Wk 8: Local Anesthetics Flashcards by Ashley Campbell

Local anesthetics are used to provide analgesia and anesthesia for various surgical and nonsurgical procedures: (4)

-Acute and chronic pain management
-Reduce perioperative stress
-Improve perioperative outcomes
-Treat dysrythmias

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Local anesthetics produce _________ conduction blockade of impulses along central and peripheral nerve pathways

reversible

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With progressive increases in __________ of local anesthetics, the transmission of autonomic, somatic sensory, and somatic motor impulses is interrupted

concentrations

(the larger the concentration, the more prevalent those changes become)

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Local anesthetics produce:
________ nervous sytem blockade
________ anesthesia
________ muscle paralysis in the area
innervated by the affected nerve

Autonomic
Sensory
Skeletal

(knowing purpose of block will guide choice of type and concentration of drug)

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In almost all instances, _____ or an _____ bond links the hydrocarbon chain to the lipophilic aromatic ring

Ester (-CO-)
Amid (-NHC-)

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The connecting _________ chain is the basis for classifying as ester or amid local anesthetics

Hydrocarbon

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The important differences between ester and amide local anesthetics relate to:
________
________

Metabolism
Potential to produce allergic
reactions

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Procaine
Chloroprocaine
Tetracaine

Esters

“No one likes one I’d Ester”

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Lidocaine
Prilocaine
Mepivacaine
Bupivacaine
Levobupivacaine
Ropivacaine

Amides

(2 I’s)

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Only amide local anesthetic with rapid onset

Lidocaine

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Only ester local anesthetic with rapid onset

chloroprocaine

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Drugs such as __________, __________, and ___________ have been incorporated into liposomes

Lidocaine
Tetracaine
Bupivacaine

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Liposomal local anesthetics ________ duration of action and _______ toxicity

Prolong
Decrease

Hemorrhoidectomy, bunionectomy, field blocks, brachial plexus blocks, etc.

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Liposomal local anesthetics can prolong duration of action up to ____ hours

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Local anesthetics prevent transmission of nerve impulses (conduction blockade) by inhibiting passage of _____ _____ through ion-selective ______ ______ in nerve membranes

sodium ions
sodium channels

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Local anesthetics inhibit passage of sodium ions through ion-selective sodium channels in nerve membranes

This _____ the rate of depolarization, therefore _______ ________ is not reached and an _________ ________ is not propagated

Slows
threshold potential
action potential

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_______________ of local anesthetic necessary to produce conduction blockade of nerve impulses

Comparable to the MAC for inhaled anesthetics

Minimum effective concentration (Cm)

(a means to compare local anesthetic potencies)

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Each local anesthetic has a unique minimum effective concentration (Cm), reflecting differing ______ of each drug

potencies

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The minimum effective concentration (Cm) of motor fibers is approximately ______ that of sensory fibers

Therefore, sensory anesthesia may not always be accompanied by skeletal muscle ________

twice

paralysis

(need higher concentration of LA to block motor fibers compared to sensory fibers)

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Despite an unchanged minimum effective concentration (Cm), _____ local anesthetic is needed for subarachnoid (spinal) anesthesia than for epidural anesthesia, reflecting greater access of local anesthetics to unprotected nerves in the subarachnoid space

less

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Changes during pregnancy

_______ sensitivity may be present during pregnancy

_______ _____ onset of conduction blockade

Increased

More rapid

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Is there clinically significant transplacental transfer of LA between mother and fetus?

Yes

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_____ in the fetus, could occur during prolonged labor, this in theory results in accumulation of local anesthetic molecules in the fetus ( ____ _______)

Acidosis

Ion trapping

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Local anesthetics are _____ _____ that have pK values somewhat _______ physiologic pH

Weak bases

above

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Local anesthetics with pKs nearest to ______ pH have the most _____ onset of action, reflecting the presence of an optimal ratio of _______ to ______ drug fraction

physiologic rapid ionized nonionized

________ _______ activity will also influence apparent potency and duration of action

Intrinsic vasodilator

Enhanced __________ action of lidocaine compared with mepivacaine results in the ________ systemic absorption and _______ duration of action of lidocaine

vasodilator greater shorter

Attempts to slow systemic absorption, and thus increaser DOA include mixing ________ or _______ with LA = combats vasodilation

epinephrine phenylephrine

Absorption of a LA from its site of injection into the systemic circulation is influenced by: (4)

Site of injection (certain areas have higher perfusion) Dosage Use of epinephrine Pharmacologic characteristics of the drug

Does the intercostal area of sciatic femoral area have a higher serum level?

