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 Blood pressure (BP) is the pressure of Circulatory system, circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term ...

, cerebral blood flow, and

consciousness Consciousness, at its simplest, is awareness of a state or object, either internal to oneself or in one's external environment. However, its nature has led to millennia of analyses, explanations, and debate among philosophers, scientists, an ...

. 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. Changes in

heart rate Heart rate is the frequency of the cardiac cycle, heartbeat measured by the number of contractions of the heart per minute (''beats per minute'', or bpm). The heart rate varies according to the body's Human body, physical needs, including the nee ...

, blood pressure, and cerebral blood flow that produce OI may be caused by abnormalities in the interactions between blood volume control, the

cardiovascular system In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. It includes the cardiovascular system, or vascular system, that consists of the heart a ...

, the

nervous system In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...

, and circulation control system.

Signs and symptoms

Orthostatic intolerance can be classified as acute OI and chronic OI.

Acute orthostatic intolerance

Patients who have 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 the triggers for the fainting spell (standing, heat,

emotion Emotions are physical and mental states brought on by neurophysiology, neurophysiological changes, variously associated with thoughts, feelings, behavior, behavioral responses, and a degree of pleasure or suffering, displeasure. There is ...

) and identifiable

prodromal In medicine, a prodrome is an early Medical sign, sign or symptom (or set of signs and symptoms, referred to as prodromal symptoms) that often indicates the onset of a disease before more diagnostically specific signs and symptoms develop. More spe ...

symptoms (nausea, blurred vision, headache) are known. 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: * Altered vision ( blurred vision, "white outs"/ gray outs, black outs, double vision) *

Anxiety Anxiety is an emotion characterised by an unpleasant state of inner wikt:turmoil, turmoil and includes feelings of dread over Anticipation, anticipated events. Anxiety is different from fear in that fear is defined as the emotional response ...

* Exercise intolerance *

Fatigue Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a signs and symptoms, symptom of any of various diseases; it is not a disease in itself. Fatigue (in the medical sense) is sometimes associated wit ...

Headache A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe ...

* 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 Hyperventilation syndrome (HVS), also known as chronic hyperventilation syndrome (CHVS), dysfunctional breathing hyperventilation syndrome, cryptotetany, spasmophilia, latent tetany, and central neuronal hyper excitability syndrome (NHS), is a r ...

) * 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 Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat. Over 30 d ...

* Neurocognitive deficits, such as

attention Attention or focus, is the concentration of awareness on some phenomenon to the exclusion of other stimuli. It is the selective concentration on discrete information, either subjectively or objectively. William James (1890) wrote that "Atte ...

problems *

Pallor Pallor is a pale color of the skin that can be caused by illness, emotional shock or stress, stimulant use, or anemia, and is the result of a reduced amount of oxyhaemoglobin and may also be visible as pallor of the conjunctivae of the eye ...

* Sensitivity to heat * Sleep problems * Other vasomotor symptoms

Causes

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 * Inadequate

fluid In physics, a fluid is a liquid, gas, or other material that may continuously motion, move and Deformation (physics), deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are M ...

and salt intake * Concussion

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 Vascular can refer to: * blood vessels, the vascular system in animals * vascular tissue Vascular tissue is a complex transporting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue ...

integrity) can also specify and simplify treatment. Patients with dysautonomia symptoms can be referred to a cardiologist, neurologist, or even a gastroenterologist for treatment and management.

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. For most severe cases and some milder cases, a combination of

medications Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmaco ...

is used. Individual responses to different medications vary widely, and a drug that 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:'' * Fludrocortisone (Florinef) *

Erythropoietin Erythropoietin (; EPO), also known as erythropoetin, haematopoietin, or haemopoietin, is a glycoprotein cytokine secreted mainly by the kidneys in response to cellular hypoxia; it stimulates red blood cell production ( erythropoiesis) in th ...

Hormonal contraception Hormonal contraception refers to birth control methods that act on the endocrine system. Almost all methods are composed of steroid hormones, although in India one selective estrogen receptor modulator is marketed as a contraceptive. The original ...

''Medications that inhibit acetylcholinesterase:'' * Pyridostigmine ''Medications that improve vasoconstriction:'' *

Stimulants Stimulants (also known as central nervous system stimulants, or psychostimulants, or colloquially as uppers) are a class of drugs that increase alertness. They are used for various purposes, such as enhancing attention, motivation, cognitio ...

: (e.g., Ritalin or Dexedrine) * Midodrine (ProAmatine) *

Ephedrine Ephedrine is a central nervous system (CNS) stimulant and sympathomimetic agent that is often used to prevent hypotension, low blood pressure during anesthesia. It has also been used for asthma, narcolepsy, and obesity but is not the preferred ...

and pseudoephedrine ( Sudafed) * Theophylline (low-dose) * Selective serotonin reuptake inhibitors (SSRIs - Prozac, Zoloft, and Paxil) '' Behavioral changes that patients with OI can make are:'' * Avoiding triggers such as prolonged sitting, quiet standing, warm environments, or vasodilating medications * Using postural maneuvers and pressure garments * Treating co-existing medical conditions * Increasing

and salt intake *

Physical therapy Physical therapy (PT), also known as physiotherapy, is a healthcare profession, as well as the care provided by physical therapists who promote, maintain, or restore health through patient education, physical intervention, disease preventio ...

and

exercise Exercise or workout is physical activity that enhances or maintains fitness and overall health. It is performed for various reasons, including weight loss or maintenance, to aid growth and improve strength, develop muscles and the cardio ...

Notable case

A notable person with OI is Greg Page, founding member and original lead singer of the Australian children's music group

The Wiggles The Wiggles are an Australian children's music group formed in Sydney in 1991. As of 2022, the group members are Anthony Field, Lachlan Gillespie, Simon Pryce, Tsehay Hawkins, Evie Ferris, John Pearce (entertainer), John Pearce, Caterina Mete ...

. Due to being diagnosed with this illness, Page left the group in late 2006, and was replaced by his understudy, Sam Moran. 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.

References

External links

{{Autonomic diseases Vascular diseases Peripheral nervous system disorders Sensitivities