Local Anesthetics Flashcards
Local Anesthetics MOA
Produce reversible blockade of conduction of electrical impulses along nerve fibers
Causes reversible and transient loss of sensation (analgesia) in a portion of the body without a loss of consciousness
Local Anesthetic Site of Action
Reversibly block voltage-gated sodium channels in neurons
Local Anesthetic Sequence of Action
First
Pain Temperature Touch Pressure Motor
Last
Local Anesthetic Classes
Amides and Esters (depends on intermediate linkage between aromatic ring and tertiary amine)
Local Anesthetic Normal pH
Weak Bases
Amide Local Anesthetic Metabolism
Metabolized in the liver by CYP1A2 and CYP3A4 can result in significant systemic levels with rapid absorption, increases potential for toxicity
Ester Local Anesthetic Metabolism
Metabolism catalyzed by plasma and tissue cholinesterase via hydrolysis rapid and occurs throughout body, reduces potential for toxicity
Amide Local Anesthetic Excretion
Kidneys
Ester Local Anesthetic Excretion
Results in water soluble metabolites that are excreted in urine
Inherent effect of Local Anesthetics on Vasculature
Vasodilation (increases risk for systemic absorption and toxicity)
Effect of Epinephrine on Local Anesthetics
Adding vasoconstrictor keeps LA at action site
Local Anesthetics Allergic Reactions
More common with Esters due to being derivatives of PABA
Less common with Amide
Local Anesthetic Toxicity
LAST (Local Anesthetic Systemic Toxicity)
Goes from circumoral numbness and blurred vision. All the way to cardiac failure, respiratory failure, and CNS depression
Treatment for LAST
Lipid emulsion 20% infusion
Local Anesthetic Metabolic Complication
Acquired Methemoglobinemia
LA metabolites include o-toluidine derivatives, which are responsible for inducing hemoglobin oxidation
Metabolite causes iron atom in hemoglobin to be oxidized from a ferrous form (Fe2+) ferric form (Fe3+) (conversion of hemoglobin to methemoglobin)
Treatment for Acquired Methemoglobinemia caused by LA
Methylene Blue 1-2 mg/kg over 5 min
Lidocaine Dosing withOUT Epi
5 mg/kg
Max Dose= 350 mg
Lidocaine Dosing WITH Epi
7 mg/kg
Max Dose= 500 mg
Bupivacaine withOUT Epi
2 mg/kg
Max Dose= 175 mg
Bupivacaine WITH Epi
3 mg/kg
Max Dose= 225 mg
Chloroprocaine withOUT Epi
11 mg/kg
Max Dose= 800 mg
Chloroprocaine WITH Epi
14 mg/kg
Max Dose= 1000 mg
Chloroprocaine Potency, Onset, and Duration
Potency= Low Onset= Fast Duration= Short
Bupivacaine Potency, Onset, and Duration
Potency= High Onset= Slow Duration= Long; Longer with Epi
Lidocaine Potency, Onset, and Duration
Potency= Intermediate Onset= Fast Duration= Intermediate; Long with Epi
Chloroprocaine Injection Concentrations
1, 2, and 3%
Lidocaine Injection Concentrations
0.5, 1, 1.5, 2%
Bupivacaine Injection Concentrations
0.25, 0.5, 0.75%
