LA Overview

8/6/2019 LA Overview

1/14

Neurophysiology Overview

The trigeminal nerve is a predominately sensory nerve with three main

branches: the ophthalmic nerve, the maxillary nerve and the mandibular nerve

which includes motor function. The cell bodies of the trigeminal nerve form the

semilunar or Gasserion Ganglion. This ganglion can be found in Meckle's Cave inthe bottom of the middle cranial fascia.

Local Anesthesia in Dentistry


2/14

1. Premedication

2. Local Anesthetic Armamentarium

3. Local Anesthetic Solution (Carpule)

4. Types of LA drugs

5. Pharmaco-kinetics of LA drugs

6. Vasoconstrictors & other components

Local anesthetic: produce loss of sensation to pain in a specific area of the

body without the loss of consciousness

Premedication

Premedication is the use of drugs to prepare the patient in an optimum state for

surgery.

Usually sedatives are given prior to operative treatment to make the patient less

aware of any discomfort & thus more relaxed & cooperative.

Also antihistaminic & other drugs for control of salivation could be used prior to

surgery.

Advantages of Premedication

1. Allay fear & anxiety making patient more relaxed & cooperative.

2. Raise the pain threshold.

3. Control gag reflex.

4. Allow for post-operative amnesia when patient remembers little of

operation on the 2nd day.

5. Losing the sense of time & patient would be unable to recall duration of

procedure, so long, difficult procedures can be done without disturbing

patient.

Drugs used in Premedication

Good knowledge of restricted number of drugs is better than having superficial

knowledge of a large variety of proprietary products.

The following are the recommended drugs that might be used in premedication

prior to local anaesthesia.

Barbiturates, Tranquilizers, Antihistamines, Anti-sialagauges


3/14

I - Barbiturates: Sedate & depress CNS without much effect on respiration.

in excessive amounts, the patient will be too drowsy to return home

In minimal doses, patient wont be adequately sedated

in too low dose they may make patient excitable

Disadvantages: they are liable to cause addiction.

Pentobarbitone Sodium (Nembutal).

Quinalbarbitone Sodium (Seconal).

Phenobarbitone Sodium (Luminal; Gardenal ).

The dosage of all these drugs is

100-200 mg orally for adults, one hour before treatment;

For children 2mg/kg body weight, not exceeding 100mg.

The approximate duration of sedation is 4 - 8 hours.

II -Tranquilizers:

They are Benzodiazepin derivatives.

These drugs have selective depression on CNS, unlike Barbiturates which cause

generalized depression.

Reduce anxiety without analgesic action. Patient is not confused or disoriented

but reactions are slowed.

There is no cardiac depression and no alternation in the blood pressure.

Examples of Benzodiazepin derivatives are:

Diazepam (Valium).

Chlordiazepoxide (Librium).

The dosage for an adult is 10 - 20 mg taken orally or by injection 1 hour before

dental treatment; for a child or elderly patient the dosage is 5-10 mg. The

duration of effect of valium and Librium is 3 - 4 hours.

Valium and Librium are also muscle relaxant. But recovery from them is fairly

rapid and the patient is fit to return home 3 hours after injection. Transient

depression occurs 3 - 4 hours after its administration.

III. Anti-histamines:


4/14

Have a powerful anti-emetic action, they possess a hypnotic effect &

potentiate action of barbiturates. Also, they guard against any allergic reactions

which might develop from any drug or materials used.

Promethazin hydrochloride Phenergan adult dose: 25 mg & for a child

over 5 years would be 10 mg. Its duration of action is approximately 12 hours.

IV. Anti-sialagauges:

Control & reduce salivary secretion to obtain a dry field for operation.

Hyoscine Scopolamine dose of 0.4mg.

Techniques of Premedication

Oral administration of a tranquillizer, eg. diazepam " Valium " 10mg about

1 hour before extraction.

For children valium can be used as oral premedication. It is given 2 - 3hours before appointment in dosage of 2 - 4 mg for children aged between

2 & 3 years, & dosage of 5 - 6 mg for those aged 5 years or older.

Another scheme recommends a suitable dose given the night before

treatment to ensure a good night-sleep, followed by repeating dose in

morning or giving it 2 hours before appointment.

