Orthostatic dysregulation is a condition where the autonomic nervous system fails to properly adjust blood pressure and heart rate when a person moves to an upright position. This inefficient response to gravity is a form of dysautonomia, a general term for a malfunction of the body’s automatic functions, and leads to a range of symptoms.
The Body’s Response to Standing
When a person stands up, gravity pulls about 750 ml of blood downward into the legs and abdomen. In a healthy individual, specialized sensors called baroreceptors, located in the arteries, detect the resulting drop in blood pressure. These sensors send signals to the brain, which then activates the sympathetic nervous system.
This activation causes two main adjustments to maintain stable blood flow to the brain. First, it signals blood vessels in the lower body to constrict, pushing blood back toward the heart. Second, it slightly increases the heart rate to ensure organs continue to receive enough oxygenated blood. This process happens almost instantly and without conscious effort.
In orthostatic dysregulation, this coordinated response is flawed. The signals to constrict blood vessels or increase heart rate may be delayed, weak, or uncoordinated. This failure means the cardiovascular system cannot effectively counteract gravity, causing blood to pool in the lower extremities. As a result, blood flow to the brain can temporarily decrease, setting the stage for various symptoms.
Recognizing Symptoms and Triggers
Individuals may experience lightheadedness, dizziness, and blurred or tunneled vision. Other symptoms include weakness, fatigue, and heart palpitations as the heart tries to compensate. In some instances, this can lead to presyncope, the sensation of nearly fainting, or syncope, a brief loss of consciousness.
Certain situations and activities can provoke or intensify these symptoms. Standing up too quickly is a common trigger, as it challenges the autonomic nervous system to respond rapidly. Prolonged periods of standing can also bring on symptoms as blood gradually pools in the legs.
Dehydration reduces overall blood volume, making it harder to maintain adequate blood pressure. Exposure to heat, such as in a hot shower, can cause blood vessels to dilate and contribute to blood pooling. Consuming a large, carbohydrate-heavy meal can divert blood to the digestive system, while physical exertion can also exacerbate symptoms.
Differentiating from Similar Conditions
The term “orthostatic dysregulation” is often used broadly but is distinct from specific conditions like Orthostatic Hypotension (OH) and Postural Orthostatic Tachycardia Syndrome (POTS). While all fall under the umbrella of orthostatic intolerance, they have specific diagnostic criteria.
Orthostatic Hypotension is defined by a significant drop in blood pressure upon standing. The diagnostic criteria for OH is a decrease in systolic blood pressure by at least 20 mmHg or diastolic blood pressure by at least 10 mmHg within three minutes of standing. In OH, the primary issue is the failure to maintain blood pressure.
Postural Orthostatic Tachycardia Syndrome (POTS) is characterized by an excessive increase in heart rate without a significant drop in blood pressure. The diagnostic criteria is a sustained heart rate increase of at least 30 beats per minute (or 40 bpm for adolescents) within ten minutes of standing. Orthostatic dysregulation may be considered when a person has symptoms of orthostatic intolerance but does not meet the strict criteria for OH or POTS.
The Diagnostic Process
Diagnosing orthostatic dysregulation begins with a review of the patient’s symptoms, medical history, and medications. A key step is measuring orthostatic vital signs, which involves checking blood pressure and heart rate while lying down and again at one and three minutes after standing. This test can reveal the abnormal changes that characterize these conditions.
If the orthostatic vital signs test is unclear, a physician may order a tilt-table test. During this procedure, the individual is secured to a motorized table that is tilted upright to an angle of 60 to 80 degrees. This simulates the change from lying to standing in a controlled environment.
Throughout the tilt-table test, which can last from 10 to 45 minutes, medical staff continuously monitor blood pressure, heart rate, and blood oxygen levels. The test is designed to safely provoke symptoms while allowing for precise measurement of the body’s cardiovascular response. This data helps doctors differentiate between conditions like OH and POTS and confirm a diagnosis.
Management and Lifestyle Adjustments
Managing orthostatic dysregulation focuses on non-medical strategies to reduce symptoms and prevent triggers. A primary approach is increasing blood volume by boosting fluid and salt intake, which helps the body retain fluid. These changes should be made under medical supervision.
Wearing waist-high compression stockings or abdominal binders applies external pressure to the lower body, preventing blood from pooling. Simple physical counter-maneuvers, such as crossing legs or squatting, can temporarily raise blood pressure when symptoms appear. Elevating the head of the bed at night also helps by conditioning the body to a more upright position.
If lifestyle modifications are not sufficient, a doctor may prescribe medication. For example, fludrocortisone can be used to increase blood volume by promoting salt and water retention. Another medication, midodrine, works by causing blood vessels to constrict, which helps stabilize blood pressure. These treatments are tailored to the patient and require medical oversight.