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Hypotension is the medical term for low blood pressure, which can mean inadequate blood flow to the heart, brain and other vital organs. Blood pressure is measured in millimeters of mercury (mm HG). For a healthy young adult, normal blood pressure is considered to be less than 140mm Hg over 90mm Hg. The first number - in this case, 140 - is systolic blood pressure, the pressure in the blood vessels when the heart contracts; the second number - in this case, 90 - is the pressure between contractions.

The pressure with which the blood is pumped around the circulation varies between individuals and throughout the day. Blood pressure at the lower end of the normal range, is not likely to produce symptoms. However if the pressure in the circulation is below the level needed (90/60 mm Hg to 130/80 mm Hg) to provide the brain with enough blood light headaches or fainting may occur.

A common type of hypotension is, postural hypotension in which suddenly standing, or sitting up leads to light headaches and fainting. Postural hypotension is considered a failure of the autonomic nervous system - the part of the nervous system that controls involuntary vital actions, such as the heartbeat - to react appropriately to sudden changes. When you stand up, some blood pools in your lower extremities. Uncorrected, this would cause your blood pressure to fall.

 
What are the Causes?  

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The causes of orthostatic hypotension can be divided into neurogenic and non-neurogenic categories.
Neurogenic causes:

 

Nonneurogenic Causes of Orthostatic Hypotension

Cardiac pump failure

  • Myocardial infarction

  • Myocarditis

  • Constrictive pericarditis

  • Aortic stenosis

  • Tachyarrhythmias

  • Bradyarrhythmias

 

Reduced intravascular volume

  • Straining on heavy lifting, urination, defecation

  • Dehydration

  • Diarrhea

  • Hemorrhage

  • Burns

  • Salt-losing nephropathy

  • Adrenal insufficiency

  • Diabetes insipidus

Venous pooling

  • Alcohol

  • Postprandial dilation of splanchnic vessel beds

  • Vigorous exercise with dilation of skeletal vessel beds

  • Heat: hot environment, hot showers and baths, fever

  • Prolonged recumbency or standing

  • Spesis

 

Medications

  • Antyhypertensives

  • Diuretics

  • Vasodilators: nitrates, hydralazine (Apresoline)

  • Alpha- and beta-blocking agents

  • Central nervous system sedatives: barbiturates, opiates

  • Tricyclic antidepressants

  • Phenothiazines

Non-neurogenic causes:

In many people low blood pressure occurs as a result of dehydration, following  loss of large amounts of fluid or salts from the body. For example heavy sweating, loss of blood or profuse diarrhea may all causes hypotension. 

Disorders that reduce the efficiency of the heart's pumping action are common cause of blood pressure. These disorders include heart failure,  heart attack  and an irregular heart beat.

Hypotension may also be caused by an abnormal widening of the blood vessels which may occur as a result of an infection in the bloodstream or a serve allergic reaction.

Postural hypotension may be caused by disorders in which, the nerve supply to the blood vessels is damaged such as diabetic neuropathy or peripheral neuropathies. Hypotension may also sometimes be the result of an adverse effect of certain drugs particularly those used in the treatment of high blood pressure  and certain types of antidepressant drugs.

Neurogenic Causes of Orthostatic Hypotension

Primary automatic system failure

  • Multisystem atrophy (Shy-Drager syndrome)

  • Pure autonomic failure

  • Subacute dysautonomia

Secondary autonomic system failure

  • Brain and brainstem

  • Tumor

  • Stroke

  • Multiple sclerosis

  • Spinal cord

  • Transverse myelitis

  • Syringomyleia

  • Tumor

  • Tabes dorsalis

  • Peripheral nervous system

  • Diabetes mellitus

  • Guillain-Barre syndrome

  • Alcoholic polyneuropathy

  • Human immunodeficiency virus infection

  • Amyloidosis

  • Porphyria

Adapted from Engstrom JW, Martin JP. Disorders of the autonomic nervous system. In: Fauci AS, ed. Harrison's Principles of internal medicine. New York: McGraw-Hill. In Press. Used with permission.

 

SYMPTOMS  

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You may not have symptoms of hypotension unless your blood pressure is very low. Symptoms may include.

