Pathophysiology of Shock Flashcards
What is meant by shock?
acute circulatory failure that results in adequate cellular oxygen utilisation
What happens during shock
Low arterial blood pressure
Inadequate tissue perfusion - cellular hypoxia
What are causes of shock
Pump- cardiogenic shock + obstructuve
Fluids - hypovolaemic
Pipes (vessels)- leaky/dilated- unable to distribute
What are physical signs
Cool, cyanosed peripheries
kidney fxn decreased
Confused - low BP to brain
What is distributive shock
Generalised vasodilation
Sepsis/anaphylaxis
decrease in PR
What is hypovolaemic shock
Loss of circulatory blood volume
internal or external losses
decrease in CO
What is cardiogenic shock
pump failure
MI, cardiomyopathy, arrhythmia, valvular heart failure
Decrease in CO
What is obstructive shock
Mechanical interference
pulmonary embolism, cardiac tampoade, tension, pneumothorax
Decrease in CO
What are the consequences of shock
Reduced arterial Blood pressure
What does reduced blood pressure lead to
decrease in cerebral blood flow - confusion/ restlessness
decrease in renal perfusion
decrease tissue perfusion - switch to anaerobic metabolism - lactic anaerobic
What are the signs and symptoms of shock
Low BP
skin changes - prolonged capillary refill, cyanosed, cold
Altered mental state
Organ dysfunction - decrease in urine output, acute kidney injury
Increase in sympathetic tone - tachycardia and sweating
Respiration compensation for metabolic acidosis - hyperventilation
What mechanisms happen when there is a fall in blood pressure.
- Autonomic nervous system
- RAAS
- Vasopressin
- Stress hormones
What does the autonomic nervous system do to combat a fall in blood pressure?
Increase sympathetic tone and catecholamine release
(nor)ardrenaline will cause increase in HR and CO
How does the RAAS compensate a fall in blood pressure?
Decrease in glomerular filtration sensed by the macular densa
Increase in renin released from juxta glomerulus apparatus
Renin cleaves angiotensin to angiotensin 1
Angiotensin 1 to Angiontensin II by ACE
Angiotensin II vasocontractions arterioles and increases the release of aldosterone which increases the release of sodium ions and water retention
How does vasopressin (ADH) compensate for a fall in blood pressure?
decrease in venous return
decrease in baroreceptor output
ADH release leads to vasoconstriction and an increase in peripheral resistance
increase in water reabsorbed by kidney
increase in blood volume
increase in venous return will lead to an increase in cardiac output
