出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/02/25 13:45:52」(JST)
Bloodletting (or blood-letting) is the withdrawal of blood from a patient to cure or prevent illness and disease. Bloodletting was based on an ancient system of medicine in which blood and other bodily fluid were regarded as "humors" that had to remain in proper balance to maintain health. It is claimed to have been the most common medical practice performed by surgeons from antiquity until the late 19th century, a span of almost 2,000 years.[1] In Europe the practice continued to be relatively common until the end of the 18th century.[2] The practice has now been abandoned by modern style medicine for all except a few very specific conditions.[3] It is conceivable that historically, in the absence of other treatments for hypertension, bloodletting could sometimes have had a beneficial effect in temporarily reducing blood pressure by reducing blood volume.[4] However, since hypertension is very often asymptomatic and thus undiagnosable without modern methods, this effect was unintentional. In the overwhelming majority of cases, the historical use of bloodletting was harmful to patients.[5]
Today, the term phlebotomy refers to the drawing of blood for laboratory analysis or blood transfusion.[6] Therapeutic phlebotomy refers to the drawing of a unit of blood in specific cases like hemochromatosis, polycythemia vera, porphyria cutanea tarda, etc., to reduce the number of red blood cells.[7][8]
The earliest descriptions of bloodletting are available in Ancient Ayurvedic Texts, wherein detailed, systematic, scientific modes of bloodletting are cited. Bloodletting is one of the oldest medical techniques, having been practiced among ancient peoples including the Mesopotamians, the Egyptians, and the Greeks.[4] In Greece, bloodletting was in use in the fifth century B.C. during the lifetime of Hippocrates, who mentions this practice but generally relied on dietary techniques.[9] Erasistratus, however, theorized that many diseases were caused by plethoras, or overabundances, in the blood and advised that these plethoras be treated, initially, by exercise, sweating, reduced food intake, and vomiting.[10] Herophilus advocated bloodletting. Archagathus, one of the first Greek physicians to practice in Rome, also believed in the value of bloodletting.
"Bleeding" a patient to health was modeled on the process of menstruation. Hippocrates believed that menstruation functioned to "purge women of bad humors". During the Roman Empire, the Greek physician Galen, who subscribed to the teachings of Hippocrates, advocated physician-initiated bloodletting.[11]
The popularity of bloodletting in the classical Mediterranean world was reinforced by the ideas of Galen, after he discovered that not only veins but also arteries were filled with blood, not air as was commonly believed at the time. There were two key concepts in his system of bloodletting. The first was that blood was created and then used up; it did not circulate, and so it could "stagnate" in the extremities. The second was that humoral balance was the basis of illness or health, the four humours being blood, phlegm, black bile, and yellow bile, relating to the four Greek classical elements of air, water, earth and fire respectively. Galen believed that blood was the dominant humour and the one in most need of control. In order to balance the humours, a physician would either remove "excess" blood (plethora) from the patient or give them an emetic to induce vomiting, or a diuretic to induce urination.
Galen created a complex system of how much blood should be removed based on the patient's age, constitution, the season, the weather and the place. "Do-it yourself" bleeding instructions following these systems were developed.[12] Symptoms of plethora were believed to include fever, apoplexy, and headache. The blood to be let was of a specific nature determined by the disease: either arterial or venous, and distant or close to the area of the body affected. He linked different blood vessels with different organs, according to their supposed drainage. For example, the vein in the right hand would be let for liver problems and the vein in the left hand for problems with the spleen. The more severe the disease, the more blood would be let. Fevers required copious amounts of bloodletting.
