Local Anaesthesia

classification, biotransformation, action of Local Anaesthesia

1. LOCAL ANAESTHESIA ARJUN SHENOY POSTGRADUATE STUDENT DEPT OF MAXILLOFACIAL SURGERY KVGDCH

2. Definition Requirements composition Mechanism of action Classification Biotransformation Indications and contraindications CONTENTS

3. DEFINITION The word was coined by Dr Oliver Holmes 1846 Greek word. An means without and aisthetos means pain . Anesthesia means loss of sensation including pain, touch, temperature and pressure perception and may be accompanied by impairment of motor function

4. Nonirritant . Should not produce any local reaction. Should not cause any permanent change in the nerve structure. Should cause minimal systemic toxicity . Should be effective and enough penetrating properties when used topically. Should have short time of onset . REQUIREMENTS

5. Duration should enough to allow the completion of procedure. Should have enough potency. Should be free from allergy producing substances. Should be sterilized of capable of being sterilized by heat without deterioration . Should be stable and readily undergo biotransformation in the body.

6. COMPOSITION AGENT FUNCTION LIGNOCAINE HYDROCHLORIDE 2% LOCAL ANAESTHETIC AGENT ADRENALINE 1:80000 VASOCONSTRICTOR SODIUM METABISULFATE REDUCING AGENT METHYLPARABEN PRESERVATIVE

7. DISTILLED WATER DILUTING AGENT RINGERS SOLUTION VEHICLE SODIUM HYDROXIDE TO ADJUST PH NITROGEN BUBBLES PREVENTS DESTRUCTION OF VASOPRESSOR BY OXYGEN

8. Acetylcholine theory . Calcium displacement theory . Surface charge theory . Membrane expansion theory . Specific theory . The theories explaining the mechanism of action of local anesthesia are

9. Local anaesthetics are membrane stabilizing drugs. Acts by inhibiting sodium influx through voltage gated sodium specific ion channels in the nueronal cells. Hence action potential cannot arise due to this inhibition and blockade of conduction is established. MECHANISM OF ACTION

10. PAIN TEMPERATURE TOUCH PROPRIOCEPTION SKELETAL MUSCLE TONE FUNCTIONS LOST WITH LA INITIALLY GRADE C FIBRES ARE BLOCKED FOLLOWED BY GRADE A

11. CLASSIFICATION BASED ON ORGIN ON BASIS OF CHEMICAL NATURE ON THE BASIS OF DURATION OF ACTION

12. NATURALLY OCCURING SYSTEMIC COMPOUNDS ON BASIS OF OCCURANCE

13. On the basis if OCCURRENCE in nature: NATURALLY OCCURING : e.g. cocaine. SYSTEMIC COMPOUNDS Derivatives of acentanillide : e.g. lignocaine ( lidocaine , xylocaine ) l Miscellaneous drugs with local anesthetic action like phenol, chlorpromazine

14. ESTERS These can be further classified as: Esters of benzoic acid e.g. cocaine butacaine . Esters of para-aminobenzoic acid e.g. procaine, propoxycaine . AMIDES e.g. articaine , bupivacine , lidocaine . BASED ON CHEMICAL NATURE

15.   short acting articaine , lidocaine , mepivacaine , prilocaine . Long acting: bupivacaine , etidocaine , bucricaine BASED ON DURATION OF ACTION

16. Incision and drainage of incised abscess. Removal of cysts, residual infection areas, hydrophilic groups and neoplastic growths, ranula and salivary calculi. In the treatment of tic douloreux by producing prolonged anesthesia with the combination of a local anesthetic agent and alcohol injection. INDICATIONS

17. Extraction of teeth and fractured roots. Odontectomy . Treatment of alveolagia . Alveolectomy . Apicoectomy . IN DENTISTRY

18. Esters are rapidly metabolised in the plasma by cholinestrase Amides are slowly destroyed in the liver by microsomal P450 enzymes BIOTRANSFORMATION

19. FACTORS INFLUENCING LA ACTION LIPID SOLUBILITY PH of the inflamed tissues vasoconstrictors

20. Premonitory signs Ringing in ears Metallic taste Numbness around lips MORE SERIOUS COMPLICATIONS- First apparent convulsions followed by CNS depression (death). CVS – arryhythmias and hypotension. UNDESIRED EFFECTS

21. MODES OF APPLICATION TOPICAL OR SURFACE APPLICATION INFILTRATIONS NERVE BLOCKS FIELD BLOCKS CENTRALLY ACTING ( SPINAL )

22. Methhaemoglobinemia neurotoxicity hypersensitivity

23. CONTRAINDICATION ABSOLUTE CONTRAINDICATION . RELATIVE CONTRAINDICATION

24. History of allergy to local anesthetic agent, or history of allergy to any of the constituents of the local anesthetic solution. ABSOLUTE CONTRAINDICATION

25. Fear and apprehension. Presence of acute inflammation or suppurative infection at the site of insertion of needle. Infants or small children. Mentally retarded patients. RELATIVE CONTRAINDICATIONS

26. Major surgical procedures with haemodynamic unstability epilepsy Presence of methhaemoglobinemia . Two drugs are to be avoided. They are benzocaine and articaine . Presence of atypical plasma cholinesterase

27. 1)patient remains awake and cooperative. 2)little disturbance of normal physiology. 3)low incidence of morbidity. 4)patient can leave the hospital unescorted. 5)additional personnel not required. ADVANTAGES

28. 6)percentage of failure is small. 7)technique not difficult master. 8)no additional expense to the patient. 9)Patient need not miss the previous meal.

29. No true disadvantages to the use of regional anesthesia, when the patient is mentally prepared and when there are no contraindications. DISADVANTAGES

30. Potency: depends solely on the chemical nature. Duration of anesthesia: depends on molecular weight and presence of vasoconstrictor If lipophillic group predominates then the ability to diffuse into the lipid rich nerve diminishes. INTERESTING FACTS OF L.A

31. Lidocaine disposition. half life NORMAL HEART FAILURE 1.8 hr 1.9 hr HEPATIC DISEASE RENAL DISEASE 4.9 hr 1.3 hr