Flashcards in Local Anesthetic Agents Deck (74):
1
The reversible block of the generation and propagation of the action potential in neural tissue is known as what?
Local anesthetic
2
Transient loss of what 3 functions can be seen with local anesthetics?
- Sensory
- Motor
- Autonomic
3
Local anesthetics target what?
Axons of A and C fibers (sensory nerves)
4
Which are more prone to hydrolysis, amide or ester links?
Ester
5
Which have a shorter duration of action, anesthetics with amide or ester links?
Ester
6
What are 4 examples of local anesthetics with esters?
- Cocaine
- Procaine
- Tetracaine
- Benzocaine
7
What are 6 examples of local anesthetics with amides?
- Lidocaine
- Prilocaine
- Mepivacaine
- Bupivacaine
- Ropivacaine
- Levo-bupivacaine
8
Where do local anesthetics act?
Site of injection.
9
Slow absorption into systemic circulation is usually desired with what?
Local anesthetics
10
What are 3 factors increasing systemic absorption?
- High dosage
- Increased blood flow at site of injection
- Vasodilation
11
Which remains at the receptor site longer, the cationic or non-charged form?
Cationic
12
Which is able to rapidly penetrate membranes, the cationic or non-charged form?
Non-charged
13
What effect does pka have on onset?
- High pka has slow onset.
- Low pka has fast onset
14
Which has a faster onset, procaine or lidocaine?
Lidocaine
15
Which has a faster onset, lidocaine or mepivacaine?
Mepivacaine
16
Which local anesthetic has the slowest onset?
Procaine
17
Which has a faster onset, mepivacaine or bupivacaine?
Mepivacaine
18
An infection can have what effect on the internal environment?
Make it acidic.
19
Increased protein binding has what effect on duration of action?
Increased duration
20
Which has a higher percentage of protein binding, procaine or lidocaine?
Lidocaine
21
Which has a higher percentage of protein binding, lidocaine or mepivacaine?
Mepivacaine
22
Which has a higher percentage of protein binding, mepivacaine or bupivacaine?
Bupivacaine
23
How is lipid solubility related to potency?
Positively
24
What effect does lipid solubility have on onset and duration?
Slower onset and longer duration
25
How does perfusion affect systemic absorption?
Highly perfused area leads to faster systemic absorption.
26
What are 2 examples of highly perfused areas?
- Mucus membranes
- Intercostal muscles
27
What are 3 examples of poorly perfused areas?
- Tendons
- Dermis
- Fat
28
What are 2 examples of vasoconstrictors?
- Epinephrine
- Phenylephrine
29
What can lead to reduced blood perfusion?
By how much?
- Vasoconstrictors
- 30%
30
T/F: Vasoconstrictors enhance the concentration of available drug in the premises of neuronal tissue.
True
31
What effect do vasoconstrictors have on duration of action?
Increase it.
32
What effect do vasoconstrictors have on analgesia?
Prolonged analgesic effects.
33
What are 2 advantages of epinephrine?
- Reduces systemic absorption of local anesthetics
- Reduces risks of systemic toxicity induced by local anesthetics
34
What is a disadvantage of epinephrine?
Potential for life-threatening arrhythmias
35
Where are amides metabolized?
Excreted?
- In the liver by cytocrome P450
- Kidneys
36
Where might amides accumulate?
Liver
37
Where are esters metabolized?
Excreted?
- In plasma by pseudocholinesterase
- Kidneys
38
What effect do local anesthetics have on nerve conduction?
Prevent sodium channels opening in neuronal axons, thus maintaining fully polarized state and blocking nerve propagation.
39
Action potentials are conducted along what part of the axon?
Ranvier nodes
40
Where do local anesthetics act on the axon?
Ranvier nodes
41
How many nodes of Ranvier need to be blocked in order for a local anesthetic to be effective?
2-3 nodes of Ranvier
42
T/F: Local anesthetics are only capable of blocking sensory nerves.
False - They are capable of blocking all nerves, not only sensory nerves.
43
Local anesthetics may cause what due to the blockade of motor neurons?
Muscle paralysis
44
Local anesthetics may cause what 2 things due to the blockade of autonomic nerves?
- Vasodilation
- Hypotension
45
Which type of fibers are more susceptible to local anesthesia?
Smaller non-myelinized fibers
46
Which type of fibers are less susceptible to local anesthesia?
Larger myelinized fibers
47
Is a blockade by local anesthetics more or less marked at higher frequencies of depolarization?
More marked
48
What type of nerves have a higher firing rate?
Why?
- Sensory nerves
- More susceptible
49
What effects does firing rate have on susceptibility?
- Higher firing rate means more susceptible
- Slower firing rate means less susceptible
50
Which have a higher firing rate, small or large diameter fibers?
Small diameter
51
Which fibers get blocked earlier or with low concentrations of local anesthetics?
Small diameter sensory nerves
52
Some local anesthetics can be used as what?
What are 2 examples of these?
- Antiarrhythmic agents
- Lidocaine and procaine
53
Some local anesthetics can cause what at high doses?
what are 2 examples of these?
- Lethal arrhythmias
- Bupivacaine and ropivacaine
54
What are 3 effects local anesthetics can have on cardiac cells?
- Suppress re-entrant ventricular arrhythmia
- Increase ventricular fibrillation threshold
- Decrease automaticity
55
What is the progression of toxicity for local anesthetics seen in the CNS?
First sedation, followed by tonic-clonic seizures, coma
56
What effect do local anesthetics have on the respiratory system?
Depression
57
What are 3 effects local anesthetics have on the CV system?
- Bradycardia
- Arrhythmias
- Hypotension
58
What are 4 possible toxic effects that can be seen with local anesthetics?
- Tissue irritation
- Allergic reactions
- Methemoglobinemia
- Apoptosis
59
In which species can methemoglobinemia be more of a problem with local anesthetics?
Cats
60
What is the order of presentation for most amide type of local anesthetic toxicity?
- CNS signs
- Respiratory system depression
- Cardiovascular system depression
61
Which drug is the exception to the normal order of presentation of local anesthetic toxicity?
What is the difference?
- Bupivacaine
- Causes cardiovascular depression first
62
What are 2 examples of isomers of bupivacaine that have less cardiac toxicity?
- Ropivacaine
- Levo-bupivacaine
63
A toxic dose of local anesthetic can cause side effects when injected how?
Rapidly IV
64
What is considered to be a toxic dose of lidocaine?
8 mg/kg
65
Do not inject more than what dose of lidocaine in a dog?
A cat?
- 4 mg/kg
- 2 mg/kg
66
What is considered to be a toxic dose of bupivacaine?
4 mg/kg
67
Do not inject more than what dose of bupivacaine in a dog?
A cat?
- 2 mg/kg
- 1 mg/kg
68
T/F: Dogs are more sensitive to local anesthetics than cats.
False - Cats more more sensitive than dogs.
69
Always do what before injecting a local anesthetic?
Aspirate to check for accidental IV needle placement. Look for blood.
70
Allergic reactions are mainly seen with what type of local anesthetic?
Ester-type
71
What is a possible sign of methemoglobinemia?
Pulseox will be about 85% due to significant hypoxia
72
Cats are more prone to develop methemoglobinemia with which 2 local anesthetics?
- Prilocaine
- Benzocaine
73
What are 3 forms of supportive care that can be used for local anesthetic toxicity?
- CV and/or respiratory support
- Steroid for allergies
- Anti-epileptic drugs
74