Shock

Question 1

classifying the causes of shock

Answer 1

• hypovolaemic
• cardiogenic
• distributive
• obstructive
• (endocrine)

Question 2

hypovolaemic shock

Answer 2

• acute haemorrhage
• “fluid deplete” states - severe dehydration, burns
• volume depletion - leading to reduced SVR
• reduced volume returning to heart - reduced preload and hence reduced CO

Question 3

cardiogenic shock

Answer 3

• “pump failure” - reduced CO
• primarily ischaemia induced myocardial dysfunction
• also cardiomyopathies, valvular problems, dysrhythmias
• if due to MI - suggests that >40% of LV is involved
• unless correctable pathology (e.g. valvular), mortality >75%)

Question 4

obstructive shock

Answer 4

• mechanical obstruction to normal cardiac output in an otherwise normal heart
• direct obstruction to cardiac output - PE, Air/fat/amniotic-fluid embolism
• restriction of cardiac filling (tamponade, tension pneumothorax)

Question 5

distributive (vasoplegic) shock

Answer 5

• “hot” shock
• septic, anaphylaxis, acute liver failure, spinal cord injuries
• due to disruption of normal vascular autoregulation, and profound vasodilatation
• poor perfusion - despite increased CO
• regional perfusion differences
• alteration of oxygen extraction

Question 6

Endocrine shock

Answer 6

• severe uncorrected hypothyroidism, Addisonian crisis - both reduced CO and vasodilation
• paradoxically - thyrotoxicosis