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• Reversible local anesthesia• Decrease rate of depolarization/repolarization
of the excitable neural membrane
• Pain• Others• Paralysis
MOA
• Inhibit Na influx via Na-specific ion channels in neuronal cell membranes
• Voltage-gated Na channels• Bind intracellular portion of channel and
inhibit influx• Action potential inhibited
• 1-2% of LA penetrated nerve fibre• Not everything equally blocked• Depends on diameter and type of nerve fibres
• B>C>Adelta(temp)>Agamma(proprio)>Abeta(touch&pressure)>Aalpha(motor)
• B>C?
Adjuvants
• Epinephrine• Inc intensity• Dec systemic absorption
• Opiods• Steroids – dexa increases duration by 50%
Side effects
• CNS toxicity• Cross BBB• More common with certain LAs (bupi)
• Inc: acidosis, Vc, epinephrine • Dec: barbiturates.benzos, dec systemic abs
(epinephrine)• 3/10,000 epidural, 1/10,000 PNB
• Cardiotoxicity• Higher doses required• Single isomers – ropi&levo-bupi• - decreased affinity for brain and cardiac
tissue• 1) less lipid-soluble (lido):• Hypotension/bradycardia/art hypoxemia• 2) more lipid-soluble (bupi):• Ventricular cardiac arrhythmias cardiovascular
collapse resistance to resus (large doses of epi)
• Bupivacaine has higher affinity for resting and inactive sodium channels.
• Bind @ systole, dissociate on diastole• Dissociates slowly incomplete recovery
• L-carnitine def = increased susceptibility
• Methemoglobinemia• Metabolite of prilocaine o-toluidine
• Myotoxicity• Dysregulation of intracellular Ca concentrion
• Allergies
Uses
• Regional anesthesia• IV regional anesthesia (Bier’s)• Peripheral nerve block• Topical• Systemic?
Treatment
• Mostly supportive• Stop LA• Supplemental oxygen• Ventilatory support and intubation if
necessary• Treat dysrhythmias
cardioversion/amiodarone• Lipid Rescue
Lipid Rescue
• Weinberg 1998• Published 2006 • Still relatively limited literature
• Removes anesthetic from sight of action
• 1) IV bolus 20% Lipid emulsion @ 1.5mL/kg• 2)continue infusion @ 0.25ml/kg/min after
restoration of cardiac function• 3)if continues, rpt bolus and increase to
0.5mL/kg/min
• Upper limit 10mL/kg over 30mins