Orthostatic hypotension in hypertensive patients: symptoms, causes and coping strategies

Why did the doctor say my dizziness was caused by low blood pressure when I clearly have high blood pressure? Dr. Zhou treated an 80-year-old woman who had high blood pressure. She followed her doctor's advice and consistently took her medication, and her blood pressure was well controlled.

However, she started experiencing dizziness upon waking up in the morning or after standing for a while, and these episodes became increasingly frequent. One morning, she even tripped and fell due to a sudden blackout. She immediately went to Dr. Zhou for hospitalization.

The woman asked, "Dr. Zhou, is my dizziness because my high blood pressure has worsened?" After performing a series of tests, including ambulatory blood pressure monitoring, it was determined that the cause of her dizziness was not high blood pressure, but low blood pressure.

"What? Low blood pressure?! My blood pressure is clearly so high, how can I have low blood pressure? Do I still need to take my medication?"

Actually, this situation is not uncommon among patients with high blood pressure, especially among the elderly. What should a patient do in this situation?

First situation: Orthostatic hypotension. Orthostatic hypotension refers to a drop in systolic blood pressure of ≥20 mmHg or diastolic blood pressure of ≥10 mmHg within 3 minutes of changing from a lying to a standing position (or tilting the head at an angle of more than 60°), leading to symptoms of cerebral ischemia.

In other words, the dizziness many people experience when suddenly standing up is almost always caused by orthostatic hypotension.

Although orthostatic hypotension occurs in most age groups, it is most common in the elderly. The incidence of orthostatic hypotension in people aged 65 and above can reach 20%–50%; in my country, the incidence in people aged 80 and above is 27.2%, and the proportion is even higher in those with hypertension.

Why does orthostatic hypotension occur?

1. In a normal person, when moving from a lying to a standing position, approximately 700 mL of fluid is transferred from the internal organs to the lower limbs, significantly reducing the amount of blood returning to the heart. This activates two sensory receptors in the body: the carotid sinus and aortic arch baroreceptors, increasing sympathetic nerve tone and thus increasing cardiac output and peripheral vascular resistance to maintain blood pressure.

However, in elderly patients, the sensitivity of these two sensory receptors decreases, leading to a greater inability of the heart rate to respond promptly and blood vessels to constrict in a timely manner to maintain blood pressure.

2. Elderly patients are more prone to dehydration. The decreased responsiveness to thirst and relative hypovolemia in the elderly also increase the risk of orthostatic hypotension.

3. Decreased renin-angiotensin-aldosterone levels in the elderly reduce their ability to regulate effective blood volume through neurohumoral regulation.

4. The degree of atherosclerosis increases the risk of orthostatic hypotension in elderly patients. As people age, the degree of atherosclerosis worsens, cardiac compliance decreases, diastolic filling is impaired, venous return to the heart decreases when standing, cardiac output decreases, and the pressure regulation reflex becomes less sensitive in the elderly, thus leading to orthostatic hypotension.