SHOCK Flashcards
what is shock?
the failure of the circulation that results in inadequate tissue perfusion
which cells secrete renin?
angiotensinogen
what can trigger the release of renin?
decreases in…
NaCl
bp
extracellular fluid volume
where is ACE secreted from?
endothelial lung cells
what are the effects of angiotensin 2?
increased secretion of aldosterone from adrenal cortex
stimulates hypothalamus to secrete ADH and thirst stimulus
smooth muscle constriction
whats the effect of increased aldosterone?
kidney distal tubules add Na+ so more is absorbed and water follows osmotically
what is the effect of SDH?
it increases aquaporins in the collecting tubules
what stimulates baroreceptors?
As blood volume increases, vessels are stretched and the firing rate of baroreceptors increases.
outline what happens to baroreceptors when bp drops?
they reduce firing so stimulation of vagus nerve is reduced = heart rate increases
stimulatory effect on catecholamine neurones = increase in bp
increase in ADH release
what is ADH also called?
vasopressin
how can you test a patients auto regulation?
The vasalva manoeuvre (forcible expiration against a closed glottis) causes the mouth pressure to increase suddenly which increases intrathoracic pressure which reduces venous return and left ventricular cavity. The body will respond by increasing the heart rate and vasoconstriction - baroreceptor response.
what is the auto regulatory range of bp?
The capacity of the cerebral circulation to alter vascular resistance in order to maintain a relatively constant Cerebral blood flow over a range of mean arterial pressure
how do you calculate cardiac output?
stroke volume x heart rate
how do you calculate mean arterial pressure?
cardiac output x systemic vascular resistance
what is starlings law?
the force of contraction of the cardiac muscle is proportional to its initial length i.e. the heart pumps out the blood that is returned to it.
what is the definition of hypotension?
a reading of less than 90/60mmHg
what are the 3 types of shock?
hypovolemia
pump failure
vasodilation
what is hypovolemic shock?
inadequate fluid volume = fall in CO
= baroreceptors increase resistance and cause tachycardia
why is hypotension usually a late sign of shock?
because of the compensation by the body - particularly in young people its frequently a sign of decompensation
what is pump failure shock?
when theres a fall in CO
◦ compensation includes increased resistance and tachycardia by baroreceptors. The renin angiotensin system also causes us to retain more salt and water which actually causes a bigger problem. It causes an increase in afterload too so we get failure of starlings law and the heart starts to dilate
what is vasodilation shock?
prime problem is vasodilation so afterload decreases
The body compenates with tachycardia, CO rise and autoregulation will try to overcome it
what are examples of vasodilation shock?
anaphylactic
neurogenic
what are the signs of hypovolemic shock?
cold and clammy peripheries weak pulse empty veins tachycarda prolonged cap refill
what are the signs of pump failure shock?
cold and clammy peripheries weak pulse full veins and raised JVP prolonged cap refull tachycardia
what are signs of vasodilator shock?
warm and dry peripheries bounding pulse full veins tachycardia short cap refill
how can we assess conscious level? 2 ways
AVPU scores and GCS score
what is the AVPU score?
alert
responds to voice
responds to pain
unconcious
what are some causes of hypovolemic shock?
blood loss
evaporation
GI losses
polyuria
what are some causes of pump failre?
tamponade
PE obstruction
cardiac muscle failure
what is systemic inflamamtory response syndrome?
an exaggerated defence response of the body to a noxious stressor to localize and then eliminate the endogenous or exogenous source of the insult.
what are some examples of noxious stimuli causes SIRS?
Iinfection, trauma, surgery, acute inflammation, burns, ischeamia or reperfusion, or malignancy
what are the conditions for having SIRS diagnosed?
2 or more of: Heart rate >90, fever >38 or <36, WCC >12000 or <4000 respiratory rate >20 or pCO2 <32
what is sepsis?
SIRS with a confirmed infection
what is severe sepsis?
sepsis with organ dysfunction
what is septic shock?
sepsis with refractory hypotension
what is refractory hypotension?
hypotension which doesnt respond to fluid)
what do alpha receptors cause?
peripheral vasoconstriction
what do beta 1 receptors cause?
increased HR
increased contraction
increased renin secretion
what do beta 2 receptors cause?
arteriolar vasodilation
what receptors does adrenaline target?
what are the effects?
alpha
beta 1
beta 2
increases HR, SV and causes vasoconstriction to increase bp
what receptors does dobutamine target?
what are the effects?
beta 1 and beta 2
increases HR, SV but has vasodilating efefcts
decreases bp
what does dopamine target?
what are its efefcts?
beta 2 and dopamine receptors
increases HR and causes splanchnic vasodilation
what receptors does noradrenaline target?
what are the effects?
alpha
vasoconstriction
whats the principle management of hypovolemic shock?
fluids and vasopressors
whats the principle management of pump failure shock?
inotropes and ventilators
whats the principle management of resistance induced shock?
vasopressors and fluids
what are vasopressors?
drugs that cause vasoconstriction e.g. noradrenaline
whats the treatment for sepsis?
give O2 sats take blood cultures IV antibiotics fluid challenge measure lactate (increased in sepsis) measure urine output (good indicator of circulating volume)
what are crystalloids and how can they be classified?
an aqueous solution composed of water and small solutes such as electrolytes and glucose
whether they are isotonic, hypotonic or hypertonic
