Local anaesthesia

The site of drug action means where a drug acts and mechanism means how the drug acts. Drug which act only at the site of application (i.e. localized region) are termed as local or topical action for example, ointments, paste, creams and certain other local preparations used externally produce only local effect. The local anaesthetics like lignocaine, procaine produce anaesthesia (local) in a localized region only. 

Me2NCH2) C2H5)(Me)C-OOC Ph-HCI. Colourless crystalline powder with a bitter taste, m.p. 177-179"C. Prepared by the action of ethyl magnesium bromide on dimethyl-aminoaceione. It is a local anaesthetic, mainly used to produce spinal anaesthesia. 

Cocaine. This lias a bitter taste, is mydriatic, produces local anaesthesia and is toxic. After absorption, or when taken internally, it acts chiefly by stimulation of the central nervous system, succeeded by depression. Since the two phases may be present in different areas simultaneously, a mixed result may ensue. With large doses the chief symptoms are those of medullary depression. Death is due to paralysis of the respiratory centre. The main use of cocaine in medicine is as a local anaesthetic. 

Tropacocaine (Benzoyl-i/r-tropine). This resembles cocaine in action, but produces local anaesthesia more rapidly and for a shorter time and causes little or no mydriasis. 

Trachelantamine, according to Syrneva, has a weak atropine-like action and also produces local anaesthesia. Its hydrolytic product, trache-lantamidine, which is structurally identical with tsoretronecanol, yields a p-aminobenzoyl derivative of -which the crystalline hydrochloride, m.p. 230-2°, is said to be as potent a local anaesthetic as cocaine hydrochloride. The chloro- -heliotridane (p. 606) formed by the aetion of thionyl ehloride on trachelantamidine reacts with 6-methoxy-8-aminoquinoline to form 6-methoxy-8-(pseMdoheliotridylamino)-quinoline,... 

Local anaesthetics are drugs that reversibly interrupt impulse propagation in peripheral nerves thus leading to autonomic nervous system blockade, analgesia, anaesthesia and motor blockade in a desired area of the organism. 

Chemicals which give strong acid reactions, often on interaction with water, e.g. mineral acids. Some organic acids can also be corrosive. Phenolics can result in local anaesthesia so that the pain will be absent for a time. 

Intrathecal (IT) Into the subarachnoid space between two of the membranes (meninges) separating the spinal cord from the vertebral column. This route is used for drugs that do not penetrate the blood-brain barrier, but which are required for their central action (e.g., antibiotics). Drugs can also be injected spinally (into the epidural space) for local anaesthesia or analgesia. 

Other local anaesthetics such as procaine (4) and procainamide (5) were also shown to be antagonists of the sympathetic neuronal 5-HT3 receptor at concentrations well below those causing anaesthesia and led to the testing of metoclopramide (6), a D2 receptor antagonist and stimulant of gastrointestinal motility. This compound too was found to be a potent antagonist (pA2 7.2) at 5-HT3 receptors [52]. 

Catecholamines, when given in combination with local anaesthetics, can induce gangrene in fingers, toes, penis, nose and ears. Local anaesthesia at these locations should be done without an vasoconstrictive additive. 

The use of local anaesthetics outside specialized surgical or anaesthetical practice is usually limited to infiltration anaesthesia, different surface anaesthetic methods, and (nerve) block of fingers and toes. Lo-... 

Infiltration anaesthesia is applied fan-shaped, with as few needle punctures as possible, in close proximity of the wound or the skin area to be treated. An aspiration should always take place to avoid intravascular injection. Suitable alternatives are lidocaine (lignocaine) or prilocaine for injection 5-10 mg/ml, with or without adrenaline. When making an incision of an abscess it is sometimes difficult to use a local anaesthetic if there is a pronounced inflammatory reaction, since the effect of the anaesthetic is reduced due to an increased acidity level. While adrenaline reduces bleeding and delays dispersion of the anaesthetic, local anaesthetic/adrenaline combinations are contraindicated for local anaesthesia of digits, on the face or where the skin survival is at risk. 

III.b.8.1. Skin. Surface anaesthesia of the skin can be produced with help of a cream containing a eutectic mixture of local anaesthetics (EMLA), which is a water/oil emulsion of equal parts of prilocaine and lidocaine with particularly good penetration capacity. EMLA is applied under occlusion, around 40-60 minutes before the planned intervention. This is an effective way of producing anaesthesia before needle punctures and minor, painful, procedures. The method is excellent, particularly in paediatrics, to reduce fear and pain. 

Dental anaesthesia—The total amount of local anaesthetics injected is much smaller (20-80 mg of lignocaine) than that used for othr purpose. Lignocaine (2%) with adrenaline (1 80,000) is the standard local anaesthetic preparation used in dentistry which produces good soft tissue and pulpal anaesthasia and also reduce postextraction bleeding. 

Lignocaine injections are indicated for production of local or regional anaesthesia by infiltration techniques such as percutaneous injection, peripheral nerve block, spinal or subarachnoid block. 

It is another local anaesthetic with longer action but most toxic. It is used for surface anaesthesia. 

It is a potent and long acting local anaesthetic used for spinal, infiltration, epidural anaesthesia and nerve block. 

Adrenaline along with local anaesthetics may be used for infiltration, nerve block and spinal anaesthesia for prolonging the action and to reduce the systemic toxicity of local anaesthetics. 

Local anaesthetics can be applied topically, deposited around peripheral nerves, or infiltrated into tissues. Central neural blockade can be produced by injection into the subarachnoid or epidural spaces. Less common uses are for intravenous regional anaesthesia and attenuation of cardiovascular responses to tracheal intubation. The membrane-stabilising effect of local anaesthetics has been utilised in the treatment of myocardial arrhythmias. 

Prilocaine is suitable for most types of local anaesthetic block but is not suitable for epidural use in obstetrics because of the need for repeat administration. Its main uses are for infiltration anaesthesia and intravenous regional anaesthesia where its low toxicity makes it the drug of choice. Levobupivacaine... 

Pitkanen M, Rosenberg PH. Local anaesthetics and additives for spinal anaesthesia—characteristics and factors influencing the spread and duration of the block. Best Pract Res Clin Anaesthesiol. 2003 17 ... 

Cerebral blood flow (CBF) was monitored in the cerebral cortex of the ischemic hemisphere corresponding to the supply territory of the middle cerebral artery by laser-doppler flowmetry (DRT4, Moor Instruments, Devon, UK). To this aim, a rectangular bent laser-doppler probe was glued onto the parietal bone (2 mm posterior and 5 mm lateral from bregma) and local CBF was continuously measured from 20 min before the onset of ischemia until 10 min after reperfusion, keeping the animal under isoflurane anaesthesia. Flow values were collected every 5 min before MCAo and after reperfusion whereas data were collected at 10 min intervals during occlusion. 

CALCIUM CHANNEL BLOCKERS ANAESTHETICS - LOCAL Case reports of severe 1 BP when bupivacaine epidural was administered to patients on calcium channel blockers Additive hypotensive effect both bupivacaine and calcium channel blockers are cardiodepressant in addition, epidural anaesthesia causes sympathetic block in the lower limbs, which leads to vasodilatation and 1 BP Monitor BP closely. Preload intravenous fluids prior to the epidural... 

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