Low Blood Pressure (Hypotension)

Blood pressure is the pressure that the blood exerts on the walls of blood vessels (arteries). The pressure is due to the force of blood during beating of the heart. Pressure is high during the pumping of the blood (systolic pressure) and is relatively low during the relaxing phase of heart (diastolic pressure). Blood pressure is measured using a device, the sphygmomanometer. The normal blood pressure of an adult is 120 (systolic)/80 (diastolic) mm of Hg.

Low blood pressure is also called hypotension (hypo-low, tension-pressure). It is a condition when the blood pressure drops to 90/60 mm of Hg or lower. In a majority of people, it is common and harmless and even undetected. Some people may experience slight dizziness or fainting, but if it is severe, it may create a life-threatening situation.

Low blood pressure can be due to several conditions that range from dehydration to serious surgical or medical conditions. The treatment is focused on treating the underlying cause if any. Therefore, finding out the cause of hypotension is the first step in successfully treating it. So, what causes low blood pressure? How can we tackle it? Read more to know about low blood pressure.

There are many types of low blood pressure or hypotension. These include:

• Postural or Orthostatic Hypotension
  When a person changes posture abruptly, such as standing up after lying down for a while, the blood pressure tends to drop down. This is a normal phenomenon. Blood pressure measured in the standing position will be slightly lower than that of the lying-down position. This is known as postural or orthostatic hypotension. It can cause lightheadedness or dizziness. It is a normal variation and usually does not require any treatment.
   
• Post-prandial Hypotension
  Post-prandial hypotension is a drop in the blood pressure occurring immediately after a meal. It usually occurs in older people with conditions, such as hypertension, diabetes, Parkinson disease, and multiple system atrophy. After meals, the stomach and intestines require a more blood flow for better digestion and absorption of nutrients; the body is not able to justify the demand and the mechanism that helps maintain the pressure fails, resulting in a drop in blood pressure. This is can be a problematic issue and which needs to be addressed, as it not only causes lightheadedness or dizziness but sometimes can cause fainting resulting in falls, which can cause serious injuries. The treatment of low blood pressure is relatively simple and requires alteration in diet and activities after meals.
   
• Neurally Mediated Hypotension
  Neurally mediated hypotension is also referred to as neurally mediated syncope or vasovagal syncope. It happens in response to a stressful trigger which can be either physical (hot environment, strenuous exercises) or mental stress (witnessing a gory scene such as profuse bleeding, being scared or anxious). The trigger causes an imbalance in the reflex between the heart and the brain and results in a sudden drop in blood pressure. This is again a serious issue, as it causes lightheadedness, nausea, giddiness, and collapse or fall, which can result in severe injuries. The treatment is relatively simple, and a modification of lifestyle would suffice.
   
• Severe Hypotension
  Severe hypotension means dropping of blood pressure below 90/60 mm of Hg. This results in poor blood flow to the brain and can be life-threatening. It usually happens in case of shock, which can be due to either excessive blood loss (after an injury), burns, or severe dehydration. Since it can get worse and can endanger life, it requires prompt treatment. (Read more - Anaphylactic shock)

For most people, a slight drop in pressure is temporary and does not produce any symptoms or may just produce slight dizziness. However, frequent episodes of a drop in blood pressure or severe signs and symptoms indicate an underlying health hazard. Signs and symptoms of low blood pressure include:

• Dizziness.
• Lightheadedness.
• Blurring of vision.
• Fatigue.
• Unsteadiness.
• Weakness.
• Cold and clammy skin.
• Fainting.

If the blood pressure drops drastically, it can create a life-threatening situation, referred to as shock. In such cases, the signs and symptoms slightly vary and are much more intense. These are as follows:

• Confusion (more intense in older people).
• Breathing becomes rapid and shallow. (Read more - Shortness of breath)
• Pulse is weak and rapid.
• Skin becomes pale, cold, and clammy.

Shock is usually an emergency that requires prompt treatment.

Causes

Almost all of us experience some drop in blood pressure at some point in our life, and it usually goes unnoticed. However, when the symptoms are prolonged or they keep reappearing, it requires an insight to determine the cause of it. Certain conditions can cause prolonged hypotension and are dangerous if untreated.

