Anesthesia 1 Anesthesia

Anesthesia 1 Anesthesia Anesthesia, or anaesthesia (see spelling differences; from Greek αν-, an-, "without"; and αἲσθησις, aisthēsis, "sensation"), has traditionally meant the condition of having sensation (including the feeling of pain) blocked or temporarily taken away. This allows patients to undergo surgery and other procedures without the distress and pain they would otherwise experience. The word was coined by Oliver Wendell Holmes, Sr. in 1846.[1] Another definition is a "reversible lack of awareness," whether this is a total lack of awareness (e.g. a general anesthetic) or a lack of awareness of a part of the body such as a spinal anesthetic or another nerve block would cause. Anesthesia is a pharmacologically induced reversible state of amnesia, analgesia, loss of responsiveness, loss of skeletal muscle reflexes and decreased stress response. Terms Today, the term general anaesthesia in its most general form can include:[2] • Analgesia: blocking the conscious sensation of pain; • Hypnosis produces unconsciousness but not necessarily freedom from pain registration; • Amnesia: preventing memory formation; if you are unconscious, by definition you will be unable to recall events. • Paralysis: preventing unwanted movement or muscle tone; • Obtundation of reflexes, preventing exaggerated autonomic reflexes. Patients undergoing anaesthesia usually undergo preoperative evaluation. It includes gathering history of previous anesthetics, and any other medical problems, physical examination, ordering required blood work and consultations prior to surgery. There are several forms of anaesthesia. The following forms refer to states achieved by anesthetics working on the brain: • General anaesthesia: "Drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation." Patients undergoing general anesthesia can often neither maintain their own airway nor breathe on their own. While usually administered with inhalational agents, general anesthesia can be achieved with intravenous agents, such as propofol.[3] • Deep sedation/analgesia: "Drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully following repeated or painful stimulation." Patients may sometimes be unable to maintain their airway and breathe on their own.[3] • Moderate sedation/analgesia or conscious sedation: "Drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation." In this state, patients can breathe on their own and need no help maintaining an airway.[3] • Minimal sedation or anxiolysis: "Drug-induced state during which patients respond normally to verbal commands." Though concentration, memory, and coordination may be impaired, patients need no help breathing or maintaining an airway.[3] The level of anesthesia achieved ranges on a continuum of depth of consciousness from minimal sedation to general anesthesia. The depth of consciousness of a patient may change from one minute to the next. The following refer to the states achieved by anesthetics working outside of the brain: • Regional anaesthesia: Loss of pain sensation, with varying degrees of muscle relaxation, in certain regions of the body. Administered with local anesthesia to peripheral nerve bundles, such as the brachial plexus in the neck. Examples include the interscalene block for shoulder surgery, axillary block for wrist surgery, and femoral nerve block for leg surgery. While traditionally administered as a single injection, newer techniques involve placement of indwelling catheters for continuous or intermittent administration of local anesthetics. Anesthesia 2 • Spinal anaesthesia: also known as subarachnoid block. Refers to a Regional block resulting from a small volume of local anesthetics being injected into the spinal canal. The spinal canal is covered by the dura mater, through which the spinal needle enters. The spinal canal contains cerebrospinal fluid and the spinal cord. The sub arachnoid block is usually injected between the 4th and 5th lumbar vertebrae, because the spinal cord usually stops at the 1st lumbar vertebra, while the canal continues to the sacral vertebrae. It results in a loss of pain sensation and muscle strength, usually up to the level of the chest (nipple line or 4th thoracic dermatome). • Epidural anesthesia: Regional block resulting from an injection of a large volume of local anesthetic into the epidural space. The epidural space is a potential space that lies underneath the ligamenta flava, and outside the dura mater (outside layer of the spinal canal). This is basically an injection around the spinal canal. • Local anesthesia is similar to regional anaesthesia, but exerts its effect on a smaller area of the body. History Herbal derivatives The first anesthesia (a herbal