5. Haemodynamic Shock

Question 1

What is haemodynamic shock?

Answer 1

Acute condition of inadequate blood flow throughout the body, catastrophic fall in arterial blood pressure leads to circulatory shock.

Question 2

How can mean AP be calculated?

Answer 2

SV x HR x TPR

Question 3

A fall in which 2 values will lead to shock?

Answer 3

CO or TPR

Question 4

What are the 3 types of shock due to a fall in CO?

Answer 4

1. Cardiogenic shock
2. Mechanical shock
3. Hypovolaemic shock

Question 5

What is cardiogenic shock?

Answer 5

Pump failure - ventricle cannot empty properly

Question 6

What is mechanical shock?

Answer 6

Obstructive - ventricle cannot fill properly

Question 7

What is hypovolaemic shock?

Answer 7

Reduced blood volume leads to decreased venous return.

Question 8

What are potential causes of cardiogenic shock?

Answer 8

1. Following MI - damage to LV
2. Serious arrythmia - bradycardia or tachycardia
3. Acute worsening of HF

Question 9

What would you expect the central venous pressure to be in cardiogenic shock?

Answer 9

Normal or raised due to backlog of blood in venous system- look at JVP in neck.

Question 10

What is the most common form of cardiac arrest?

Answer 10

Ventricular fibrillation

Question 11

What form of cardiac arrest will appear normal on an ECG?

Answer 11

Pulseless electrical activity

Question 12

What is asystole?

Answer 12

Cardiac arrest due to loss of electrical and mechanical activity

Question 13

What conditions increase the risk of ventricular fibrillation?

Answer 13

Following MI
Electrolye imbalance - K+
Arrythmias - lengthened AP

Question 14

Why is adrenaline given to treat cardiac arrests?

Answer 14

• Increases TPR

- Increases contractility of the heart

Question 15

What are possible causes of mechanical shock (ventricle cannot fill)?

Answer 15

Cardiac tamponade

Pulmonary embolism

Question 16

How can cardiac tamponade lead to mechanical shock?

Answer 16

Limits EDV, decreased SV leads to a decrease in CO.

Question 17

What would you expect CVP to be in cardiac tamponade?

Answer 17

High - backlog in venous system

Question 18

How can a massive PE lead to mechanical shock?

Answer 18

Embolus occludes a large pulmonary artery, PA pressure is high, RV cannot empty, reduced filling of LV.

Question 19

What percentage blood loss is likely to cause hypovolaemic shock?

Answer 19

20-30% might cause some signs of shock

30-40% will cause a serious shock response

Question 20

What happens to the Starling’s forces during hypovolaemia shock to cause ‘internal transfusion’?

Answer 20

Increased peripheral resistance reduces capillary hydrostatic pressure and causes net movement INTO capillaries to try and maintain blood volume and pressure.

Question 21

What signs will be present in a patient with hypovolaemic shock?

Answer 21

Tachycardia
Weak pulse
Pale skin
Cold, clammy extremities

Question 22

What is the danger of decompensation in hypovolaemic shock?

Answer 22

Peripheral vasoconstriction causes hypoxia and tissue damage, release of vasodilator chemical mediators which cause a fall in TPR and another dramatic fall in BP.
Vital organs cannot be perfused - > Multi-system organ failure.

Question 23

What is distributive shock?

Answer 23

Shock due to a decrease in TPR - blood volume remains constant

Question 24

What are 2 type of distributive shock?

Answer 24

Toxic shock/ Sepsis

Anaphylactic shock

Question 25

How does sepsis cause distributive shock?

Answer 25

Excessive inflammatory response -> vasodilation, decrease in TPR and arterial pressure -> impaired perfusion of vital organs.
Vasoconstriction response overridden by vasodilators.

Question 26

What is septic shock?

Answer 26

Persisting hypotension requiring treatment to maintain blood pressure despite fluid resuscitation.

Question 27

How will the patient present differently in septic shock compared to hypovolaemic shock?

Answer 27

Warm, red extremities initially

Question 28

What is anaphylactic shock?

Answer 28

Severe allergic reaction causing release of histamine from mast cells.
Powerful vasodilator which causes decrease in TPR and massive drop in arterial BP.

Question 29

Why will patients suffering from anaphylactic shock have difficulty breathing?

Answer 29

Mediators also cause bronchoconstriction and laryngeal oedema

Question 30

What is given to treat anaphylactic shock?

Answer 30

Adrenaline