Causes of low blood pressure include:

Medical Conditions

There are many medical conditions that can cause hypotension. These include:

• Pregnancy
  During pregnancy, the circulatory system expands (as the blood has to be supplied to the growing baby as well), which results in a drop in blood pressure. This is normal for almost all mothers, and the blood pressure levels become normal (pre-pregnancy levels) after delivery.

• Dehydration
  When the body loses excessive water, the amount of total circulating blood can reduce, which results in a drop in the blood pressure. It usually causes dizziness, increased thirst, and weakness. Vomiting, loose motions, fever, and strenuous exercises can cause dehydration.

• Blood loss
  Haemorrhage (bleeding) or severe blood loss due to a major injury or bleeding diseases can reduce the amount of circulating blood, and this leads to a drop in the blood pressure.

• Severe infection (sepsis)
  When there is a severe infection that enters the blood, the blood pressure drops, which can be life-threatening and is called as septic shock.

• Heart problems
  Certain heart diseases, such as heart attack, heart failure, bradycardia (low heart rate), or heart valve problems, can cause low blood pressure. (Read more - Valvular heart disease)

• Endocrine problems
  Problems related to glands, such as thyroid, parathyroid, or adrenal (Addison’s disease), can cause a drop in the blood pressure. In addition, diabetes or hypoglycemia (low blood sugar level), can cause low blood pressure. (Read more - Hyperthyroidism, Thyroid cancer)

• Anaphylaxis (severe allergic reaction)
  An exaggerated allergic reaction to certain food, drugs, or insect bites can cause a sudden drop in the blood pressure. This can be a life-threatening situation and is associated with other symptoms, such as skin rashes (hives), itching, and a swollen throat. (Read more - Allergy)

• Nutritional deficiencies
  Certain nutrients, such as vitamin B12 (methylcobalamin), folic acid, can cause anaemia (megaloblastic anaemia); this can also lower the blood pressure.

Surgical Conditions

After any surgery, even if it’s a small routine procedure, there is a risk of a drop in the blood pressure.

• Anaesthesia 
  The anaesthetic drugs that are used to put you to sleep during surgery are known to lower the blood pressure. In some patients, anaesthesia causes a drastic drop in the blood pressure.

• Sepsis 
  Again, similar to medical illness, sepsis is rare but seen after surgery. In this case, hypotension can be life-threatening due to septic shock.

• Hypovolemic shock
  It usually happens in case of major surgeries, where there is either huge blood loss or fluid loss, which can result in a drop in blood amount and causing a drop in blood pressure levels. This can also be a life-threatening condition.

Medications

Certain medications are known to cause a drop in the blood pressure.

• Diuretics (furosemide, hydrochlorothiazide)
  Medicines that increase urination can cause mild dehydration and can result in a drop in pressure. These medicines are used for treating high blood pressure; so, if taken either in higher dose (than recommended) or in excess, it can result in a drop in pressure.

• Alpha-blockers (prazosin)
  These are also a class of medicines used for controlling blood pressure; usually, this medicine slows down the heartbeat and can result in a drop in pressure (again if it is taken in higher dosage or in excess).

• Beta-blockers (atenolol, propranolol)
  They are also antihypertensive drugs and when taken in excess or in higher dosage, can cause a drop in blood pressure.

• Anti-Parkinson drugs (pramipexole)
  Drugs containing levodopa are known to reduce the activity of the heart and cause bradycardia, which in turn results in the drop in blood pressure.

• Anti-depressants (doxepin, imipramine)
  These medicines reduce the brain activity and also depress the functioning of the area, which is associated with the pulse rate; it slows down the pulse rate and results in a drop in pressure.

• Drugs for erectile dysfunction
  Drugs, such as sildenafil or tadalafil, when taken along with nitroglycerine can result in a sudden drop in blood pressure.

Risk factors

Reduced blood pressure or low blood pressure can affect anyone at any age, but certain types of low blood pressure are common in certain age groups or under certain circumstances.

• Age
  Certain age groups are prone to a certain type of low blood pressure, for example, orthostatic hypotension or post-prandial hypotension, is common in older individuals (usually above 65 years of age), while neurally mediated hypotension is common on children and adolescent or even young adults.

• Diseases
  Certain disease conditions, such as diabetes, heart conditions (mitral stenosis or conductive defect), Parkinson disease, can predispose a person to hypotension or episodes of hypotension.

