Physiology - Cardiovascular Responses to Shock

Question 1

What is shock?

Answer 1

It is the abnormality of the ciruclatory system resulting in the inadequate tissue perfusion and oxygenation. Slide 3

Question 2

Adequate tissue perfusion does not depend on adequate blood pressure and adequate cardiac output. True or False?

Answer 2

False, it does as MAP relies on CO and CO relies on SV. Slide 6

Question 3

What is hypovolaemic shock and how does it cause inadequate tissue perfusion?

Answer 3

Due to the loss of blood there is decreased blood volume. That means there is less venous return which inturn decreases the stroke volume. Cardiac output is decreased and so too is BP which causes inadequate tissue perfusion. Slide 7

Question 4

What is sustained hypotension caused by?

Answer 4

Decreased cardiac contractility. Slide 9

Question 5

How does cardiogenic shock cause inadequate tissue perfusion?

Answer 5

There is decreased contractility and this decreases SV.

Due to the decreased SV there is a lower CO and BP which means tissues are not adequately perfused. Slide 10

Question 6

How does a tension pneumothorax cause tissues to not be perfused well?

Answer 6

There is increased intrathoracic pressure whcih decreases venous return due to the pressure gradient. The SV is decreased causing CO and BP to be decreased. This causes inadequate tissue perfusion. Slide 12

Question 7

How does neurogenic shock cause tissues to not be perfused well?

Answer 7

There is a loss of sympathetic tone which causes massive venous and arterial dilation. This decreases venous return and SVR. The CO and BP decreases causign tissues to not be perfused well. Slide 13

Question 8

How does vasoactive shock cause tissues to not be perfused well?

Answer 8

There is a release of vasoactive mediators whcih cause vasodilation and increases capillary permeability.
There is decrease VR and SVR which decreases CO and BP. Tissues aren’t well perfused. Slide 14

Question 9

How is shock treated?

Answer 9

ABCDE approach
High flow O2
Volume replacement 
Inotropes for cardiogenic shock
Chest drain
Adrenaline for anaphylactic
Vassopressors for septic shock. Slide 15

Question 10

What are some causes of hypovolaemic shock?

Answer 10

Haemorrhage due to trauma, surgery reduces blood volume.

Vomiting, diarrheoa reduces ECFV which reduces blood volume. Slide 17

Question 11

When do compensatory mechanisms not work anymore of maintaining BP?

Answer 11

When more than 30% of blood volume is lost. Slide 18

Question 12

What are the 4 classes of haemorrhagic shock?

Answer 12

Class I - up to 750 ml
Class II - 750-1500 ml
Class III - 1500-2000 ml
Class IV - >2000 ml
Slide 19

Question 13

Why is BP normal in class II?

Answer 13

As the baroreceptors are working hard to maintain BP. Slide 19

Question 14

What are signs of haemorrhagic shock?

Answer 14

Tachycardia
Small volume pulse (rapid, weak)
Cool peripheries. SLide 20