  • Tiredness or fatigue

  • General weakness

  • Light headaches and fainting

  • Blurred vision

  • Dizziness

  • Nausea

  • Unsteadiness

  • Head or neck discomfort

  • Fever higher than 101 degrees

  • Severe upper back pain

  • Cough with phlegm

Postural hypotension, particularly in the elderly, may increase the risk of falls, leading to the potential for bone fractures and other injuries.

These symptoms, are usually temporary and blood pressure rises when the cause is treated. However if blood pressure is too low to provide an adequate blood supply to vital it can be fatal.
 

DIAGNOSIS

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Symptoms of dizziness and lightheadedness upon standing do not necessarily mean that you have postural hypotension. A wide range of underlying conditions, may cause these symptoms. An accurate diagnosis must be based on repeated evaluation of blood pressure and pulse rate after you have been lying down for at least five minutes and then after you stand quietly for one minute and then for three minutes. A hypotensive response may be immediate or delayed. Prolonged standing or a tilt test may be needed to detect a delayed hypotensive response.

Test used are listed below:

  1. Bronchoscopy - a diagnostic procedure in which a tube with a tiny camera on the end is inserted through the nose or mouth into the lungs. The procedure provides a view of the airways of the lung and allows doctors to collect lung secretions and to biopsy for tissue specimens.

     

  2. Lung scan- A type of nuclear scan involving radioactive gallium which helps determine whether a patient has inflammation in the lungs.
     

  3. Pulmonary function tests - a broad range of tests that are usually done in a health care provider's office or a specialized facility. They measure how well the lungs take in and exhale air and how efficiently they transfer oxygen into the blood. Spirometry measures how well the lungs exhale. The information gathered during this test is useful in diagnosing certain types of lung disorders, but is most useful when assessing for obstructive lung diseases (especially asthma and chronic obstructive pulmonary disease, COPD).
     

  4. Sputum analysis (if the cough produces sputum) -  Sputum is a secretion that is produced in the lungs and the bronchi. This mucus-like secretion may become infected, bloodstained, or contain abnormal cells that may lead to a diagnosis. Sputum is what comes up with deep coughing. The patient is asked to cough deeply and spit any sputum in a sterile cup. The sputum is then taken to the laboratory. There, it is placed in a medium under conditions that allow the organisms to grow.

  5. X-ray of the chest-  lungs, heart, large arteries, ribs, and the diaphragm


 

TREATMENT OPTIONS

 

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Patient's blood pressure will be  measured while  lying down, and then standing to find the  obvious reasons for low blood pressure. For example,  dehydration might need treatment with intravenous fluids, those with disorders, such as  a heart condition, may be admitted to hospital for tests and treatment. If you medications is causing hypotension your doctor will probably advise a change of drug or dosage.

Treatment of Orthostatic Hypotension

Nonpharmacologic treatments

  • Avoidance of prolonged standing

  • Slow, careful changes in position, especially on arising in the morning

  • Avoidance of alcohol

  • Avoidance of hot environments and hot showers or baths

  • Multiple small meals

  • Avoidance of rigorous exercise

  • Sleeping with lead-up tilt

  • Scheduling of activities in the afternoon

  • Increased salt and fluid intake

Pharmacologic treatments

  • Removal of medications that exacerbate hypotension, when possible

  • Fludrocortisone (Florinef)

  • Sympathetic antagonists such as midodrine (ProAmatine) and over-the-counter sympathomimetics

  • Erythropoietin

 

PREVENTING: 

 

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  • Quit smoking or don't smoke in the first place.

  • Stay away from secondhand cigarette smoke and airborne irritants.

  • If you have seasonal allergies like hay fever, stay indoors during days or seasons when airborne allergens are high and, if possible, keep the windows closed. Use an air conditioner; avoid using fans that draw in air from outdoors; avoid air drying your clothes; shower and change your clothes after being outside.

  • If you have allergies year round, cover your pillows and mattress with dust mite covers, use an air purifier, avoid pets and other triggers.

  • Get regular exercise to promote blood flow.

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  • Avoid heavy lifting.

  • Avoid straining while on the toilet.


 

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