Shock

Question 1

what is circulatory shock?

Answer 1

an abnormality of the circulatory system that results in reduced organ perfusion and tissue oxygenation

Question 2

what are the causes of reduced cardiac output (CO)?

Answer 2

• hypovolaemia
• vomiting
• diarrhoea
• diuresis
• burns
• cardiogenic (e.g. MI)
• obstructive (e.g. PE)

Question 3

what are the causes of reduced systemic vascular resistance (SVR)?

Answer 3

• septic shock
• anaphylactic shock
• neurogenic shock

Question 4

how is blood pressure calculated?

Answer 4

BP = CO X SVR

Question 5

how is cardiac output calculated?

Answer 5

CO = HR X SV

Question 6

what are the three factors that determine stroke volume (SV)?

Answer 6

• preload
• myocardial contractility
• afterload

Question 7

what is preload?

Answer 7

• the ventricular wall tension at the end of diastole, reflecting myocardial muscle fibre stretch
• it is influenced by volume status, venous capacitance, and the pressure difference between mean venous pressure and right atrial pressure

Question 8

how does preload relate to stroke volume?

Answer 8

preload affects SV through the frank-starling mechanism:

• increased fibre length initially increases SV
• excessive stretching reduces SV, as seen in cardiac failure

Question 9

what is myocardial contractility?

Answer 9

• the heart’s intrinsic ability to contract independently of preload and afterload
• positive inotropes increase contractility, causing the frank-starling curve to shift upwards

Question 10

what is afterload?

Answer 10

the ventricular wall tension at the end of systole and is the resistance to anterograde blood flow

Question 11

what are the symptoms of shock?

Answer 11

• dyspnoea
• confusion
• light-headedness
• drowsiness
• oliguria/anuria
• kussmaul’s breathing
• cold, pale peripheries
• CRT >2 s
• tachycardia
• hypotension

Question 12

what is the management of shock?

Answer 12

• ABCDE
• high-flow oxygen (15L/min) via a reservoir mask to maintain an oxygen saturation of >94%
• pulse-oximetry
• non-invasive BP monitoring
• three-lead cardiac monitoring
• ECG
• CXR
• ABG
• IV fluid
• urinary catheterisation
• fluid-balance monitoring
• ? referral to HDU/ICU

Question 13

what is the specific management of haemorrhagic shock?

Answer 13

• haemorrhage control (e.g. direct compression, pelvic binder, splinting of long bone fractures, surgical ligation of bleeding vessels)
• restore adequate circulating volume
• crossmatch
• major haemorrhage protocol
• transfuse O negative blood
• correct coagulopathy (e.g. transfuse platelets, FFP, and cryoprecipitate)

Question 14

what is the specific management of anaphylactic shock?

Answer 14

0.5mg IM adrenaline

Question 15

what are the long-term complications of shock?

Answer 15

• organ hypoperfusion
• cognitive impairment
• gangrene
• MI
• arrhythmia
• autonomic dysreflexia