Shock

Question 1

What is shock?

Answer 1

A syndrome in which tissue perfusion is inadequate for the tissue’s metabolic requirement

Question 2

Normal tissue perfusion relies on what 3 factors?

Answer 2

Cardiac function
Capacity of vascular bed
Circulating blood volume

Question 3

What surrogate markers do we use to determine normal perfusion?

Answer 3

Blood pressure
Consciousness (brain perfusion)
Urine output (renal perfusion)
Lactate (general tissue perfusion)

Question 4

MAP = ?

Answer 4

MAP = Cardiac output (CO) x systemic vascular resistance (SVR)

Question 5

What are the four main causes of shock?

Answer 5

Hypovolaemic
Cardiogenic
Distributive
Obstructive

Question 6

What is hypovolaemic shock?

Answer 6

Volume depletion -> reduced SVR -> vasoconstriction -> reduced preload -> reduced CO

Question 7

What are causes of hypovolaemic shock?

Answer 7

Acute haemorrhage
Fluid deplete states (severe dehydration, burns)

Question 8

What are causes of cardiogenic shocks?

Answer 8

Primarily ischaemia induced myocardial dysfunction
Also: cardiomyopathies, valvular problems, dysrhythmias

Question 9

What is cardiogenic shock?

Answer 9

Pump failure - Reduced CO

Reduced contractility (Reduced SV)
Reduced HR

Question 10

What is obstructive shock?

Answer 10

Mechanical obstruction to normal CO in an otherwise normal heart

Question 11

What are causes of obstructive shock?

Answer 11

Direct obstruction to CO - PE, Air/fat/amniotic fluid embolism

Restriction of cardiac filling - tamponade, tension pneumothorax

Question 12

What are causes of distributive (vasoplegic) shock?

Answer 12

Sepsis
Anaphylaxis
Acute liver failure
Spinal cord injuries

Question 13

What is distributive shock?

Answer 13

Disruption of normal vascular autoregulation so causes profound vasodilatation

Poor perfusion - despite increased cardiac output

Question 14

What are causes of endocrine shock?

Answer 14

Severe uncorrected hypothyroidism, addisonian crisis - both reduced CO and vasodilation

Paradoxically - thyrotoxicosis

Question 15

What different pathways are there to preserve normal cardiac output and therefore BP?

Answer 15

Question 16

What is the neuroendocrine response to shock?

Answer 16

Release of pituitary hormones - adrenocorticotrophic hormone, ADH, endogenous opioids

Release of cortisol - fluid retention, antagonises insulin

Release of glucagon

Suggestion that some shock states (sepsis) blunts response to ACTH

Question 17

What are signs of shock?

Answer 17

Hypotension +

Signs of myocardial failure
Raised JVP, pulses paradoxes, signs of cause

Pyrexia, vasodilation, rapid cap refill, hypotension

Profound vasodilation, erythema, bronchospasm, oedema

Question 18

What examination monitoring should you do for shock?

Answer 18

Examination - pale, cold skin, prolonged CRT

Urine output - sensitive indicator of renal perfusion

Neurological - disturbed consciousness a good indicator of cerebral hypoperfusion

Biochem - acidosis, lactate levels

Question 19

How do manage shock?

Answer 19

Prompt diagnosis andtreatment
ABCDE
Establishment of reliable wide bore IV access and resuscitate while investigating
identify and treat underlying cause

Question 20

What are aims of management in shock?

Answer 20

Aim of resus - to re-establish sufficient perfusion to allow adequate tissue oxygen delivery

As before - perfusion difficult to measure, so surrogates and assumptions made

MAP - although target for most 65-70mmHg, needs assessed with rest of clinical picture

Question 21

What fluid management should you do for shock?

Answer 21

Increase pre-load
Rapid fluid replacement (minutes)

Question 22

What is a fluid challenge?

Answer 22

Rapid adminisration of a fluid with an assessment of response

Rapid enough to get a response but not so fast to provoke stress response

Typically 300-500ml over 10-20 minutes

Have a target in mind: increased MAP, decreased HR, increased urine output

Avoid other things that may confuse matters

Question 23

What drugs can you use for shock?

Answer 23

Noradrenaline first line (predominantly alpha agonist (vasoconstriction))

Vasopressin (ADH)
Dopamine (natural precursor to the above; complex dose-dependent effects)
Dobutamine / dopexamine

Adrenaline - alpha / beta adrenergic agonist, but at low dose primary beta (Inc HR, contractility, vasodilation)