Venous and arterial vasodilation, and increased capillary permeability
-->
Decreased venous return, and SVR
-->
Decreased cardiac output and Bp
-->
Inadequate perfusion

Question 21

Give a condition that can cause cardiogenic shock

Answer 21

Myocardial infarction

Question 22

List causes of vasoactive shock`

Answer 22

• Septic shock

- Anaphylactic

Question 23

Give a cause of neurogenic shock

Answer 23

Spinal chord injury

Question 24

Are systemic vascular resistance (SVR) and total peripheral resistance (TPR) the same thing?

Answer 24

Yes

Question 25

List the general treatments for shock

Answer 25

• ABCDE approach
• High flow oxygen
• Volume replacement (except for cardiogenic shock)

Question 26

Why do you not give volume replacement for cardiogenic shock?

Answer 26

It would put more strain on an already failing heart

Question 27

What is the immediate treatment for obstructive shock due to a tension pneumothorax?

Answer 27

Chest drain

Question 28

What is the immediate treatment for an anaphylactic shock?

Answer 28

Adrenaline

Question 29

What is the treatment for septic shock?

Answer 29

Vasopressors

Question 30

What is the treatment for cardiogenic shock?

Answer 30

+ve inotropic drugs

Question 31

Compensatory mechanisms can cope with blood loss until what % of volume is lost?

Answer 31

> 30%

After 30% the Bp starts to drop and haemorrhagic shock occurs

Question 32

List some of the clinical signs of haemorrhagic shock, and their causes

Answer 32

Tachycardia - due to baroreceptor reflex

Small volume pulse - due to decreased cardiac output

Cool peripheries - Increased systemic vascular resistance via baroreceptor reflex

Question 33

What corrective mechanism is activated by the acute drop in blood volume seen in haemorrhagic shock?

Answer 33

Baroreceptor reflex

Question 34

List causes of hemorrhagic shock

Answer 34

Bleeding due to:

• trauma
• surgery
• haemorrhage

Question 35

List causes of non-hemorrhagic hypovolemic shock

Answer 35

• Vomiting
• Diarrhea
• Excessive sweating

Question 36

Describe the mechanism of non-hemorrhagic hypovolemic shock

Answer 36

Vomiting, diarrhea etc.
-->
Decreased ECF volume
-->
Decreased plasma volume
-->
EDV decreases
-->
Stroke volume and CO decrease
-->
Inadequate perfusion