Shock Flashcards
What is hypovolaemic shock?
insufficient circulating volume to fill the circut
What can cause hypovolaemic shock?
blood loss
interstitial fluid deficit
pure water deficit
What are the different compensatory mechanisms?
baroreceptor reflexes
sympathetic mediated hormonal response
capillary absorption of interstitial fluid
hypothalamo-adrenal-pituitary response
What is the baroreceptor reflex to hypovolaemic shock?
decreased stretch causes decreased afferent input to the medullary CV centre
What is the sympathetic mediated hormonal response to hypovolaemic shock?
releases circulating vasodilators redirecting fluid from peripheral + secondary organs
How does capillary absorption of interstitial fluid change due to hypovolaemic shock?
causes reduced capillary hydrostatic pressure which causes inward net filtration
How does the hypothalamo-adrenal-pituitary response change in relation to hypovolaemic shock?
intra renal baroreceptors mediate renin release from JGA this results in Ang 2 which enhances vasoconstriction + ADH secretion
which enhances renal absorption of Na + H20
What happens if you increase fluids in hypovolaemia?
increase stroke volume
What happens if you give fluids to a hypovolaemic patient with heart failure?
get an increase in end diastolic volume which causes pulmonary congestion
What is cardiogenic shock?
inability of the heart as a pump to meet circulatory demands
What causes cardiogenic shock?
acute MIs
valve dysfunction - acute mitral prolapse
myocarditis, cardiomyopathy, myocardial contusion
How does cardiogenic shock present?
hypotension due to poor forward flow fatigue syncope backpressure causing pulmonary oedema elevated JVP hepatic congestion
How can you treat cardiogenic shock?
inotropes - dopaminergic and beta stimulation
dopamine, dopexamine, dopabutamine, adrenaline
What is the next step if the heart cannot be helped by inotropy?
intra-aortic balloon pump - provides counter perfusion
What is obstructive shock?
physical obstruction to either the heart or the great vessels
How do you treat obstructive shock?
REMOVE UNDERLYING CAUSE
What can cause obstructive shock?
PE - hyperkinetic apex
cardiac tamponade
tension pneumothorax
What is distributive shock?
circut becomes too big so there is vasodilation and the pressure decreases causing decreased BP
still high cardiac output but insufficient to maintain forward perfusion
What are the 3 types of distributive shock?
septic shock
anaphylactic shock
neurogenic shock
What is septic shock?
bacterial endotoxin mediated capillary dysfunction - early use of vasopressors improves function
What is anaphylactic shock?
mast cell release of histaminergic vasodilators
How is anaphylactic shock confirmed?
serum mast cell tryptase - confirms the diagnosis of mast cell degranulation
How is anaphylactic shock treated?
adrenaline which is a vasoconstrictor and mast cell stabaliser
What is neurogenic shock?
loss of thoracic sympathetic outflow following spinal cord or central cord trauma
causes hypotension due to loss of descending sympathetic tone + innapropriate bradycardia due to unopposed vagal tone
How is neurogenic shock treated?
dopamine and vasopressors
