LA REVISION - I

Dr.V.RAMKUMARCONSULTANTDENTAL&FACIOMAXILLARYSURGEON

REGNO:4118 TAMILNADU-INDIA(ASIA)

Local anesthesia has been defined as a 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.

Properties deemed most desirable for a LA solution –

It should not be irritating to the tissue. It should not cause any permanent

alteration of nerve structure. Its systemic toxicity should be low. It must be effective regardless of whether

it is injected into the tissue or applied locally to mucous membranes.

The time of onset of anesthesia should be as short as possible.

The duration of action must be long enough to permit completion of the procedure.

It should be relatively free from producing allergic reactions.

It should be stable in solution and readily undergo biotransformation in the body.

Electrophysiology of nerve conduction

Exitation of nerve segment leads to an increase in permeability of the cell membrane to Na ions

At firing threshold permeability increases dramatically

Reversed polarity

Repolarization (the action potential is terminated)

Mode and site of action of LA

LA interfere with the excitation process in a nerve membrane in one or more of the following ways

Altering the basic resting potential of the nerve membrane

Altering the threshold potential (firing level) Decreasing the rate of depolarization Prolonging the rate of repolarization

Where do local anesthetics work?

Various theories –

Acetylcholine theory

Calcium displacement theory (most popular)

Surface charge (repulsion) theory

Membrane expansion theory

Specific receptor theory

How LA work?

Ca++ which exist in bound form within the cell membrane are thought to exert a regulatory role on the movement of Na+ ions

Ca++Ca++

Ca++Ca++

Displacement of Ca++ ions from the Na+ channel receptor site

Binding of LA molecule to this receptor site produces –

Blockade of the Na+ channel –

and results in conduction blockade

Pharmacology of LA

Classification of LA

1…Esters

Benzoic acid Paraaminobenzoic acid

ButacaineCocaineEthyl aminobenzoate (benzocaine)HexylcainePiperocaineTetracaine

ChlouopeocaineProcainePropoxycaine

2…Amides Articaine Bupivacaine Dibucaine Etidocaine Lidocaine Mepivacaine Prilocaine Ropivacaine

3…Quinoline Centbucridine

Half life of LA Lidocaine – 1.6 hours

Bupivacaine – 3.5 hours

Pharmacology of vasoconstrictors

Vasoconstrictors are drugs that constrict blood vassals.

Advantages – Decreases blood flow to the site of

administration. Absorption of LA into the CVS is slowed. Minimizing the risk of LA toxicity. Increasing the duration of action of LA.

Classification

Catecholamines Noncatecholamines

EpinephrineNorepinephrineLevonordefrin

AmphetamineMethamphetaminePhenylephrine

Felypressin (vasoconstrictor), a synthetic analogue of the polypeptide vasopressin.

Maximum doses of LA Lidocaine with epinephrine

7 mg/kg of body weight for the adult (not to exceed a dose of 500 mg).

Lidocaine without epinephrine 4.4 mg of body weight for the adult (not to

exceed a dose of 300 mg).

Same dose for children.

Calculation of number of cartridges (for70 kg)

Lidocaine with epinephrine

According to manufacturer –

20 mg/ml i.e. in 1 ml - 20 mg Considering cartridge as 1.8 ml

i.e. in 1.8 ml - 36mg(1.8×20)

or in 1 Cartridge - 36 mg Not to exceed a dose of 500 mg

So total no of cartridges 500/36 = 13.88 cartridges

Lidocaine without epinephrine

According to manufacturer –

20 mg/ml i.e. in 1 ml - 20 mg Considering cartridge as 1.8 ml

i.e. in 1.8 ml - 36mg(1.8×20)

or in 1 Cartridge - 36 mg Not to exceed a dose of 300 mg

So total no of cartridges 300/36 = 8.33 cartridges

Armamentarium

Tow types of armamentarium

Major components

Syringe Needle Cartridge

Other components

Topical antiseptic Topical anesthetic Applicator sticks Cotton gauze (2×2

inches) Hemostat

Syringe – It is the vehicle whereby the contents of the

anesthetic cartridge are delivered through the needle to the patient.

Needle –The needle permits the local anesthetic

solution to travel from the dental cartridge into the tissues surrounding the needle tip.

Cartridge – Is a glass cylinder containing the local

anesthetic drug.

Topical anesthetic -

Applicator sticks –

Cotton gauze (2×2 inches) –

Hemostat –

LA REVISION – II

Types of Local anesthetic injection

Local infiltration – Small terminal nerve endings in the area of the

dental treatment are flooded with local anesthetic solution.

