Hypotension is a state of low blood pressure in the cardiovascular system. It represents the opposite cardiovascular condition to that of hypertension, or high blood pressure. Hypotension presents a lesser risk of poor health or death to a person suffering from this condition than does hypertension. There are many people who have lower than normal blood pressures who are healthy in every other respect. Low blood pressure in such persons is rarely subject to any medical treatment. It is quite common for high performance or elite-level athletes to possess lower than normal blood pressures. The term hypotension is often used to differentiate between blood pressure that presents a dangerous condition and healthy low blood pressure situations. Hypotension can be a very dangerous condition.

Like hypertension, one cause of hypotension is the genetic structure of the person; some people have a predisposition to onset of this ailment. Hypotension will arise most commonly in adults as opposed to children. The other usual causes of hypotension can include the impact of a prescription medication; emotional stress; a recent blood donation, which reduces blood volume in the cardiovascular system; a significant loss of blood through injury or accident; the use of diuretics, both prescribed and those contained in the human diet, such as caffeine and alcohol; diabetes; and use of narcotic analgesics, or painkillers.

Although there are many healthy variables to the often stated "ideal" blood pressure, medical science has accepted the standard of 120/80 as normal for the general population over 40 years of age; healthy young adults may have blood pressures in the range of 110/75. Blood pressure is tested through the use of a sphygmomanometer, an inflatable sleeve that is placed around the upper arm. The device is then inflated to a sufficient pressure to stop the flow of blood, and as the pressure is slowly released, the force of the blood returning to the arteries can be measured. As with many scientific determinations reduced to a popular short form, the expression has a more complicated meaning. The reading produced through the use of the sphygmomanometer is a measurement of pressure in mm of mercury, or mmHg. The expression 120/80 is two blood pressure measurements. The first is systolic, which is the calculation of the peak pressure placed on the arterial walls of the cardiovascular system as the heart beats. The second figure represents the diastolic pressure that is generated by the blood flow at the small arteries of the system during the interval between heartbeats. A consistent systolic pressure of less than 100, a diastolic pressure of below 65, or both readings occurring together, are compelling indications of the existence of hypotension.

A common sports circumstance that creates hypotension is the dehydration that often occurs in an endurance event. If the athlete does not hydrate properly, the production of perspiration by the body in the regulation of its internal temperature will often dramatically reduce body fluid. Loss of fluid will cause a corresponding loss of blood volume, reducing blood pressure. In such circumstances, when the athlete is competing hard, all stresses upon the anatomy are magnified. The first symptom of hypotension as an impact on performance is a feeling of dizziness or lightheadedness; in a progressive fashion, if steps are not taken to both stop the activity and to obtain aid, a condition known as ischemia may result. Ischemia is the reduction in the amount of blood flowing to the heart or the brain. Like the accompanying dehydration, ischemia is not restricted to hot weather athletics, although it more commonly occurs during such events as the pronounced fluid loss required to reduce blood pressure is often heat related.

The situational low blood pressure that can arise through dehydration is readily combated through the employment of an effective hydration strategy, both before, during, and after the event.

Orthostatic hypotension is a condition that arises when a person experiences feelings of lightheadedness or disorientation when the body position is changed, such as from being seated to standing upright. In this circumstance, the blood vessels are not able to adjust to the change in pressure.

Unlike hypertension, there are few treatment options for low blood pressure, other than the elimination or reduction of the noted risk factors. In rare cases, medication to raise blood pressure may be prescribed.

SEE ALSO Cardiovascular system; Genetics; Hypertension.