Regional Anesthesia Blocks in Head and Face Resident Physician: Leon Martinez, MD Faculty Mentor: Paul Brindley, MD, FACS The University of Texas Medical Branch – UTMB Health Department of Otolaryngology Grand Rounds Presentation December 15, 2014 Series Editor: Francis B. Quinn, Jr., MD, FACS -- Archivist: Melinda Stoner Quinn, MSICS 1 Local anesthetic review  Advantages and disadvantages  Blocks   Trigeminal  Orbital  Maxillary  Mandibular  Scalp  Ear 2 Followed general anesthesia by 40 years  Koller used cocaine for the eye in 1884  Halsted used cocaine as nerve block  First synthetic local-- procaine in 1905  Lidocaine synthesized in 1943  Speaker Notes: Also sold Bayer heroin aid for cough, Morphine for teething children, Marijuana for nerves 3 Mechanism of action  is by reversibly blocking sodium channels to prevent depolarization Anesthetic enters on  axioplasmic side and attaches to receptor in middle of channel Speaker Notes: Local anesthetics depolarize the nerve membranes and prevent achievement of a threshold potential. A propagated action potential fails to develop and a onduction blockade is achieved. This occurs by the interference of nerve transmission by blocking the influx of sodium through the excitable nerve membrane [12]. 4 Linear molecules that  have a lipophilic and hydrophilic end (ionizable) low pH-- more in  ionized state and unable to cross membrane (abscess) adding sodium  bicarb-- more in non- ionizedstate 5 Two groups: esters  and amides Esters metabolized by  plasma cholinesterase Cocaine, Procaine, Chloroprocaine, Tetracaine Amides metabolized  by cytochrome p-450 Lidocaine, Mepivacaine, Bupivacaine, Etidocaine 6 Local Anesthetics • Agent: Dose: Onset/Duration: • Lidocaine with epi (1 or 2%) 7mg/kg Fast/medium • Lidocaine without epi 4.5mg/kg Fast/short • Mepivacaine without epi (3%) 5.5mg/kg Fast/short • Bupivacaine with epi (0.5%) 1.3mg/kg Long/long • Articaine with epi (4.0%) 7mg/kg Fast/medium • Bupivacaine with liposome 266 mg Long/long suspension (1.3%) (1 vial) Speaker Notes: Bupivacaine with liposome suspension (1.3%) toxic dose is 10mg/Kg animal studies 7 Central nervous system  Initially--  lightheadedness, circumoral numbness, dizziness, tinnitus, visual change Later-- drowsiness,  disorientation, slurred speech, loss of consciousness, convulsions Finally-- respiratory  depression 8 Primarily from intravascular injection or  excessive dose  aspirate often with slow injection  ask about CNS toxicity  have monitoring available  prepare with resuscitative equipment, CNS depressant, drugs, cardiovascular drugs  ABC’s 9 Cardiovascular   myocardial depression and vasodilation-- hypotension and circulatory collapse Allergic reactions-- rare (less than 1%)   preservatives or metabolites of esters, rare in amides  rash, bronchospasm 10