Orthostatic intolerance

Orthostatic intolerance (OI) is the inability to correctly regulate blood pressure, cerebral blood flow and consciousness when upright, usually when standing, but it can also occur when sitting. If irregular blood pressure and heart rate initiate while in a supine position (lying down, faceup), then officially it is not OI.

Prevalence
Orthostatic intolerance is a common dysfunction in ME/CFS. Estimates of the rate of orthostatic intolerance in Chronic Fatigue Syndrome and myalgic encephalomyelitis patients vary widely, with estimates as low as 50% to as high as 97% of patients.

Orthostatic intolerance is also commonly associated with fibromyalgia.

Testing
Orthostatic intolerance can be diagnosed by a tilt table test, although a tilt table test isn't required. It is part of the Institute of Medicine report's proposed diagnostic criteria for Systemic Exertion Intolerance Disease.

Symptom recognition

 * In the London criteria, orthostatic intolerance is mentioned under the criteria of periods of impaired circulation compatible with autonomic dysfunction.

Postural orthostatic tachycardia syndrome
Postural orthostatic tachycardia syndrome (POTS) is one of a group of disorders that have orthostatic intolerance (OI) as their primary symptom. The primary symptom of OI is lightheadedness or fainting. In POTS, the lightheadedness or fainting is also accompanied by a rapid increase in heartbeat of more than 30 beats per minute, or a heart rate that exceeds 120 beats per minute, within 10 minutes of rising.

Orthostatic hypotension
Also called postural hypotension, it is a form of sudden low blood pressure that occurs upon standing. It can often cause dizziness. it is defined as a fall in systolic blood pressure of at least 20 mm Hg or diastolic blood pressure of at least 10 mm Hg when a person assumes a standing position.

Neurally mediated hypotension
Also called neurally mediate syncope, in NMH, peripheral vasodilation causes blood to pool in the extremities. It is associated with a decrease in blood pressure, and a slow or lowered heart rate upon standing.

Notable studies

 * 2016, Orthostatic Changes in Hemodynamics and Cardiovascular Biomarkers in Dysautonomic Patients
 * 2015, Intravenous Hydration for Management of Medication-Resistant Orthostatic Intolerance in Adolescents and Young Adults
 * 2000, The Roles of Orthostatic Hypotension, Orthostatic Tachycardia, and Subnormal Erythrocyte Volume in the Pathogenesis of the Chronic Fatigue Syndrome "Method: 'Fifteen patients were randomly selected from a large population of patients with chronic fatigue syndrome, studied, and observed for several years (by DSB). Blood pressure (BP) and heart rate (HR) measured with Dinamap every minute for 30 minutes supine and 60 minutes standing were compared with these findings in 15 healthy age- and gender-matched control subjects and later during lower body compression with military antishock trousers (MAST). Plasma catecholamines and circulating erythrocyte and plasma volumes were also measured by isotopic dilution methods.' Results: 'Abnormal findings in the patients included excessive orthostatic reductions in systolic (P < 0.001) and diastolic BP (P < 0.001) and excessive orthostatic tachycardia (P < 0.01), together with presyncopal symptoms in 11 of the 15 patients and in none of the control subjects after standing for 60 min. Lower body compression with the MAST restored all orthostatic measurements to normal and overcame presyncopal symptoms within 10 min. Circulating erythrocyte but not plasma volumes were subnormal in the 12 women (P < 0.01) and plasma norepinephrine concentration rose excessively after standing for 10 min.'"

Talks & interviews

 * 2016, Remaining Upright: Approach to Orthostatic Intolerance - Melissa Cortes

Learn more

 * 2016, Remaining Upright: Approach to Orthostatic Intolerance (Bateman Horne Center)
 * 2016, NIH gives $246,000 for study of oral rehydration in ME/CFS patients with orthostatic intolerance