CVS - Shock

Question 1

What 2 mechanisms can cause haemodynamic shock?

Answer 1

Reduced CO

Reduced TPR

Question 2

What 4 types of shock are there?

Answer 2

Hypovolaemic
Pump failure
Mechanical failure - pump cannot fill
Excessive vasodilation (fall in TPR)

Question 3

What can cause the heart pump to fail?

Answer 3

Following MI
Ventricular arryhthmias (VF VT)
Acute worsening of HF

Question 4

What would you see clinically with cardiogenic shock?

Answer 4

• Dramatic drop in BP
• Loss of urine output - kidneys poorly perfused
• Central venous pressure may be raised (IJV)

Question 5

What can cardiogenic shock lead to if untreated?

Answer 5

Cardiac arrest

Question 6

What is cardiac arrest? What types?

Answer 6

Unresponsiveness with lack of pulse - sudden stop in effective blood flow due to inadequacy of the heart to pump blood.

Asystole
PEA
VT
VF

Question 7

How would you treat cardiac arrest?

Answer 7

Basic Life Support - compressions
Defibrillation
Adrenaline

Question 8

Why give adrenaline in cardiac arrest?

Answer 8

• Increases peripheral resistance

- Enhances myocardial function

Question 9

What arterial and venous pressures would you see with cardiac tamponade?

Answer 9

• High venous

- Low arterial

Question 10

How can a massive PE lead to shock?

Answer 10

Blocks PA - pressure increases in lungs - Right heart and therefore venous pressure increases as right heart cannot empty - reduced return of blood to left side of heart from pulmonaries - left atrial pressure low - arterial blood pressure low - shock

Question 11

What is a mechanical cause of shock?

Answer 11

Cardiac tamponade

Question 12

Which law states that when venous pressure falls, cardiac output falls?

Answer 12

Starlings

Question 13

How does the CVS compensate for a drop in BP?

Answer 13

Baroreceptors –> sympathetic stimulation

Question 14

What is ‘internal transaction’ and when would you see this occurring?

Answer 14

With hypovolaemia you get reduces hydrostatic pressure and net movement of fluid into capillaries

Question 15

What are some causes of hypovolaemic shock? What clinical signs would you see?

Answer 15

Blood loss, severe burns, diarrhoea

Pale
Clammy
Weak pulse
Cold skin to touch

Question 16

What is ‘shutdown’ (peripheral vasoconstriction) and why is this dangerous in hypovolaemic shock?

Answer 16

Peripheral vasoconstriction acts to try and increase BP but causes ischaemia of tissues - tissue damage due to hypoxia - release chemical mediators - vasodilators - reduced TPR - blood pressure falls dramatically - organs no longer perfused - multisystem failure

Question 17

What is distributive shock? Give some examples

Answer 17

Low resistance shock - reduced TPR - normovolaemic

E.g. toxic shock (Septic), anaphylactic shock

Question 18

How can sepsis lead to septic shock? Why can’t you just give fluids alone to increase BP?

Answer 18

Endotoxins from bacteria causing excessive inflammatory response - vasodilation and dramatic drop in TPR, also capillaries become leaky - so need vasopressors (e.g. adrenaline) as well as fluids to increase BP

Question 19

Define septic shock

Answer 19

Persistent hypotension following sepsis, despite attempts to fluid resuscitate to maintain BP

Question 20

What are the clinical signs of septic shock?

Answer 20

Tachycardia
Warm, red extremities - but later vasoconstriction and localised hypo perfusion
Also DIC - pupura - rash

Question 21

What mediator is involved in causing anaphylactic shock?

Answer 21

Histamine - released in granules from mast cells

Question 22

What happens during anaphylactic shock?

Answer 22

Histamine release - vasodilator - fall in TPR, sympathetic NS can’t compensate for vasodilation –> reduced perfusion of organs

Mediators also cause bronchoconstriction and laryngeal oedema

Question 23

How would a patient present with anaphylaxis?

Answer 23

• Difficulty breathing
• Collapsed
• Tachy
• Red, warm extremities