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anaesthesia(1) Loss of pain sensation, as intentionally induced by drugs or medication.
(2) The loss of sensation. In medicine, this loss is “passive” (i.e., involuntary), as in crossed anaesthesia and tactile anaesthesia; in surgery, the loss of sensation is “active” (i.e., artificially-induced and controlled). Due in part to the potential for confusion, the alternate term, block, is widely preferred for local (surgical) anaesthesia; for systemic (e.g., general, intravenous) anaesthesia, confusion is less likely.
Some authors use the term analgesia in the same context as block, a practice which, as with anesthesia, may lend to confusion.
Nausea, vomiting, aspiration pneumonitis, renal failure, liver dysfunction.
anaesthesiaLoss of the sensations of touch, pressure, pain or temperature in any part of, or in the whole of, the body. This may be due to injury or disease of nerves or brain, or to deliberate medical interference. Drugs are commonly used to effect either general or local anaesthesia.
anaesthesiageneral or local loss of sensation, due to pharmacological or pathological suppression of nerve function; the syringe should be aspirated prior to the deposition of injectable anaesthetic
ankle block anaesthesia the introduction of local anaesthetic (ILA) to nerve trunks supplying the foot as they cross the ankle joint (deep injections to reach the tibial and deep peroneal nerves, and superficial/subcuticular injections to reach the superficial peroneal, sural and saphenous nerves) to achieve whole-foot anaesthesia (see named sites below)
Bier's block anaesthesia ILA into the venous circulation of a limb after the application of pressure cuffs inflated to above systolic pressure to prevent venous drainage of the limb, to achieve whole-limb anaesthesia
common peroneal block anaesthesia ILA to subcuticular tissue at neck of fibula, to achieve dorsal foot anaesthesia; this injection also causes footdrop that persists for the duration of anaesthesia
deep peroneal block anaesthesia ILA to the deep peroneal nerve where it crosses the anterior ankle joint, deep to the extensor retinaculum, to anaesthetize the dorsal area of the first interdigital cleft; the needle is introduced either between tibialis anterior and extensor hallucis longus tendons, passing through the extensor retinaculum to the anterior tibia; or adjacent to dorsalis pedis pulse where the nerve becomes superficial (injection into the adjacent artery is avoided by aspirating the syringe prior to deposition of LA solution)
digital block anaesthesia ILA to digital nerves (dorsal/medial; dorsal/lateral; plantar/medial; plantar/lateral) at the base of the toe, to achieve whole-digit anaesthesia
epidural anaesthesia ILA into cerebrospinal fluid to anaesthetize all tissues distal to the injection site
field block anaesthesia; regional anaesthesia ILA about all nerves subserving part or all of a limb/body region, to achieve anaesthesia of all tissues distal to the injection sites, e.g. ankle block, digital block, popliteal block, epidural anaesthesia
first-ray block anaesthesia; Mayo block anaesthesia ILA to branches of the medial plantar, superficial and deep peroneal nerves at the base of the first metatarsal, to achieve anaesthesia of the distal first ray
general anaesthesia; GA central suppression of conscious awareness of pain and other sensations, induced by an intravenous anaesthetic agent, and maintained by inhaled agents, often supplemented with muscle relaxants
high saphenous nerve anaesthesia ILA to the saphenous nerve at the medial side of the knee joint to achieve anaesthesia of the medial aspect of the lower leg and the medial longitudinal arch
infiltration anaesthesia; local infiltration anaesthesia the introduction of a small volume (e.g. 1 mL) of local anaesthetic solution into the subcuticular tissues underlying a skin lesion, to permit painless treatment of the lesion (see bleb)
intermetatarsal anaesthesia ILA to branches of the medial and/or lateral plantar, superficial and deep peroneal nerves at the bases of adjacent lesser metatarsals, to achieve anaesthesia of adjacent rays, interposed soft tissues and distal structures
local anaesthesia; LA loss of tissue sensation and pain by the injection or topical application (e.g. Emla) of local anaesthetic agents; LAs cause reversible conduction block of sensory, motor and autonomic nerve fibres
local infiltration anaesthesia see infiltration anaesthesia
Mayo block anaesthesia see first-ray block anaesthesia
medial dorsal cutaneous nerve anaesthesia see superficial peroneal block anaesthesia
peroneal block anaesthesia see common peroneal block anaesthesia
popliteal block injection ILA to the tibial nerve at the superior lateral area of the popliteal fossa, at a point approximately 5 cm proximal to a line joining the medial and lateral condyles and 1 cm lateral to the vertical bisection of the knee joint, i.e. before the nerve trunk divides to form the sural communicating and tibial nerves, in order to achieve anaesthesia of all parts of the lower leg and foot except the medial longitudinal arch; the deep location of the popliteal nerve is identified by a nerve stimulator
proximal digital block ILA just proximal to the medial and lateral aspects of the metatarsophalangeal joint to achieve anaesthesia of dorsal and plantar digital nerves just before they divide to form the proper plantar and dorsal digital nerves; the needle is introduced at right angles to dorsal skin to one side of the metatarsal neck and a bolus of LA solution deposited, the needle is advanced through the intermetatarsal soft tissues towards the plantar aspect of the foot and a further bolus of LA solution deposited just deep to the dermoepidermal junction; the plantar tissues will blanch on delivery of the plantar LA bolus
ray block ILA to the medial and lateral aspects of a metatarsal, as in intermetatarsal anaesthesia, in order to achieve ray anaesthesia
regional anaesthesia see field block anaesthesia
ring block anaesthesia see digital block anaesthesia
saphenous block injection ILA to saphenous nerve as it crosses the medial/ anterior ankle joint, superficial to the extensor retinaculum, in order to achieve anaesthesia of the medial/plantar longitudinal; the needle is introduced subdermally, medial to tibialis anterior tendon and directed towards the medial border of the ankle, parallel to the skin surface; LA is deposited as a 'sausage' in the subcuticular tissue between the anterior ankle and the medial malleolus
spinal anaesthesia reversible block of nerve transmission from all distal tissues by the introduction of local anaesthetic solution into the spinal cord subarachnoid space
superficial peroneal anaesthesia; medial dorsal cutaneous nerve anaesthesia ILA to the superficial peroneal nerve (medial dorsal cutaneous nerve) as it crosses the anterior ankle joint, superficial to the extensor retinaculum, to achieve anaesthesia of the majority dorsum of the foot (except the dorsal area of the first interdigital cleft); the needle is introduced subdermally adjacent to the extensor digitorum longus tendons, and directed towards the lateral border of the ankle, parallel to the skin surface; LA is deposited as a 'sausage' within the subcuticular tissue along the anterior ankle
sural nerve block anaesthesia ILA to the sural nerve as it crosses the lateral/ posterior ankle joint, superficial to the extensor retinaculum, to achieve anaesthesia of the lateral border of the foot and fifth toe; the needle is introduced subdermally behind the lateral malleolus and the tip of the needle aimed in the direction of the hallux
tibial block anaesthesia ILA to the tibial nerve in order to achieve anaesthesia of the plantar surface; anaesthetic solution is deposited around the tibial nerve posterior to the medial malleolus; the needle should pass through the retinaculum to the posterior, directing the tip of the needle toward the little toe; injection into the adjacent tibial artery is avoided by aspirating the syringe before depositing LA solution
toe block anaesthesia see digital block anaesthesia
topical anaesthesia Application of a local anaesthetic agent to an area of the skin or mucous membrane (e.g. conjunctiva) to produce anaesthesia. The application may be via direct instillation, soaked swabs, ointments or sprays. Syn. surface anaesthesia.