20. Shock Flashcards
What is shock?
Acute failure of the cardiovascular system to adequately supply the tissues with nutrients and gases
What are the 3 types of shock?
Cardiogenic
Distributive
Hypovolaemic
Why might cardiac output be decreased in cardiogenic shock?
Decreased contractility of heart
Arrhythmias
Restriction of cardiac filling
Obstruction to outflow
What are the two types of distributive shock?
Vasogenic (allergic reaction of sepsis)
Neurogenic (loss of sympathetic control)
What is distributive shock characterised by?
Vasodilation
Low blood pressure
Give three reasons for hypovolaemic shock?
Haemorrhage
Burns
Dehydration
What is compensated shock?
- Decreased blood pressure causes baroreflex activation
- Low blood volume activates volume reflexes
- Low BP mobilises blood from capillaries
- Very low BP activates CNS ischaemic reflex
What are symptoms of shock?
Cold, clammy skin
Tachycardia
Rapid respiration
What does the sympathetic activation of cardiac beta-adrenoceptors do?
Increases force of ventricular contraction
Increases heart rate
What effects does vasoconstriction have?
Mobilises blood reservoir from veins
Decreased glomerular filtration rate
Both increase blood volume
What effect does the release of rennin have?
Activates angiotensin
Causes further renal arteriole constriction
Aldosterone causes Na+ and water reabsorption
What happens to capillaries in hypovolaemia?
Arterioles are constricted which decreases capillary BP
Re-absorption of interstitial fluid (due to Starling forces)
Increased blood volume
What is the general treatment of shock?
Fluids Vasopressor drugs Cardiac stimulant drugs Antibiotics if septic Antihistamines if anaphylactic
What happens in irreversible shock?
- Reflexes fail to restore BP and coronary blood flow falls
- Vasomotor failure
- Slow movement in vessels leads to thrombosis
- Increased capillary permeability
- Release of toxic by ischaemic tissue
