Local Anesthetics Flashcards

1
Q

How do local anesthetics work?

A

They bind in open Na-Channels, causing slowed rate of depolarization, reduced amplitude, increases threshold potential. Does not change resting potential.
–Prevent propagation of the AP–

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2
Q

Why do local anesthetics selectively bind to C-fibers and noriceptive fibers?

A

In the case of an injury, the pain fibers are firing more rapidly, thus the channels are open more frequently allowing the anesthetic to get into the channels.

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3
Q

What is the order of sensory that are affected with local anesthetics?

A

First: Pain, Cold, Warmth
Later: Touch, Deep pressure, and Motor

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4
Q

What kind of neurons are most sensitive to local anesthetic?

A
  • smallest diameter and unmyelinated

C-fibers and B-fibers

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5
Q

Why are vasoconstrictors used with local anesthetics?

A

They restrict blood flow away from the site of injection to prevent systemic effects of the anesthetic and keeps more drugs locally where they were injected.

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6
Q

How does pH play a role in local anesthetic effectiveness?

A

The drugs have two forms B and BH+, the B form can penetrate the membrane and then the BH+ form is the one that binds in the channel.
-Wounds typically have lower pH allowing more to penetrate the neurons.-

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7
Q

What are common systemic effects if local anesthetics get into the blood stream?

A

CNS- stimulation first, then progresses to depression

CV- decreases contractility, BP, and rate of conduction, eventually leading to coma/CV depression.

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8
Q

What are the two methods of metabolism of local anesthetics?

A

Ester Anesthetics = inactivated by esterases in the plasma
Amide Anesthetics = inactivated/metabolized in liver
–Caution with individuals with liver disease-

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9
Q

Which local anesthetic has both anesthetic properties and vasoconstriction effects?

A

Cocaine. (Ester-based)

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10
Q

What is the most common use for cocaine use as an anesthetic?

A

Typically used in upper respiratory tract and nasal surgeries where both properties are useful.

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11
Q

Which local anesthetic has low potency, slow onset, and short duration?

A

Procaine (ester-based). Less commonly used now.

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12
Q

Which ester anesthetic is common used for spinal anesthesia that has long action?

A

Tetracaine - commonly used in topical and ophthalmic solutions.

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13
Q

Which local anesthetic is primarily used topically and is bought OTC?

A

Benzocaine (ester)

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14
Q

What is the most widely used local anesthetic?

A

Lidocaine (amide-class)

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15
Q

How does Lidocaine compare to Procaine?

A

Faster, longer action, more potent than procaine.
–Typically used with epinephrine for higher dose–
Also Lidocaine is metabolized in the liver.

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16
Q

What amide anesthetic has long acting effects used for nerve blocks?

A

Bupivicaine.

More selective to sensory over motor.

17
Q

What is a more concerning side effect of Bupivicaine?

A

More cardiotoxic systemically compared to Lidocaine, can cause fetal arrhythmias and myocardial depression.

18
Q

What amide anesthetic is less cardiotoxic compared to Bupivicaine?

A

Ropivacaine - same effects as Bupivicaine, even more selective towards sensory.