remedy) was administered in prehistory. Opium poppy capsules were collected in 4200 BC, and opium poppies were farmed in Sumeria and succeeding empires. The use of opium-like preparations in anesthesia is recorded in the Ebers Papyrus of 1500 BC. By 1100 BC poppies were scored for opium collection in Cyprus by methods similar to those used in the present day, and simple apparatus for smoking of opium were found in a Minoan temple. Opium was not introduced to India and China until 330 BC and 600–1200 AD respectively, but these nations pioneered the use of cannabis incense and aconitum. Sushruta Samhita, a 3rd century B.C Indian text, advocates the use of wine with incense of cannabis for anaesthasia[4] . In the second century, according to the Book of the Later Han and Records of Three Kingdoms, the physician Hua Tuo performed abdominal surgery using an unknown anesthetic called mafeisan (麻沸散 "cannabis boil powder") dissolved in liquor. Throughout Europe, Asia, and the Americas a variety of Solanum species containing potent tropane alkaloids were used, such as mandrake, henbane, Datura metel, and Datura inoxia. Classic Greek and Roman medical texts by Hippocrates, Theophrastus, Aulus Cornelius Celsus, Pedanius Dioscorides, and Pliny the Elder discussed the use of opium and Solanum species. In 13th century Italy Theodoric Borgognoni used similar mixtures along with opiates to induce unconsciousness, and treatment with the combined alkaloids proved a mainstay of anesthesia until the nineteenth century. In the Americas coca was also an important anesthetic used in trephining operations. Incan shamans chewed coca leaves and performed operations on the skull while spitting into the wounds they had inflicted to anesthetize the site. Alcohol was also used, its vasodilatory properties being unknown. Ancient herbal anesthetics have variously been called soporifics, anodynes, and narcotics, depending on whether the emphasis is on producing unconsciousness or relieving pain. In the famous 10th century Persian work, the Shahnameh, the author, Ferdowsi, describes a cesarean section performed on Rudabeh when giving birth, in which a special wine agent was prepared as an anesthetic[5] by a Zoroastrian priest in Persia, and used to produce unconsciousness for the operation. Although largely mythical in content, the passage does at least illustrate knowledge of anesthesia in ancient Persia. Arabic and Iranian anesthesiologists were the first to utilize oral as well as inhalant anesthetics. In Islamic Spain, Abulcasis and Ibn Zuhr (Avenzoar), among other Muslim surgeons, performed hundreds of surgeries under inhalant anesthesia with the use of narcotic-soaked sponges. Abulcasis and Avicenna wrote about anesthesia in their influential medical encyclopedias, the Al-Tasrif and The Canon of Medicine.[6] [7] The use of herbal anesthesia had a crucial drawback compared to modern practice—as lamented by Fallopius, "When soporifics are weak, they are useless, and when strong, they kill." To overcome this, production was typically standardized as much as feasible, with production occurring from specific famous locations (such as opium from the fields of Thebes in ancient Egypt). Anesthetics were sometimes administered in the spongia somnifera, a sponge into which a large quantity of drug was allowed to dry, from which a saturated solution could be trickled into the nose of Anesthesia 3 the patient. At least in more recent centuries, trade was often highly standardized, with the drying and packing of opium in standard chests, for example. In the 19th century, varying aconitum alkaloids from a variety of species were standardized by testing with guinea pigs. Despite these refinements, the discovery of morphine, a purified alkaloid that soon afterward could be injected by hypodermic for a consistent dosage, was enthusiastically received and led to the foundation of the modern pharmaceutical industry. Another factor affecting ancient anesthesia is that drugs used systemically in modern times were often administered locally, reducing the risk to the patient. Opium used directly in a wound acts on peripheral opioid receptors to serve as an analgesic, and a medicine containing willow leaves (salicylate, the predecessor of aspirin) would then be applied directly to the source of inflammation. In 1804, the Japanese surgeon Seishū Hanaoka performed general anesthesia for the operation of a breast cancer (mastectomy), by combining Chinese herbal medicine know-how and Western surgery techniques learned through "Rangaku", or "Dutch studies". His patient was a 60-year-old woman named Kan Aiya.[8] He used a compound he called Tsusensan, based

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