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Orthostatic hypotension is defined as an excessive fall in blood pressure when an upright position is assumed This excessive fall in blood pressure is greater than 20mmHg systolic or greater than10mmHg diastolic or both After this fall in blood pressure the patient may experience symptoms such as lightheadedness blurred vision confusion or feeling pre syncopal On an extreme end patients may actually have syncopal episodes or even seizures Higginson 2016 Typically when a person stands up blood pools in the lower extremities and trunk Up to 1L of blood may pool which then decreases the venous return to the heart There are baroreceptors in the aortic arch and carotid bodies that activate the sympathetic nervous system which helps the blood pressure quickly rise back to normal levels This activation also causes an increase in cardiac contractility and heart rate and increases peripheral vascular resistance These responses increase peripheral blood pressure and increase the cardiac output Finally there is vagal inhibition which inhibits slowing down of the heart rate further increasing the heart rate and thus cardiac output Therefore upon standing there are many mechanisms in place to ensure the blood pressure does not drop significantly Higginson 2016 Normally systolic blood pressure will fall 5 10mmHg diastolic pressure will rise 5 10mmHg and heart rate will increase by 10 25 beats minute Kaufmann 2015 Orthostatic hypotension occurs when one of these back up mechanisms fail In the elderly it has been found that they have decreased baroreceptor sensitivity This decreased sensitivity will then cause a decrease in the response of the sympathetic nervous system and decreased inhibition of the vagal nerve This then allows the systolic and diastolic blood pressure to drop without an increase in heart rate