Intercostal Highly perfused = picked up much faster into systemic circulation

The ______ water solubility of local anesthetics usually limits renal excretion of unchanged drug to less than ____ % Exception is cocaine, of which ___ % to ____ % of unchanged drug can be recovered in urine

poor 5% 10-12%

Water-soluble metabolites of local anesthetics, such as ______ __________ ____ ( ______ ) resulting from metabolism of ester local anesthetics, are readily excreted in urine

para-aminobenzoic acid (PABA)

Amide local anesthetics undergo varying rates of metabolism by ________ _______ located primarily in the ______

microsomal enzymes liver

Amides _______ undergoes the most rapid metabolism

Prilocaine

Amides _______ and _______ are intermediate metabolisms

Lidocaine and mepivacaine

Amides __________ and __________ undergo the slowest metabolism

Bupivacaine and ropivacaine

Compared with that of ester local anesthetics, the metabolism of amide local anesthetics is more ______ and _______

complex and slower (amides have potential to last longer than esters)

_______ metabolism means that sustained increases of the plasma concentrations of amide local anesthetics, and therefore systemic ________, are more likely than with ester local anesthetics

Slower toxicity

__________ drug effects of amide local anesthetics are more likely than with ester local anesthetics

Cumulative (especially if re-dosing or giving multiple boluses)

Ester local anesthetics undergo _______ by ____________ enzyme principally in the _______

hydrolysis cholinesterase plasma

Esters _________ is the most rapidly metabolized

Chloroprocaine

Esters ___________ is intermediately metabolized

Procaine

Esters __________ is the slowest metabolized

Tetracaine

Esters The resulting metabolites are pharmacologically ________, although para-aminobenzoic acid may be an _______ responsible for subsequent _______ _______-

inactive antigen allergic reactions

Allergic reactions to local anesthetics are ______ despite the frequent use of these drugs Estimated that < ____ % of all adverse reactions to local anesthetics are due to an allergic mechanism

rare <1%

Esters of local anesthetics that produce metabolites related to _____ - __________ _____ are more likely than amide local anesthetics to evoke an allergic reaction

para-aminobenzoic acid

_____ ________ _______ ______ (_____) is due to an excess plasma concentration of the drug

Local anesthetic systemic toxicity (LAST)

LAST Accidental direct ________ _______ of local anesthetic solutions during performance of peripheral nerve block anesthesia or epidural anesthesia is the most common reason for excess plasma concentrations of local anesthetic

intravascular injection

Dose dependent effect of lidocaine 1-5 mcg lidocaine

Analgesia

Dose dependent effect of lidocaine 5-10mcg lidocaine

Circumoral numbness Tinnitus Skeletal muscle twitching Systemic hypotension

Dose dependent effect of lidocaine 10-15mcg lidocaine

Seizures Unconsciousness

Dose dependent effect of lidocaine 15-25mcg lidocaine

Apnea Coma

Dose dependent effect of lidocaine >25mcg lidocaine

Cardiovascular depression

Treatment of LAST-induced seizures includes: (3)

Ventilation Benzodiazepine to suppress LAST-induced seizures Early use of lipid emulsion (Intralipid)

Treatment of LAST, lipid emulsion administration

Initial bolus 1.5ml/kg 20% emulsion followed by 0.25ml/kg per minute of infusion for at least 10 minutes after circulatory stability is attained

Rare life-threatening complication that causes oxidation of hemoglobin

Methemoglobinemia

Methemoglobinemia Rare life-threatening complication (decreased oxygen-carrying capacity) that causes _________ of hemoglobin to methemoglobin more rapidly than methemoglobin is _______ to hemoglobin

oxidation reduced

2 local anesthetics that Methemoglobinemia have been implicated in

Prilocaine Benzocaine

Treatment of Methemoglobinemia

Reversed with methylene blue, 1-2mg/kg IV over 5 minutes total dose should not exceed 7-8 mg/kg

Regional anesthesia is classified according to the 6 sites of placement of local anesthetic solution

Topical or surface anesthesia Local infiltration Peripheral nerve block IV regional anesthesia (Bier block) Epidural anesthesia Spinal (subarachnoid) anesthesia

Why isn't cocaine used as often anymore?

Cardiovascular events d/t vasoconstricting properties

Nebulized _________ can produce surface anesthesia of the upper and lower respiratory tract before fiberoptic laryngoscopy and/or bronchoscopy

lidocaine

Lidocaine can be used for patients experiencing intractable ________

coughing

____________ or extravascular placement of local anesthetic in the area to be anesthetized by: _____________ _____________

Local infiltration Lidocaine Bupivacaine

Epinephrine-containing solutions should not be injected into tissues supplied by ____ -________ ______, ______, _____, and _______

end-arteries fingers, toes, ears, and nose (so we don't cut off supply to end arterioles)

________ ______ ______ _______ is achieved by injection of local anesthetic solutions into tissues surrounding individual peripheral nerves or nerve plexuses such as the brachial plexus

Peripheral nerve block anesthesia

Duration of peripheral nerve block anesthesia depends on the (4)

Dose of local anesthetic Lipid solubility Degree of protein binding Use of vasoconstrictor

