CVS Session 12- Shock

Question 1

What is shock?

Answer 1

An acute circulatory failure with inadequate or inappropriate tissue perfusion due to inadequate flow and therefore a lack of oxygen.

Question 2

What is the main characteristic of shock?

Answer 2

A dramatic fall in arterial blood pressure.

Question 3

What is cardiogenic shock?

Answer 3

Shock due to pump failure. This means that the ventricles can’t empty properly.

Question 4

When does cardiogenic shock occur? (3)

Answer 4

• following an MI
• due to a serious arrythmia
• worsening HF

Question 5

What happens in cardiogenic shock? (3)

Answer 5

• the central venous pressure may be normal or raised
• the heart fills but is unable to pump effectively
• arterial BP dramatically falls

Question 6

What is mechanical shock?

Answer 6

Shock due to obstruction, meaning that the heart cannot be filled adequately.

Question 7

What are the two main causes of mechanical shock?

Answer 7

Cardiac tamponade

Pulmonary embolism

Question 8

What happens due to cardiac tamponade? (2)

Answer 8

There is a high CVP because the heart cannot fill properly, therefore blood backs up into the venous system.
There is a low arterial BP as there is little blood in the heart to pump out.

Question 9

What happens due to pulmonary embolism? (4)

Answer 9

The pulmonary artery pressure increases due to occlusion
The RV can’t empty due to the occlusion, therefore blood backs up and causes high CVP.
There is reduced blood return to the L heart as filling is limited.
L atrial pressure is low and therefore arterial pressure is low.

Question 10

What is Hypovolaemic shock?

Answer 10

Shock due to reduced blood volume and therefore poor venous return.

Question 11

What is the most common cause of Hypovolaemic shock?

Answer 11

Haemorrhage

Question 12

What is the severity of shock related to? (2)

Answer 12

The amount and speed of blood loss

Question 13

What happens in Hypovolaemic shock due to haemorrhage? (4)

Answer 13

Haemorrhage causes a fall in venous pressure
Cardiac output falls as less blood in means less out.
Arterial a blood pressure falls.
This is detected by the baroreceptors, which cause a sympathetic response.

Question 14

What is internal transfusion and when is it seen? What is it the result of?

Answer 14

It is the net movement of fluid into the capillaries due to an increase TPR that means that hydrostatic pressure inside the capillaries is reduced.
This causes increase blood volume.
It is seen in Hypovolaemic shock as a result of sympathetic stimulation.

Question 15

What are the signs and symptoms of Hypovolaemic shock? (4) what are they due to?

Answer 15

Tachycardia
Weak pulse
Pale skin
Cold, clammy extremities

Due to sympathetic compensatory mechanism

Question 16

What is decompensation? When is it seen?

Answer 16

It is peripheral vasoconstriction as a result of sympathetic compensation.
It is seen in Hypovolaemic shock.
The vasoconstriction causes tissue damage, meaning chemical mediators are released and cause vasodilation. This causes TPR to fall and arterial pressure to fall dramatically.

Question 17

What is toxic shock?

Answer 17

Septicaemia.
Endotoxins are released by bacteria and cause vasodilation
This causes decreased TPR and consequent low arterial BP.
The low arterial BP is detected by baroreceptors and sympathetic stimulation therefore occurs.

Question 18

What are the signs and symptoms of toxic shock? (2)

Answer 18

Tachycardia

Warm, red extremities.

Question 19

What is anaphylactic shock?

Answer 19

Shock due to an allergic reaction.

Question 20

What happens in anaphylactic shock? (3)

Answer 20

Histamine is released by mast cells and causes vasodilation.
This lowers TPR and BP as a result.
There is a sympathetic response which causes increased CO, but this can’t overcome the vasodilation.

Question 21

What are the signs and symptoms of anaphylactic shock? (4)

Answer 21

Difficulty breathing (as mediators cause bronchoconstriction)
Collapsed
Rapid HR
Red, warm extremities

Question 22

What is the treatment for anaphylactic shock?

Answer 22

Adrenaline

Question 23

What is cardiac arrest?

Answer 23

Unresponsiveness associated with a lack of pulse.