FARHANA ADNIN B.Optom,4th batch, ICO,CU.

Anaesthesia means loss of sensation.

Drugs that cause anaesthesia are called anaesthetic.

They are used to relief from pain during tests & surgical operation.They relief a patient from

1)pain 2)touch 3)temperature 4)pressure

2 KIND ~ 1) General anaesthesia 2)Local anaesthesia

Definition:

The agents that induces~ * loss of pain * adequate muscle relaxation * loss of reflexes * without loss of conciousness & memory in a localized area.

Classification: Based on inter bridge chain ~

1} Ester linkage 2}Amide linkage

MORE . . .MORE . . .• CocaineCocaine

• ProcaineProcaine

• TetracaineTetracaine

• Oxybuprocaine (0.4%) Oxybuprocaine (0.4%) {commonly used}{commonly used}

Duration- (10-30) minutesDuration- (10-30) minutes

Short actingShort acting

More toxic ~More toxic ~

{PEE: Punctate Epithelial Erosion (cornea)}{PEE: Punctate Epithelial Erosion (cornea)}

1}Ester Linkage

Oxybuprocaine is a most common medicine that is used in topical anaesthesia of eye.

Onset: about 30 sec USE: used in the outermost layers of the cornea

& conjunctiva for the following reason ~ *to remove small foreign objects *to perform a contact/applanation tonometry

ADVERSE EFFECTS:*irritation *hypersensitivity *Irreversible corneal damage

2}Amide Linkage

• Long actingLong acting

• Less toxicLess toxic

• Metabolized in liverMetabolized in liver

Example:Example:

Ledocaine/LignocaineLedocaine/Lignocaine

Bupivacain 5%Bupivacain 5%

MepivacaineMepivacaine

MECHANISM: It reversibly blocks impulse conduction

along nerve axons, rate of firing & formation of action potential by blocking Na+ channel in neuronal membranes.

Short acting drug Topical 4%~ onset 10 min Injectable 2%~ duration 30 min

MECHANISM : Same as lignocaine long acting & potent * onset ~[15-20]min * duration~ [5-8] hours

WHY LIGNO AND BUPI ARE USED COMBINDLY DURING INTRAOCULAR SURGERY?{e.g.CATARACT}

ANS-----TO GET EARLY ONSET WITH LONG DURATION OF ACTION

*INTERMEDIATE ACTION

{Adrenaline is a hormone, helps in anaesthesia}

Veso Constriction

contra indicated→Hypertension/ Heart disease

↓ Systemic Absorption Prolong action Prolong action of anestheticsof anesthetics

↓ Bleeding

Why adrenaline is used Why adrenaline is used With lignocain? With lignocain?

An anaesthetic agent paralyses sensory nerve An anaesthetic agent paralyses sensory nerve endings or nerve fibers at the site of application. The endings or nerve fibers at the site of application. The conduction of nerve impulses is blocked by stopping conduction of nerve impulses is blocked by stopping the entry of Na+ into nerve cells.the entry of Na+ into nerve cells.

In short ~In short ~

*Inhibit dipolarization and repolarization at the node of *Inhibit dipolarization and repolarization at the node of ranvior ranvior

•↑↑ Threshold level of Threshold level of excitation excitation

•Thus prevent conduction Thus prevent conduction of nerve impulse of nerve impulse

MechanisM of action

Side effectS• TopicalTopical -- PEE(Punctate epithelial erosion) PEE(Punctate epithelial erosion)

Delays wound healingDelays wound healing

•SystemicSystemic - - HypersensitivityHypersensitivity

PalpitationPalpitation

TachycardiaTachycardia

ArrhythmiaArrhythmia