Name: Orthostatic Intolerance


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Orthostatic intolerance (OI) is defined as "the development of symptoms during

upright standing relieved by recumbency," or by sitting back down again. There are

many types of orthostatic intolerance. OI can be a subcategory of dysautonomia, a

disorder of the autonomic nervous system occurring when an individual stands up.

It affects more women than men (female-to-male ratio is at least 4:1), usually under

the age of 35. Up to 97% of those who have chronic fatigue syndrome (CFIDS) have

been said been shown in studies to have some form of OI.

Orthostatic intolerance occurs in humans because standing upright is a fundamental

stressor and requires rapid and effective circulatory and neurologic compensations to

maintain blood pressure, cerebral blood flow, and consciousness. When a human stands,

approximately 750 mL of thoracic blood is abruptly translocated downward. People who

suffer from OI lack the basic mechanisms to compensate for this deficit. Changes

in heart rate, blood pressure, and cerebral blood flow that produce OI "may be

related to abnormalities in the interplay between blood volume control, the

cardiovascular system, the autonomic nervous system and local circulatory mechanisms

that regulate these basic physiological functions."

    1 Triggers
    2 Symptoms
        2.1 Acute OI
        2.2 Chronic OI
    3 Diagnosis
    4 Management and prognosis
    5 Famous patients
    6 See also
    7 References


Symptoms of OI are triggered by the following:

    An upright posture for long periods of time (e.g. standing in line, standing in a

shower, or even sitting at a desk).
    A warm environment (such as in hot summer weather, a hot crowded room, a hot

shower or bath, after exercise).
    Emotionally stressful events (seeing blood or gory scenes, being scared or

    Inadequate fluid and salt intake.


Orthostatic intolerance is divided, roughly based on patient history, in two

variants: acute and chronic.
 Acute OI

Patients who suffer from acute OI usually manifest the disorder by a temporary loss

of consciousness and posture, with rapid recovery (simple faints, or syncope), as

well as remaining conscious during their loss of posture. This is different than a

syncope caused by cardiac problems because there are known triggers for the fainting

spell (standing, heat, emotion) and identifiable prodromal symptoms (nausea, blurred

vision, headache). As Dr. Julian M. Stewart, an expert in OI from New York Medical

College states, "Many syncopal patients have no intercurrent illness; between faints,

they are well."


    Altered vision (blurred vision, "white outs," black outs)
    Hyperpnea or sensation of difficulty breathing or swallowing (see also

hyperventilation syndrome)
    Heart palpitations, as the heart races to compensate for the falling blood

    Exercise intolerance

A classic manifestation of acute OI is a soldier who faints after standing rigidly at

attention for an extended period of time.
 Chronic OI

Patients with chronic orthostatic intolerance have symptoms on most or all days.

Their symptoms may include most of the symptoms of acute OI, plus:

    Sensitivity to heat
    Neurocognitive deficits, such as attention problems
    Sleep problems
    Other vasomotor symptoms.


OI is "notoriously difficult to diagnose." As a result, many patients have gone

undiagnosed or misdiagnosed and either untreated or treated for other disorders.

Current tests for OI (Tilt table test, autonomic assessment, and vascular integrity)

can also specify and simplify treatment. (See Dr. Julian Stewart's article,

"Orthostatic Intolerance: An Overview" for a more detailed description of OI tests.)
 Management and prognosis

Most patients experience an improvement of their symptoms, but for some, OI can be

gravely disabling and can be progressive in nature, particularly if it is caused by

an underlying condition which is deteriorating. The ways in which symptoms present

themselves vary greatly from patient to patient; as a result, individualized

treatment plans are necessary.

OI is treated both pharmacologically and non-pharmacologically. Treatment does not

cure OI; rather, it controls symptoms.

Physicians who specialize in treating OI agree that the single most important

treatment is drinking more than two liters (eight cups) of fluids each day. A steady,

large supply of water or other fluids reduces most, and for some patients all, of the

major symptoms of this condition. Typically, patients fare best when they drink a

glass of water no less frequently than every two hours during the day, instead of

drinking a large quantity of water at a single point in the day.

For most severe cases and some milder cases, a combination of medications are used.

Individual responses to different medications vary widely, and a drug which

dramatically improves one patient's symptoms may make another patient's symptoms much

worse. Medications focus on three main issues:

Bookmarks The following information, which has been distilled by the casebook author from this and other websites is particularly relevant to this casebook.
Bookmarks - Web
Web Page Notes Concepts
 Orthostatic hypotension (postural hypotension) - Mayo Clinic
 Orthostatic intolerance GARD
 Orthostatic Intolerance Syndromes National Dysautonomia Research Foundation
 CFIDS Chronic Fatigue Syndrome Foundation
 070105 Management of Orthostatic Intolerance
 Vanderbilt Autonomic Dysfunction Center - Orthostatic Intolerance/Tachycardia (POTS) Vanderbilt University Autonomic Dysfunction Center
 Orthostatic Intolerance An excellent review from Medscape

This web-site is for informational purposes only and is not intended as a substitute for advice from your doctor. It should not to be used for self-diagnosis or treatment.