Lecture 29. Physiological Responses of the CV System: In Health and Injury Flashcards
What is a haemorrhage?
Rapid loss of blood
What maintains cardiac output?
Blood pressure
What happens to cardiac output during a haemorrhage?
Loss of pressure leads to lower cardiac output
Dangerously rapid loss of blood: Fall in blood volume → fall venous return
What causes initial corrections during a haemorrhage?
Baroreceptor complexes
What does increasing cardiac output do to a haemorrhage?
Increases rate of haemorrhage
What does an increased drive to vasculature (sympathetic) cause during a haemorrhage?
Stops blood flow to metabolising tissue
What does oncotic pressure recruit as hydrostatic pressure decreases?
Insterstitial fluid
Reabsorption of fluid throughout the capillary bed at the expense of viscosity
What is secreted to correct loss of blood volume?
Renin and Angiotensin II
What is secreted to correct for loss of red blood cells?
Erythropoietin
How many classes of haemorrhage are there?
4
What are class I haemorrhages?
15% of blood volume lost
No change in vital signs (i.e. blood donation)
What are class II haemorrhages?
15-30% of total blood volume lost
Tachycardia, narrowing of the difference between the systolic and diastolic blood pressures, peripheral vasoconstriction
Skin looks pale and is cool to the touch
The patient may exhibit changes in behaviour
What are class III haemorrhages?
30-40% of blood volume lost
Heart rate increases, blood pressure drops, the peripheral hypoperfusion (shock), mental status worsens
Fluid resuscitation with crystalloid and blood transfusion are necessary
What are class IV haemorrhages?
> 40% of blood volume lost
The limit of the body’s compensation is reached and aggressive resuscitation is required to prevent death
What does exercise require?
Redistribution of blood supply to skeletal muscles
