Common shock exam questions for medical finals, OSCEs and MRCP PACES
Define the term ‘circulatory shock’
- Shock is an abnormality of the circulatory system that results in reduced organ perfusion and tissue oxygenation.
What are the six categories of shock?
- Hypovolaemic shock
- Cardiogenic shock
- Obstructive shock
- Septic shock
- Anaphylactic shock
- Neurogenic shock
What is the equation to express the relationship between blood pressure (BP), cardiac output (CO) & systemic vascular resistance (SVR)?
- BP = CO x SVR
What is the equation to express the relationship between CO, HR & SV?
- CO = HR x SV
What are the three determinants of stroke volume?
- Myocardial contractility
What is the Frank-Starling mechanism?
- Increased myocardial muscle fibre length initially leads to an increased SV but above a certain point, the fibres become overstretched and further filling results in a decreased SV, as is the case in cardiac failure
Why does shock cause a lactic acidosis?
- Inadequate organ perfusion and tissue oxygenation results in cells switching from aerobic to anaerobic metabolism
- This generates a lactic acidosis that disrupts the cellular environment and causes myocardial depression
How do you classify haemorrhagic shock into type 1-4 (what are the parameters)?
- Volume of blood loss (ml)
- Percentage blood loss (%)
- Heart rate (beats/min)
- Blood pressure
- Pulse pressure
- Respiratory rate (breaths/min)
- Urine output (ml/hour)
- Mental state
What are the four main strategies for the ward-based management of shock?
- Give oxygen 15 L/min via reservoir mask
- Titrate to sats 94-98%
- IV fluid resuscitation
- Monitor lactate and urine output
- Identify and treat the cause
What are three further strategies for HDU/ICU-based management of shock?
- Central line insertion with central venous pressure (CVP) and central venous oxygen saturation (ScvO2) monitoring
- Arterial line insertion and invasive arterial BP monitoring
- Vasopressor and/or inotrope infusion