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Pharmacology > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

What is the general effect of all local anesthetics?

A

Local anesthetics bind to sodium channels in nerves to block nerve transmission

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2
Q

What kinds of nerves are easiest to block?

A
  • Myelinated
  • Small
  • High firing frequency
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3
Q

What is the function of Aδ nerves?

A

Pain

Cold temprature

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4
Q

What is the function of Aβ nerves?

A

Tactile

Proprioception

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5
Q

What is the function of Aα nerves?

A

Motor

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6
Q

What is the function of B nerves?

A

Preganglionic Sympathetic

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7
Q

What is the function of C nerves?

A

Visceral Pain

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8
Q

What is the order in terms of easiest to hardest nerves to block in the type A nerves?

A

δ > β > α

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9
Q

In terms of the nerves overall, what are the easiest to hardest nerves to block?

A

B > A > C

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10
Q

What is the onset time of LAs dependent upon?

A

pH and pKa

High pH will increase the speed of onset.

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11
Q

What is the potency of LAs dependent upon?

A

Lipid solubility

As lipid solubility increases the potency of the LA will increase.

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12
Q

What is the duration of effect of LAs dependent upon?

A

Local protein binding NOT plasma binding

Increased protein binding will mean longer duration of action.

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13
Q

What can be added to LAs to increase the speed of onset?

A

NaHCO3

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14
Q

What can be added to LAs to localize them to the area?

A

EPI used to vasoconstrict to keep the drugs locally to the injection area

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15
Q

Is EPI useful in localizing LAs that are highly protein bound?

A

No because vasoconstriction would not be useful for localization when proteins are already functioning in that role

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16
Q

What Na+ gates are open at rest?

A

h open

m closed

17
Q

What Na+ gates are open at activation?

A

h open

m open

18
Q

What Na+ gates are open at inactivation?

A

m open

h closed

19
Q

What is the function of A𝛄 nerves?

A

Muscle tone

20
Q

What are the first signs of spinal/epidural anesthesia?

A

􏰁 Sympathectomy>sensory>motor

21
Q

What are the first signs of peripheral anesthesia?

A

First sign may be lack of proximal muscle coordination - finger to nose

22
Q

What are the LA esters?

A

Cocaine
Procaine
Tetracaine
Benzocaine

23
Q

What are the LA amides?

A

Lidocaine

Bupivicaine

24
Q

Where does binding occur on the Na receptor?

A

Binding occurs on the cytoplasmic (inside) side of the receptor so LA must traverse the membrane. Only the uncharged can cross but the charged form is the active form.

25
Q

What are some contraindications to LA use?

A

Bacteremia
Pre-existing neurologic disease
Abnormal coagulation

26
Q

Where is LA administered for spinal?

A

Needle inserted at L3 - L5 and the drug is deposited around cauda equina

27
Q

Where is LA administered for epidural?

A

Any level is possible and the site of action is the nerve roots

28
Q

What are the respiratory effects of LA at the thoracic level?

A

􏰁Minimal reduction in vital capacity with abdominal muscle

paralysis but the loss of proprioception can be upsetting to patient as they cannot feel their own breathing

29
Q

What are the respiratory effects of LA at the high spinal level?

A

BP will be reduced due to B type nerve block that causes the brainstem to trigger suppression of respiration.

NEVER due to phrenic nerve paralysis

30
Q

How is respiratory arrest due to LA effects treated?

A

Vasopressors and supportive ventilation

31
Q

What are the cardiovascular effects of neuraxial LA?

A

Arterial dilation and decrease in BP and decrease in HR due to decreased filling.

32
Q

How are LA esters eliminated?

A

Plasma cholinesterase

33
Q

How are LA amides eliminated?

A

Liver via cytochrome P450

34
Q

What is the toxicity of LA on neurons?

A

Can inhibit inhibitory neurons that will lead to increased excitatory neuron action

35
Q

How are LA induced seizures treated?

A

Benzodiazepines

Succinylcholine

36
Q

How is LA toxicity prevention performed?

A

Fractionated injection with intermittent aspiration to make sure you are not in a blood vessel

Use of epinephrine as intravascular marker

37
Q

What is a treatment for LA toxicity?

A

Intralipid. It is lipophilic and creates a “sink” that LA can be sequestered into

38
Q

What is a common side effect of neuraxial anesthesia?

A

Postdural puncture headache (PDPH) is a common complication of neuraxial anesthesia its incidence is influenced by many factors

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