Local Anesthesia (LA) is defined as a loss of sensation in a circumscribed area of the body caused by the depression of excitation in nerve endings
What is Local Anesthesia?
Local Anesthesia (LA) is defined as a loss of sensation in a circumscribed area of the body caused by the depression of excitation in nerve endings or inhibition of conduction process in peripheral nerves. It plays a major role in the dentistry. It helps to perform the various surgical procedure without pain to the patient. So, It creates positive impact on the patient towards the dentist.
Composition of Local Anesthesia (LA)
- 2% Lignocaine hydrochloride (HCL)
- 0.5 mg Sodium meta-bisulphite
- 1 mg Methylparaben
- Distilled water
- Thymol
- 6mg of Sodium chloride or Ringer’s solution
- Adrenaline—1:80,000
- Sodium hydroxide(NaOH)
- Nitrogen bubble
Mechanism of Action
Local Anesthetic molecules blocks the nerve receptor site by displacing the the Calcium ions (Ca+). So, It causes the blockage of exchange of Sodium (Na+) ions in the receptor site. It causes no more conduction of the pain.
Classification of Local Anesthesia
According to Chemistry,
ESTERS
I) Benzoic acid
- Cocaine
- Butacaine
- Piperocaine
- Benzocaine
- Hexylcaine
- Tetracaine
II) Para aminobenzoic acid esters
- Procaine
- Propoxycaine
- Chloroprocaine
AMIDES
- Prilocaine
- Bupivacaine
- Mepivacaine
- Etidocaine
- Articaine
- Lidocaine
QUINOLONES
- Centbucridine
According to Action on Biological Site,
Class A
Agent acting at receptor site—external surface of nerve membrane
Class B
Agent acts at receptor site- internal surface of nerve membrane
Class C
Agent acts by a receptor independent -Benzocaine
Class D
Combination of physiochemical receptors and receptor independent mechanism (most LA Comes Under this Category such as Lignocaine, Mepivacaine)
According to their Duration of Action,
Ultrashort Acting
Eg: Lignocaine, Prilocaine, Mepivacaine
Short Acting
Eg: Procaine, Chloroprocaine
Intermediate Acting
Eg: Lignocaine, Prilocaine
Long Acting
Eg: Bupivacaine, Etidocaine, Tetracaine
According to Mode of Administration,
I) Injectable
II) Surface Anesthetic
Complications of Local Anesthesia (LA)
LA complication can be defined as any deviation from the normal pattern during or after the injection of the anesthesia.
These complication can be classified into,
- Primary & Secondary
- Mild & Severe
- Temporary & Permanent
Primary Complication
It is caused and manifested at the time of anesthesia.
Eg: Syncope
Secondary Complication
It is manifested sometimes after the injection of LA.
Eg: Trismus
Mild Complication
It causes slight deviation from the normal pattern and go back to normal pattern without any specific treatment.
Severe Complication
It causes notable deviation from their normal expected pattern and requires a definite plan of treatment.
Temporary Complication
It is severe at the time of occurence and leaves without effect.
Permanent Complication
It leaves with a effect.
Complications may be further divided into
I) Local Complications
II) Systemic Complications
Local Complications of Local Anesthesia (LA)
These complications are associated with the administration of Local anesthetics. In other words, faulty adminstration of LA. It includes
- Needle breakage
- Paresthesia
- Facial nerve paralysis due to damage
- Trismus or Locked jaw
- Soft tissue injury
- Burning on injection
- Pain on injection
- Edema
- Sloughing of tissues
Systemic Complications of Local Anesthesia (LA)
Systemic complications involves the overdosage of the LA or patient shows allergic to LA. It includes,
- Toxicity
- Idiosyncrasy
- Allergic and Anaphylactic reactions
Toxicity of Local Anesthesia
The overdosage of the LA causes toxicity which affects the central nervous system as well as the circulatory system. CNS causes include excitement, convulsions, depressions, sleepiness. In circulatory system causes depression of myocardium, increases in blood pressure.
Idiosyncrasy
It is a bizarre type of reaction, which cannot be classified as toxic or allergic.
Allergic and Anaphylactic reactions
Allergic reaction is the specific hypersensitivity to the drug. Anaphylactic reactions shows immediate reaction involves skin, blood vessels, mucous membrane and respiratory system.
Symptoms
Rashes, rhinitis, asthmatic symptoms, Urticaria.
Treatment
Antihistamines, Aminophylline, Epinephrine will be given to overcome the allergic and anaphylactic reactions.
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