TY - CHAP M1 - Book, Section TI - Chapter 120. Local Anesthetics and Adjuvants A1 - Keddis, Robert N. A2 - Atchabahian, Arthur A2 - Gupta, Ruchir PY - 2013 T2 - The Anesthesia Guide AB - Weak bases, hydrophilic, tertiary amines that block voltage-gated Na+ channels, preventing depolarizationSensitivity of nerve fibers to blockade: More sensitive: small diameter and lack of myelinSpinal and peripheral nerves: autonomic > sensory > motorOnset/duration of action: Unionized (uncharged) form: lipid-soluble, crosses membranesIncreased lipid solubility = decreased onset time, increased duration, increased potencyIncreased concentration and total dose =faster onsetSite of injection: more vascularized means shorter duration due to systemic uptakeNote: Epinephrine is frequently added to increase duration of blockade; however, it is unstable in alkaline conditions: Bottles containing epinephrine have an acidic pH = slower onset than when epinephrine added extemporaneouslySystemic vascular absorption (greatest to least): Intercostal nerve block > caudal > epidural > brachial plexus > sciatic–femoral > subcutaneousDivided into two groups: Amides (mnemonic: have two I's in the name): Metabolized in the liver; liver disease can increase duration and toxicityEsters: Mostly metabolized by pseudocholinesterasePseudocholinesterase deficiency severely prolongs duration; avoid in these patients SN - PB - The McGraw-Hill Companies CY - New York, NY Y2 - 2024/03/29 UR - accessanesthesiology.mhmedical.com/content.aspx?aid=57262333 ER -