The Talmud recommended a specific day of the week and days of the month for bloodletting, and similar rules, though less codified, can be found among Christian writings advising which saints' days were favourable for bloodletting. During medieval times bleeding charts were common, showing specific bleeding sites on the body in alignment with the planets and zodiacs.[13] Islamic medical authors too advised bloodletting, particularly for fevers. The practice was probably passed to them by the Greeks; when Islamic theories became known in the Latin-speaking countries of Europe, bloodletting became more widespread. Together with cautery, it was central to Arabic surgery; the key texts Kitab al-Qanun and especially Al-Tasrif li-man 'ajaza 'an al-ta'lif both recommended it. It was also known in Ayurvedic medicine, described in the Susruta Samhita.
Even after the humoral system fell into disuse, the practice was continued by surgeons and barber-surgeons. Though the bloodletting was often recommended by physicians, it was carried out by barbers. This led to the distinction between physicians and surgeons. The red-and-white-striped pole of the barbershop, still in use today, is derived from this practice: the red represents the blood being drawn, the white represents the tourniquet used, and the pole itself represents the stick squeezed in the patient's hand to dilate the veins.[citation needed] Bloodletting was used to "treat" a wide range of diseases, becoming a standard treatment for almost every ailment, and was practiced prophylactically as well as therapeutically.
The benefits of bloodletting only began to be seriously questioned in the second half of the 1800s, as the development of evidence-based medicine led to new statistical methods for evaluating treatment effectiveness.[14] While many physicians in England at the time had lost faith in the general value of bloodletting, some still considered it beneficial in some circumstances, for instance to "clear out" infected or weakened blood or its ability to "cause hæmorrhages to cease"—as evidenced in a call for a "fair trial for blood-letting as a remedy" in 1871.[15] Bloodletting persisted into the 20th century and was even recommended by Sir William Osler in the 1923 edition of his textbook The Principles and Practice of Medicine.[16]
A number of different methods were employed. The most common was phlebotomy, or venesection (often called "breathing a vein"), in which blood was drawn from one or more of the larger external veins, such as those in the forearm or neck. In arteriotomy, an artery was punctured, although generally only in the temples. In scarification (not to be confused with scarification, a method of body modification), the "superficial" vessels were attacked, often using a syringe, a spring-loaded lancet, or a glass cup that contained heated air, producing a vacuum within (see fire cupping). There was also a specific bloodletting tool called a scarificator, used primarily in 19th century medicine. It has a spring-loaded mechanism with gears that snaps the blades out through slits in the front cover and back in, in a circular motion. The case is cast brass, and the mechanism and blades steel. One knife bar gear has slipped teeth, turning the blades in a different direction than those on the other bars. The last photo and the diagram show the depth adjustment bar at the back and sides.
Leeches could also be used. The withdrawal of so much blood as to induce syncope (fainting) was considered beneficial, and many sessions would only end when the patient began to swoon.
William Harvey disproved the basis of the practice in 1628,[2] and the introduction of scientific medicine, la méthode numérique, allowed Pierre Charles Alexandre Louis to demonstrate that phlebotomy was entirely ineffective in the treatment of pneumonia and various fevers in the 1830s. Nevertheless, in 1840, a lecturer at the Royal College of Physicians would still state that "blood-letting is a remedy which, when judiciously employed, it is hardly possible to estimate too highly",[17] and Louis was dogged by the sanguinary Broussais, who could recommend leeches fifty at a time. Some physicians resisted Louis' work because they "were not prepared to discard therapies 'validated by both tradition and their own experience on account of somebody else's numbers'."[18]
Bloodletting was used to treat almost every disease. One British medical text recommended bloodletting for acne, asthma, cancer, cholera, coma, convulsions, diabetes, epilepsy, gangrene, gout, herpes, indigestion, insanity, jaundice, leprosy, ophthalmia, plague, pneumonia, scurvy, smallpox, stroke, tetanus, tuberculosis, and for some one hundred other diseases. Bloodletting was even used to treat most forms of hemorrhaging such as nosebleed, excessive menstruation, or hemorrhoidal bleeding. Before surgery or at the onset of childbirth, blood was removed to prevent inflammation. Before amputation, it was customary to remove a quantity of blood equal to the amount believed to circulate in the limb that was to be removed.[19]
