Postural changes
Standing up
Arterial pressure = HR x SV x SVR
- Increases venous pooling
- reduced venous return to heart
- Reduced stroke volume and cardiac output
- Reflex sympathetic responses [carotid baroreceptors] ensure maintained blood pressure
- Reflex tachycardia + vasoconstriction (to maintain status quo)
- Reduction in vagal activity
Postural hypotension
- Failure to increase HR
- Vaso-vagal
- Fixed heart rate (drugs, heart block)
- Reduced stroke volume
- Fixed afterload
- Aortic stenosis
- PE
- Reduced SVR
- Vasodilators
- Sepsis
- Autonomic failure - chronic DM
