Presented byDr. Mehreen riaz

Demonstrator, omfsiidh

LOCAL ANAESTHESIA

DEFINITION

Loss of sensation in a circumscribed area of the body caused by a depression of excitation in nerve endings or an inhibition of the conduction process in peripheral nerves.

OTHER METHODS:-1) Mechanical trauma2) Low Temperature3) Anoxia4) Chemical Irritant5) Neurolytic agents6)Chemical agents

CLASSIFICATION

ACCORDING TO SITE:-1)Topical2)Infiltration3)Regional Block • ACCORDING TO CHEMICAL COMPOSITION:-1)Amides2)Esters3)Alcohols4)Others e.g oxathazin, chlorbutol, Clove Oil, Eugenol

CLASSIFICATION

ESTERS:-Esters of Benzoic acid:-

Butacaine Cocaine Ethyl aminobenzoate (benzocaine) Hexyclaine Piperocaine Tetracaine

Esters of PABA:-• Chloroprocaine• Procaine• Propoxycaine

AMIDES:-• Articaine• Bupivacaine• Dibucaine• Etidocaine• Lidocaine• Mepivacaine• Prilocaine• Ropivacaine

MECHANISM OF ACTION

Displacement of Ca ion from Na channel receptor

Binding of the L.A mol. To this

receptor site which thus produces

Blockade of the Na channel and a…

Dec in Na conductances Depression of the rate of electrical depolarization and a….

Failure to achieve the threshold potential with a… Lack of development of propogated action potential

which is called…. Conduction Blockade

which permits

PHARMACOLOGY

PHARMACOKINETICS:- Uptake:- L.A produce a degree of vasoactivity . Most producing

vasodilatation except Cocaine. Procaine is the most potent vasodilator.

Topical route:- Tracheal Mucosa:- Absorption is as rapid as IV Pharyngeal Mucosa :- Absorption is slower Eosaphagus and Bladder mucosa :- Uptake is even slower

IV:- It’s the most rapid route of administration. Used in PVC’s

PHARMACOKINETICS

DISTRIBUTION:- Distributed throughout the body Highly perfused organs Not highly perfused organs e.g. skeletal muscles Cross BBB Cross Placental Barrier Procaine and Chloroprocaine shortest half life ( 0.1 hrs) Etidocaine Longest Half Life ( 2.6 hrs )

PHARMACOKINETICS

METABOLISM (BIOTRANSFORMATION):- ESTERS:- Hydrolyzed in plasma by the enzyme pseudocholinesterase Chloroprocaine ……most rapidly hydrolyzed Tetracaine …………16 times more slowly and is toxic Allergic reaction due to PABA Atypical Pseudocholinesterase Difficulty during previous GA should be taken

AMIDE LOCAL ANESTHETICS:-• Primary site is liver• Prilocaine gets metabolized in liver Primarily but

also in lungs• Liver disease …. Rate of biotransformation

anesthetic blood levels in blood toxicity

PHARMACOKINETICS

EXCRETION:- Kidneys Primary organ for L.A and its metabolites Renal Impairment eg glomerulonephritis , pyelonephritis, renal

dialysis.

SYSTEMIC ACTIONS CNS:-• Depression • Anticonvulsant properties ( procaine, lidocaine, mepivacaine)

CVS:- Myocardium:- Myocardial depression Dec. electrical excitability Dec . Conduction rate Dec. force of contraction Therapeutic advantage in cardiac arythmias , PVCs, Vtech.

(lidocaine)

Blood Vessels:-Cocaine VasoconstrictionAll other vasodilationHypotension ( procaine more effective) due to

myocardial depression and vasodilation .LOCAL TISSUE TOXICITY:-Skeletal muscles Longer acting LA such as EtidocaineMuscle regenerates after 2 wks after LA inj.

Respiratory Sys:-• Non Over dose levels direct relaxant effect• Overdose Respiratory arrest may occur

VASOCONSTRICTOR

Catecholamines Noncatecholamime

Epinephrine AmphetamineNor Epinephrine MethamphetamineLevonordefrin EphedrineIsoproterenol MephentermineDopamine Hydroxuamphetamine

MethoxaminePhenylephrine

*Fellypressin .

EPINEPHRINE

Source:- Available as synthetic Adrenal Medulla of animals

Mode of action :- α and β adrenergic receptors. β effects predominate

Systemic Actions:-Cardiovascular dynamics:- Inc in systolic and diastolic pressures Inc in Cardiac output• Inc in stroke Vol.• Inc in strength of contraction Inc in Myocardial O2 consumption

Hemostasis:- Used as a hemostatic agent Initial action on α receptors and vasoconstriction and as

tissue conc dec. its affect will be on β receptors and vasodilation occurs.

Respiration:- Epi is a potent bronchodilator Asthma drug of choice

CNS:- Not a CNS stimulant in normal doses

In inc doses effects are prominent

Metabolism:-Inc O2 consumption in all tissues

Stimulates Glycogenolysis in the liver and skeletal muscles

Elimination:-Re uptake by adrenergic nerves

Enzyme MAO & COMT ( catechol-O-methyltranferase)

Clinical Application:- Allergic reactions

Bronchospasm Cardiac Arrest Vasoconstrictor

Mydriasis.