• Medications
  Certain medications, such as those used to control high blood pressure (alpha-blockers, diuretics, or beta-blockers), can increase the risk of hypotension.

If low blood pressure is long-standing or continuing in nature, a slight alteration in lifestyle and diet can help in overcoming the issue. Here are some changes that can help:

• Stay adequately hydrated throughout the day. Drinking sufficient fluids, especially if you are on diuretics or during the summer season can prevent hypotension.

• Exercise regularly. When you make a habit of staying fit and exercising daily it helps in regulating your blood pressure and prevents hypotension.

• Avoid alcoholic beverages. These beverages may cause a further drop in your blood pressure levels.

• Avoid sudden changes in posture. Try and avoid abrupt postural changes, such as getting up too quickly after waking up in the morning.

• Take slightly extra salt in the diet.

• For post-prandial hypotension, resting immediately after meals for about 15 minutes. This can help you prevent syncope episodes. Opt for taking smaller and frequent meals. This can also help in avoiding post-prandial hypotension.

• Avoid heavy and strenuous exercise.

• Before you start waking, do ankle or feet movements before getting up, as this improves blood circulation.

Low blood pressure is usually diagnosed using a blood pressure monitoring device (sphygmomanometer). However, that may not help in solving the problem. The goal of investigations is to find out the cause of the drop in blood pressure. This can be done by:

• Blood tests
  Evaluating haemoglobin levels, red blood cell counts, blood sugar levels, and vitamin B12 or folic acid levels help in determining the cause of hypotension.

• ECG and echocardiogram 
  ECG, when taken continuously (24 hours), also known as the Holter’s test, can help determine rhythm abnormalities of the heart, which can indicate hypotension; alternatively, echocardiography can help determine heart valve defect or defect in heart structure, which could lead to low blood pressure.

(Read more - Arrhythmia)

• Stress test 
  A stress test is a type of an ECG recorded while you are walking on a treadmill. This helps detect the drop in blood pressure when your heart is stressed or working harder.

• Tilt table test
  This is a classical test that helps detect orthostatic hypotension. The test involves recording the pressure in standing and lying-down position.

• Valsalva manoeuvre
  This is a test that helps determine the functioning of the autonomic nervous system. It is a method of recording blood pressure and heart rate after several cycles of deep breaths. It helps evaluate neurally mediated hypotension.

Usually, low blood pressure is unnoticed and does not produce any major symptoms or may produce mild symptoms, so rarely requires treatment. However, if the symptoms are continuous and have an underlying cause to it, knowing the cause and treating it resolves the issue. If low blood pressure is caused due to any medication, then changing the medicine or altering the dosage usually solves an issue.

If the cause of hypotension is not clear, the motto of the treatment is to raise blood pressure and maintain it and obviously reducing signs and symptoms. General guidelines include:

• Increase your salt intake
  It causes an increase in the fluid volume of blood and thus raises the pressure.

• Have more fluid
  Increasing water intake works similar to an increase in salt intake; it increases the fluid volume and in turn, increases blood pressure.

• Take medications prescribed by your doctor
  Your doctor may prescribe certain medicines, such as fludrocortisone or midodrine to help in increasing blood pressure. These are commonly used in the treatment of continued orthostatic hypotension.

• Wear compressions or stockings
  Compressions or stockings keep your calves contracted, which is known to pool around the blood, and these compressions do not allow the blood to settle there, thus pushing it back in circulation and raising the pressure levels.

Prognosis

The outcome of hypotension is usually excellent. If treated very well, the success rate is very high. The treatment is simple and can be administered even at home. Patients’ education plays the biggest role in the success of treatment. Most people are well educated about their condition and their clear understanding helps in not only treating but also preventing hypotension.

Complications

• If there is a mild to moderate drop in blood pressure, it can cause giddiness or dizziness, fainting, weakness, and a risk of injury due to fall. This injury can be to the head, trunk, or extremities and can cause blows or fractures.
• If there is severe hypotension, which can result in low blood flow to important organs, such as the brain or heart, it can result in permanent damage to the brain or heart. This can lead to:
  • Stroke/paralysis
  • Coma
  • Repeated fainting spells
  • Heart diseases