Orthostatic Hypotension

What orthostatic hypotension is

When you stand, gravity pulls about half a liter to a liter of blood down into the legs and belly. Normally, pressure sensors in the neck and chest detect the drop within seconds. The autonomic nervous system tightens blood vessels and speeds up the heart a little, so blood pressure barely changes.

In orthostatic hypotension, this reflex is too slow or too weak, or there is not enough blood volume to begin with. Blood pressure falls, the brain gets less blood flow, and you feel faint.

Types by timing

• Classic: a drop within 3 minutes of standing. This is the standard definition.
• Initial: a brief, large drop in the first 15 seconds, the "head rush" many healthy young people get. It is usually harmless.
• Delayed: a drop that happens after more than 3 minutes of standing, often an early sign of autonomic failure.

In people with high blood pressure when lying down, a drop of 30 mmHg systolic is sometimes used as the threshold.

Neurogenic vs non-neurogenic

Causes and risk factors

Common, often reversible causes

• Dehydration from vomiting, diarrhea, fever, heat, or not drinking enough
• Medicines: diuretics, alpha-blockers (tamsulosin, doxazosin), other blood pressure tablets, nitrates, erectile dysfunction drugs, tricyclic antidepressants, antipsychotics, Parkinson's medicines and opioids
• Alcohol
• Prolonged bed rest or deconditioning
• Large meals, especially high in carbohydrates, which divert blood to the gut (postprandial hypotension)
• Blood loss or anemia
• Hot baths, saunas and hot weather

Heart causes

Heart failure, aortic stenosis, a very slow or irregular heart rhythm and heart attack can all limit the heart's ability to raise output on standing.

Nerve (neurogenic) causes

• Diabetes and other causes of autonomic neuropathy, such as amyloidosis, vitamin B12 deficiency, alcohol and some autoimmune conditions
• Parkinson's disease, multiple system atrophy, Lewy body dementia and pure autonomic failure
• spinal cord injury above the mid-chest

Endocrine causes

Adrenal insufficiency (Addison's disease) and, rarely, other hormone disorders.

Risk rises with age because blood vessels stiffen, the reflex slows and people take more medicines.

Symptoms

Symptoms happen on standing up, after standing for a while, or after exertion, and ease when you sit or lie down:

• lightheadedness, dizziness or feeling about to faint
• blurred, grayed or tunnel vision
• weakness or wobbly legs
• difficulty concentrating or feeling foggy
• an ache across the back of the neck and shoulders ("coat hanger" pain)
• nausea
• fainting (syncope)

Symptoms are usually worse in the morning, after meals, in heat, after exercise and after alcohol. Some older adults have large blood pressure drops without symptoms, but still have an increased risk of falls.

Orthostatic hypotension vs other causes of fainting

How it is diagnosed

• Orthostatic vital signs: blood pressure and heart rate after 5 minutes lying down, then at 1 and 3 minutes after standing. This simple test confirms most cases.
• Medicine review: including over-the-counter drugs and supplements.
• Blood tests: blood count, kidney function, electrolytes, glucose, B12 and morning cortisol if adrenal insufficiency is suspected.
• ECG and sometimes an echocardiogram or heart rhythm monitor.
• Tilt-table test: monitors blood pressure and heart rate while you are tilted upright on a table. It detects delayed orthostatic hypotension and separates it from vasovagal syncope and POTS.
• Autonomic function tests and neurological assessment if a nerve cause is suspected.

Treatment

Remove or adjust the cause

Treat dehydration, bleeding or infection, and review medicines. Stopping or lowering a diuretic or alpha-blocker, or taking it at bedtime, often fixes the problem. Do not stop prescribed medicines without talking to your doctor.

Everyday measures

• Stand up in stages: sit on the edge of the bed for a minute, then stand. Flex your calves or march on the spot before walking.
• Drink enough: usually 2 to 2.5 liters (about 8 to 10 cups) a day unless you have heart or kidney failure. Drinking about 500 ml (2 cups) of water quickly can raise blood pressure for an hour, useful before getting up in the morning.
• Increase salt if your doctor advises it, sometimes with salt tablets.
• Eat smaller, lower-carbohydrate meals and limit alcohol.
• Compression: waist-high compression stockings or an abdominal binder reduce pooling.
• Counter-maneuvers: crossing your legs, squeezing your buttocks and thighs, or squatting when you feel faint.
• Raise the head of your bed by about 10 to 20 degrees. This reduces overnight fluid loss and high blood pressure when lying down.
• Avoid triggers: hot showers, standing still for long periods and straining.
• Stay active with recumbent exercise such as cycling or swimming to avoid deconditioning.

Medicines

When symptoms persist, especially in neurogenic orthostatic hypotension, doctors may prescribe:

• midodrine, which tightens blood vessels; taken during the day and not within several hours of lying down
• droxidopa, approved for neurogenic orthostatic hypotension
• fludrocortisone, which helps the body retain salt and water
• pyridostigmine, in some cases

These can cause high blood pressure when lying down, so home blood pressure checks lying and standing are important.

Complications and outlook

The main risks are falls, fractures and head injuries. Orthostatic hypotension is also linked to higher rates of heart disease, stroke and cognitive decline, especially when it is neurogenic. Medicine-related and dehydration-related cases usually resolve once the cause is corrected. Neurogenic orthostatic hypotension is usually long-term but can be well managed with the measures above.

Frequently asked questions

What is the definition of orthostatic hypotension?

It is a sustained drop in systolic blood pressure of at least 20 mmHg, or diastolic of at least 10 mmHg, within 3 minutes of standing from lying down. Symptoms are common but not required for the diagnosis.

Is orthostatic hypotension the same as postural hypotension?

Yes. Both terms describe low blood pressure on standing. "Orthostatic" means related to standing upright. Some people use postural hypotension more casually for dizziness on changing position, but medically they mean the same thing.

What is the most common cause of orthostatic hypotension?

In older adults, medicines and dehydration are the most common causes, often together. Diuretics, alpha-blockers for the prostate and other blood pressure drugs are frequent culprits. In younger people, dehydration and prolonged bed rest are common triggers.

Can orthostatic hypotension be cured?

When it is caused by dehydration, a medicine or bed rest, it usually goes away once the cause is fixed. Neurogenic orthostatic hypotension from nerve damage is usually long-term, but symptoms can be controlled with fluids, salt, compression, careful position changes and medicines.

What drink raises blood pressure quickly?

Drinking about 500 ml (2 cups) of plain water quickly can raise blood pressure within 5 to 15 minutes in people with autonomic failure, and the effect lasts about an hour. Salty fluids such as broth also help. Caffeine has a modest effect in some people.