Low blood pressure (medically referred to as hypotension) can be defined as blood pressure below the normal blood pressure range. Most of the time it is benign but at times it can be fatal if ignored.
Low blood pressure readings can differ from person to person.
Quite a few people suffer from low blood pressure, but they need not worry unless they experience certain health symptoms like dizziness and fainting.
In such cases, they should seek medical advice because symptoms usually appear when the blood pressure is too low. The causes of the low blood pressure have to be detected and accordingly treated.
What is blood pressure?
Blood Pressure is the pressure exerted on the inner walls of the arteries by the blood during its flow. It varies during the contraction and relaxation of the heart, and accordingly, it is called systolic blood pressure and diastolic blood pressure.
The normal blood pressure readings for systolic and diastolic are defined and when the blood pressure falls below the normal levels, it is called low blood pressure.
The American Heart Association (AHA) recommends having a target blood pressure below 120 mm Hg systolic and 80 mm Hg diastolic.
What is the systolic and diastolic blood pressure range?
The pressure of blood exerted at the time of contraction of the heart (systolic pressure) is higher than the pressure exerted during the relaxation of the heart (diastolic pressure).
The normal healthy systolic blood pressure range is 120 to 140 mm of Hg and the normal diastolic pressure range is 60 to 90 mm Hg. The blood pressure is thus mentioned as 120/80 mm of hg which simply means that the systolic pressure is 120 and the diastolic pressure is 80 mm hg. The lower the blood pressure within the normal range, the better it is.
‘ Hg ‘ is the chemical abbreviation for mercury and a mercury column is used in the glass tube of the conventional blood pressure measuring instrument called the sphygmomanometer.
There are other types of instruments also available for measuring blood pressure such as the dial instrument or the digital instrument.
What is the Low Blood Pressure Range?
Hypotension, or low blood pressure, occurs when blood pressure is too low. The AHA defines this as 90/60 mm Hg.
Blood Pressure readings below 90/60 mm hg are considered to be low. To be defined as a low blood pressure patient, you need to have only one of the readings to be below the normal range.
Most of the time there are no effects on the body and no symptoms present themselves. In such cases, even though low blood pressure is detected, the physician does not advocate any treatment.
However, lower blood pressure can give rise to problems and this warrants immediate medical intervention. Certain symptoms and complications arise and you should not neglect them. Seek medical help.
Low blood pressure causes less flow of blood to the various organs in the body like the brain, the heart, the liver, the kidneys, etc.
This reduced blood supply and the resulting deficient oxygen supply cause the organs to function less than they should, and symptoms and signs pertaining to those organs are manifested.
For example, less blood flow to the brain tissue will result in the patient feeling dizzy or may even faint. These signs and symptoms are discussed under the relevant title.
A sudden fall in blood pressure can be serious. A drop of just 20 mm Hg can make you feel giddy or faint. For example, such symptoms can develop after a drop in systolic pressure from 110 mm Hg to 90 mm Hg.
Bigger drops can be life-threatening due to the complications that can develop. Severe hypotension can be caused by shock due to sudden blood loss, acute infection, heart attack, or severe allergic reaction (anaphylaxis).
Prolonged and severe hypotension causes a lack of blood flow to the body’s organs causing them to fail. Lack of blood supply to the brain can result in stroke.
Similarly, lack of blood supply to the heart can lead to a heart attack, lack of blood supply to the kidneys can cause kidney failure, and to the bowels can lead to bowel ischemia (decreased blood supply to the small and large intestines). Shock and death ultimately result from prolonged severe low blood pressure.
Types of Hypotension
Hypotension is of three types: postural hypotension, postprandial hypotension, and neurally mediated hypotension.
Postural or orthostatic hypotension
The American Academy of Family Physicians (AAFP) defines postural hypotension as follows:
“Orthostatic hypotension is defined as a decrease in systolic blood pressure of 20 mm Hg or a decrease in diastolic blood pressure of 10 mm Hg within three minutes of standing when compared with blood pressure from the sitting or supine position.”
At such times, when your blood pressure drops, less blood can go to your muscles and organs such as the brain. This can cause dizziness and make you more likely to fall.
Most people with postural hypotension do not have any symptoms, except dizziness on getting up from a sitting or lying down position.
Some people have other symptoms and they can vary from person to person. The most common symptoms that can develop include dizziness or lightheadedness, feeling faint, passing out, or falling down, headaches, and blurry vision.
Symptoms usually appear in the morning when you get up from the bed. Factors that trigger the symptoms include:
- A large meal
- Alcohol
- Exercise
- Straining when passing stools
- Anxiety
Causes of postural hypotension can be associated factors such as:
- Chronic conditions such as high blood pressure, diabetes, heart failure, atherosclerosis
- Medications such as diuretics, antidepressants, or blood pressure medicines,
- Neurological conditions like Parkinson’s disease and dementia
- Anemia
- Dehydration
- Vitamin B12 deficiency
- Alcoholism
- Prolonged bed rest
Treatment is mainly supportive and consists of avoiding the trigger factors. It is explained in detail in this post.
Postprandial hypotension
The AAFP defines postprandial hypotension as follows:
“In postprandial hypotension, there is a decrease in systolic blood pressure of at least 20 mm Hg within 75 minutes of a meal.“
This temporary fall in blood pressure can cause symptoms such as dizziness, nausea, and even fainting increasing the risk of fall-related injuries.
Postprandial hypotension is more common in older people and those with chronic health conditions such as diabetes and Parkinson’s disease.
However, in most individuals with postprandial hypotension, the condition is mild and they do not have any other symptoms. In some people, postprandial hypotension can become quite serious.
Older people with high blood pressure, type 2 diabetes, or Parkinson’s disease are most likely to be affected. It can also affect those on antihypertensive medication.
While the cause of postprandial hypotension is not completely understood, it is possibly due to the excess pooling of blood in the abdominal organs after a meal during digestion.
Due to this excess pooling of blood in the digestive tract, the amount of blood in the general circulation is reduced causing a drop in blood pressure and various symptoms.
Neurally mediated hypotension
Neurally mediated hypotension, also referred to as neurally mediated syncope, vasovagal syncope, and neurocardiogenic syncope, is a transient loss of consciousness characterized by peripheral arterial vasodilation and bradycardia.
It is a subtype of orthostatic hypotension and happens due to a drop in blood pressure that occurs after prolonged standing. This happens due to autonomic dysfunction caused by faulty communication between the brain and heart.
This type of hypotension mostly affects young adults and children. It might result from certain trigger factors such as stress due to standing for prolonged periods, emotional stress, urination, coughing, and physical exercise.
Symptoms and signs can include slow heart rate, lightheadedness, dizziness, pressure or pain in the left side of the chest, visual disturbances, loss of consciousness, weakness, and slurred speech.
It is treated with increased water and salt intake to correct dehydration, avoiding trigger factors, and use of abdominal binders and compression stalking. Some drugs that regulate blood pressure may be used.