Hypotension: Low Blood Pressure Facts and Causes
- Publish Date: 2013/08/19 - (Rev. 2018/06/29)
- Author: Thomas C. Weiss
- Contact : Disabled World
Outline: Information, causes and affects of low blood pressure or Hypotension when systolic blood pressure is less than 90 mm Hg or diastolic less than 60 mm Hg.
In physiology and medicine, hypotension is defined as low blood pressure, especially in the arteries of the systemic circulation. Hypotension is generally considered systolic blood pressure less than 90 millimeters of mercury (mm Hg) or diastolic less than 60 mm Hg.
A desired blood pressure is less than 120/80. In people who are considered to be healthy, low blood pressure without experiencing any symptoms is commonly not a concern and does not need to be treated. Low blood pressure may be a sign of an underlying issue, particularly in seniors, where it might cause inadequate blood floor to their heart, vital organs, and brain.
A person's blood pressure reading appears as two numbers:
- The first and higher of the two numbers is a measure of "systolic" pressure or the pressure in the person's arteries when their heart beats and fills them with blood.
- The second number measures, "diastolic," pressure or the pressure in the person's arteries when their heart rests between beats.
Fortunately, chronic low blood pressure without symptoms is rarely serious.
Health issues may happen; however, when a person's blood pressure suddenly drops and their brain is deprived of an adequate blood supply. The condition may lead to lightheadedness or dizziness. A sudden drop in blood pressure usually happens in a person who has risen from a prone or sitting position to a standing one. When this occurs it is referred to as, 'orthostatic hypotension,' or, 'postural hypotension.' Another type of low blood pressure may happen when a person stands for extended periods of time; it is referred to as, 'neurally mediated hypotension.'
Postural hypotension is considered to be a failure of a person's cardiovascular system or nervous system to react appropriately to sudden changes. Usually, when a person stands up, some of their blood pools in their lower extremities. If this remains uncorrected, it would cause the person's blood pressure to fall or decrease. A person's body usually compensates by sending messages to their heart to beat faster and to their blood vessels to constrict, offsetting the drop in blood pressure. If this does not happen, or does not happen quickly enough, postural hypotension is the result.
Chart showing potential causes of low blood pressure
The risk of low and high blood pressure commonly increases as a person ages due in part to changes during the aging process. The flow of blood to a person's heart muscle and brain declines as a person ages, many times as a result of plaque buildup in their blood vessels. Approximately 10-20% of people over the age of 65 experience postural hypotension. While the causes of low blood pressure may not always be clear, it might be associated with things such as:
- Heart failure
- Liver disease
- Heart arrhythmias
- Widening of the blood vessels
- Some over-the-counter drugs
- Heat exhaustion or heat stroke
- Some prescription medications
- Hormonal issues such as an under-active thyroid, diabetes, or low blood sugar
Causes of Sudden Drops in Blood Pressure
Chart showing causes of sudden drops in blood pressure
Sudden drops in a person's blood pressure may be life-threatening. A number of different things may cause this type of hypotension. The causes of sudden drops in blood pressure may include:
- Loss of blood
- Heart muscle disease
- Low body temperature
- High body temperature
- A reaction to alcohol or medication
- Anaphylaxis, a severe allergic reaction
- Severe dehydration from diarrhea, vomiting, or fever
People at Risk of Postural Hypotension
Postural hypotension, or low blood pressure when a person stands up quickly, may happen to anyone for a number of reasons such as lack of food, dehydration, or simply being overly fatigued. It might also be influenced by a person's genetic make-up, medication, aging, psychological factors, dietary ones, or acute triggers such as allergy or infection. Postural hypotension happens most often in people who are taking medications to control high blood pressure or, 'hypertension.' It may also be related to strong emotions, pregnancy, diabetes, or hardening of a person's arteries. Seniors are affected by postural hypotension in particular, especially seniors who experience high blood pressure or autonomic nervous system dysfunction.
Hypotension after eating is a common cause of dizziness or even falls.
It is most common after large meals containing a lot of carbohydrates. Medical science believes it is caused by blood pooling into a person's vessels in their stomach and intestines. A number of medications are associated with postural hypotension as well. The medications may be divided into two major categories:
Medications used to treat high blood pressure such as beta-blockers, diuretics, calcium-channel blockers, and angiotensin-converting enzyme (ACE) inhibitors
Medications that have hypotension as a side effect such as anti-psychotics, neuroleptics, nitrates, anti-anxiety agents, tricyclic antidepressants, sedative-hypnotics, and medications for Parkinson's disease
Some Causes of Naturally Occurring Postural Hypotension Exist
For example, dehydration and electrolyte loss might result from vomiting, diarrhea, excessive blood loss during menstruation, or other conditions.
A person's age associated decline in blood pressure regulation is another example and is something that might worsen due to certain health conditions or medications.
Some diseases may cause postural hypotension as well. Diseases such as Shy-Drager syndrome or, 'multiple system atrophy,' nerve issues such as peripheral neuropathy or autonomic neuropathy, cardiovascular disorders, nutritional diseases, or alcoholism may cause postural hypotension.