Monday, 8-22-Local Anesthetics-DSA-Kruse Flashcards
What chemical class are benzocaine, cocaine, procaine, and tetracaine part of?
Esters
__ local anesthetics are widely distributed after IV bolus administration, while tissue distribution of __ type agents have not been extensively evaluated d/t their extremely short plasma 1/2 lives
Amide
Ester
___ agents are metabolized in the plasma while ___ types are metabolized in the liver and then excreted in the urine as charged substances
Ester type
Amide
___ compounds are hydrolyzed by circulating butyrylcholinesterase enzymes (plasma cholinesterase)
Ester type
__ are hydrolyzed by liver CYP 450 enzymes and toxicity from these type of anesthetics are more likely to occur in pts with hepatic disease
Amide linkage of amide-type agents
Local anesthetics block __ channel currents and stop the spread of APs across the nerve axons
Voltage-gated Na
Receptor site for local anesthetics is at the inner vestibule of the Na channel
the ___ the local anesthetic, the faster the rate of interaction with the Na channel and the more potent the agents actions
Smaller and more lipophilic
These drugs are more lipophilic than lidocaine, procaine, and mepivacaine and are therefore more potent and have longer durations of action
Tetracaine, bupivacaine, and ropivacaine
Local anesthetics preferentially block __ fibers because the distance over which such fibers can passively propagate an electrical impulse is shorter
Small fibers
What type of fiber is more likely to become blocked first: a preganglionic B fiber or a smaller unmyelinated C fiber?
Preganglionic B fibers
Myelinated nerves tend to become blocked before unmyelinated nerves of the same diameter
Which fibers will likely be blocked earlier: large A alpha fibers or type A delta and C fibers?
Type A delta and C fibers are blocked earlier than the large A alpha fibers
Fibers that fire at higher frequencies of depolarization are blocked before those that fire slower
__ anesthesia is injection of local anesthetic directly into tissue in the vicinity of peripheral nerve endings without taking into consideration the course of cutaneous nerves.
Infiltration
Can be superficial enough to include only the skin and deep enough to include intraabdominal organs
___ anesthesia is in injections of local anesthetics in major nerve trunks and the purpose is to anesthetize a region distal to the site of injection
Block
Femoral n block for surgery distal to the knee, brachial plexus block for procedures on UE’s or shoulders
__ anesthesia is injection of local anesthetic into the CSF in the lumbar space
Spinal
Produces anesthesia over a considerable fraction of the body with a dose of local anesthetic that produces negligible plasma levels
__ anesthesia can be performed in the sacral hiatus or in the L, T, or C regions of the spine
Epidural
Injection of a local anesthetic into the epidural space
__ anesthesia can be used for short surgical procedures (
IV regional
Coadministration of local anesthetics and __ decrease the rate of anesthetic absorption into circulation, reduces the rate at which the local anesthetic is metabolized, and reduces systemic toxicity
Vasoconstrictors
___ containing solutions should not be injected into tissues supplied by end arteries (fingers, toes, nose, ears, penis) because resulting vasoconstriction may cause gangrene
Epinephrine
When large doses of a local anesthetic are required, premedication with __ can provide prophylaxis against CNS toxicity by raising the seizure threshold
Parenteral benzodiazepine (diazepam or midazolam)
___ may be the most cardiotoxic due to its long durations of action
Bupivacaine
__ is a Class Ib antiarrhythmic by suppressing automaticity of conduction tissue by increasing electrical stimulation thresholds of ventricles, His-purkinje system, and spontaneous depolarization of the ventricles during diastole by a direct action on the tissues
Lidocaine
The most common adverse effect of IV lidocaine is __ toxicity, which is typically mild, dose-dependent, and always resolves upon discontinuation
CNS
Allergic rxns to __ local anesthetics are most common due to metabolism to allergy-causing compounds
Ester type
Allergies to amide-type local anesthetics are extremely rare)
Pts who are allergic to 1 ester-type agent will most likely be allergic to another ester-type agent
___ has poor solubility in water, used only as a topical agent. It can be used topically for dermatologic conditions, hemorrhoids, premature ejaculation, and as an anesthetic lubricant (NG and endocopic tubes and catheters)
Benzocaine