In large surgical procedure as surgical removal of impacted tooth or cyst

enucleation schemes (A & B) can be used with LA

Scheme A:

1. Night before operation: 100 mg Gardinal or Nembutal.2. One hour before operation:

a) 100 mg Gardinal or Nembutal.

b) 25 mg phenergan.

c) 0.4 mg scopolamine.

Scheme B:

1. Night before operation : 10 mg Valium "orally ".2. One hour before operation:

a) 10 mg valium .

b) 25 mg phenergan .

c) 0.4 mg scopolamine .

Local Anesthetic Armamentarium


5/14

Syringe,Carpule, NeedleTypes of Syringes

1. Metallic

2. Disposable

3. Combined / self-aspirating

4. Computer Controlled LA Delivery Systems

Syringe Components

1. Needle adaptor

2. Syringe Barrel

3. Piston + Harpoon

4. Finger grip

5. Thumb grip

Needle Components

Gauge: the larger the gauge the smaller the internal diameter of needle: 27 g,

25 g, and 30 g.

Length: Long 35 mm, Short 25 mm, extra-long, ultra-short

1. Bevel (mono-beveled)

2. Shank

3. Hub

4. Syringe adaptor

5. Syringe penetrating end

The Carpule ( Cartridge )


6/14

1.8 mL ( USA ) - 2.2 mL ( UK & AU )

Stored at room temperature 21C to 22 C

Should not be soaked in Alcohol

Should not be Autoclaved

Should not be exposed to direct sunlight

Preparation of Armamentarium

Remove syringe from sterile pack

Attach needle

Retract piston fully

Insert cartridge

Engage the harpoon

Carefully remove cap

Local Anesthetic Solution (Carpule)

1. Local anesthetic agent.

2. Vasoconstrictor.

3. Preservative.

4. Reducing agent.

5. Fungicide

6. Vehicle.

Local anesthetic agent : Ideal LA drug

1. Produce efficient & potent anesthetic action.

2. Rapid onset of anesthesia with reasonable duration.

3. Reversible action on nerve tissues

4. Selective action on sensory nerves

5. Soluble in water to be used in solution in order to diffuse into the

tissues & nerve fibers

6. Compatible with salts to form isotonic solution

7. Non-irritating to tissues: no local 2ry effects: hyperemia, inflammation,

sloughing or necrosis


7/14

8. Sterilized without deterioration or loss of action

9. Should not affect healing process of tissues

10.Should have no systemic side effects after its absorption

11.Should have a vasoconstrictor action or compatible with adrenaline or

another vasoconstrictor

12.Chemical composition must be stable & can be stored for a reasonable

time

13.It should not be expensive

Common Properties of LA drugs

1. They are all synthetic .

2. They all contain amine groups.

3. They all form salts with strong acids.

4. The salts are water soluble.

5. Alkali will hydrolyze salt to free the alkaloid base.

6. The alkaloid base is soluble in lipids.

7. Anesthetic salts are acidic in reaction & relatively stable.

8. The actions of all drugs are reversible

Chemical Groups of LA drugs

Ester Group, Amide Group

Importance of Knowing Type of Drug lies in:

Biotransformation & Allergic Reaction

intermediate chain ester linkage intermediate chain amide

linkage

Both have

Aromatic lipophilic group & Hydrophilic 2ry /3ry amino group

PROPERTIES AMINOESTERS AMINOAMIDES


8/14

Metabolismrapid by plasma

cholinesteraseslow, hepatic

Systemic

toxicityless likely more likely

Allergic reactionpossible - PABA derivatives

formvery rare

Stability in

solution

breaks down in ampules

(heat,sun)very stable chemically

Onset of action slow as a general rule moderate to fast

pKa's higher than PH = 7.4 (8.5-8.9) close to PH = 7.4 (7.6-8.1)

Dose of LA drugs

1% = 10 g/L

1% = 10 mg/mL

Therefore:

2% = 20 mg/mL

A cartridge contains 1.8 mL

Therefore a cartridge of 2% LA contains 20 mg/mL X 1.8 mL = 36 mg of

LA


9/14

Pharmaco-kinetics of LA drugs

Mode of Action of Local Anesthetic Drugs

The precise mode of action of the free base on the nerve tissue is not

understood, but there are various theories:

1. Mechanical Theory:

Free base of LA drug is dissolved in lipoid contents of nerve protoplasm causing

its temporary coagulation, & this will mechanically occlude conduction of

impulses.

