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LOCAL ANAESTHETICS

LOCAL ANAESTHETICS. These are drugs that causes reversible loss of sensation, without loss of consciousness, affecting a localized area. Classification of Local Anaesthetics. Injectable Low potency, short duration Procaine, Chloroprocaine Intermediate potency and duration

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LOCAL ANAESTHETICS

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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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