Low Blood Pressure
(Hypotension)

• Low blood pressure, also called hypotension, is blood pressure that is low enough that the flow of blood to the organs of the body is inadequate and symptoms and/or signs of low blood flow develop.
• Low pressure alone, without symptoms or signs, usually is not unhealthy.
• The symptoms of low blood pressure include lightheadedness, dizziness, and fainting. These symptoms are most prominent when individuals go from the lying or sitting position to the standing position (orthostatic hypotension).
• Low blood pressure that causes an inadequate flow of blood to the body's organs can cause strokes, heart attacks, and kidney failure. It's most severe form is shock.
• Common causes of low blood pressure include a reduced volume of blood, heart disease, and medications.
• The cause of low blood pressure can be determined with blood tests, radiologic studies, and cardiac testing to look for arrhythmias.
• Treatment of low blood pressure is determined by the cause of the low pressure.

Blood pressure is the force exerted by circulating blood on the walls of blood vessels. It constitutes one of the critically important signs of life or vital signs which include heart beat, breathing, and temperature. Blood pressure is generated by the heart pumping blood into the arteries modified by the response of the arteries to the flow of blood.

An individual's blood pressure is expressed as systolic/diastolic blood pressure, for example, 120/80.The systolic blood pressure (the top number) represents the pressure in the arteries as the muscle of the heart contracts and pumps blood into them. The diastolic blood pressure (the bottom number) represents the pressure in the arteries as the muscle of the heart relaxes following its contraction. Blood pressure always is higher when the heart is pumping (squeezing) than when it is relaxing.

The range of systolic blood pressure for most healthy adults falls between 90 and 120 millimeters of mercury (mm Hg). Normal diastolic blood pressure ranges between 60 and 80 mm Hg. Current guidelines define normal blood pressure range as lower than 120/80. Blood pressures over 130/80 are considered high. High blood pressure increases the risk of developing:

• heart disease,
  
  
• kidney disease,
  
  
• hardening of the arteries (atherosclerosis or arteriosclerosis),
  
  
• eye damage, and
  
  
• stroke.

Low blood pressure (hypotension) is pressure so low it causes symptoms or signs due to the low flow of blood through the arteries and veins. When the flow of blood is too low to deliver enough oxygen and nutrients to vital organs such as the brain, heart, and kidney, the organs do not function normally and may be temporarily or permanently damaged.

Unlike high blood pressure, low blood pressure is defined primarily by signs and symptoms of low blood flow and not by a specific blood pressure number. Some individuals routinely may have blood pressures of 90/50 with no symptoms and therefore do not have low blood pressure. However, others who normally have higher blood pressures may develop symptoms of low blood pressure if their blood pressure drops to 100/60.

Source: MedicineNet.com
http://www.medicinenet.com/low_blood_pressure/article.htm