Blood pooling explained Gravity dramatically affects blood flow whenever you stand up from sitting or lying down — on average, about ml of blood temporarily pools in the blood vessels of the legs. Sensors called baroreceptors located in the three major arteries — the aorta and the two carotid arteries — detect this drop in blood pressure.
In a healthy person, the cardiovascular system and the autonomic nervous system quickly respond by increasing the heart rate and directing blood vessels in the legs and abdomen to constrict tighten. These measures maintain adequate blood pressure to the brain. This compensatory mechanism to increase blood pressure does not occur, or may be delayed, in a person with orthostatic hypotension.
Their blood pressure remains low, which triggers symptoms. Blood pressure typically returns to normal once the person sits or lies down again, but this depends on the severity of the underlying cause. Causes of orthostatic hypotension Orthostatic hypotension usually results from an underlying disorder. It is not a disease in itself. Other causes of dizziness Remember there are other causes of dizziness, light-headedness and nausea, apart from postural hypotension.
One example is ear disease. It is always important to seek medical advice for any unexplained symptoms. Old age is an important risk factor The incidence of orthostatic hypotension increases with age. One US study found that every elderly participant had some degree of orthostatic hypotension. Factors that seem to increase the risk in elderly people include: Digestion — when you eat and then digest food, an increased blood supply is sent to your intestines. Orthostatic hypotension is more likely to occur about 15 to 45 minutes after eating a meal this is known as post-prandial hypotension.
Standing — if you stand up for a long time, it causes a slow but steady drop in blood pressure. Frailty and chronic sickness — these are more common in old age. Diagnosis of orthostatic hypotension Tests used to diagnose orthostatic hypotension include: Medical history, including medical conditions and drugs taken on a regular basis Physical examination Measuring blood pressure when lying down versus standing up Blood tests to check, for example, blood sugars or adrenal hormones Echocardiography, an imaging scan of the heart, to check for certain heart conditions Other tests, depending on individual factors.
Treatment of orthostatic hypotension Treatment depends on the cause. Options may include: Fluids to treat dehydration Management of diabetes, such as regular insulin injections Changes in medication or altered doses if drugs are the cause sometimes, however, stopping or altering the dose of a particular medication may cause more harm than good and must be carefully considered in consultation with your doctor Medication, surgery or both to treat heart conditions Medication to increase blood volume or pressure, including corticosteroids Medications to treat orthostatic hypotension including pyridostigmine, a drug used in the treatment of myasthenia gravis A range of treatments, since orthostatic hypotension may have two or more causes In some cases, a lower body pressure suit is required.
Get up slowly from a sitting or lying position to allow your blood vessels time to adjust. Wear support stockings to reduce the pooling of blood in the legs, which helps to boost blood pressure throughout the body.
Eat small, frequent meals instead of three large meals per day. Symptoms of faintness, light-headedness, dizziness, confusion, or blurred vision occur within seconds to a few minutes of standing particularly after lying in bed or sitting for a long time and resolve rapidly when the person lies down. However, some people fall, faint, or very rarely have a brief seizure. Vomiting, diarrhea, excessive sweating, burns, kidney failure, and use of diuretics may cause dehydration.
People feel thirsty, and as dehydration Some younger people experience similar symptoms upon standing but without having a drop in blood pressure. Often, their heart rate increases tachycardia more than normal upon standing, so this condition is called postural orthostatic tachycardia syndrome POTS.
The reason why such people feel dizzy despite having normal blood pressure is not yet clear. Dizziness or light-headedness when standing up occurs as a result of abnormal blood pressure regulation. Normally, when people stand, gravity causes blood to pool in the veins of the legs and trunk.
This pooling lowers the blood pressure and the amount of blood the heart pumps to the brain. Low blood flow to the brain causes the dizziness and other symptoms. To compensate, the nervous system quickly increases the heart rate and constricts blood vessels, which rapidly returns blood pressure to normal before symptoms can develop.
The part of the nervous system responsible for this compensation is the autonomic nervous system Overview of the Autonomic Nervous System The autonomic nervous system regulates certain body processes, such as blood pressure and the rate of breathing. Many disorders can cause problems with blood pressure regulation and lead to dizziness when standing up. Categories of causes include. The most common causes of dizziness when standing up that has been present for a long time chronic include.
People who become dizzy or light-headed when standing up often recover quickly when they sit down and then slowly stand again. However, it is usually important to determine what is causing the dizziness. The following information can help people decide when to see a doctor and help them know what to expect during the evaluation. In people who become dizzy or light-headed when standing up, certain symptoms and characteristics are cause for concern.
They include. People who have warning signs should see a doctor right away. Other people who have frequent or ongoing episodes of dizziness upon standing should see a doctor when practical. Typically a delay of a week or so is not harmful. People who have only an occasional episode of dizziness upon standing should call their doctor. The doctor will decide whether and how quickly to see the person depending on the other symptoms and medical history.
The doctor first asks questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause of the dizziness and the tests that may need to be done. Whether the person has experienced conditions that are known to cause dizziness such as bed rest or fluid loss.
Whether the person has a disorder such as diabetes, Parkinson disease, or a cancer that may cause dizziness. The doctor then does a physical examination. The person lies down for 5 minutes, and then the doctor measures the blood pressure and heart rate. Blood pressure and heart rate are measured again after the person stands or sits up for 1 minute and again after standing or sitting for 3 minutes.
Orthostatic hypotension — also called postural hypotension — is a form of low blood pressure that happens when you stand up from sitting or lying down. Orthostatic hypotension can make you feel dizzy or lightheaded, and maybe even cause you to faint. Orthostatic hypotension may be mild, and episodes can last for less than a few minutes.
However, long-lasting orthostatic hypotension can signal more-serious problems, so it's important to see a doctor if you frequently feel lightheaded when standing up. Occasional acute orthostatic hypotension is usually caused by something obvious, such as dehydration or lengthy bed rest, and is easily treated. Chronic orthostatic hypotension is usually a sign of another health problem, so treatment varies. The most common symptom is lightheadedness or dizziness when you stand up after sitting or lying down.
Symptoms usually last less than a few minutes. Occasional dizziness or lightheadedness may be fairly minor — triggered by mild dehydration, low blood sugar or overheating. Dizziness or lightheadedness may also happen when you stand after sitting for a long time. If these symptoms happen only occasionally, there's likely no cause for concern.
It's important to see your doctor if you have frequent symptoms of orthostatic hypotension because they can signal serious problems. It's even more urgent to see a doctor if you lose consciousness, even for just a few seconds. Keep a record of your symptoms, when they occurred, how long they lasted and what you were doing at the time. If these occur at dangerous times, such as while driving, discuss this with your doctor.
When you stand up, gravity causes blood to pool in your legs and abdomen. This decreases blood pressure because there's less blood circulating back to your heart. Normally, special cells baroreceptors near your heart and neck arteries sense this lower blood pressure. The baroreceptors send signals to centers in your brain, which signals your heart to beat faster and pump more blood, which stabilizes blood pressure. These cells also narrow the blood vessels and increase blood pressure.
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