Local Anesthetics Flashcards
How are local anesthetics classified?
By the type of intermediate bond
Are esters or amides
What are some differences between esters and amides?
Esters: unstable, metabolized in plasma, may cause allergic reactions (e.g. Cocaine, benzocaine, procaine)
Amides: stable, enzymatic degradation (lidocaine, bupivicaine)
What affects the onset of local anesthetics?
Lipophilicity PKA (and therefore tissue pH) Concentration Dose Volume Proximity to nerve Type of nerve
What affects the duration of local anesthetics?
Vascular effect Tissue blood flow Vasoconstriction Dose Affinity to Na+ receptor Lipophilicity
What is the mechanism of action of local anesthetics?
Na+ channel blockers
Affects cell depolarization and decreases conduction
What factors affect local anesthetic action?
pH/pKa Proximity Dose Volume Spread
How does pH/pKa affect local anesthetic action?
If a tissue has a low pH (such as in infected tissue), the anesthetic will not work
What types of toxicities are seen with local anesthetics?
Neurologic: tremors, nervousness, seizures
CV: bradycardia, sinus arrest, fibrillation
Which local anesthetic should never be used IV?
Bupivicaine
What is an example of topical action of local anesthetics?
Splash blocks
Decrease laryngeal spams during induction (cats)
What is a ring block?
3 blocks used for declaw procedures- 2 dorsal, 1 palmar
Blocks the ulnar, media, and radial nerves
What are some substitute epidural blocks?
Femoral compartmental block
Sciatic block
