Shock Flashcards
what is haemodynamic shock
acute condition of inadequate blood flow throughout the body so that there is a catastrophic fall in arterial blood pressure
a reduction in what causes shock
cardiac output or total peripheral resistance
what does a reduction in cardiac output cause
- pump failure
- loss of blood volume
- pump not filling properly
what does a fall in peripheral resistance cause
excessive vasodilation
what is cardiogenic shock
the ventricles don’t empty properly (pump failure)
what is mechanical shock
the ventricles don’t fill properly
what is hypovolaemic shock
reduced blood volume leads to poor venous return
what causes cardiogenic shock
- MI causing damage to LV
- arrthythmias
- heart failure
how does tachycardia cause cardiogenic shock
if the heart beats too fast then there is not enough time for the heart to fill and empty
what are the effects of cardiogenic shock
tissues are poorly perfused
what type of shock does cardiac tamponade lead to
mechanical shock
what happens to the central venous pressure in cardiac tamponade
it increases as the blood returning cant fill the heart
how does a pulmonary embolism cause mechanical shock
- occludes a large pulmonary artery giving a high pressure.
- the RV cant empty which raises the venous pressure
- reduced heart return to the left heart
- left arterial pressure is lowered leading to shock
how does an embolism reach the lungs
portions of a thrombosis in the legs breaks off and travels in the venous system to the lungs
what most commonly causes hypovolaemic shock
haemorrhage
what proportion of blood must be lost to cause hypovolaemic shock
20-30% too show sign
30-40% for a serious response
how does a haemorrhage cause hypovolaemic shock
the venous pressure falls which causes the cardiac output to fall by starlings law.
what is done by the body to compensate for a haemorrhage
there is increased sympathetic stimulation causing tachycardia which increases the force of contraction and causes vasoconstriction
during hypovolaemic shock what happens to the net movement of fluid in the capillaries
fluid moves into the capillaries due to a lower hydrostatic pressure
what does a patient in hypovolaemic shock have
- weak pulse
- tachycardia
- pale skin
- cold, clammy extremities
what can severe burns, diarrhoea or vomiting cause
hypovolaemic shock
what are the dangers of compensating for hypovolaemic shock
vasoconstriction will cause tissue damage by hypoxia
this causes the release of chemical mediators which cause vasodilation causing bp to fall more
what type of shock result from a decrease in TPR
distributive shock
what is distributive shock
where there is profound vasodilation as the volume of circulation has increased but the blood volume is normal
what are the 2 types of distributive shock
- anaphylactic
- toxic shock
what is toxic/septic shock
- persisting hypotension requiring treatment to maintain blood pressure despite fluid resuscitation due to shock
what causes septic shock
endotoxins released by circulating bacteria cause vasodilation through an excessive inflammatory response causing a decrease in TPR
why does a patient which shock have tachycardia
baroreceptors detect a decrease in pressure and so increase heart rate and stroke volume compensate
what is anaphylactic shock
severe allergic reaction due to the release of histamine from mast cells causing vasodilation
what should be administered to someone suffering from an anaphylactic shock
adrenaline - causes vasoconstriction vis alpha 1 adrenoreceptors
