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Low Blood Pressure Symptoms, Signs and Causes

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Knowing low blood pressure symptoms, signs and its causes helps to understand it and recognize if you are affected by it.

What is Blood Pressure?

Blood pressure (BP) is the force exerted against the walls of arteries when the heart contracts to pump blood out and when it relaxes to fill with blood. It is the driving force which propels blood to the tissues where it delivers nutrients and oxygen and which enables it to return to the heart for replenishing with oxygen and removal of carbon dioxide.

If your BP is too low the body cannot adequately perform these functions and you experience symptoms. The amount of fluid in the arteries, strength of contraction of the heart and the degree of constriction of the blood vessels (vascular resistance) are the main factors that determine your blood pressure.

What is Low Blood Pressure?

Medical professionals call low BP hypotension. It is a BP with which you experience symptoms of inadequate blood flow to your tissues. In general terms, hypotension is a BP reading of less than 90/60. This means a systolic BP reading of less than 90, a diastolic BP reading of less than 60 or both. A definition of hypotension based strictly on BP readings does not apply to all people though. That is because individuals differ with respect to how low their blood pressure needs to be before they began experiencing symptoms.

Signs and Symptoms of Low Blood Pressure

Low blood pressure symptoms and signs or those related to the tissues suffering from decreased blood flow (perfusion) and the body’s attempt to compensate. The main tissues that cause symptoms of low blood pressure are those of the brain.

The most common brain related symptoms are dizziness and fainting. Dizziness does not mean the same to everyone. Dizziness associated with hypotension is lightheadedness as opposed to vertigo. Lightheadedness is a feeling of wanting to faint. Vertigo on the other hand is a sensation of things around you moving. One type of vertigo is rotatory, in which your surroundings are spinning like you just got off a merry-go-round. If the degree of reduced blood flow to the brain is severe it can also cause confusion or fainting (syncope). Blurred vision might occur if perfusion to the part of the brain which governs vision is inadequate.

Generalized decreased perfusion might cause a feeling of weakness. In an attempt to compensate for decreased oxygen in tissues the body mounts reflexes which result in a faster heart rate and more rapid breathing. The faster heart rate can sometimes cause palpitations. If the cause of the low BP is decreased fluid volume in the arteries, thirst might be a symptom. The skin may be dry and pale or cold and clammy, depending on the cause of the low blood pressure and whether or not the body is trying to compensate.

Low Blood Pressure Causes

In considering the causes of low BP it is practical to think in terms of three main categories. They are: conditions that compromise the heart’s ability to fill with or pump blood out; states that decrease the fluid volume in the blood vessels; and conditions that interfere with the normal degree of constriction of the blood vessels.

Some common, not necessarily life-threatening causes related to the heart are cardiomyopathy and valvular heart disease. Some more serious causes include heart-attack, arrhythmia, pericardial effusion and certain birth defects of the heart.

Common states that cause hypotension due to reduced fluid volume in blood vessels are excessive fluid loss, inadequate fluid intake, blood loss, and anemia due to iron or other deficiencies. Excessive fluid loss can be due to greater than normal sweating, too much urination, or a combination of both. Heat stroke and heat exhaustion are common forms of excessive perspiration. In addition, inadequate fluid intake contributes to the low BP associated with these conditions. Diuretic medication and uncontrolled diabetes mellitus are common causes of decreased blood vessel volume resulting from excessive urination. Other endocrine causes of hypotension are disorders of the thyroid and adrenal glands.

Rapid, intermediate, or slow blood loss can cause low blood pressure. Bleeding from an low blood pressure symptomsinjury and certain conditions causing bleeding from the intestinal tract are some examples of rapid blood loss which cause pressure to drop in arteries because blood cells comprise part of the volume within the vessels. The most common setting in which chronic slow blood loss results in hypotension is slow hemorrhage from the gastrointestinal tract with secondary iron deficiency. The deficiency of iron in turn leads to reduced production of red blood cells. Common examples are a tumor of the colon and chronic ulcer disease. Other deficiencies that cause reduced red blood cell production and low blood pressure on that basis are those involving vitamin B12 and folic acid. Heavy menstrual periods can cause low blood pressure on the basis of rapid, intermediate, or slow blood loss.

Conditions that cause a decrease in the degree of blood vessel constriction are less common reasons for a low blood pressure, but they do exist. They are those that affect the part of the nervous system (sympathetic nervous system) certain chemical substances which the body produces (hormones) and certain medications which regulate that constriction.



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  1. What cause or causes of low blood pressure would you like information on in a future post?

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