Orthostatic intolerance
Encyclopedia
Orthostatic intolerance (OI) is a subcategory of dysautonomia
, a disorder of the autonomic nervous system
occurring when an individual stands up.
OI can also be defined as "the development of symptoms during upright standing relieved by recumbency," or by sitting back down again. 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 related to abnormalities in the interplay between blood volume control, the cardiovascular system, the autonomic nervous system and local circulatory mechanisms that regulate these basic physiological functions."
), as well as remaining conscious during their loss of posture. This is different than 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.
, 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.)
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:
. It is due to this illness that Page chose to leave the group in 2006.
Dysautonomia
Dysautonomia is a broad term that describes any disease or malfunction of the autonomic nervous system. This includes postural orthostatic tachycardia syndrome , inappropriate sinus tachycardia , vasovagal syncope, mitral valve prolapse dysautonomia, pure autonomic failure, neurocardiogenic...
, a disorder of the autonomic nervous system
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
occurring when an individual stands up.
OI can also be defined as "the development of symptoms during upright standing relieved by recumbency," or by sitting back down again. 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
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
, 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 related to abnormalities in the interplay between blood volume control, the cardiovascular system, the autonomic nervous system and local circulatory mechanisms that regulate these basic physiological functions."
Triggers
Symptoms of OI are triggered by the following:- An upright posture for long periods of time (e.g. standing in line, standing in a shower, or even sitting at a desk).
- A warm environment (such as in 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).
- Inadequate fluid and salt intake.
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 syncopeSyncope (medicine)
Syncope , the medical term for fainting, is precisely defined as a transient loss of consciousness and postural tone characterized by rapid onset, short duration, and spontaneous recovery due to global cerebral hypoperfusion that most often results from hypotension.Many forms of syncope are...
), as well as remaining conscious during their loss of posture. This is different than 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
New York Medical College
New York Medical College, aka New York Med or NYMC, is a private graduate health sciences university based in Westchester County, New York, a suburb of New York City and a part of the New York Metropolitan Area...
states, "Many syncopal patients have no intercurrent illness; between faints, they are well."
Symptoms:
- Lightheadedness
- Headache
- Fatigue
- Altered vision (blurred vision, "white outs," black outs)
- Weakness
- HyperpneaHyperpneaHyperpnea or hyperpnoea is increased depth of breathing when required to meet metabolic demand of body tissues, such as during or following exercise, or when the body lacks oxygen , for instance in high altitude or as a result of anemia....
or sensation of difficulty breathing or swallowing (see also hyperventilation syndromeHyperventilation syndromeHyperventilation syndrome is a respiratory disorder, psychologically or physiologically based, involving breathing too deeply or too rapidly...
) - Tremulousness
- Sweating
- Anxiety
- Heart palpitations, as the heart races to compensate for the falling blood pressure
- Exercise intolerance
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:- Sensitivity to heat
- Nausea
- Neurocognitive deficits, such as attention problems
- Sleep problems
- Pallor
- Other vasomotor symptoms.
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 testTilt table test
A tilt table test, occasionally called upright tilt testing, is a medical procedure often used to diagnose dysautonomia or syncope. Patients with symptoms of dizziness or lightheadedness, with or without a loss of consciousness , suspected to be associated with a drop in blood pressure or...
, 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:
- FludrocortisoneFludrocortisoneFludrocortisone is a synthetic corticosteroid with moderate glucocorticoid potency and much greater mineralocorticoid potency. The brand name in the U.S. and Canada is Florinef.-Uses:...
(Florinef) - ErythropoietinErythropoietinErythropoietin, or its alternatives erythropoetin or erthropoyetin or EPO, is a glycoprotein hormone that controls erythropoiesis, or red blood cell production...
- Hormonal contraceptionHormonal contraceptionHormonal 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 hormonal method—the combined oral contraceptive...
- ClonidineClonidineClonidine is a sympatholytic medication used to treat medical conditions, such as high blood pressure, some pain conditions, ADHD and anxiety/panic disorder...
Medications that inhibit acetylcholinesterase:
- PyridostigminePyridostigminePyridostigmine is a parasympathomimetic and a reversible cholinesterase inhibitor. Since it is a quaternary amine, it is poorly absorbed in the gut and does not cross the blood-brain barrier, except possibly in stressful conditions.-Mode of action:...
Medications that improve vasoconstriction:
- Stimulants: (e.g., Ritalin or Dexedrine)
- MidodrineMidodrineMidodrine is a vasopressor/antihypotensive agent. Midodrine was approved in the United States by the Food and Drug Administration in 1996 for the treatment of orthostatic hypotension...
(Proamatine) - EphedrineEphedrineEphedrine is a sympathomimetic amine commonly used as a stimulant, appetite suppressant, concentration aid, decongestant, and to treat hypotension associated with anaesthesia....
and pseudoephedrinePseudoephedrinePseudoephedrine is a sympathomimetic drug of the phenethylamine and amphetamine chemical classes. It is used as a nasal/sinus decongestant and stimulant, or as a wakefulness-promoting agent....
(SudafedSudafedSudafed is a brand name and registered trademark for over the counter decongestants manufactured by McNeil Laboratories for sale in Australia, New Zealand, Canada, Ireland, the United Kingdom, and the United States...
) - TheophyllineTheophyllineTheophylline, also known as dimethylxanthine, is a methylxanthine drug used in therapy for respiratory diseases such as COPD and asthma under a variety of brand names. Because of its numerous side-effects, the drug is now rarely administered for clinical use. As a member of the xanthine family, it...
(low-dose) - Selective serotonin reuptake inhibitors (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 salt and fluid intake, and
- physical therapyPhysical therapyPhysical therapy , often abbreviated PT, is a health care profession. Physical therapy is concerned with identifying and maximizing quality of life and movement potential within the spheres of promotion, prevention, diagnosis, treatment/intervention,and rehabilitation...
and exercise
Famous patients
A notable sufferer of orthostatic intolerance is Greg Page, formerly of The WigglesThe Wiggles
The Wiggles are a children's group formed in Sydney, Australia in 1991. Their original members were Anthony Field, Phillip Wilcher, Murray Cook, Greg Page, and Jeff Fatt. Wilcher left the group after their first album...
. It is due to this illness that Page chose to leave the group in 2006.