1 / 35

Local anesthetics

Local anesthetics. Objectives. Recall how an action potential is generated and propagated Classify local anesthtics Describe the machanism of action, pharmacokinetics and toxic effects of local anesthetics Describe the different techniqes of use of LA

todd
Download Presentation

Local anesthetics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Local anesthetics

  2. Objectives • Recall how an action potential is generated and propagated • Classify local anesthtics • Describe the machanism of action, pharmacokinetics and toxic effects of local anesthetics • Describe the different techniqes of use of LA • Describe the risks and benefits of using vasoconstrictors with LA

  3. Overview • Local anesthetics 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.

  4. ANESTHETICS

  5. Local anesthetics - esters or amides • a lipophilic aromatic group • to a hydrophilic, ionizable amine. • Most are weak bases

  6. Classification of LA Esters • Benzocaine • Procaine/ • Proparacaine

  7. Classification of LA Amide • Bupivacaine • Levobupivacaine • Lidocaine/Lignocaine • Mepivacaine

  8. Ionized

  9. Local anesthetics gain access to the inner axonal membrane by • traversing sodium channels while they are more often in an open configuration • passage directly through the plasma membrane

  10. Block inititation and propagation of action potential

  11. Sequence of clinical anesthesia • Sympathetic block (vasodilatation) • Loss of pain and temperature sensation • Loss of proprioception • Loss of touch and pressure sensation • Loss of motor function

  12. Anesthetic Potency • Potency = lipid solubility • Higher solubility = can use a lower concentration and reduce potential for toxicity

  13. DURATION OF ACTION • Duration = protein binding • Bupivacaine 95%Lidocaine 65%

  14. Pharmacokinetics • Effective within 5 min • Duration of action – 1-1.5 h • Activity is Ph dependent • Increased action in acidic ph

  15. CLEARANCE • ESTERShydrolysis via cholinesterase • AMIDESmetabolism via hepatic enzymes

  16. LA • Infiltration anesthesia • Regional anesthesia • Surface anesthesia

  17. LA • Infiltration anesthesia • Regional anesthesia • Surface anesthesia

  18. Gegional anaesthesia • Nerve block • Intravenous • Extradural • Intrathecal block/ spinal anaesthesia

  19. Nerve block • Inject a drug around the nerve • Anaesthetise a region

  20. Intravenous • 0.5-1% lidocaine without adrenaline

  21. Extradural/epidural • Thoracic, lumbar, sacral • Act on nerve roots • No hypotention

  22. Spinal anesthesia • Sympathetic nerve block • hypotension

  23. LA • Infiltration anesthesia • Regional anesthesia • Surface anesthesia

  24. On intact skin – eutectic mixture of bases of prilocaine (EMLA) • Slow absorption

  25. Prolongation of action • Add vasoconstrictor – adrenaline • Can use a larger dose • Not to – fingers, toes, nose, penis

  26. Adverse effects • LA’s cause some vasodilatation at site • LA toxicity related to rate of absorption via blood flow

  27. Systemic Toxicity • Blockage of voltaged-gated Na channel affects action potential propagation throughout the body • Potential is present for systemic toxicity

  28. Effects of local anesthetics • Excitation – anxiety, agitation, restlessness • Convulsions • Reduced myocardial contractility • Vasodilatation

More Related