Haemorrhage

Question 1

What is a circulatory shock?

Answer 1

acute failure of the CV system to perfuse the tissues of the body adequately

Question 2

what is hypovolemic shock?

Answer 2

shock that is caused by a fall in blood or plasma volume which may be due to external fluid loss eg haemorrhage

Question 3

What are examples of the signs and symptoms of shock?

Answer 3

pale skin
weak but rapid pulse
weakness in muscles
reduction in MAP
decreased urine putput

Question 4

How do you classify the severity of a haemorrhage?

are shock and MAP affected?

Answer 4

based on the amount of blood that is lost
* class I haemorrhage - 10-15% which is the standard donation amount - no shock caused and MAP is unaffected
* Class II - rapid blood loss of 15-30% willl cause shock and reduce MAP, will cause tachycardia
* Class III - rapid loss of blood of over 30% - this causes severe and sometimes irreversible shock, a significant fall in MAP - there can be a reduction in sympathetic outflow which can cause bradycardia

Question 5

What things does hypovolemia decrease?

Answer 5

• decreases central venous pressure - as there is less blood in the circulation
• this reduces end siastolic volume
• this then reduces stroke volume
• which reduces pulse pressure and MAP
• a reduction in pressure decreases the baroreceptor activity

Question 6

How does the body respond initially to hypovolemia?

Answer 6

• As there is a** reduction in blood volume and pressure**, there is a decline in baroreceptor activity which increases the sympathetic outflow
• the sympathetic outflow will **cause vasoconstriction **and therefore increase total peripheral resistance - which helps to maintain BP
• due to the low blood pressure and decrease in renal blood flow, renin is released and activates angiotensin II which also stimulates the** adrenal gland to release NA** and also secretion of ADH - they all support the sympathetic outflow and constrict the vessels to help maintain blood pressure

Question 7

What affect does ADH have on coronary and cerebral arteries?

Answer 7

ADH can cause vasodilatation of the cornoary and cerbral arteries to increase perfusion - CARDIAC OUTPUT IS REDISTRIBUTED TO THE HEART AND BRAIN

Question 8

Explain briefly the difference in the compensated vs decompensated phases of the haemorrhage

Answer 8

• compensated (non - hypotensive phase) - loss of up to 15% blood volume and MAP is maintained
• Decompensated (hypotensive phase) - loss of over 30% of blood volume and **MAP falls rapidly **

Question 9

What mechanisms does the componsated phase involve?

Answer 9

it involves a negative feedback loop (allows for regulation)
* there is an increased sympathetic outflow and decreased parasymp outflow - which increases heart rate and cardaic output and causes vasoconstriction
* NA and other vasoconstrictor hormones further increase total periperal resistance
* adrenaline and glucagon also stimulate glycogenolysis - which raises osmolarity of plasma and IF to draw fluid from the ICF into the circulation