1. LAST: PREVENTION AND TREATMENT
PART A

2. PART A: OVERVIEW What are local anesthetics Classification MOA
Anesthetic potency
Clearance
Uses
Prolongation of action

3. PART B: ADVERSE EFFECTS&SYSTEMIC TOXICITY
Allergic reaction
Local toxicity
Systemic toxicity

4. What are LA
Weak bases which produce a transient and reversible loss of sensation (analgesia) in a circumscribed region of the body without loss of consciousness.
Normally, the process is completely reversible.

5. Classification Local anesthetics - esters or amides.
Major difference is their potential for producing adverse effects and the mechanisms of their metabolism.

6. Esters Eg: Procaine, Cocaine, tetracaine
The ester linkage is cleaved by plasma cholinesterase. Short half life( abt 1min).
Amides:
Eg: lidocaine, Marcaine(Bupivacaine), ropivacaine. Amide linkage is cleaved in the liver. Half life is about 2-3 hrs

7. MECHANISM OF ACTION
LA block nerve conduction by impairing propagation of action potential in axons. Interact directly with Na+ channels and stop Na+ ion influx. May also act on K+ & Ca+ channels.
LA need to diffuse passively in uncharged state (lipophilic) to reach target-axoplasmic side of Na+ channel.

9. HOW MUCH IS TOO MUCH? ESTERS MAX DOSE(mg/kg) DURATION (HOURS)
Chloroprocaine 12
0.5 – 1
Procaine
Cocaine 3
Tetracaine
1.5 – 6

10. Amides Max Dose (mg/kg) Duration (h) Lidocaine 4.5/(7 with epi)
0.75 – 1.5
Mepivacaine
1– 2
Prilocaine 8
0.5 – 1
Bupivacaine 3
1.5 – 8
Ropivacaine

11. ANESTHETIC POTENCY
The more LA is lipophilic the more potent it is ( increased rate of diffusion).
More protein binding prolongs the effect. Bupivacaine is approximately 95% protein-bound.
Intermediate-duration LAs (lidocaine and mepivacaine) have a smaller protein-bound fraction (60-70%).
pH; higher pH speeds action (keeps LA uncharged).
pKa: lower pKa faster onset.
Concentration; higher conc. =rapid onset (mass effect).

12. CLEARANCE ESTERS hydrolysis via tissue cholinesterase
AMIDES metabolism via hepatic enzymes

13. USES
Surface anesthesia
Infiltration anesthesia
Regional anesthesia

14. SURFACE ANESTHESIA On intact skin – eutectic mixture of
Local anesthetics
(EMLA)
Slow absorption,
Action up to ½ Hr

15. INFILTRATION ANESTHESIA
LA infiltrates locally into tissues to numb the area.
Purpose of pain free procedures-before injections with large needles, lumbar puncture

16. REGIONAL ANESTHESIA Nerve block Intravenous Epidural/Extradural
Intrathecal block/ spinal anaesthesia

17. NERVE BLOCKS
Inject a drug around the nerve
Anaesthetise a region

18. INTRAVENOUS ANESTHESIA
0.5-1% lidocaine without adrenaline
Bier’s Block

19. EPIDURAL
Thoracic, lumbar, sacral
Act on nerve roots
Less hypotention

20. SPINAL BLOCK
Sympathetic nerve block
hypotension