Redirected from Conduction anesthesia
Note: The phrase local anesthesia is colloquially used to describe various local and regional anesthetic techniques; in this article however, conduction anesthesia is used, according to the definition given above.
Many surgical procedures can be done under conduction anesthesia. In some cases (e.g. caesarean section) conduction anesthesia is thought to carry a lower risk and is therefore usually preferred over general anesthesia. In other situations conduction and general anesthesia can be used alternatively or in combination. Conduction anesthesia is also used for purposes of pain therapy and diagnostic procedures.
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To achieve conduction anesthesia a local anesthetic is injected or applied to a body surface. The local anesthetic then diffuses into nerves where it inhibits the propagation of signals for pain, muscle contraction, regulation of blood circulation and other body functions. With relatively high drug doses and/or concentrations, all qualities of sensation (pain, touch, temperature etc.) as well as muscle control are inhibited. With lower doses and/or concentrations it is possible to inhibit pain sensation, to some degree, selectively, without affecting muscle power. This effect, termed differential block, is made use of in some techniques of pain therapy (e.g. "walking epidural" for labor pain).
Anesthesia persists as long as there is a sufficient concentration of local anesthetic at the nerve or nerves to be blocked. Sometimes a vasoconstrictor drug is added to decrease local blood flow, thereby slowing the transport of the local anesthetic away from the site of injection. Depending on the drug and technique used, the anesthetic effect may persist for less than an hour to several hours. When a catheter is used for continuous infusion or repeated injection, conduction anesthesia can be extended for days or weeks. This is typically done for purposes of pain therapy.
Almost every nerve between the peripheral nerve endings and the central nervous system can be blocked using local anesthetics. The most peripheral technique is topical anesthesia to the skin or other body surface. Small and large peripheral nerves can be anesthetized individually (peripheral nerve blocks[?]) or in anatomic nerve bundles (plexus anesthesia[?]). Spinal anesthesia[?] and epidural anesthesia[?] are applied near the spinal cord where the peripheral nervous system merges into the central nervous system.
Some techniques that are clinically used are:
Virtually every part of the body can be anesthetized using conduction anesthesia. However, only a limited number of techniques are in clinical use. Sometimes conduction anesthesia is combined with general anesthesia for the patientīs comfort and ease of surgery. Typical operations that can be done under conduction anesthesia are:
Acute pain may occur due to trauma, surgery, infection, disruption of blood circulation or many other conditions in which there is tissue injury. In a medical setting it is usually desirable to alleviate pain when its warning function is no longer needed. Besides improving patient comfort, pain therapy can also reduce harmful physiological consequences of untreated pain.
Acute pain can often be managed using analgesics. However, conduction anesthesia may be preferable because of superior pain control and fewer side effects. For purposes of pain therapy, local anesthetic drugs are often given by repeated injection or continuous infusion through a catheter. Low doses of local anesthetic drugs can be sufficient so that muscle weakness does not occur and patients may be mobilized.
Some typical uses of conduction anesthesia for acute pain are:
Topical anesthesia is often used for all kinds of punctures (e.g. ascites drainage, amniocentesis, access to blood vessels for angiography and many others). Some diagnostic procedures such as bronchoscopy (visualization of the lower airways) or cystoscopy (visualization of the inner surface of the bladder) are often performed under surface anesthesia.
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 aminoester local anesthetic 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 few years, spinal anesthesia became widely used for surgical anesthesia and was accepted as a safe and effective technique. Although atraumatic (non-cutting-tip) cannulas and modern drugs are used today, the technique has otherwise changed very little over many decades.
Epidural anesthesia by a caudal approach had been known in the early 20th century, but a well-defined technique using lumbar injection was not developed until the 1930s. With the advent of thin flexible catheters, continuous infusion and repeated injections have become possible, making epidural anesthesia a highly successful technique to this day. Beside its many uses for surgery, epidural anesthesia is particularly popular in obstetrics for the treatment of labor pain.
New York School of Regional Anesthesia (http://www.nysora.com)
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