Lab # 2 Local Anesthetic Drugs Local Anesthetic Drugs

Definition of local anesthetic drugs They are drugs used to abolish pain sensation in certaion area of the body. They depress the afferent nerve impulses which travel to the CNS. They cause reversible block of nerve conduction when applied locally to the nerve tissue in appropriate concentration. Samiah AL-shehri

Mechanism of action of L.A (-) the generation & propagation of the nerve impulses at its site of action on the cell membrane. (-) Na+/ k+ ATPase, so no Na+ influx & no K+ outflux → membrane stabilization. the activity of Na+ / Ca+ exchange causing membrane stabilization. (block Na channle → prevent depolrization) the threshold of excitability or block the conduction of nerve impulses. Mechanism of action of L.A Samiah AL-shehri

Method for administration of L.A Surface anesthesia. Infiltration anesthesia. Nerve block anesthesia. Spinal anesthesia. Samiah AL-shehri

Method for administration of L.A 1. Surface Anesthesia: By direct application of the drug to the surface. E.g. eye, skin, cornea. E.g. Lidocaine , coccaine 2. Infiltration Anesthesia: The local anesthetic is injectected (S.C)in order to paralyze nerve ending at the site of operation. E.g. Lidocain, Procaine Samiah AL-shehri

Method for administration of L.A 3. Nerve Block Anesthesia: The local anesthetic is injected in the vicinity of the major nerve trunks e.g. trachea plexus (neck) e.g. lidocaine, procaine 4. Spinal Anesthesia: The local anesthetic is injected in the subarachnoid space so that it reaches the roots of the spinal nerves between Lumber (L1 & L2 ) e.g. procaine Method for administration of L.A Samiah AL-shehri

Identification & Evaluation of L.A : Corneal method (surface). Intradermal wheel method (infilteration). Nerve block ( frog plexus method). Samiah AL-shehri

1-Corneal method (Surface): Principle: The L.A. is applied & the change in the response of the animal to the painful stimulus is recorded. Animal: Rabbit . Painful stimulus: is induced by a fine cotton applicators applied on the cornea. Samiah AL-shehri

1-Corneal method (Surface): Anesthetic used: Lidocaine 1% Response: blinking of the eye. N.B. The response is compared Before and after application of lidocaine . Samiah AL-shehri

1-Corneal method (Surface): Procedure: 1- clip the eye laches of the rabbit 2- check the normal coroneal reflex 3- aplply 0.2 ml Lidocain to eye & other eye is used as control 4- after every min check corneal reflex in both eyes 5 times Samiah AL-shehri

2-Intradermal wheel method(infiltration): Animal: Guinea pig . Painful stimulus: Pin prick . Anesthetic used: Lidocaine 0.2 % Response: shrinkage of the skin (L.A. will prevent feeling of pain during the prick) . Samiah AL-shehri

2-Intradermal wheel method(infiltration): Procedur: 1- clip the hair of the back of G.P & shave the skin 2- apply painful stimuli (using pin prick) to the skin of Rt or Lt sides, the animal response by shrinking of the skin 3- inj. Lidocain 0.2% to the Rt side only intradermal where the Lt side leaved control 4- pin prick are made every 5” until loss of pain sensation Samiah AL-shehri

3-Nerve Block Method (frog plexus method): Animal: Frog . Painful stimulus: dil. Hcl .( 0.05% , 0.1% , 0.2%) Anesthetic used: Procaine .(0.1% , 0.2%) Response: Withdrawal of the leg . Samiah AL-shehri

3-Nerve Block Method (frog plexus method): Procedure: 1- decapitate the frog with out pithing of the spinal cord 2- atransverse incision is made in the abdominal below the sternum, where the viscera is removed, through this opening . Becarful not to damage the nerve 3- hang the frog by a hook 4- test each leg with tap water , the frog should no give reflex action to tap water (indicate loss conscious movement) Samiah AL-shehri

3-Nerve Block Method (frog plexus method): 5- immerse the foot in 0.05 N Hcl , observe the withdrawel reflex within 10 sec ,then wash the foot till the muscle are relaxed 6- inj. L.A into the abd. Cavity , so that the plexus is sub merged with the drug 7- test the withdrawal reflex every min ,always to wash the leg after acid apply Samiah AL-shehri

3-Nerve Block Method (frog plexus method): the foot is immersed to dil.Hcl for no longer than 10” to avoid damage of the skin When aresponse is no longer obtained with 10” try with 0.2 N Hcl for 10” 8- determine the total onset time of L.A Samiah AL-shehri

3-Nerve Block Method (frog plexus method): Local Anesthetic Drugs 3-Nerve Block Method (frog plexus method): Result: Onset time of 0.1% Procaine = Onset time of 0.2% Procaine = Total 0.2 N Hcl 0.1 N Hcl 0.05 N Hcl 0.1 procaine 0.2 procaine Samiah AL-shehri

THANK YOU Samiah AL-shehri