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Understanding Local Anaesthetics Applications and Effects

Learn about the various classifications, mechanisms of action, pharmacological effects, administration techniques, and merits/demerits of local anaesthetics. Explore different drug types, clinical conditions, and how to prolong their effects. Discover surface, infiltration, nerve block, and spinal anesthesia methods. Dive into EMLA for intact skin anesthesia and its benefits.

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Understanding Local Anaesthetics Applications and Effects

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  1. LOCAL ANAESTHETICS

  2. These are drugs that causes reversible loss of sensation, without loss of consciousness, affecting a localized area

  3. Classification of Local Anaesthetics • Injectable • Low potency, short duration Procaine, Chloroprocaine • Intermediate potency and duration Lignocaine, Prilocaine • High Potency, Long duration Tetracaine , Bupivacaine, Ropivacaine, Dibucaine

  4. II) Surface Anaesthetic a)Soluble Cocaine Lignocaine Tetracaine Benoxinate b) Insoluble Benzocaine Butylaminobenzoate (Butamben) Oxethazine Classification of Local Anaesthetics III) Other Drugs Propranolol, Chlorpromazine, Quinine

  5. Mechanism Of Action [MOA] Block voltage gated Na+ channel ↓ Depolarization ΘConduction

  6. Pharmacological Actions of Lignocaine • Local Actions Topical Application Block Ganglionic synapse Sensory & Motor nerve endings Neuro muscular junction Nerve trunks

  7. Systemic Actions

  8. CNS Local anaesthetics CNS stimulation Euphoria, Excitement, Restlessness, Tremor, Convulsions CNS Depression Unconsciousness, Respiratory depression, Death

  9. CVS • Cardiac depressant • ↑ dose ↓ automaticity, ↓ excitability ↓ contractility ↓ conductivity ↓ ERP • Antiarrhythmic action • ↑ ↑ dose cardiac arrhythmia

  10. Blood vessels Sympathetic blockade • ↓ BP Arteriolar relaxation Adverse effects Injection  painful Light headedness, dizziness, mental confusion Auditory & Visual disturbances Shivering, Twitchings, Convulsions Bradycardia, Hypotension, Cardiac arrhythmia Rashes , Angioedema, Dermatitis

  11. How to Prolong the action of LA • Add a vasoconstrictor • ie; ADRENALINE

  12. Merits • Prolongs the duration of action of LA • ↑ intensity of block • ↓ systemic toxicity of LA • Provides blood less field for surgery Demerits • Injection will be more painful • Local tissue edema, necrosis • Delays wound healing • ↑ BP & promote arrhythmia

  13. Techniques of Local Anesthesia • Surface Anesthesia local anesthetic solution applied topically mucous membrane anesthesia Clinical Conditions: Tonometry, Nasal lesion, sore throat, tonsillectomy, intubations

  14. Drugs used as Surface anesthetics Amethocaine : eye , throat, rectum, skin Benzocaine & Lignocaine: all mucous membrane Dibucaine : ear, rectum, skin Proparacaine: eye

  15. ii) Infiltration Anesthesia Injected local anesthetic tissue Clinical Conditions:drainage of abscess, incision, excision Drugs:- Lignocaine, procaine skin Intra abdominal organs

  16. iii) Nerve Block Injected around local anesthetic Peripheral nerves & Nerve plexuses Clinical Conditions: Surgeries on; lower abdominal wall upper limbs neck tooth extraction Drugs : Lignocaine, Prilocaine, Ropivacaine, Bupivacaine

  17. iv) Spinal anesthesia Injected local anesthetic subarachnoid space Good analgesic Anesthetic Muscle relaxant Sympathetic blockade Hypotension , Bradycardia Clinical conditions : surgeries in lower limb, lower abdomen, pelvis, caesarian section Headache, Respiratory paralysis

  18. EMLA ( Eutectic Mixture of Local Anesthetics) • Unique preparation which anesthetise intact skin after surface application • Eutectic lowering of melting point when two solids are mixed • LIDOCAINE + PRILOCAINE (equal proportion at 250C) oil cream • Anesthesia upto depth of 5mm, lasts 1-2hr • Can be applied over occlusive dressing 1 hr before i.v cannulation, skin graft harvesting Emulsified

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