A fall in the systolic blood pressure of at least 20 mm Hg or in the diastolic blood pressure of at least 10 mm Hg after 3 minutes of standing is diagnostic of orthostatic hypotension. The history and physical examination, as well as laboratory testing (complete blood count, electrolytes, blood glucose level, serum immunoelectrophoresis, vitamin B12 level, and a morning cortisol level) should be focused on ruling out non-neurologic causes (e.g., blood loss, dehydration, and cardiovascular or endocrine disorders) and determining whether other features of primary autonomic degenerative disorders (e.g., Shy–Drager syndrome, Parkinson's disease, or Lewy-body dementia) or autonomic peripheral neuropathies (e.g., diabetes, amyloidosis, or Sjögren's syndrome) are present. If the diagnosis remains unclear, additional testing, including autonomic testing and imaging studies, may be useful.
Drugs that Can Cause Orthostatic Hypotension
The recognition and removal (when possible) of reversible causes of orthostatic hypotension are important. Diuretics, antihypertensive agents, antianginal agents, α-adrenoreceptor antagonists for the treatment of benign prostatic hyperplasia, antiparkinsonism agents, and antidepressants are the most common offending agents.
Q: What are some nonpharmacologic treatments for orthostatic hypotension?
A: Nonpharmacologic treatments for orthostatic hypotension include wearing custom-fitted elastic stockings, or an abdominal binder, or both to reduce peripheral pooling in the lower limbs and splanchnic circulation, increasing fluids and salt intake, raising the head of the bed by 10 to 20 degrees, moving from a supine to a standing position gradually, particularly in the morning, and employing physical maneuvers including crossing the legs, stooping, squatting, and tensing the muscles of the leg, abdomen, or buttock or of the whole body to help maintain blood pressure during daily activities. Rapid ingestion (e.g., over a period of 3 to 4 minutes) of approximately 0.5 liter of tap water elicits a marked pressor response and improvement in symptoms in many, but not all, patients with autonomic failure. Midodrine [ProAmatine], a peripheral, selective, direct α1-adrenoreceptor agonist, is the only medication presently approved by the Food and Drug Administration for the treatment of orthostatic hypotension.
Q: How does standing cause a temporary reduction in blood pressure?
A: Standing results in pooling of 500 to 1000 ml of blood in the lower extremities and splanchnic circulation. There is a decrease in venous return to the heart and reduced ventricular filling, resulting in diminished cardiac output and blood pressure. These hemodynamic changes provoke a compensatory reflex response, initiated by the baroreceptors in the carotid sinus and aortic arch, that results in increased sympathetic outflow and decreased vagal-nerve activity.
Teaching topics from the New England Journal of Medicine - Vol. 358, No. 6, February 7, 2008