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."
2.1 Acute OI
2.2 Chronic OI
4 Management and prognosis
5 Famous patients
6 See also
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.
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
Heart palpitations, as the heart races to compensate for the falling blood
A classic manifestation of acute OI is a soldier who faints after standing rigidly at
attention for an extended period of time.
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
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:
|National Dysautonomia Research Foundation|
|Chronic Fatigue Syndrome Foundation|
|Management of Orthostatic Intolerance|
|Vanderbilt University Autonomic Dysfunction Center|
|An excellent review from Medscape|