Low blood pressure (LBP) or Hypotension occurs as a result of inadequate flow of blood to the body’s organs. In other words, LBP occurs when blood pressure in the arteries is abnormally low. People with a blood pressure reading under 90/60mmHg are usually regarded as having low blood pressure (that is, if the top number is 90 or less and if the bottom number is 60 or less).

The American Heart Association (AHA) notes that as long as a person does not experience symptoms, low blood pressure is not a problem. Having a low reading is often considered an advantage, as it reduces the risk of a dangerously high blood pressure. However, low blood pressure can be a sign of serious, even life-threatening disorders.

 

Types of low blood pressure

Low blood pressure (hypotension) is often broken down into different categories, depending on the causes or factors responsible. Some types of low blood pressure include:

  • Orthostatic, or postural, hypotension (Low blood pressure on standing up) – This occurs when there is a sudden drop in blood pressure when you stand up from a sitting or lying position.
  • Postprandial hypotension (Low blood pressure after eating) – It happens when there is a sudden drop in blood pressure after eating. Older adults are mostly affected.
  • Neurally mediated hypotension (Low blood pressure from faulty brain signals).This disorder causes blood pressure to drop after standing for long periods.
  • Multiple system atrophy with orthostatic hypotension (Low blood pressure due to nervous system damage) – Also known as Shy-Drager syndrome, it is a rare disorder that causes progressive damage to the autonomic nervous system, which controls involuntary functions such as blood pressure, heart rate, breathing and digestion. Its main characteristic is severe orthostatic hypotension in combination with very high blood pressure when lying down.

 

Causes of LBP

Some conditions that can cause low blood pressure include:

  • Pregnancy- Because a woman’s circulatory system expands rapidly during pregnancy, it is normal for your blood pressure to likely drop, and usually returns to your pre-pregnancy level after you’ve given birth.
  • Heart problems- Some heart conditions such as extremely low heart rate (bradycardia), heart valve problems, heart attack and heart failure can lead to low blood pressure. This happens because they prevent your body from being able to circulate enough blood.
  • Endocrine problems- Thyroid condition such as parathyroid disease, adrenal insufficiency (Addison’s disease), low blood sugar (hypoglycemia) and, in some cases, diabetes can trigger low blood pressure.
  • Dehydration- Occurs When your body loses more water than it takes in as a result of fever, vomiting, severe diarrhea, overuse of diuretics and strenuous exercise. Dehydration can lead to weakness, dizziness and fatigue.

Hypovolemic shock, a life-threatening complication of dehydration can also occur when low blood volume causes a sudden drop in blood pressure and a reduction in the amount of oxygen reaching your tissues. If untreated, severe hypovolemic shock can cause death within a few minutes or hours.

  • Blood loss- Losing too much blood from an injury or internal bleeding, reduces the amount of blood in your body, leading to a severe drop in blood pressure.
  • Severe infection (septicemia) – This can happen if an infection in the body enters the bloodstream leading to a life-threatening drop in blood pressure called septic shock.
  • Severe allergic reaction (anaphylaxis) – This is a severe and potentially life-threatening allergic reaction triggered by foods, certain medications, insect venoms and latex.
  • Lack of essential nutrients in your diet- Lack of some vitamins such as Vitamins B-12 and folate can cause your body not to produce enough red blood cells (anemia), causing low blood pressure.
  • Prolonged bed rest.
  • Some medications can also cause Hypotension. Examples are:
  1. Diuretics (water pills)- such as furosemide (Lasix) and hydrochlorothiazide (Microzide, Oretic)
  2. Alpha blockers- such as prazosin (Minipress) and labetalol
  3. Beta blockers- such as atenolol (Tenormin), propranolol (Inderal, Innopran XL, others) and timolol
  4. Drugs for Parkinson’s disease- such as pramipexole (Mirapex) or those containing levodopa
  5. Certain types of antidepressants (tricyclic antidepressants)- including doxepin (Silenor), imipramine (Tofranil), protriptyline (Vivactil) and trimipramine (Surmontil)
  6. Sildenafil (Viagra) or tadalafil (Cialis)- particularly in combination with the heart medication nitroglycerin

 

Symptoms of LBP

Chronically low blood pressure is considered dangerous if it causes noticeable signs and symptoms, such as:

  • Dizziness or lightheadedness
  • Nausea
  • Fainting (syncope)
  • Dehydration and unusual thirst
  • Lack of concentration
  • Blurred vision
  • Cold, clammy, pale skin
  • Rapid, shallow breathing
  • Fatigue
  • Depression

 

Diagnosis and test of LBP

Testing for low blood pressure is done to find the underlying cause, determine the correct treatment and identify any heart, brain or nervous system problems that may cause lower than normal readings. To reach a diagnosis, one or more of the following tests is recommended:

  • Blood pressure test- Measuring the blood pressure with an inflatable arm cuff and a pressure-measuring gauge. The reading is given in millimeters of mercury (mm Hg), with two numbers. The first, or upper, number measures the pressure in your arteries when your heart beats (systolic pressure). The second, or lower, number measures the pressure in your arteries between beats (diastolic pressure).
  • Blood tests – This provides information about your health generally, as well as whether you have low blood sugar (hypoglycemia), high blood sugar (hyperglycemia or diabetes) or a low number of red blood cells (anemia), all of which can cause lower than normal blood pressure.
  • Electrocardiogram (ECG) – This is a painless, noninvasive test, where soft, sticky patches (electrodes) are attached to the skin of your chest, arms and legs. The patches detect your heart’s electrical signals while a machine records them on graph paper or displays them on a screen.

