Shock Flashcards
What is Shock?
a serious and potentially fatal condition characterised by acute failure of the cardiovascular system to adequately perfuse the tissues of the body (hypoperfusion).
what is the normal circulating blood volue?
70mls/kg
so a 70 kg man has 70x70 = 4900 mls
What is compensation/decompensation as it relates to shock?
compensation =hypoxic and metabolic effects of under perfusion - initially cause only reversible cellular damage due to compensatory response of the body
decompensated = persistence of the underperfused state eventually causes irreversible tissue damage and death
what is ‘cardiogenic shock’?
failure of the heart to pump resulting in shock
ex) electrical fault of hear, failure to contract in congestive heart failure, ischaemic damage, MI, cardiac tamponade
what is ‘distributive shock’?
changes in vascular tone leading to underperfusion
ex) septic shock, spinal injury, drug overdose, anaphylaxis
what is hypovolaemic shock?
reduction in circulating fluid volume either whole blood, plasma, extracellular or intracellular fluid
ex) blood loss due to haemorrhage, plasma loss following burns, fluid loss due to vomiting or diarrhoea
what are the four classes of hypovolaemic shock?
depends on the rate of loss as well - acute/chronic
class 1 = lose less than 15%
class 2= lose 15-30%
class 3 = lose 30-40%
class 4= lose more than 40%
what sort of compensatory response do we see in hypovolaemic shock?
in acute loss we see
- increased heart rate
- decreased urine flow
- pale/cold extremities
- increased respiratory rate
the compensatory signs/symptoms can mostly be explained by two responses to blood loss - what are they?
- hypothalamic - pituitary adrenal axis = stimulates cortisol relsease from adrenal cortex
- sympatho-adrenal axis
what is the bodies ‘priority organ’ during shock?
protection of the cerebral and myocardial circulations is priority at the expense of reduced perfusion of most major organs
what are some neural/hormonal compensatory responses to hypovolaemic shock?
activation of sympathetics - cardiovascular control, effects on adrenal medulla and restoration of blood volume
secretion of hormones to increase cardiovascular control, provide enough metabolic fuel, and restore volume
what are some hormones released during hypovolaemia?
vasoactive hormones: angiotensin 2, ADH, catecholamines (adrenaline/noradrenaline)
metabolically active: cortisol, glucagon, adrenaline,
volume conserving: ADH, aldosterone
why do we see an increase in ADH, aldosterone and thirst during acute hypovolaemia?
blood loss leads to
decreased arterial pressure leads to
decreased glomerular filtration rate leads to
increased renin release leads to
increased angiotensin 2 -
how does our body utilize tissue fluid during hypovolaemia?
“internal transfusion”
- due to fall in capillary hydrostatic pressure associated with arterial vasoconstriction, fluid from the interstitium/intracellular space is reabsorbed into the capillaries
- restores volume but dilutes plasma proteins and RBCs
what is ‘Starlings hypothesis’?
the following forces determine capillary exchange
- Pressure in capillary
- Pressure in intersitial fluid
- colloid osmotic pressure of capillary
- colloid osmotic pressure of interstitial fluid
