Local Anesthetics Flashcards
An ideal local anesthetic has _____ paralysis of sensory nerves.
reversible
Ideal local anesthetic is addictive. True or False.
False - nonaddictive
An ideal local anesthetic is ___ soluble and stable in water.
readily
an ideal local anesthetic has a pH near ____
neutrality
An ideal local anesthetic is nonirritating to tissues. True or False.
True
An ideal local anesthetic has ___ systemic toxicity.
minimum
An ideal local anesthetic is absorbed _____ (quickly, slowly)
slowly
An ideal local anesthetic is _____ and ____ detoxified.
readily and rapidly
An ideal local anesthetic is compatible with ____
epinephrine
An ideal local anesthetic has no hyperesthesia following recovery of sensation. True False.
True
An ideal local anesthetic is able to withstand heat sterilization. True or False.
True
An ideal local anesthetic is expensive. True or False.
False - inexpensive
3 parts of the molecule (which ones are hydrophilic/lipophilic?)
(1) Unsaturated aromatic group - lipophilic
(2) intermediate chain - site o degredation - aminoesters, aminoamides
(3) Tertiary amine - hydrophilic
The tertiary amine is a ____ base.
weak
the pKs of the tertiary base are above ______ pH
physiologic
At a pH of 7.4; more than 50% of drug is ____
ionized
Which form of drug interacts with cell membranes (ionized/non-ionized)?
nonionized
More nonionized drug means _____ (faster or slower) onset and ______ (higher or lower) potency.
faster onset; higher potency
_____ decreases nonionized form of drug.
acidosis
Local anesthetics inhibit _____ of nerve impulses.
Propagation (conduction)
Local anesthetics block ____ channels which cause rapid ______ by allowing rapid ____ movement of ____.
sodium; rapid depolarization; rapid inward movement of Na
Anesthetic potency depends on…. and determines ….
lipid solubility; determines ability of the molecule to reach its site of action
Ionized form of drug is used for? and nonionized?
ionized form to dissolve in body fluids; nonionized to enter cell membrane
Onset of action depends on these three things
(1) physiochemical properties
(2) Dose and concentration
(3) Site of injection
Anesthetics is removed by ____ circulation.
systemic
Local anesthetics themselves have vascular effects. True or False.
True
Local anesthetics at clinical doses cause _____ (vasoconstriction or vasodilation)?
Vasodilation (except cocaine
Why is epinpehrine added in some anesthetics?
sometimes added to produce vasoconstriction to prolong the local anesthetic’s effect
Not all fibers respond the same. Their sensitivity is determined by:
fiber size, fiber type, nerve location, length of nerve exposed to local anesthetic, time for equilibrium in tissue; agent used
Which nerves are blocked first?
Sympathetic and pain fibers; followed by sensory fibers
Which nerves are blocked last?
Motor fibers
Aminoesters are rapidly hydrolyzed in plasma by _____
non-specific pseudocholinesterases
Aminoamides undergo more varied metabolism usually in this organ.
Liver
Metabolites are excreted in the ____
urine
Side effects on systemic toxicity - CNS toxicity
Initially excitement; followed by depression and cardiopulmonary collapse
Side effects on systemic toxicity - cardiovascular toxicity on the heart
Electrophysiological - decrease in rate of depolarization; mechanical - decrease in cardiac output
Side effects on systemic toxicity - cardiovascular toxicity on peripheral vasculature
Low concentrations cause vasoconstriction; higher concentrations causes vasodilation
Side effects on local toxicity
histotoxic on skeletal muscle, nerves (high concentrations), not usually significant; vasoconstriction - addition of epi, can cause tissue damage due to compromised blood supply
Anesthetics may cause methemoglobinemia as a toxic effect. True or False.
True
Allergic reactions are more common with this type of anesthetic.
aminoesters
Uses of local anesthetics
Topical, local infiltration, peripheral (conduction) nerve block; intravenous block; epidural and spinal blocks
Lidocaine - potency, onset, duration after infiltration, max single dose for infiltration, toxic plasma concentration, pK, protein binding %
Potency = 1; Onset = rapid; Duration after infiltration = 60-120 minutes; Max single dose for infiltration = 300 mg; toxic plasma concentration = >5 ug/ml; pK = 7.9; protein binding = 70%
Mepivacaine - potency, onset, duration after infiltration, max single dose for infiltration, toxic plasma concentration, pK, protein binding %
potency = 1; onset = slow; duration after infiltration = 90-180; max single dose for infiltration = 300; toxic plasma concentration = >5 ug/mL; pK = 7.6; protein binding = 77%
Bupivacaine - potency, onset, duration after infiltration, max single dose for infiltration, toxic plasma concentration, pK, protein binding %
potency = 4; onset = slow; duration after infiltration = 240-480 min; max single dose for infiltration = 175 mg; toxic plasma concentration = >3 toxic plasma concentration ug/mL; pK = 8.1; protein binding = 95%
Ropivacaine - potency, onset, duration after infiltration, max single dose for infiltration, toxic plasma concentration, pK, protein binding %
Potency = 4; onset = slow; duration after infiltration = 240 - 480 minutes; max single dose for infiltration = 200 mg; toxic plasma concnetration = >4 ug/mL; pK = 8.1; protein binding = 94%
