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Information about LOCAL ANAESTHETIC

Published on January 30, 2016

Author: sonika.bphm

Source: authorstream.com

LOCAL ANAESTHETICS: LOCAL ANAESTHETICS SONIKA SHRIVASTAV Slide 2: Local Anaesthetics : are drugs which upon local application or local injection cause reversible loss of sensory perception, specially of a pain in a restricted area of the body. They block generation and conduction of nerve impulse ,without causing structural demage . Difference between General and local anaesthetic: Difference between General and local anaesthetic Comparative feature General Local Action site CNS Peripheral nerve Body area Whole body Restricted area consciousness lost unaltered Care of vital function essential Usually not required Safety level in poorhealth patient risky safe With non coperative patient possible Not possible Major surgery preferred Not used Minor surgery Not preferred preferred classification: classification Injectable Surface anaesthetic Low potency intermediate high soluble insoluble procaine Lignocaine ( lidocaine ) tetracaine cocaine benzocaine chlorprocaine prilocaine bupivacaine lignocaine oxethazaine ropivacaine tetracaine Mechanism of action: Mechanism of action Local anaesthetics block the initiation and propagation of action potentials by preventing the voltage-dependent increase in Na + conductance and their main action is to block sodium channels. Slide 7: Drug action Lignocaine(lidocaine): Lignocaine ( lidocaine ) Most widely used anaesthetic . It is a versatile anaesthetic and good for surface application as well as injection. More preferrable than procaine because when it injected around nerve it block conduction within 3 min whereas procaine may take 15 min. And anaesthetia is more intense and longer lasting. It also used as a antiarrhythmic agent. Slide 9: Systemic action CNS drowsiness and lethargy Higher dose cause excitation followed by depression Basic action is neuronal inhibition At high dose all neurones are inhibited and found flatering of waves in EEG. CVS LA are cardiac depressant,but no significant effect are observed at conventional dose. At higher dose it causes: Decrease in automaticity Decrease in exitability Decrease in contractility Decrease in conductivity Slide 10: Blood vessels: Fall in B.P. due to sympathetic blockage Higher dose cause direct relaxation of arteriolar smooth muscle Pharmacokinetics: Soluble surface anaesthesia are rapidly absorb from the mucous membrain but poorly absorb from intact skin. Bound with plasma 1 glycoprotein. Slide 11: Adverse effect: In cns --- dizziness,auditory and visual disturbance, mental confusion, shivering,tremors , respiratory arrest etc. In cvs --- bradycardia , hypotension.arrhythmias Injection of local anaesthetic may be painful. Hypersenstivity reaction like rashes, edema, dermatitis, asthma may occur. Local anaesthetic in dentistry: Local anaesthetic in dentistry LA are mainly used by nerve block or by infilteration / regional block tech. to carry out surgical procedure. Applied topically on oral ulcer and superficial lesion. Less amount (20-80mg of lignocaine ) required for dental anaesthesia and for children marginaly less than that in adults. Some common side effects: Palpitation Sweating Giddiness Nausea Tremour Preparation: Preparation Lignocaine (2%) with adrenaline(1:80000) is the std LA preparation. It produce good soft tissue as well as pulpal anaesthesia and reduces post extration bleeding. Pulpal Anaesthesia obtain---2-3 min Last ----40-60 min Soft tissue anaesthetised ----2-3 hours Topically Lignocaine may applied on painful oral ulcer , prior to intra oral injection and before dental x-ray. Slide 14: Bupivacaine (0.5%) with adrenaline (1:200000) is less frequently used. Because of: Very high lipid solubility,largly taken up by peridontal tissue and penetration into bone is poorer. Onset of pulpal anaesthesia is slow Ropivacaine is ocassionaly used Methods of Administration: Methods of Administration 1- Surface anesthesia : direct application of the drug on the surface such as skin and mucous membrane Only superficial layer is anaesthetised . Surface anaesthesia found in different form like ointment,lozenges,suspension,cream,jelly etc. Onset and duration of action depend on the site,drug and concentration of drug. 2- Infiltration anesthesia : injection of LA is infillered in subcutaneous tissue in order to block sensory nerve endings at the site of action. Onset of action is immediate. Infiltration is used for minor operation and small area. 3- Conduction block: The LA is injected around nerve trunks so that area distal to injection is anaesthetised . Slide 16: Field block : It is produced by injecting the LA subcutaneously in a mannor th at all nerve coming to a particular field are blocked Nerve block : It is produced by injecting the LA appropriate nerve trunks or plexuses. In dentistry this type of administration is prefer. 4.Epidural anesthesia : injection of LA into the epidural space.this space filled with semiliquid fat through which nerve roots travel. According to site of action there are 3 categories : Thoracic Lumber Caudal 5- Spinal anesthesia : injection of LA into subarachnoid space in the lumber region between L2-3 or L3-4 Spinal anaesthesia is used for operation on the lower limbs,pelvis,lower abdomen etc. Lignocaine along with the adrenaline: Lignocaine along with the adrenaline Vasoconstrictor is a substance used to keep the anesthetic solution in place at a longer period and prolongs the action of the drug vasoconstrictor delays the absorption which slows down the absorption into the bloodstream Lower vasodilator activity of a local anesthetic leads to a slower absorption and longer duration of action Vasoconstrictor used the naturally hormone called epinephrine (adrenaline). Epinephrine decreases vasodilator. It also provide blood less area for surgery. Side effects of epinephrine Epinephrine circulates the heart, causes the heart beat stronger and faster, and makes people feel nervous. Slide 18: Thank you

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