Local Anesthetics Flashcards
(39 cards)
Neurons maintain a resting membrane potential of?
-60 to -70 mV
3 states of Na channels:
- Resting (non conducting)
- Open (conducting)
- Inactivated (non conducting)
Voltage-gated Na channels are membrane-associated proteins comprising of one large ___ subunit through which Na ions pass, and one or two smaller ____ subunits
Alpha; beta
Ester LA are predominately metabolized by?
Pseudocholinesterase
Amide LA are metabolized by?
P-450 metabolites in the liver
Binding of which subunit prevents channel activation?
Alpha
Local anesthetics have a greater affinity for Na channel when?
Open or inactivated state (not resting)
What is the basis of the classification of LA as either esters or amides?
The nature of the intermediate chain
LA consist of a _____ group separated from a _____ group by an intermediate chaine
Lipophilic; hydrophilic
Factors that affect the minimum concentration of LA that will block impulse conduction:
Fiber size, myelination, pH, stimulation frequency, electrolyte concentration
acid + acid & base + base =?
Non-ionized
Acid + base = ?
Ionized
Lipid solubility correlates with?
Potency of LA
M-gate closed
Resting or closed phase
M-gate and H-gate are open
Activated or open phase
H-gate is closed
Inactivated phase
LA interaction with which gate causes the effect? What charge is necessary?
H-gate; a positive charge
Lipid soluble. Acid form. Generally hydrophobic. Readilly penetrates BBB/placenta
Non-ionized
Water soluble. Charged form. Conjugate base form.
Ionized
What drug is the exception to the rule that the closer pKa is to physiologic pH, the faster the onset? Is it protein bound?
Chloroprocaine (pKa 9.1) No protein binding
What can be added to LA to prolong duration?
Epinephrine
What can be added to LA to gain a quicker onset?
Bicarbonate
What dose of bicarb is needed when using bupivacaine?
0.1 mEq per 20 ml of bupivacaine
What dose of bicarb is needed when using Lidocaine?
1 mEq bicarb per 10 ml of lidocaine
