Shock

Question 1

Definition

Answer 1

Cardiac failure resulting in inadequate organ perfusion. Often defined by a decrease in BP (systolic < 90mmHg) or decrease in mean arterial pressure (MAP < 65mmHg)
With evidence of tissue hypo perfusion (mottled skin, urine output < 0.5mL/kg/h, serum lactate >2mmol/L

Question 2

MAP + CO equations

Answer 2

MAP = cardiac output * systemic vascular resistance
CO = stroke volume * heart rate
Shock can result from adequate co or loss of svr or both

Question 3

Causes of inadequate cardiac output

Answer 3

Hypovolaemia
- bleeding: trauma, ruptured aortic aneurysm, GI bleed
- fluid loss: vomiting, burns, ‘third-spacing’ losses e.g. pancreatitis, heart, exhaustion
Pump failure:
- cardiogenic shock e.g. ACS, arrhythmias, aortic dissection, acute valve failure
- secondary causes e.g. PE, tension pneumothorax, cardiac tamponade

Question 4

Causes of peripheral circulatory failure loss (loss of svr)

Answer 4

Sepsis
Anaphylaxis
Neurogenic e.g. spinal cord injury, epidural, or spinal anaesthesia
Endocrine injury: Addison’s, hypothyroidism,
Other: anaesthesia, antihypertensives, cyanide poisoning

Question 5

Hypovolaemic shock