Shock Flashcards
What is shock?
A syndrome in which tissue perfusion is inadequate for the tissue’s metabolic requirement
Normal tissue perfusion relies on what 3 factors?
Cardiac function
Capacity of vascular bed
Circulating blood volume
What surrogate markers do we use to determine normal perfusion?
Blood pressure
Consciousness (brain perfusion)
Urine output (renal perfusion)
Lactate (general tissue perfusion)
MAP = ?
MAP = Cardiac output (CO) x systemic vascular resistance (SVR)
What are the four main causes of shock?
Hypovolaemic
Cardiogenic
Distributive
Obstructive
What is hypovolaemic shock?
Volume depletion -> reduced SVR -> vasoconstriction -> reduced preload -> reduced CO
What are causes of hypovolaemic shock?
Acute haemorrhage
Fluid deplete states (severe dehydration, burns)
What are causes of cardiogenic shocks?
Primarily ischaemia induced myocardial dysfunction
Also: cardiomyopathies, valvular problems, dysrhythmias
What is cardiogenic shock?
Pump failure - Reduced CO
Reduced contractility (Reduced SV)
Reduced HR
What is obstructive shock?
Mechanical obstruction to normal CO in an otherwise normal heart
What are causes of obstructive shock?
Direct obstruction to CO - PE, Air/fat/amniotic fluid embolism
Restriction of cardiac filling - tamponade, tension pneumothorax
What are causes of distributive (vasoplegic) shock?
Sepsis
Anaphylaxis
Acute liver failure
Spinal cord injuries
What is distributive shock?
Disruption of normal vascular autoregulation so causes profound vasodilatation
Poor perfusion - despite increased cardiac output
What are causes of endocrine shock?
Severe uncorrected hypothyroidism, addisonian crisis - both reduced CO and vasodilation
Paradoxically - thyrotoxicosis
What different pathways are there to preserve normal cardiac output and therefore BP?
What is the neuroendocrine response to shock?
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
What are signs of shock?
Hypotension +
Signs of myocardial failure
Raised JVP, pulses paradoxes, signs of cause
Pyrexia, vasodilation, rapid cap refill, hypotension
Profound vasodilation, erythema, bronchospasm, oedema
What examination monitoring should you do for shock?
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
How do manage shock?
Prompt diagnosis andtreatment
ABCDE
Establishment of reliable wide bore IV access and resuscitate while investigating
identify and treat underlying cause
What are aims of management in shock?
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
What fluid management should you do for shock?
Increase pre-load
Rapid fluid replacement (minutes)
What is a fluid challenge?
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
What drugs can you use for shock?
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)
