1. Local anesthetics
Drug produce reversible conduction block of neural impulses transmission of autonomic, sensory and motor neural impulses

2. History
The natives of Peru have chewed the leaves of the indigenous plant “Erythroxylon coca” the source of cocaine, to induce a feeling of well-being
Koller used cocaine for the eye in 1884
Halsted used cocaine as nerve block
First synthetic local-- procaine in 1905
Lidocaine synthesized in 1943

4. Mechanism of action is by reversibly blocking sodium channels to prevent depolarization
Structure
Linear molecules that have a lipophilic and hydrophilic end (ionizable)
low pH-- more in ionized state and unable to cross membrane
adding sodium bicarb-- more in non-ionized state

5. Two groups: esters and amides
esters metabolized by plasma cholinesterase
amides metabolized by cytochrome p-450

6. Clinical uses Local anesthetics
Nerve block (brachial plexus block, wrist block, ankle block----etc.)
Local infiltration
Ointment, spray, lotion, lozenges, EMLA
Regional block (spinal, epidural, caudal)
Intravenous regional block (Bier’s block)

7. Lidocaine uses:
Prevent or treat cardiac ventricular dysrhythmias
Attenuate presser responses associated with intubation of the trachea
Prevent or treat increases in intracranial pressure as are often associated with intubation of the trachea
Minimize coughing during intubation or extubation of the trachea

8. Addition of epinephrine to local anesthetic solutions
Epinephrine 1: or 5μg/ml
Advantage:
Limits systemic absorption
Prolongs the duration of local anesthetics by keeping them in contact with nerve fibers
Decreasing the possibility of systemic toxicity cause the rate of metabolism will match the rate of absorption
As test in epidural regional anesthesia

9. Addition of epinephrine to local anesthetics is not recommended in:
Unstable angina pectoris
Cardiac dysrhythmias
Uncontrolled hypertension
Uteroplacental insufficiency
Peripheral nerve block anesthesia in areas that may lack collateral blood flow (digits, penis)
Intravenous regional anesthesia

10. Local Anesthetic Toxicity Central nervous system
Side effects
Local Anesthetic Toxicity
Central nervous system
initially-- lightheadedness, circumoral numbness, dizziness, tinnitus, visual change
later-- drowsiness, disorientation, slurred speech, loss of consciousness, convulsions
finally-- respiratory depression

11. Cardiovascular
myocardial depression and vasodilation-- hypotension and circulatory collapse specially with bupivacaine
2. Allergic reactions-- rare (less than 1%)
preservatives or metabolites of esters
rash, bronchospasm

13. Prevention and Treatment of Toxicity
Primarily from intravascular injection or excessive dose – anticipation or from absorption from tissue injection sites
aspirate often with slow injection
ask about CNS toxicity
have monitoring available
prepare with resuscitative equipment, CNS-depressant drugs, cardiovascular drugs
ABC’s

14. All cases Seizures Hypotension Dysrthymia Assure adequate ventilation
Administer supplemental oxygen
Seizures
Diazepam
Hypotension
Trendelenburg position (head down legs up)
IV fluid bolus (isotonic saline or Ringer lactate)
Vasopressor (dopamine)
Dysrthymia
accordingly

15. Thank you