Understanding Low Blood Pressure
What Is Low Blood Pressure?
Hypotension is the medical term for low blood pressure (less than 90/60). Normal blood pressure is usually in the range of 120/80 (systolic/diastolic). In healthy people, especially athletes, low blood pressure is a sign of good cardiovascular (heart and blood vessel) health. But low blood pressure can be a signal of an underlying problem especially in the elderly. In this population, low blood pressure may cause inadequate blood flow to the heart, brain and other vital organs.
Chronic low blood pressure is almost never serious. But health problems occur when blood pressure drops suddenly and the brain is deprived of an adequate blood supply. This can lead to dizziness or lightheadedness. It most commonly occurs in someone who's rising from a prone or sitting position to a standing position. In such cases, it is known as postural hypotension, orthostatic hypotension, or neurally mediated orthostatic hypotension.
Postural hypotension is considered a failure of the autonomic nervous system -- the part of the nervous system that controls involuntary vital actions, such as the heartbeat to react appropriately to sudden changes. When you stand up, some blood pools in your lower extremities. Uncorrected, this would cause your blood pressure to fall. However, normally your body compensates by sending messages to your heart to beat faster and to your blood vessels to constrict. This offsets the drop in blood pressure. If this does not happen, or happens too slowly, postural hypotension results.
The incidence of both low and high blood pressure normally increases with age, due in part to normal changes. In addition, blood flow in the brain declines with age, often as a result of plaque buildup in blood vessels. So the prevalence of postural hypotension also increases with age; an estimated 10-20% of elderly people have postural hypotension.
What Causes It?
The cause of low blood pressure isn't always clear. It may be associated with the following:
Sudden drops in blood pressure can be life-threatening. Causes of this type of hypotension include:
- Hormonal problems such as an underactive thyroid
(hypothyroidism), overactive thyroid (hyperthyroidism), diabetes and low blood sugar (hypoglycemia).
- Many over-the-counter medications.
- Overdose of high blood pressure drugs.
- Heart failure.
- Heart arrhythmias (abnormal heart rhythms).
- Widening, or dilation, of the blood vessels.
- Heat exhaustion or heat stroke.
- Liver disease.
Postural hypotension can happen to anyone for a variety of reasons, such as dehydration, lack of food, prolonged standing in the heat, or being generally run down. It can also be influenced by genetic make-up, aging, medication, dietary and psychological factors, and acute triggers, such as infection and allergy.
Postural hypotension occurs most frequently in people who are taking drugs to control high blood pressure (hypertension). It can also be related to pregnancy, strong emotions, hardening of the arteries (atherosclerosis), or diabetes. The elderly are particularly affected, especially those who have high blood pressure or autonomic nervous dysfunction. Postprandial (after meals) hypotension is estimated to affect up to one-third of elderly people and is a common cause of dizziness and falls after eating.
Several drugs are commonly associated with postural hypotension. These medications can be divided into two major categories 1) medications and 2) other common causes:
- Loss of blood (bleeding).
- Low body temperature.
- High body temperature.
- Heart muscle disease causing heart failure.
- Sepsis, a severe blood infection.
- Severe dehydration.
- A reaction to medication.
- Severe allergic reaction (anaphylaxis).
Common causes of naturally occurring postural hypotension include:
- Drugs used to treat high blood pressure, such as diuretics, beta-blockers, calcium channel blockers, and angiotensin-converting enzyme (ACE) inhibiting drugs.
- Drugs that have hypotension as a side effect, including nitrates, drugs for Parkinson's disease, antipsychotics, neuroleptics, anti-anxiety agents, sedative-hypnotics and tricyclic antidepressants.
Common causes of pathologic (attributable to a disease) postural hypotension include:
- Dehydration and electrolyte loss, which may result from another condition, such as diarrhea or vomiting or excessive blood loss during female menstruation.
- Age-associated decline in blood pressure regulation, which may be worsened by certain health conditions or medications.
- Central nervous system disorders, such as Shy-Drager syndrome. (multiple system neuropathy)
- Peripheral neuropathy and autonomic neuropathy (nerve problems), such as may be caused by diabetes.
- Cardiovascular disorders.
- Nutritional diseases.
Less common causes include diseases such as amyloidosis (caused by deposits of a waxy substance called amyloid in the body), vitamin deficiencies, spinal cord injuries, and neuropathies associated with cancer, particularly lung cancer or pancreatic cancer.
What Are the Symptoms of Low Blood Pressure?
- Dimming or blurring of vision
- Cognitive impairment
- Head or neck discomfort
- Cold, clammy skin
Call Your Doctor If:
You experience an increased frequency of symptoms of low blood pressure that are interfering with your lifestyle, that pose a risk for injury from falling, or that you suspect may be a side effect of prescription or nonprescription medication.
If blood pressure gets severely low, there's a significant danger that the body will not receive enough oxygen to carry out normal function. Decreased oxygen to the body can result in impaired functioning of the heart and brain and cause difficulty with breathing. In addition, someone with low blood pressure can lose consciousness or go into shock, where the organs shut down.
Thus, it is important to seek medical care immediately if you experience any signs of low blood pressure.
How Do I Know If I Have Low Blood Pressure?
Your doctor can determine if you are having significant low blood pressure. Symptoms of dizziness and lightheadedness upon standing do not necessarily mean that you have postural hypotension, or low blood pressure. A wide range of underlying conditions may cause these symptoms. It's important to identify the cause of the low blood pressure so the appropriate treatment can be given.
What Are the Treatments?
If you have an underlying medical problem that causes low blood pressure, seek treatment for the underlying condition. For many people, chronic low blood pressure can be effectively treated with diet and lifestyle changes.
Initially, your doctor may counsel you to increase your blood pressure by making these simple changes: