OMIM 604715 | MeSH D054971 | |
Orthostatic intolerance (OI) is the development of symptoms when standing upright which 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.
Contents
There is a substantial overlap between syndromes of orthostatic intolerance on the one hand, and either chronic fatigue syndrome (CFS) or fibromyalgia (FM) on the other. It affects more women than men (female-to-male ratio is at least 4:1), usually under the age of 35.
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 caused by abnormalities in the interactions between blood volume control, the cardiovascular system, the nervous system and circulation control systems.
Triggers
Symptoms of OI are triggered by the following:
Symptoms
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 from 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."
Symptoms:
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:
Diagnosis
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:
Medications that increase blood volume:
Medications that inhibit acetylcholinesterase:
Medications that improve vasoconstriction:
Behavioral changes that patients with OI can make are:
Famous patient
A notable sufferer of orthostatic intolerance is Greg Page, founding member and original lead singer of the famous Australian children's music group The Wiggles. It was due to being diagnosed with this illness that Greg left the group in 2006. Two years later, he went on to create his own fund for OI to help fund research into this then little known disorder. Greg recovered sufficiently enough to temporarily return to The Wiggles in 2012 to help with the transition to the next generation of Wiggles, after which he again left the group.