CONTENTS

Local anesthetic cartridgePresevative..MethylparabenAntioxidant…Na bi sulphite, NA

metabisulphiteAlkalizing agent …Na hydroxideNaCl isotonicFungicide …Thymol

Maximum Safe Dose of Epi.

Maximum Safe dose for a healthy adult is 0.2 mg or 200µg per app.

Maximum safe dose for a pt. with clinically significant CVS disease is 0.04mg or 40 µg per appointment.

Maximum Safe Dose of L.AMax Safe dose =4.4mg/kg body weight1 kg=4.4mg60kg=4.4 x 60=264mg1 dental cartridge =36mg per 1.8ml 264mg /36=7 cartridges.

TOPICAL ANAESTHETICS

SPRAYS:- JET SPRAY:-• 1 0% lignocaine Punct

wound• 1min onset Surface

anesthesia produced• DOA 10 mins OINTMENTS:-• 5% Lignocaine• 3-4 mins to produce anesthesia• Enzyme hyaluronidase• Amethocaine & Benzocaine• Deep gingival scaling EMULSIONS:-• 2% Lignocaine HCL• Full mouth Impressions• Relief Post op tenderness ETHYL CHLORIDE:-• Refrigeration• Fluctuant abscess• Snow appears

ARMAMENTARIUM

Different techniques of achieving LA

Local infiltrationField blockNerve blockIntraligamentryIntraseptalIntrapulpalIntraosseous injectionJet injector Computer controlled local anesthetic delivery systemElectronic dental anesthesiaTopical anesthesia

Local infiltration

In local infiltration, small terminal nerve endings in the area of the surgery are flooded with local anesthetic solution, rendering them insensitive to pain or preventing them becoming stimulated & creating an impulse.

Incision is made into the same area in which the LA has been deposited.

Field block

Method of securing regional anesthesia consisting of depositing a suitable LA solution in proximity to the large terminal nerve branches so that the area to be anesthetized is circumscribed to prevent the central passage of afferent impulses

Incision is made into an area away from the site of injection

Nerve block

Method of securing regional anesthesia by depositing LA solution within close proximity to a main nerve trunk

Usually at a distance from the site of operative intervention

Periodontal ligament injection

Indications1. Pulpal anesthesia of one or two teeth in a quadrant

2.Treatment of isolated teeth in mandibular quadrant

3. Patient for whom residual soft tissue anesthesia is undesirable

4. Situations in which regional block is contraindicated

Contraindications

1. Infection or inflammation at the site of injection

2. Primary teeth when the permanent tooth bud is present

3. Patient who requires a “numb” sensation for psychological discomfort

Intraseptal injection

IndicationsWhen both haemostasis & pain control are desired for soft tissue & osseous periodontal treatment

Contraindications Infection or severe inflammation at the site of injection

Intrapulpal injection

Deposition of LA directly into the pulp chamber of a pulpally involved tooth provides effective anesthesia for pulpal extirpation & instrumentation where other techniques have failed.

Intraosseous injection

Indications Pain control for

dental treatment on single or multiple teeth in a quadrant

Contraindications Infection or severe inflammation at the site of injection

Jet injector

Principle- based on principle that liquid forced through

very small openings, called jets, at very high pressure

can penetrate intact skin or mucous membrane

The primary use of jet injector is to obtain topical

anesthesia before the insertion of a needle

In addition it may be used to obtain mucosal

anesthesia of palate.

Advantages

1. Does not require use of needle

2. Delivers very small amount of LA

3. Used in lieu of topical anesthesia

Disadvantages

1. Is inadequate for pulpal anesthesia or regional anesthesia

2. May damage periodontal tissue

3. Many patients dislike the feeling accompanying use of the jet injector

4. Post-injection soreness of soft tissue may develop

Computer-controlled local anesthetic delivery system

The system enables a dentist or hygienist to accurately manipulate needle placement with fingertip accuracy and deliver the LA with a foot-activated control

Advantages

1. Precise control of flow rate & pressure, hence a more comfortable injection

2. Increased tactile feel

3. Non-threatening

4. Automatic aspiration

5 Rotational insertion technique minimizes needle deflection

Disadvantages

1. Need for additional armamentarium

2. Increased cost

Electronic Dental Anesthesia

The method of achieving local anesthesia involves the use of the principle of transcutaneous electrical nerve stimulation {TENS} which has been used for the relief of pain

Indications

1. In patients with needle phobia

2. Ineffective LA

3. Instances where LA cannot be administered

Contraindications

1. Cardiac pacemakers

2. Neurological disorders

3. Pregnancy

4. Very young pediatric patients

5. Older patients with senile dementia

Refrences

Stanley F. Malamed –Handbook of local anesthesia, fifth edition, published by Elsevier, page no. 255-268 & 352-358