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Orthostatic Hypotension While standing, you suddenly feel lightheaded, like you might faint. The symptoms improve when you sit or lie down (just the opposite of BPPV). The dizziness may be more noticeable first ­ thing in the morning or ­ after standing for long periods of time, particularly on a hot day. Symptoms may be related to taking medi­ cations that lower heart rate or blood pressure. For thousands of years, doctors commonly performed bloodletting as a therapeutic intervention. This intervention likely contributed to or caused the deaths of millions of ­ people. George Washington was bled four liters within ten hours before his death for treatment of a throat infection in 1799. As in many other areas of medicine, the story of how bloodletting began to fall out of ­ favor apparently began at least partially in Eu­ rope. The nineteenth-­ century French doctor Pierre Piorry devised rules about which patients should be bled and which should not. In 1830, it was common to perform bloodletting even in patients with blood loss from trauma. Piorry recognized that this practice only made the prob­ lem worse. In his writings, he described coming upon a man who was unconscious ­ after bleeding from a traumatic injury. Well-­ meaning relatives had propped him up to make him more comfortable. CHAPTER  2 Dizz y Spells with a Change in Position 34 Piorry laid the man flat, and he immediately, almost magically, woke up. With his “lying down therapy,” Piorry recognized that gravity could help or hinder blood circulation to the brain. Several de­ cades ­ after Piorry’s discoveries, the idea that low blood flow to the ­ whole brain could cause medical symptoms was beginning to get some attention on the other side of the Atlantic. In 1917, while chair of the Harvard University­ department of physiology, Walter Cannon published a brief note in the journal Science observing that the release of adrenaline by the adrenal glands increases heart rate and blood pressure. Cannon coined the term “fight-­ or-­ flight response” to describe the situation in which a threatened animal experiences a cascade of automatic responses (including the release of adrenaline) that increase the chance of escape and survival . A key part of the fight-­ or-­ flight response is the ability to maintain sufficient blood flow to brain. As far as the average American doctor was concerned, however, it was unclear ­ whether ­ these changes in the autonomic ner­ vous system ­ were an impor­ tant cause of medical symptoms or just a curiosity of the physiology laboratory. That was about to change. As the 1920s roared in, a few American doctors reported phenomena similar to ­ those Piorry had noted years earlier in France. In the first issue of the American Heart Journal, published in 1925, Samuel Bradbury and Cary Eggleston, working at the Cornell Division of Bellevue Hospital in New York, described three patients whose blood pressure—­ and therefore, presumably, blood flow to the brain—­ dropped to dangerously low levels when standing, causing the patients to have fainting episodes. During subsequent de­ cades, doctors called this condition Bradbury-­ Eggleston syndrome. In modern parlance, we would say ­ these patients had a failure of their automatic neurological reflexes, also known as dysautonomia, leading to orthostatic hypotension. Orthostatic hypotension Orthostatic Hypotension 35 means that upon moving from a lying down to ­ either a sitting up or standing position, ­ there is a substantial and sustained decrease of blood pressure. Orthostatic hypotension symptoms result from abnormally low blood flow to the brain. It’s easy for the heart to pump blood downhill to the legs, abdomen, and pelvis, but pumping blood uphill to the brain when you are on your feet takes more work. As you might imagine, depriving the ­ whole brain of blood can cause a broad range of symptoms, including dizziness and weakness. ­ People with orthostatic hypotension describe their dizziness as a lightheaded, woozy, or near fainting sensation. The affected person may feel hot, and ­ there can be associated sweating and nausea; in extreme instances, the person may actually faint. Almost every­ one has jumped up from a lying or sitting position and felt a brief lightheaded sensation. This is more likely to occur on a hot day or ­ after lying in bed for a long time. A variety of cardiovascular reflexes typically kick in automatically to increase blood pressure and heart rate so that the lightheaded sensation is brief. What ­ factors might predispose a person to develop orthostatic hypotension? The most common ­ factor is dehydration, which technically means a deficiency of ­ water...

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Additional Information

ISBN
9781421420912
Related ISBN
9781421420905
MARC Record
OCLC
964524376
Pages
208
Launched on MUSE
2016-12-10
Language
English
Open Access
No
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