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.
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 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.
The NASA 10-minute Lean Test is a variant of a test used by NASA researchers to test for orthostatic intolerance following space flight. The adaption for ME/CFS patients was developed by Dr. Lucinda Bateman, which she recommends all ME/CFS and fibromyalgia patients undergo to assess for orthostatic intolerance. The NASA 10-minute Lean Test in less taxing on the patient and can be done in any physician's office. Instructions are available for printout for both healthcare providers and patients.
- In the London criteria, orthostatic intolerance is mentioned under the criteria of periods of impaired circulation compatible with autonomic dysfunction.
Type of orthostatic intolerance
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.
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.
- 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 (Bateman Horne Center)
- 2016, NIH gives $246,000 for study of oral rehydration in ME/CFS patients with orthostatic intolerance
- 2015, Orthostatic Intolerance
- Stewart, Julian M; Medow, Marvin S (2 Feb 2015), "Orthostatic Intolerance", Medscape
- Miwa, Kunihisa (Jul 2015), "Cardiac dysfunction and orthostatic intolerance in patients with myalgic encephalomyelitis and a small left ventricle", Heart and Vessels, 30 (4): 484–489, PMID 24736946, doi:10.1007/s00380-014-0510-y
- London Criteria
- Nilsson, David; Sutton, Richard; Tas, Widet; et al. (6 Aug 2015), "Orthostatic Changes in Hemodynamics and Cardiovascular Biomarkers in Dysautonomic Patients", PLoS ONE, 10 (6), PMID 26053073, doi:10.1371/journal.pone.0128962
- Moak, Jeffrey P; Leong, Derek; Fabian, Robin; et al. (2015), "Intravenous Hydration for Management of Medication-Resistant Orthostatic Intolerance in the Adolescent and Young Adult", Pediatric Cardiology, 37 (2): 278–282, doi:10.1007/s00246-015-1274-6
- Streeten DH, Thomas D, Bell DS.(2000). The roles of orthostatic hypotension, orthostatic tachycardia, and subnormal erythrocyte volume in the pathogenesis of the chronic fatigue syndrome. American Journal of the Medical Science, 320 (1):1-8.Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/10910366