Shock Flashcards
What is the definition of ‘shock’?
A condition of inadequate perfusion to sustain normal organ function
Name the 5 main classes of shock?
Hypovolaemic Cardiogenic Obstructive Distributive Cytotoxic
Hypovolaemic is solely due to loss of blood. true/false?
FALSE
It can also be a loss of interstitial fluid or pure water
Which hypovolaemic compensation mechanism involves:
inhibition of the vagus nerve and enhancement of sympathetics via nerve signals that originate from stretch receptors in the carotids and aortic arch?
Baroreceptor reflex
Describe the sympathetic mediated neurohormonal response to hypovolaemia
Sympathetic chronotropy and inotropy
Release of vasoconstrictors (adrenaline, NA, angiotensin, vasopressin etc.)
Redirection of fluids from peripherals and secondary organs
Lactic acidosis causing enhanced chemoreceptor response
When decompensating- increased vasodilators
What does capillary absorption of interstitial fluid do when in a hypovolaemic state?
Reduces capillary hydrostatic pressure
Describe the hypothalamic-pituitary-adrenal response to hypovolaemia?
Intrarenal baroreceptors=> renin release from juxtaglomerular apparatus
Angiotensin II enhances vasoconstriction and ADH secretion
=> enhanced renal reabsorption of Na and H20
What are the three basic ways to increase cardiac output?
Increase HR
increase SV (inotropy)
Increase both
Young people struggle to control HR. true/false?
FALSE
they often struggle to control stroke volume!
What happens to the Frank-Starling curve when inotropes are physiologically released/given?
Curve shifts up
= increased contractility
What happens to FS curve when contractility is decreased?
Shifts down
Describe some compensations made in HF, and what the consequences are?
Failing heart= decreased contractility
End diastolic volume increases to maintain stroke volume.
end result in pulmonary congestion
Patients with heart failure often respond poorly to fluid challenges, true/false?
true.
lower challenges are given and it is impossible to get a full response due to decreased contractility of the heart
What must you remember when prescribing fluids?
They are a drug.
Appropriate dose
Appropriate fluid and electrolyte components for that patient
Remember the difference between resuscitation and maintenance!
What is the main principle behind cardiogenic shock?
Heart pump failing to meet circulation demands.
name some causes of cardiogenic shock?
Acute MI Acute mitral prolapse Myocarditis Cardiomyopathy Myocardial Contusion (traumatic bruising)
What would be the resulting symptoms/signs resulting from failure to pump blood forward?
hypotension/shock
fatigue
syncope
What would be some symptoms/signs resulting from cardiac back pressure?
Pulmonary oedema (struggle to breath lying down, SOB)
sacral oedema
ankle oedema
What does positive inotropy mean?
an increase in the force of cardiac contraction for any preload
what has a positive inotropic effect physiologically?
the sympathetic nervous system
what exogenous drug can induce a positive inotropic effect?
B-Adrenoceptors: Dobutamine, adrenaline
Dopaninergic: dopamine, dopexamine
describe what inotropes and fluids do to the Frank-Starling Curve?
Inotropes=> UP
Fluids=> RIGHT
What device can be used to:
- provide counter pulsation
- assist inflation during ventricular diastole and deflation during ventricular systole?
Intra-aortic balloon pump
What is the main factor behind obstructive shock?
Something is obstructing the filling of the heart
Name some causes of obstructive shock
Pulmonary embolus
cardiac tamponade
tension pneumothorax
How would a PE be diagnosed on echo?
Hypokinetic right ventricle
Bowing of septum into Left side (due to higher pressure in right side)
PE treatment
anticoagulation +/- throbolysis
How would tamponade be diagnosed on echo?
fluid accumulation in pericardium
compression of each chamber with decreased filling
What does a tension pneumothorax look like on CXR?
blacked out lung space
How does a tension pneumothorax cause reduced venous return?
intrathoracic pressure is higher than venous pressure
- compression of vessels= obstruction of blood flow
describe distributive shock in a basic way
dilated circuit, normal blood volume
what is the initial compensation for distributive shock?
increased CO, however this will start to fall as venous return falls
what are the subtypes of distributive shock?
Septic shock
Anaphylactic shock
Neurogenic shock
Describe the cause septic shock
Bacterial toxin release causing capillary dysfunction
Describe the treatment for septic shock
Sepsis 6 + vasopressors
vasopressors improve perfusion and minimise excessive fluid volumes)
Describe the cause of anaphylactic shock
mast cell release of histiminergic vasodilators
describe anaphylactic shock treatment
adrenaline (vasopressor AND mast cell stabiliser)
What test can confirm anaphylactic origin?
serum mast cell tryptase
describe the cause of neurogenic shock
loss of sympathetic tone after a spinal injury causing inappropriate bradycardia as CNX is unopposed
what is the treatment for neurogenic shock?
dopamine and vasopressors
what interventions may exacerbate neurogenic shock?
PR exam (vagal stimulation) ET tube suction (vagal stimulation)
what should always make you think neurogenic shock?
hypotensive with BRADYCARDIA
what are the 4Hs (reversible cardiac arrest)
Hypovolaemia
hypothermia
hypoxia
hypo/hyperkaaemia
What are the 4Ts (reversible cardiac arrest)
Tamponade
thromboembolism
toxins
tension pneumothorax
what does CPR do physiologically?
cyclical changes in intrathoracic pressure that alternatively pushes blood out of and sucks it back into chest
what cardiac rhythm would you most likely see in arrest caused by hypovolaemia?
Pulseless electrical activity
What cardiac rhythm would most likely be seen in arrest caused by severe hypoxia?
asystole
what cardiac rhythm would most likely be seen in arrest caused by acute MI, toxins and electrolyte abnormalities?
VF and VT