ECG detects irregularities in your heart rhythm, structural abnormalities in your heart, and problems with the supply of blood and oxygen to your heart muscle. It can also tell if you’re having a heart attack or if you’ve had a heart attack in the past.

However, if your heart rhythm is abnormal or come and go, an ECG may not find any problems. If this happens, you may be asked to wear a 24-hour Holter monitor to record your heart’s electrical activity as you go about your daily routine.

  • Echocardiogram –This includes an ultrasound of your chest, showing detailed images of your heart’s structure and function by transmitting ultrasound waves, and recording their echoes with a transducer held outside your body. A computer uses the information from the transducer to create moving images on a video monitor.

Stress test – This is used because some heart problems that can cause low blood pressure are easier to diagnose when your heart is working harder than when it’s at rest. When your heart is working harder, your heart and blood pressure is monitored with electrocardiography or echocardiography.

During a stress test, you may be told to exercise, such as walking on a treadmill or given medications to make your heart work harder if you’re unable to exercise.

  • Valsalva maneuver – This test checks the functioning of your autonomic nervous system by analyzing your heart rate and blood pressure after several cycles of a type of deep breathing. You are asked take a deep breath and then force the air out through your lips, as if you were trying to blow up a stiff balloon.
  • Tilt table test – It is mostly conducted for individuals with low blood pressure on standing, or from faulty brain signals (neurally mediated hypotension). Your health care provider may suggest a tilt table test to evaluate how your body reacts to changes in position.

During the test, you lie on a table that’s tilted to raise the upper part of your body, which simulates the movement from horizontal to a standing position.

 

Prevention of LBP

The symptoms of some hypotension can be reduced through the following:

  • Standing up gradually particularly first thing in the morning. It may also be useful to try other physical movements such as stretching in bed before you get up, or crossing and uncrossing your legs if you’re seated and about to stand first to increase your heart rate and the flow of blood around your body.
  • Avoid standing for long periods of time to help prevent neutrally mediated hypotension (low blood pressure caused by miscommunication between the heart and brain).
  • Wear support stockings also called compression stockings (tight-fitting elastic socks or tights), they provide extra pressure to your feet, legs and tummy, which can help improve circulation and increase blood pressure. However, they’re not suitable for everyone; it should be used based on recommendation from your doctor.
  • Avoid caffeine intake at night and limit your alcohol intake. It can help you to avoid dehydration, which can also cause low blood pressure.
  • Eat small, frequent meals rather than large ones, lying down after eating or sitting still for a while may also help. It can help prevent postprandial hypotension (low blood pressure after eating).

 

Treatment of LBP

Low blood pressure that causes only mild symptoms or none at all rarely requires treatment. The most appropriate treatment for LBP with symptoms usually depends on the underlying cause and addressing the primary health problem (dehydration, heart failure, diabetes or hypothyroidism).

When low blood pressure is caused by medications, the medication is stopped entirely or the dose is changed. But if the cause of LBP is not clear or no effective treatment exists, the blood pressure is raised to reduce signs and symptoms. This is done depending on your age, health status and the type of low blood pressure you have. For example, you may be asked to:

  • Use more salt in your diet, to help raise your sodium level since experts usually recommend limiting the amount of salt the diet for people with raised blood pressure.

But because excess sodium can lead to heart failure, especially in older adults, it’s important to check with your doctor before increasing the salt in your diet.

  • Drink more water toprevent dehydration and increase your blood volume. Although nearly everyone can benefit from drinking enough water, this is especially true if you have low blood pressure.
  • Wear compression or elastic stockings (the type commonly used to relieve the pain and swelling of varicose veins), it may help reduce the pooling of blood in your legs.

Medications such as fludrocortisone is often used to help boost your blood volume, which raises blood pressure,  midodrine (Orvaten) to raise standing blood pressure levels in people with chronic low blood pressure that occurs when you stand up (orthostatic hypotension) by restricting the ability of your blood vessels to expand, which raises blood pressure.

Several medications, either used alone or together, can also be prescribed.

 

Article by: eDokita Team.

 Reference

  •  Shaw, Gina. ‘Pressure Drop: New evidence suggests low blood pressure may hasten mental decline in elderly people at risk for dementia’. American Academy of  Neurology. 2016.
  • American Heart Association. ‘Low Blood Pressure – When Blood Pressure Is Too Low’. 2016. Web
  • Christian Nordqvist. ‘What is Low Blood Pressure or Hypothension’. Medical News Today (MNT). 2016. Web.
  • John P. Cunha, Jay W. Marks. ‘Low Blood Pressure (Hypothension)’. MedicineNet. Com. 2016
  • Mayo Clinic Staff. ‘Low Blood Pressure (Hypothension)’. May Clinic. 2014. Web.
  • NHS. ‘Low Blood Pressure (Hypothension): Treatment’. 2015. Web.