The duration of action is prolonged more safely by _________ than by increasing the dose of local anesthetic, which also increases the likelihood of _______ ________

epinephrine systemic toxicity

Intravenous Regional Anesthesia is also known as

Bier Block

Bier block The IV injection of local anesthetic solution into an extremity isolated from the rest of the systemic circulation by a _________ produces _____ onset of anesthesia and skeletal muscle ________

tourniquet rapid relaxation

Bier block _____ and _____ local anesthetics produce satisfactory effects when used for IV regional anesthesia

ester and amide

Bier block _________ is the most frequently selected amid local anesthetic

Lidocaine (Usually Lidocaine 0.5%, 50 ml)

Epidural anesthesia Local anesthetic solutions placed in the ________ or _______ ______ space produce epidural anesthesia

epidural sacral caudal

Epidural anesthesia Local anesthetic ________ across the ______ to act on ________ and the spinal cord sites of action is the _________

diffuses dura nerve roots nerve roots

Epidural anesthesia The slow diffusion process accounts for the ___ to ____ minute delay in onset of the sensory anesthesia after placement of local anesthetic solutions in the epidural space

15 to 30

Spinal anesthesia Local anesthetic solutions placed into ________ CSF act on superficial layers of the spinal cord The primary site of action is the __________ __________ as they leave the spinal cord in the _______ _______

lumbar preganglionic fibers as they leave the spinal cord in the anterior rami

Spinal anesthesia Dosages of local anesthetics used for spinal anesthesia vary according to the: (3)

Height of the patient (determines volume of the subarachnoid space) Segmental level of anesthesia desired Duration of anesthesia desired

Spinal anesthesia The _____ _____ of local anesthetic administered for spinal anesthesia is more important than the ________ of drug or _______ of the solution injected

total dose concentration volume

__________, __________ ,_________, and _________ are local anesthetics most likely to be administered for spinal anesthesia

Bupivacaine, ropivacaine, mepivacaine, and chloroprocaine

How do we know how much to give? _______ and ________ are dependent on location and purpose -IV induction -Spinal -Epidural -Nerve block

Volume and concentration

Generally speaking, ______ concentrations given for analgesia _________ concentrations given for anesthesia

smaller higher

Alkalinization of local anesthetics solutions _______ the onset of neural blockade ________ the depth of sensory and motor blockade ________ the spread of epidural blockade

shortens enhances increases

Alkalinization of local anesthetics Adding ____________ will speed onset of peripheral nerve block and epidural block by ____ to ____ minutes

sodium bicarbonate 3 to 5 minutes

The duration of action of a local anesthetic is proportional to the time the drug is in contact with ________

nerve fibers

_________ [ __ : _________ or __mcg/ml] added to local anesthetic solutions produces vasoconstriction

Epinephrine [1:200,0000 or 5mcg/ml]

Epinephrine limits _______ absorption and maintains drug concentrations in the vicinity of _________ to be anesthetized

systemic nerve fibers

Decreased systemic absorption of local anesthetic due to __________ decreases the possibility of systemic __________

vasoconstriction toxicity (i.e. adding epinephrine)

Tumescent liposuction The "tumescent" technique for liposuction is carried out via the ___________ infiltration of large volumes ( ___ or more liters) of solution containing highly diluted lidocaine ( ___ % to ____ %) with epinephrine ( __ : ________)

subcutaneous 5 0.05% to 0.10% 1:100,000

Tumescent liposuction Slow and sustained release of lidocaine into the circulation is associated with plasma concentrations less than ____mcg/ml that peak ____ to ____ hours after injection and then decline gradually over the next ___ to ___ hours

1.5mcg/ml 12 to 14 6 to 14

Tumescent liposuction Causes of death may include lidocaine ______ or local anesthetic-induced depression of cardiac _____ and ________

toxicity conduction contractility

Tumescent liposuction Overall complication rate in a nationwide quality improvement study was ____% in which _____% were minor complications and ____ % were major complications

0.7% 0.57% 0.14%

Tumescent liposuction When highly diluted lidocaine solutions are administered for tumescent liposuction, the dose of lidocaine may range from ____ to _____ mg/kg ("mega-dose lidocaine")

35-55 mg/kg

Dibucaine is an ______ local anesthetic known for its ability to inhibit activity of normal ________________

amide butyrylcholinesterase (plasmacholinesterase)

Dibucaine inhibits plasma cholinesterase by more than ____ % compared with only approximately ____% inhibition of the activity of atypical enzyme

70% 20%

Laboratory evaluation of patients suspected of having atypical pseudocholinesterase is facilitated by measurement of the degree of enzyme _____ by ________, a test termed the __________ _______

suppression dibucaine dibucaine number

Normal dibucaine number = ____ (normal pseudocholinesterase) Low dibucaine #= ____ (atypical pseudocholinesterase)

80 20

Wk 8: Local Anesthetics Flashcards

(96 cards)