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Apex > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

What is the primary determinant of testing membrane potential?

A

Potassium!

Decreased serum K+ —> RMP is more negative

Increased serum K+ —> RMP is more positive

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2
Q

What is the primary determinant of threshold?

A

Calcium!

Hypocalcemia —> TP becomes more negative

Hypercalcemia —> TP becomes more positive

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3
Q

What determines the cell’s ability to depolarize?

A

The difference b/t RMP and Threshold

When RMP is closer to threshold, the cell is easier to depolarize

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4
Q

Are local anesthetics acids or bases?

A

Weak bases

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5
Q

What binds to the local anesthetic binding site (alpha-subunit)? Does it bing inside or outside?

A

Conjugate acid
Binds INSIDE the cell

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6
Q

When considering the molecular structure of local anesthetics, what determines lipophilicity?

A

Aromatic ring

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7
Q

When considering the molecular structure of local anesthetics, what determines hydrophilicity or the ability to accept a proton?

A

Tertiary amine

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8
Q

When considering the molecular structure of local anesthetics, what determines drug class, metabolism, and allergic potential?

A

Intermediate chain

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9
Q

What are examples of esters?

A

Benzocaine
Cocaine
Chloroprocaine
Procaine
Tetracaine

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10
Q

What are examples of Amides?

A

Bupivacaine
Dibucaine
Lidocaine
Mepivacaine
Ropivacaine

Amides have two “i”

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11
Q

How are ester local anesthetics metabolized?

A

Pseudocholinesterases

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12
Q

How are amide local anesthetics metabolized?

A

Hepatic clearance (P450)

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13
Q

Which local anesthetic class has cross sensitivity within its own class?

A

Esters

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14
Q

What is the equate to the following items? Think local anesthetics

Onset ~
Potency ~
Duration is action ~

A

Onset ~ pKa (also dose/concentration)

Potency ~ lipid solubility (intrinsic vasodilating effect)

Duration of action ~ protein binding (lipid solubility, addition of vasoconstrictors)

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15
Q

How do local anesthetics have a biphasic response on vascular smooth muscle?

A

At lower concentrations (below clinical use) they cause vasoconstriction

At higher concentrations (clinical use) they cause vasodilation.

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16
Q

Ionization is dependent on what two factors?

A

The pH of the solution
pKa of the drug

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17
Q

What is the pKa of Bupivacaine?

A

8.1

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18
Q

What is the pKa of Ropivacaine?

A

8.1

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19
Q

What is the pKa of Lidocaine?

A

7.9

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20
Q

What is the pKa of prilocaine?

A

7.9

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21
Q

What is the pKa of Mepivacaine?

A

7.6

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22
Q

What is the pKa of procaine?

A

8.9

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23
Q

What is the pKa of Chloroprocaine?

A

8.7

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24
Q

What is the pKa of tetracaine?

A

8.5

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25
Q

What is the pKa of benzocaine?

A

3.5!!

This is an odd man out!

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26
Q

What is a significant risk with benzocaine?

A

Methemoglobinemia

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27
Q

What are the levels of absorption of local anesthetics (from most to least)
What is the mnemonic

A

I Think I’ll Ingest cookies each Beautiful Friday for a Special Snack

I: IV
Think: Tracheal
I’ll: Interpleural
Ingest: Intercostal
Cookies: Caudal
Every: Epidural
Beautiful: Brachial Plexus
Friday: Femoral

For a

Special: Sciatic
Snack: subcutaneous

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28
Q

What protein to local anesthetics preferentially bind to?

A

Alpha 1-acid glycoproteins

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29
Q

How is exparel dispense and what is the max dose?

A

133 mg in 10 mL or 266 mg in 20 mL

Max dose: 266 mg

30
Q

What are the rules for administering Lidocaine and exparel to a patient?

A

After administering lido —> no bupi for at least 20 mins

After administering Bupi —> no lido (in any form) for at least 96hours

31
Q

What is the max dose (in both total dose and mg/kg) for Bupivacaine?

A

2.5 mg/kg
175 mg total

32
Q

What is the max dose (in both total dose and mg/kg) for Bupivacaine with epi?

A

3 mg/kg
200 mg total

33
Q

What is the max dose (in both total dose and mg/kg) for Ropivacaine?

A

3 mg/kg
200 mg total

34
Q

What is the max dose (in both total dose and mg/kg) for Lidocaine?

A

4.5 mg/kg
300 mg

35
Q

What is the max dose (in both total dose and mg/kg) for Mepivacaine?

A

7 mg/kg
400 mg total

36
Q

What is the max dose (in both total dose and mg/kg) for Lidocaine with epi?

