Orthostatic intolerance (OI) is a condition that causes many symptoms when a person changes to an upright position from a sitting or lying position. Someone who suffers from this condition can experience many different symptoms. The symptoms that are experienced can vary from low blood pressure to visual changes, so aspects of both cardiology and neurology can be applied and sometimes will result in a misdiagnosis.
OI is also called orthostatic hypotension. It is a type of dysautonomia that affects the autonomic nervous system (ANS). The ANS controls sweating, saliva, breathing, digestion, heart rate and more. Patients who have OI will experience an increased heart rate and a drop in blood pressure. The increase in heart rate is classified as postural orthostatic tachycardia syndrome because it occurs only with the change to an upright position.
Acute and chronic OI both have different sets of symptoms that are experienced. Acute OI is not as severe and is often classified by lightheadedness, headache, weakness and fatigue. Other symptoms include changes in vision, difficulty breathing, sweating and anxiety. Chronic OI is more severe and is classified by nausea, sleep problems, attention problems and sensitivity to heat in addition to the same symptoms as the acute version.
As of 2010, an exact cause of orthostatic intolerance was unknown. The main issues with this condition appear to many researchers and doctors to be problems with cardiovascular regulation. Some studies suggest that the condition occurs after a patient suffers from a viral infection, but others do not provide conclusive possibilities.
The severity of this condition varies with each patient. The majority of sufferers can expect symptoms to disappear with time and treatment. A small number of people with orthostatic intolerance have severe symptoms that can cause longer recovery or no recovery at all.
Treatments also vary widely. Each person will respond differently, especially because the symptoms that are experienced are different. Using a combination of orthostatic exercising, beta blockers and alpha agonists shows the most results. Less-severe cases of orthostatic intolerance might respond well with minimal treatment, but more stubborn or severe cases might need a more comprehensive plan.
Some behavioral changes also might be necessary and can help relieve symptoms. Patients should most importantly avoid the actions that trigger the symptoms experienced, including reducing the amount of time in a sitting position. Doctors must also treat the conditions that are likely to exist in addition to the OI. Patients should increase the amount of water they drink throughout the day, which has shown to provide marked benefits in symptom reduction for many sufferers.