Orthostatic intolerance (OI) is the development of symptoms when standing upright that are relieved when reclining. 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. Some animal species with orthostatic hypotension have evolved to cope with orthostatic disturbances.

A substantial overlap is seen between syndromes of orthostatic intolerance on the one hand, and either chronic fatigue syndrome or fibromyalgia on the other. It affects more women than men (female-to-male ratio is at least 4:1), usually under the age of 35. OI can also be a symptom of mitochondrial cytopathy.

Orthostatic intolerance occurs in humans because standing upright is a fundamental stressor, so requires rapid and effective circulatory and neurologic compensations to maintain blood pressure, cerebral blood flow, and consciousness. When a human stands, about 750 ml of thoracic blood are abruptly translocated downward. People who have OI lack the basic mechanisms to compensate for this deficit.

  • Altered vision (blurred vision, "white outs"/gray outs, black outs, double vision)
  • Anxiety
  • Exercise intolerance
  • Fatigue
  • Headache
  • Heart palpitations, as the heart races to compensate for the falling blood pressure
  • Hyperpnea or sensation of difficulty breathing or swallowing (see also hyperventilation syndrome)
  • Lightheadedness
  • Sweating
  • Tremulousness
  • Weakness

A classic manifestation of acute OI is a soldier who faints after standing rigidly at attention for an extended period of time.

Chronic orthostatic intolerance

Patients with chronic orthostatic intolerance have symptoms on most or all days. Their symptoms may include most of the symptoms of acute OI, plus:

  • Nausea
  • Neurocognitive deficits, such as attention problems
  • Pallor
  • Sensitivity to heat
  • Sleep problems
  • Other vasomotor symptoms

Triggers

Symptoms of OI are triggered by:

  • An upright posture for long periods (e.g. standing in line, standing in a shower, or even sitting at a desk)
  • A warm environment (e.g. 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 anxious)
  • Return from an extended stay in space, when the body is not yet readapted to gravity
  • Extended bedrest

Diagnosis

Many patients go undiagnosed or misdiagnosed and either untreated or treated for other disorders. Current tests for OI (tilt table test, NASA Lean Test, adapted Autonomic Profile (aAP), autonomic assessment, and vascular integrity) can also specify and simplify treatment.

Management

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 that 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 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 2 liters (8 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. Two years later in late 2008, he went on to create his own fund for OI to help fund research into this then-little known disorder. Page recovered enough to temporarily return to The Wiggles in early 2012 to help with the transition to the next generation of Wiggles, after which he again left the group at the end of 2012 and was replaced by Emma Watkins and again by Tsehay Hawkins.

See also

  • List of investigational orthostatic intolerance drugs
  • Orthostatic hypertension
  • Orthostatic hypotension
  • Postural orthostatic tachycardia syndrome (POTS)
  • Vasovagal response

References