Anaesthetics

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  • Topic: Anesthesia, Local anesthetic, Local anesthesia
  • Pages : 25 (7329 words )
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  • Published : February 3, 2013
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INTRODUCTION

The word "anesthesia", coined by Oliver Wendell Holmes, Sr. (1809–1894) in 1846 from the Greek αν-, an-, "without"; and aisthēsis, "sensation"), refers to the inhibition of sensation. An anesthetic (American English) (or anaesthetic, (Commonwealth English)) is a drug that causes anesthesia—reversible loss of sensation. They contrast with analgesics (painkillers), which relieve pain without eliminating sensation. These drugs are generally administered to facilitate surgery. A wide variety of drugs are used in modern anesthetic practice. Many are rarely used outside of anesthesia, although others are used commonly by all disciplines. Anesthetics are categorized into two classes: general anesthetics, which cause a reversible loss of consciousness, and local anesthetics, which cause a reversible loss of sensation for a limited region of the body while maintaining consciousness. Combinations of anesthetics are sometimes used for their synergistic and additive therapeutic effects. Adverse effects, however, may also be increased.

TYPES OF ANAESTHETICS

* Local anesthetics

A local anesthetic (LA) is a drug that causes reversible local anesthesia, generally for the aim of having a local analgesic effect, that is, inducing absence of pain sensation, although other local senses are often affected as well. Also, when it is used on specific nerve pathways (nerve block), paralysis (loss of muscle power) can be achieved as well. Clinical local anesthetics belong to one of two classes:

* Amino amide local anesthetics, and
* Amino ester local anesthetics.
Synthetic local anesthetics are structurally related to cocaine. They differ from cocaine mainly in that they have no abuse potential and do not act on the sympathoadrenergic system, i.e. they do not produce hypertension or local vasoconstriction, with the exception of Ropivacaine and Mepivacaine that do produce weak vasoconstriction. Local anesthetics vary in their pharmacological properties and they are used in various techniques of local anesthesia such as: * Topical anesthesia (surface)

* Infiltration
* Plexus block
* Epidural (extradural) block
* Spinal anesthesia (subarachnoid block)
The local anesthetic lidocaine (lignocaine) is also used as a Class Ib anti-arrhythmic drug.

Review Of Literature
The leaves of the coca plant were traditionally used as a stimulant in Peru. It is believed that the local anesthetic effect of coca was also known and used for medical purposes. Cocaine was isolated in 1860 and first used as a local anesthetic in 1884. The search for a less toxic and less addictive substitute led to the development of the amino ester local anesthetics stovaine in 1903 and procaine in 1904. Since then, several synthetic local anesthetic drugs have been developed and put into clinical use, notably lidocaine in 1943, bupivacaine in 1957 and prilocaine in 1959. Shortly after the first use of cocaine for topical anesthesia, blocks on peripheral nerves were described. Brachial plexus anesthesia by percutaneous injection through axillary and supraclavicular approaches was developed in the early 20th century. The search for the most effective and least traumatic approach for plexus anesthesia and peripheral nerve blocks continues to this day. In recent decades, continuous regional anesthesia using catheters and automatic pumps has evolved as a method of pain therapy. Intravenous regional anesthesia was first described by August Bier in 1908. This technique is still in use and is remarkably safe when drugs of low systemic toxicity such as prilocaine are used. Spinal anesthesia was first used in 1885 but not introduced into clinical practice until 1899, when August Bier subjected himself to a clinical experiment in which he observed the anesthetic effect, but also the typical side effect of postpunctural headache. Within a few years, spinal anesthesia became widely used for surgical anesthesia and was accepted as...
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