Leeches became especially popular in the early nineteenth century. In the 1830s, the French imported about forty million leeches a year for medical purposes, and in the next decade, England imported six million leeches a year from France alone. Through the early decades of the century, hundreds of millions of leeches were used by physicians throughout Europe.[20]
One typical course of medical treatment began the morning of 13 July 1824. A French sergeant was stabbed through the chest while engaged in single combat; within minutes, he fainted from loss of blood. Arriving at the local hospital he was immediately bled twenty ounces (570 ml) "to prevent inflammation". During the night he was bled another 24 ounces (680 ml). Early the next morning, the chief surgeon bled the patient another 10 ounces (285 ml); during the next 14 hours, he was bled five more times. Medical attendants thus intentionally removed more than half of the patient's normal blood supply—in addition to the initial blood loss which caused the sergeant to faint. Bleedings continued over the next several days. By 29 July, the wound had become inflamed. The physician applied 32 leeches to the most sensitive part of the wound. Over the next three days, there were more bleedings and a total of 40 more leeches. The sergeant recovered and was discharged on 3 October. His physician wrote that "by the large quantity of blood lost, amounting to 170 ounces [nearly eleven pints] (4.8 liters), besides that drawn by the application of leeches [perhaps another two pints] (1.1 liters), the life of the patient was preserved". By nineteenth-century standards, thirteen pints of blood taken over the space of a month was a large but not an exceptional quantity. The medical literature of the period contains many similar accounts-some successful, some not.[21]
Bloodletting was also popular in the young United States of America, where Benjamin Rush (a signatory of the Declaration of Independence) saw the state of the arteries as the key to disease, recommending levels of bloodletting that were high even for the time. George Washington asked to be bled heavily after he developed a throat infection from weather exposure. Within a ten hour period, a total of 124-126 ounces (3.75 liters) of blood was withdrawn prior to his death from a throat infection in 1799.[22]
One reason for the continued popularity of bloodletting (and purging) was that, while anatomical knowledge, surgical and diagnostic skills increased tremendously in Europe from the 17th century, the key to curing disease remained elusive, and the underlying belief was that it was better to give any treatment than nothing at all. The psychological benefit of bloodletting to the patient (a placebo effect) may sometimes have outweighed the physiological problems it caused. Bloodletting slowly lost favour during the 19th century, but a number of other ineffective or harmful treatments were available as placebos—mesmerism, various processes involving the new technology of electricity, many potions, tonics, and elixirs.
In the absence of other treatments, bloodletting actually is beneficial in some circumstances, including hemochromatosis, the fluid overload of heart failure, and possibly simply to reduce blood pressure. In other cases, such as those involving agitation, the reduction in blood pressure might appear beneficial due to the sedative effects. In 1844, Joseph Pancoast listed the advantages of bloodletting in "A Treatise on Operative Surgery". Not all of these reasons are outrageous nowadays:
Today it is well established that bloodletting is not effective for most diseases. Indeed it is mostly harmful, since it can weaken the patient and facilitate infections. Bloodletting is used today in the treatment of a few diseases, including hemochromatosis and polycythemia; however, these rare diseases were unknown and undiagnosable before the advent of scientific medicine. It is practiced by specifically trained practitioners in hospitals, using modern techniques. In most cases, phlebotomy now refers to the removal of small quantities of blood for diagnostic purposes. However, in the case of hemochromatosis, which is now recognized as the most common genetic, or inherited, disorder, frequent bloodletting has become an essential, and life-saving procedure.[citation needed]
Though bloodletting as a general health measure has been shown to be harmful, it is still commonly indicated for a wide variety of conditions in the Ayurvedic, Unani, and traditional Chinese systems of alternative medicine.[23][24][25][26][27][28][29] Unani is based on a form of humorism, and so in that system, bloodletting is used to correct supposed humoral imbalance.
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| リンク元 | 「exsanguination」 |