2. Metabolic Theory:

Free base interferes with normal metabolism of nerve tissues, mainly with its

oxygen intake causing distorted intracellular oxidation of glucose, succinate &ascorbate, & thus leading to temporary paralysis of nerve tissues which stops

conduction of impulses.

3. Pharmacological Theory:

Free base of LA drug have direct toxic selective action on nerve tissue causing

temporary cessation of function.

4. Electric or Depolarization Theory:

In the rest stage the Na+ ion is present on outer side of cell membrane, & K+ ionis present on inner side. An effective stimulus will cause depolarization i.e. Na+


10/14

& K+ will exchange their places so that Na + will be on inner & K+ will be on

outer surface of cell membrane, thus giving rise to an impulse. LA agent

reduces the influx of Na+ into never membrane, thus depolarization is prevented

& no impulse is conducted.

Factors affecting duration of LA

Individual response to drug.

Accuracy of deposition of LA

Status of tissues at the site of drug deposition.

Anatomical variations.

Type of injection administered

Metabolism ( Detoxification Process ) of LA drugs

Excretion of By- products

Vasoconstrictors

It reduces toxic effects by retarding the absorption of the constituents

of the LA solution.

By confining the anesthetic agent to a localized area it increases the

depth and duration of anesthesia which may decrease the amount of

local anesthetic solution needed .

It produces a relatively bloodless field of operation for surgical

procedures.


11/14

It prevents haematogenous absorption of local sepsis or pus during

the surgical manipulation.

Other components of LA Carpule

Preservative

Methy paraben : LA preservation (not recommended) develops allergic

reactions. Modern LA are very stable and & often have a shelf life of 2 years or

more, but small amounts of Capryl-hydro-cuprienotoxin preserve their sterility.

Reducing Agent

Sodium meta-bisulphite Vasoconstrictor preservative, because VC are

unstable in solution & may be oxidized & turn into yellowish brown. Addition of

small amount ofSodium meta-bisulphite will take any oxygen from solution

Na meta-bisulphate

Fungicide

A small quantity of Thymol serve as fungicide & prevent the proliferation of

minute fungae

Vehicle

LA drugs & additives are dissolved in isotonic vehicle, Ringer's solution = NaCl

0.5 gm; KCl 0.02 gm & Aqua 100c.c. which also minimizes the discomfort during

injection.

Techniques

Maxilla

3 major types of injections can be 3 major types of injections can be performed

in the maxilla for pain control performed in the maxilla for pain control

Local infiltration


12/14

Field block Field block

Nerve block

Infiltration

Able to be performed in the maxilla due to the able to be performed in the

maxilla due to the thin cortical nature of the bone thin cortical nature of the bone

Involves injecting to tissue immediately involves injecting to tissue immediately

around surgical site around surgical site

Supraperiosteal injections

Intraseptal injections

Periodontal ligament injections

Field blocks

Local anesthetic deposited near a larger local anesthetic deposited near a larger

terminal branch of a nerve terminal branch of a nerve

Periapical injections

Nerve blocks

Local anesthetic deposited near main nerve local anesthetic deposited near main

nerve trunk and is usually distant from operative trunk and is usually distant

from operative site site

Posterior superior alveolar

Infraorbital

Middle superior alveolar

Greater palatine

Anterior superior alveolar

Nasopalatine

Mandibular anesthesia

Mental nerve blockInferior alveolar nerve block (IAN)

Technique involves blocking the inferior Technique involves blocking the inferior

alveolar nerve prior to entry into the alveolar nerve prior to entry into the

mandibular lingula on the medial aspect of mandibular lingula on the medial

aspect of the mandibular ramus the mandibular ramus

Multiple techniques can be used for the IAN nerve block nerve block


13/14

IAN, Akinosi, Gow Gates

Complications from Local Anesthesia

Toxicity/Overdosage

Paresthesias/Anesthesias

Infection

Complications from Nerve Block

Complications resulting from a maxillary nerve block are rare, but mayinclude:

* regional sixth nerve block, results in temporary teplopia for the patient* hematoma (rare)* retrobulbar block (rare)* optic nerve block, which can result in temporary blindness (rare)


14/14

ANASTHESI

MUHAMMAD HAFIZ MOHD YUNOS

160110063003

UNIVERSITAS PADJADJARAN

FACULTY OF DENTISTRY

BANDUNG

2010

Documents

LA Overview