Hypotension

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.

Hypotension

Definition

Hypotension is the medical term for low blood pressure.

Description

The pressure of the blood in the arteries rises and falls as the heart and muscles handle demands of daily living, such as exercise, sleep and stress. Some healthy people have blood pressure well below the average for their age, even though they have a completely normal heart and blood vessels. This is often true of athletes who are in superior shape. The term "hypotension" is usually used only when blood pressure has fallen so far that enough blood can no longer reach the brain, causing dizziness and fainting.

Causes and symptoms

Postural hypotension is the most common type of low blood pressure. In this condition, symptoms appear after a person sits up or stands quickly. In normal people, the cardiovascular system must make a quick adjustment to raise blood pressure slightly to account for the change in position. For those with postural hypotension, the blood pressure adjustment is not adequate or it doesn't happen. Postural hypotension may occur if someone is taking certain drugs or medicine for high blood pressure. It also happens to diabetics when nerve damage has disrupted the reflexes that control blood pressure.

Many people have a chronic problem with low blood pressure that is not particularly serious. This may include people who require certain medications, who are pregnant, have bad veins, or have arteriosclerosis (hardening of the arteries).

The most serious problem with low blood pressure occurs when there is a sudden drop, which can be life-threatening due to widespread ischemia (insufficient supply of blood to an organ due to blockage in an artery). This type of low blood pressure may be due to a wide variety of causes, including:

• trauma with extensive blood loss
• serious burns
• shock from various causes (e.g. anaphylaxis)
• heart attack
• adrenal failure (Addisonian crisis)
• cancer
• severe fever
• serious infection (septicemia)

Diagnosis

Blood pressure is a measure of the pressure in the arteries created by the heart contracting. During the day, a normal person's blood pressure changes constantly, depending on activity. Low blood pressure can be diagnosed by taking the blood pressure with a sphygmomanometer. This is a device with a soft rubber cuff that is inflated around the upper arm until it's tight enough to stop blood flow. The cuff is then slowly deflated until the health care worker, listening to the artery in the arm with a stethoscope, can hear the blood first as a beat forcing its way along the artery. This is the systolic pressure. The cuff is then deflated more until the beat disappears and the blood flows steadily through the open artery; this gives the diastolic pressure.

Blood pressure is recorded as systolic (higher) and diastolic (lower) pressures. A healthy young adult has a blood pressure of about 110/75, which typically rises with age to about 140/90 by age 60 (a reading now considered mildly elevated).

Treatment

Treatment of low blood pressure depends on the underlying cause, which can usually be resolved. For those people with postural hypotension, a medication adjustment may help prevent the problem. These individuals may find that rising more slowly, or getting out of bed in slow stages, helps the problem. Low blood pressure with no other symptoms does not need to be treated.

Prognosis

Low blood pressure as a result of injury or other underlying condition can usually be successfully treated if the trauma is not too extensive or is treated in time. Less serious forms of chronic low blood pressure have a good prognosis and do not require treatment.

Resources

BOOKS

Smeltzer, Suzanne C., and Brenda G. Bare. Brunner and Suddarth's Textbook of Medical and Surgical Nursing. 8th ed. Philadelphia:Lippincott-Raven Publishers, 1996.

KEY TERMS

Arteriosclerosis— A group of disorders that causes thickening and loss of elasticity in artery walls.

hypotension A low arterial blood pressure. The range of blood pressure in health is quite wide, and the term hypotension is not applied simply to an individual whose blood pressure is habitually at the low end of the normal range (say, 110/60 mm Hg). Rather, it refers to some abnormal situation when the blood pressure falls, such as in fainting, after serious haemorrhage, in heart failure, or in shock. Postural hypotension refers to a fall in blood pressure on standing up. Significant hypotension is that which deprives the brain of an adequate blood supply. The brain ‘defends itself’ against this by widening its blood vessels, but a profound fall in blood pressure (below about 70/40 mm Hg) is beyond the limit of this compensation, and consciousness is lost.

Stuart Judge

hypotension (hy-poh-ten-shŏn) n. a condition in which the arterial blood pressure is abnormally low. It occurs after excessive fluid or blood loss. Other causes include myocardial infarction, pulmonary embolism, Addison's disease, severe infections, allergic reactions, arrhythmias, antihypertensive or antipsychotic medication, and acute abdominal conditions (e.g. pancreatitis). postural (or orthostatic) h. hypotension experienced when rising from a horizontal position.

hypotension Condition in which blood pressure is abnormally low. It is commonly seen after heavy blood loss or excessive fluid loss due to prolonged vomiting or diarrhoea. It also occurs in many serious illnesses. Temporary hypotension may cause sweating, dizziness, and fainting. See also hypertension