Example: administration of LA into an interproximal papilla.

Field block –LA solution is deposited near the larger

terminal nerve branches so the anesthetic area will be circumscribed.

Nerve block –LA is deposited close to a main nerve trunk.

Common Techniques of Anesthesia (Maxillary / Mandible)

1…Supraperiosteal (infiltration)2…Periodontal ligament injection

(intraligamentary injection)

3…Intraseptal

4…Intracrestal

5…Intraosseous

Posterior superior alveolar nerve block

Techniques of maxillary anesthesia

Infraorbital nerve block

Middle superior alveolar nerve block Is present in only about 28% of the

population

Palatal anesthesia Greater palatine nerve block

Nesopalatine nerve block

Techniques of mandibular anesthesia Inferior alveolar nerve block

Lingual nerve block –

After depositing LA solution for inferior alveolar nerve pull the needle half way out, aspirate and deposit the LA solution for lingual nerve

Advantage – nicking of soft tissue will be avoided.

Buccal nerve block –a. Parallel with occlusal plane on the side of

injection but buccal to it.b. Distal and buccal to the last molar.

Mental nerve block

Mandibular nerve block: the GOW-GATES technique

VAZIRANI-AKINOSI closed-mouth mandibular block

Complications of local anesthesia Local complications Needle breakage Persistent anesthesia or

paresthesia Facial nerve paralysis Trismus Soft-tissue injury Hematoma Pain on injection Burning on injection Infection Edema Sloughing of tissues Post-anesthetic intraoral

lesions

Systemic complications Vasodepressor syncope Over dosage (toxic

reaction) Allergy Psychogenic reactions

Local complications

Needle breakage

Causes – Weakening of the dental needle by

bending it before it’s insertion. Sudden unexpected movement by the

patients.

Prevention – Use a 25-gauge needle. Use long needle requiring penetration (>

18 mm).

Persistent anesthesia or paresthesia

Causes – Trauma to any nerve. Injection of contaminated LA solution. Hemorrhage into or around the neural

sheath (Bleeding increases pressure on the nerve)

Prevention – Strict adherence to injection protocol. Proper care and handling of dental

cartridges.

Causes – Transient facial nerve paralysis is commonly caused by

the introduction of LA into the capsule of the parotid gland.

Prevention – Adhering to protocol with the IANB . A needle tip should be in contact with the bone.

Management – Reassure the patient Contact lance should be removed An eye patch should be applied to the affected eye. “tincture of time” is the recommended medicine.

TrismusCauses – Trauma to muscles or blood vessels. Contaminated LA solution. Hemorrhage. A low grade infection. Excessive volumes of LA solution.

Prevention – Practice atraumatic insertion and injection technique.

Management – Heat therapy, physiotherapy. Warm saline rinses. Anti-inflammatory, Analgesics, Muscle relaxants,

Antibiotics.

Soft-tissue injury

Causes – Common in younger children and mentally or

physically disabled children or adults.

Prevention – Proper instruction and education of guardian

HematomaCauses – The effusion blood into extravascular spaces due to

nicking of blood vessel (artery or vein) during injection.

Prevention – Use a short needle for PSA nerve block. Minimize number of needle penetration.

Management – Direct pressure should be applied to the site of

bleeding. Do not apply heat to the area for at least 4 to 6 hours.

Pain on injection

Causes – Careless injection technique.

Prevention - Proper technique. Use of sharp needle. Use of topical anesthetic. Inject LA slowly.

Burning on injection

Causes – pH of the solution (pH = 5 acidic) Rapid injection of LA. Contamination of LA cartridges

Prevention – Slowing the injection ( ideal rate 1 mm per sec.)

InfectionCauses – Contamination of needle. Injecting LA solution into an area of infection.

Management – Rx treatment consist of those procedures to

manage Trismus.

EdemaSwelling of tissue is a clinical sign of the presence

of some disorder.

Causes – Trauma, Infection, Allergy, Hemorrhage.

Prevention – Complete medical evaluation of the patient

before drug administration.

Sloughing of tissues Prolonged irritation or ischemia of gingival

soft tissue may led to – Epithelial desquamation Sterile abscess

Post-anesthetic intraoral lesions

These are recurrent aphthous stomatitis and Herpes simplex.

Management – Primary management is symptomatic.

Systemic complications Vasodepressor syncope Over dosage (toxic reaction) Allergy Psychogenic reactions

Thank You