Knowra Orthostatic hypotension Orthostatic hypotension Orthostatic hypotension is a sustained fall in blood pressure after standing from sitting or lying down. It can reduce blood flow to the brain, causing dizziness, blurred vision, or fainting.
Baroreflex : A rapid autonomic reflex that stabilizes blood pressure by adjusting heart rate, vascular tone, and cardiac output. Its failure to compensate for blood pooling after standing is a common mechanism.
Orthostatic vital signs : Blood pressure and heart rate measurements taken after lying down and at timed intervals after standing. They document the pressure change used to assess suspected orthostatic hypotension.
Dehydration : A deficit of body water that can reduce circulating blood volume. Lower circulating volume makes standing-related pressure drops more likely.
Postural orthostatic tachycardia syndrome : A chronic orthostatic intolerance syndrome marked by excessive heart-rate increase on standing without orthostatic hypotension. Its defining heart-rate rise occurs without the qualifying sustained blood-pressure fall.
Venous pooling : Accumulation of blood in the veins, especially in the legs, when venous return to the heart is reduced. Gravity increases pooling on standing, lowering the blood returning to the heart.
Initial orthostatic hypotension : A brief, marked blood pressure drop occurring within seconds of standing. Its rapid onset distinguishes it from sustained orthostatic hypotension.
Medication-induced orthostatic hypotension : Orthostatic hypotension caused or worsened by medications that affect blood volume, vascular tone, or heart rate. Medication review can identify a reversible contributor to the pressure drop.
Vasovagal syncope : A reflex faint caused by sudden vasodilation and often slowing of the heart, commonly after prolonged standing or emotional triggers. It can follow upright posture but involves a distinct reflex episode rather than persistent orthostatic pressure loss.
Autonomic nervous system : The nervous system that regulates involuntary functions, including heart rate, blood pressure, and digestion. Its sympathetic responses normally constrict vessels and support pressure after standing.
Delayed orthostatic hypotension : A sustained blood pressure fall that appears after more than three minutes upright. It can be missed when standing measurements stop too early.
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