Cardiovascular responses to shock

Question 1

What is shock?

Answer 1

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

Question 2

What does shock cause?

Answer 2

inadequate tissue perfusion –> inadequate tissue oxygenation –> anaerobic metabolism –>accumulation of metabolic waste products –>cellular failure

Question 3

What does adequate tissue perfusion depend on?

Answer 3

adequate blood pressure

adequate cardiac output

Question 4

What happens in hypovolaemic shock?

Answer 4

decreased blood volume –>decreased venous return –> decreased EDV –> decreased SV –>Decreased CO and BP –>inadequate tissue perfusion

Question 5

What is cardiogenic shock?

Answer 5

Sustained hypotension caused by decreased cardiac contractility –> decreased stroke volume –> decreased CO and BP –>inadequate tissue perfusion

Question 6

What happens in tension pneumothorax : obstructive shock?

Answer 6

increased intrathoraic pressure–>decreased venous return –> decreased EDV –> decreased SV –>Decreased CO and BP –>inadequate tissue perfusion

Question 7

Why does increased intrathoracic pressure cause decreased venous return?

Answer 7

Venous return is dependant on pressure gradient between thorax and big veins so if there is a high level in thorax, there is no pressure gradient

Question 8

What happens in neurogenic shock?

Answer 8

loss of sympathetic tone –> massive venous and arterial vasodilation –> decreased venous return and decreased TPR –> decreased CO and BP–> inadequate tissue perfusion

Question 9

What happens in vasoactive shock?

Answer 9

release of vasoactive mediators –> massive venous and arterial vasodilatation and increase capillary permeability –> decreased venous return and decreased TPR –> Decreased CO and BP –> inadequate tissue perfusion

Question 10

What are the outlines for treatment of shock?

Answer 10

• ABCDE
• high flow of oxygen
• volume replacement
• inotropes for cardiogenic shock
• immediate chest drain for tension pneumothorax
• adrenaline for anaphylactic shock
• vassopressors for septic shock

Question 11

What are the two causes of hypovolaemic shock?

Answer 11

• haemorrhage- trauma , surgery
• non haemorrhage - vomiting, diarrhoea, excessive sweating
• both cause loss of blood volume and so decrease in CO

Question 12

Up to what percentage can compensatory mechanisms maintain blood pressure?

Answer 12

until 30% of blood volume is lost