Local anesthetics Flashcards by Adrie McFarland

Conduction velocity of a nerve is increased by larger or smaller diameter?

Larger

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What are the 4 subtypes of A fibers?

alpha
beta
delta
gamma

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How myelinated are all of the subtypes of A fibers?

alpha: heavy
beta: heavy
delta: medium
gamma: medium

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Function of A alpha fibers?

Motor and propioception

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Function of beta A fibers

touch
pressure

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Function of A delta fibers

Fast pain
Temp
Touch

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What level of myelination do B fibers have?

Light

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What function do B fibers have?

Pre-ganglionic ANS fibers

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What level of myelination do C fibers have?

None

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Function of C fibers

Slow pain
Temp
Touch

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What nerve/s get blocked first?

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What nerve/s get blocked second?

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What nerves get blocked 3rd?

A delta and gamma

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What nerves get blocked 4th?

A alpha and A beta

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Minimum effective concentration of LA is similar to what value of inhaled anesthetics?

MAC

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Fibers that are more easily blocked have a higher or lower Cm?

Lower

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In what order are nerves blocked? What about return of function?

B fibers > C fibers> Small diameter A fibers (gamma and delta) > Large diameter A fibers (alpha and beta)

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What subunit do LAs bind to of the voltage-gated sodium channel.

alpha

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What are the 3 states Na channels can possible exist in?

Resting
Active
Inactive

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Resting state voltage of Na channel

-70 mV

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Active state voltage of Na channel

-70 to +35 mV

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Inactive state voltage of Na channel

+35 to -70 mV

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Which states can LA bind to Sodium channels?

Active
Inactive

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RMP for nerve cell

-70 mV

Threshold potential for nerve cell

-55 mV

LA are weak acids or bases?

bases

LA molecule is made up of 3 key components:

Benzene ring Intermediate chain (ester or amide) Tertiary amine

What part of the structure of a LA makes it lipophilic

Benzene

What part of the LA structure makes it hydrophilic

Tertiary Amine

How are esters metabolized? Amides?

Pseudocholinesterase P450

Which LA class has higher potential for allergy?

Ester

What is it about esters that can cause allergic reaction?

PABA

Match these factors of LAs Pka, Protein binding, Lipid solubility with DOA, Potency, Onset of action

Pka = Onset of action Protein binding = DOA Lipid solubility = potency

How does chloroprocaine work so quick even with a high pKA?

A higher dose is given. More molecules --> works quicker

Which class has higher pKa? Ester or amide

Esters (8.5- 8.9) Compared to amides (7.6-8.1)

Odd man out!! What is the pKA of Benzocaine

3.5

What is a risk of Benzocaine? How is it treated?

Methemoglobinemia Methylene Blue

Pneumonic for most vascular to least vascular sites

I think illogical Imposters Cant Educate But Fabulous Schools Should IV Tracheal Interpleural Intercostal Caudal Epidural Brachial Plexus Femoral Sciatic SubQ

Which protein do LA's preferentially bind to?

Alpha 1

LA can be divided into esters and amides. Both are metabolized either by PCHe or P450. Which one of them is metabolized by both?

Cocaine

Exparel is a long acting LA. What is the drug?

Bupivacaine

Max dose of Experel

266 mg

After infiltrating Lidocaine how long do you have to wait to give Experel?

20 min

After infiltrating liposomal Bupivacaine how long do you have to wait to give Experel?

No Bupivacaine (in any form) for at least 96 hours

Max dose of Bupivacaine

175 mg

Max dose of Ropi

200 mg

Max dose of Lido

300 mg

Max dose Mepivacaine

400 mg

Max dose of Prilocaine

if less than 70 kg -> 500 mg if more than 70 kg -> 600 mg

Max dose of Procaine

600 mg

Max dose chloroprocaine

800 mg

Max dose Bupi + Epi

200 mg

Max dose Lido + Epi

500 mg

Max dose Chloroprocaine + Epi

1,000 mg

LAST with which drug will be the hardest to resuscitate?

Bupi It stays on the receptor the longest!!!

What is the problem with treating cocaine toxicity with a beta selective beta blocker?

Unopposed alpha 1 stimulation

Max dose for cocaine

200 mg

If you try to treat a sz from LAST with a Benzo but it doesn't work, what should be given next

NDMB or Sch to help stop muscle contraction that uses O2 up

Should you treat seizure during LAST with Propofol?

No because it can augment myocardial depression even though it helps decrease seizures at lower doses

If epi is used to treat LAST, what dose should you try and stay below?

1 mcg/kg

What drug should be used as an anti arrhythmic during LAST resuscitation?

Avoid giving another LA. *Use amiodarone

20 % lipid emulsion should be bolused then infused at what doses (over and under 70 kg)

Bolus over 70 kg: 100 mL Infusion over 70 kg: 250 mL over 20 min Bolus under 70 kg: 1.5 mL/kg lean body weight Infusion under 70 kg: 0.25 mL/kg/min

At what plasma concentration of Lidocaine does analgesia occur

1-5

At what plasma concentration of Lidocaine does tinnitus, sk. m. twitching, numbness of lips and tongue occur

5-10

At what plasma concentration of Lidocaine do seizures and loss of consciousness occur

10-15

At what plasma concentration of Lidocaine does coma occur

15-25

At what plasma concentration of Lidocaine does hypotension and myocardial depression occur

5-10

At what plasma concentration of Lidocaine does respiratory depression occur

15-25

At what plasma concentration of Lidocaine does CV collapse occur

> 25

most common cause of death related to liposuction

Max dose of Tumescent Lidocaine

55 mg/kg

How does hemoglobin become methemoglobin?

Iron (Fe ++) molecule on the RBC gets oxidized to (Fe +++)

Can methgb bind O2?

Which direction does oxyhgb curve shift with methgb?

Left

What kind of oximeter is needed to detect methemoglobinemia?

Co-oximiter

What 2 LA can lead to methemoglobinemia?

Benzocaine Prilocaine Cetacaine (has Benzocaine) EMLA cream has Prilocaine

Cyanosis in the presence of a normal PaO2 is highly suggestive of _

methemoglobinemia

Dose of methylene blue for methemoglobinemia

Dose: 1-2 mg/kg max: 7-8 mg/kg

Which drug can improve LA diffusion through tissues

hyaluronidase

What 3 drugs can prolong the DOA of LA?

Epinephrine Dexamethasone Dextran

How can Epi provide supplemental analgesia?

Alpha 2 agonism

What do you need to know about chloroprocaine and epidurals?

Decreases efficacy of opiods

How much bicarb should be added to LA solution to increase onset time?

1 mL to 10 mL