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Donald H. Lambert

Pharmacology of Local Anesthetics. Donald H. Lambert. Nerve. Muscle. Compound action potential = sum of individual AP. Individual fibers blocked = decline in comp. AP. BH +. B + H +. H+. The Local Anesthetic Molecule.

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Donald H. Lambert

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  1. Pharmacology of Local Anesthetics Donald H. Lambert

  2. Nerve Muscle

  3. Compound action potential = sum of individual AP Individual fibers blocked = decline in comp. AP

  4. BH+ B + H+

  5. H+

  6. The Local Anesthetic Molecule • Local anesthetics consist of an aromatic ring and an amine, separated by a hydrocarbon chain Hydrophilic Hydrophobic • Two types of local anesthetics based on the hydrocarbon chain linkage • Esters have [-CO-O-] linkage • Amides have [-N-CO-] linkage

  7. ESTERS

  8. AmideBupivacaine Analogues

  9. AmideLidocaineAnalogues

  10. Amides v. Esters Parameter Amides Esters StabilityMetabolismAllergy Stable Unstable Liver/kidney Plasma Rare Less rare

  11. AGENTS OF LOW POTENCYAND SHORT DURATION AGENT CHEMICAL RELATIVE ONSET DURATION CLASS POTENCY (MINUTES) PROCAINE ESTER 1 SLOW 60 - 90 CHLOROPROCAINE ESTER 1 FAST 30 - 60

  12. AGENTS OF INTERMEDIATEPOTENCY AND DURATION AGENT CHEMICAL RELATIVE ONSET DURATION CLASS POTENCY (MINUTES) LIDOCAINE AMIDE 2 FAST 90 -200 MEPIVACAINE AMIDE 2 FAST 120 - 240 PRILOCAINE AMIDE 2 FAST 120 - 240

  13. AGENTS OF HIGH POTENCYAND LONG DURATION

  14. Lipid Solubility = Potency (and Duration) Lipid Bi-layer

  15. Protein Binding = Duration Protein Na+ Channel Lipid Bi-layer

  16. pKa = ONSET

  17. Effect of Dose on Onset, Duration, and Quality of Anesthesia • Onset time decreases from 12 min. to 5 min. • As dose increases • Adequacy increases from 40% to 100% • Duration increases from 100 to 260 min. • The more you inject thefaster it comes on, the betterthe block, the longer itlasts, and the greater the toxicity

  18. Neuron Types

  19. Factors Influencing Local Anesthesia • pH of local anesthetic • Pregnancy • Site of injection

  20. Adding sodium bicarbonate raises the pH of the local anesthetic solution

  21. ????

  22. Median Nerve Block in Pregnant and Non-Pregnat Women J Butterworth, et al. Anesthesiology 1990;72:962-5

  23. Collection of data of local anesthetic blood levels (mainly plasma concentrations) from various sources indicating the pattern of order of peak concentrations associated with various regional anesthetic blocks. Intercostal > caudal > epidural > brachial plexus > subcutaneous Rosenberg PH, Veering BT, Urmey WF: Reg Anesth Pain Med 2004; 29: 564-75

  24. The Pharmacology of Local Anesthetics Important stuff for everyday practice! And for exams!!

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