A

7 mg/kg
500 mg

37
Q

What is the max dose (in both total dose and mg/kg) for Prilocaine?

A

8 mg/kg
< 70 kg ~ 500 mg
> 70 kg ~ 600 mg

38
Q

What is the max dose (in both total dose and mg/kg) for Procaine?

A

7 mg/kg
350 - 600 mg total

39
Q

What is the max dose (in both total dose and mg/kg) for Chloroprocaine?

A

11 mg/kg
800 mg total

40
Q

What is the max dose (in both total dose and mg/kg) for Chloroprocaine and with Epi?

A

14 mg/kg
1,000 mg total

41
Q

What is the most common cause of toxic plasma concentrations?

A

Inadvertent intravascular injection

42
Q

Is LAST more common with peripheral nerve blocks or epidural anesthesia?

A

Peripheral nerve blocks

43
Q

At what plasma concentration of Lido would you see analgesia?

A

1-5 mcg/mL

44
Q

At what plasma level of lidocaine do you see tinnitus, numbness, and/or blurred vision? AND hypotension/cardiac depression?!

A

5-10 mcg/mL

45
Q

At what plasma level of Lido do you see seizures and/or LOC?

A

10-15 mcg/mL

46
Q

At what plasma level of lidocaine do you see coma and/resp arrest?

A

15-25

47
Q

What are factors that increase CNS toxicity with local anesthetics?

A

Hypercarbia —> increased Blood flow
Acidosis —> decreases convulsion threshold
Hyperkalemia —> raises RMP

48
Q

What factors decreases CNS effects?

A

Hypocarbia —> decrease cerebral blood flow
Hypokalemia —> decreases resting membrane potential
CNS depressants —> raise seizure threshold

49
Q

Which local anesthetic has a greater affinity of voltage gated sodium channel receptors in the heart?

A

Bupivacaine > Levobupivacaine > Ropivacaine >Lidocaine

50
Q

What is the primary risk of cocaine toxicity?

A

Excessive SNS stimulation

51
Q

What is the dose for cocaine? Mg/kg and max?

A

1.5-3 mg/kg
150-200 mg total

52
Q

In terms of LAST, what should be avoided as far as vasopressors?

A

Avoid vasopressin
Keep epi dose low 1mcg/kg

53
Q

What is the 20% lipid emulsion therapy for someone > 70 kg

A

Bolus: 100 mL over 2-3 minutes
Infusion: 250 mL over 15-20

54
Q

What is the 20% lipid emulsion therapy for someone < 70 kg

A

Bolus: 1.5 mL over 2-3 minutes
Infusion: 0.25 mL/kg/min

55
Q

What is the maximum dose of lidocaine during tumescent anesthesia?

A

55 mg/kg

56
Q

What is the most common cause of death in liposuction?

A

PE

57
Q

When is general anesthesia recommended when administering a tumescent infusion?

A

> 2-3 L

58
Q

What are some causes of acquired methemoglobinemia? Local anesthetics

A

Benzocaine (also bupi is in Cetacaine)
Prilocaine (together with Lido = EMLA)
Lidocaine

59
Q

What is the light waveform for deoxygenated blood?

A

Red 660

60
Q

What is the light waveform for oxygenated blood?

A

Infrared 940

61
Q

What is the light absorption for methemoglobin?

A

Both Red 660 AND infrared 940!!

62
Q

What are the key findings in methemoglobinemia?

A

Decreased SpO2 (usually 85%)
Normal PaO2

63
Q

What is the treatment to methemoglobinemia? What is the dose?

A

Methylene blue 1-2 mg/kg

64
Q

When does methemoglobinemia occur? MOA?

A

It’s produced when the iron molecule becomes oxidized to its ferric form (Fe 3+)

65
Q

How does methemoglobin affect the oxyhemoglobin curve?

A

Shifts to the left

66
Q

What are some S&S of methemoglobinemia?

A

Chocolate colored blood
Hypoxia
Cyanosis (slate grey pseudocyanosis)

67
Q

What is the max dose of EMLA?

A

0-3 months (<5kg): 1 g
3-12 months (>5kg): 2 g
1-6 years (>10kg): 10 g
7-12 years (>20kg): 20g

68
Q

What drugs prolong the duration of action of local anesthetics?

A

Epinephrine
Decadron
Dextran

69
Q

What drugs provide supplemental analgesia to local anesthetics?

A

Clonidine
Epinephrine
Opioids

70
Q

What drugs shorten onset time of local anesthetics?

A

Sodium bicarb

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