venous pooling

Pathology

• component of orthostatic hypotension
• inadequate vasoconstrictor mechanisms in both arterioles & veins resulting in venous pooling, or hypovolemia - diminished blood volume - diminished venous return
• standing causes a gravitational shift of 300-700 mL of intravascular fluid into the lower extremities & abdomen
• the gravitational pooling of blood results in a decrease pressure detected by baroreceptors in the heart, intrathoracic vessels & carotids resulting in autonomic responses to maintain cardiac output & cerebral perfusion
• these autonomic baroreceptor responses mainly involve an increase in peripheral vasoconstriction
• an increase in venous pooling in older adults is due to decreased skeletal muscle tone & increased venous compliance

Clinical manifestations

• dizziness, orthostatic hypotension

Complications

• falls in the elderly
• a decrease in reflex peripheral vasocontriction is the most common cause of syncope

More general terms

• sign/symptom