Local anesthesia

  • Mechanism of action: enter neurons and block Na+ influx → inhibit neuronal conduction
    • Tertiary form = lipid soluble (at basic pH)
    • Quaternary form = water soluble (at acidic pH)
      • Infected tissue is acidic, making anesthetic molecule charged and less able to cross membrane = need more local
  • Epinephrine - causes vasoconstriction making anesthetic stay locally - reduces risk of systemic toxicity; prolongs anesthesia duration
    • Don't use if arrhythmia, or in locations w poor collateral blood supply (penis, ear)
  • Local anesthetic toxicity 
    • CNS (think inhibited neurons) - tinnitus, perioral numbness, metallic taste, blurry vision, muscle twitches, drowsiness, ultimately coma.
    • Cardiac - hypotension, bradycardia, arrhythmia
      • Hypotensive patient w epidural = turn off epidural
    • Treat with intralipid (prevents from crossing lipid membrane into neurons)
 

Max dosing

1% = 1 g/100 mL = 10 mg/mL		    
Lidocaine

3 mg/kg = 0.3 cc/kg of 1%

7 mg/kg if has epi

    
Bupivicaine/Marcaine 2 mg/kg = 0.8 cc of 0.25% Lasts longer than lidocaine  
       
       
       
author: last edited: Jan. 21, 2019, 11:36 p.m. | pk: 155 | unpublished