Local Anesthetics Flashcards
(82 cards)
1
Q
What is the prototype ester local anesthetic?
A
Procaine
2
Q
What local anesthetic has the shortest onset?
A
Cholorprocaine
3
Q
What are the benefits to using Epinephrine in conjunction with a local anesthetic?
A
Can give more local anesthetic, epi slows absorptionProlongs LA due to vasoconstrictionEpi can detect if we are injecting LA in a vessel
4
Q
What is the prototype amide local anesthetic?
A
Lidocaine
5
Q
How do amide local anesthetics undergo metabolism?
A
Hepatic metabolism
6
Q
What factors affect duration of action of a local anesthetic?
A
Protein binding and available blood supply to area
7
Q
How do ester local anesthetics undergo metabolism?
A
Non-specific plasma esterases
8
Q
What is the potency ratio of Procaine?
A
1
9
Q
What is the potency ratio of Choloroprocaine?
A
4
10
Q
What is the potency ratio of Tetracaine?
A
16
11
Q
What is the potency ratio of Lidocaine?
A
1
12
Q
What is the potency ratio of Ropivacaine?
A
4
13
Q
What is the potency ratio of Bupivacaine?
A
4
14
Q
What is the max dose of Procaine without Epi?
A
7mg/kg
15
Q
What is the max dose of Tetracaine without Epi?
A
1-2mg/kg
16
Q
What is the max dose of Choloroprocaine without Epi?
A
11mg/kg
17
Q
What is the max dose of Lidocaine without Epi?
A
5mg/kg
18
Q
What is the max dose of Bupivacaine without Epi?
A
2-3mg/kg
19
Q
What is the max dose of Ropivacaine without Epi?
A
3mg/kg
20
Q
What is the max dose of Lidocaine with Epi?
A
7mg/kg
21
Q
What is the max dose of Tetracaine with Epi?
A
3mg/kg
22
Q
What is the max dose of Choloroprocaine with Epi?
A
14mg/kg
23
Q
What is the max dose of Bupivacaine with Epi?
A
3mg/kg
24
Q
What is the max dose of Ropivacaine with Epi?
A
3mg/kg
25
What is the duration of action of Procaine?
45-60mins
26
What is the duration of action of Tetracaine?
60-180mins
27
What is the duration of action of Choloroprocaine?
35-40mins
28
What is the duration of action of Lidocaine?
60-120mins
29
What is the duration of action of Bupivacaine?
240-480mins
30
What is the duration of action of Ropivacaine?
240-480mins
31
What is the mechanism of action for local anesthetics?
Local anesthetics bind to voltage gated Na channels and block depolarizing Na current through these channels, they prevent or relieve pin by interrupting nerve conduction
32
How do local anesthetics prevent the generation of a nerve impulse?
They bind to the alpha subunit of the Na channel and prevent the influx of Na into the cell
33
What neurons are more easily blocked, those that are active or inactive?
Active, more sodium channels are in the ready position
34
How does bicarbonate effect the onset of local anesthetics?
Bicarb decreases the onset of local anesthetics
35
What does greater lipid solubility in a local anesthetic indicate?
Greater lipid solubility increases both the potency and duration of their action
36
What is the therapeutic index of lipid soluble LA compared to others that aren't as lipid soluble?
Greater lipid solubility also increases toxicity, decreasing the therapeutic index
37
What size nerve fibers are more susceptible to local anesthetics?
Smaller nerve fibers are more susceptible to LA than large fibers
38
What type of nerve fibers are more susceptible to Local anesthetics?
Myelinated fibers are more easily blocked than non-myelinated, the local anesthetics pools near the axonal membrane
39
What is the first sensation to disappear with local anesthetics?
Pain
40
What is the last modality lost with the use of local anesthetics?
Motor function
41
What other modalities are lost with spinal anesthesia?
Sensation of cold, warmth, touch, deep pressure
42
What is a good way to check if a block is setting up?
Check the affected area for temperature sensation, if they can't feel temperature, in theory they shouldn't be able to feel pain
43
What factors determine the plasma concentration of local anesthetics?
Dose administered
Rate of absorption
Site injectedMetabolism/Elimination of drug
Amount bound to protein
44
How can you tell if the LA is an Ester or an Amine just by looking at the name?
One I = EsterTwo I's = Amine
45
What are the signs of local anesthetic systemic toxicity?
```
Drowsiness
Paresthesia in mouth or tongue (metallic taste)
Ringing in ears
Muscular spasm
Seizure
Coma
Respiratory Arrest
Cardiac Arrest
```
46
What local anesthetic is associated with cardiovascular toxicity?
Bupivacaine (central cardiac depressant)
47
What is often the first sign of bupivacaine toxicity?
Cardiac arrest
48
Where is the primary site of action of local anesthetics in the heart?
Myocardium, where they decrease electrical excitability, conduction rate and the force of myocardial contraction
49
How do local anesthetics contribute to hypotension?
Most LAs cause arteriolar dilation
50
What protein is most associated with local anesthetics?
Alpha1 acid glycoprotein (AAG)
51
Why are pregnant women and newborns more susceptible to local anesthetics?
Low circulating AAG, avoid bupivacaine
52
What local anesthetic should never be injected IV?
Bupivacaine, cardiac specific will cause arrest
53
Where is cocaine derived?
Leave of the coca shrub
54
Why type of local anesthetic is cocaine?
Ester of benzoic acid
55
What is the clinical action of cocaine?
Blockade of nerve impulse and vasoconstriction secondary to inhibition of local norepi re-uptake
56
Why has Cocaine lost favor in practice?
Toxicity and potential for abuse
57
What gives cocaine its euphoric properties?
Inhibition of catecholamine uptake, particularly dopamine at CNS synapses
58
What is cocaine currently used in practice for?
Topical anesthesia, vasoconstrictor (decrease bleeding) and shrinking of the mucosa
59
What local anesthetic has the most rapid onset and metabolism?
Choloroprocaine (about 20min motor block)
60
What type of local anesthetic is Choloroprocaine?
Ester
61
Why don't we typically give more than one anesthetic agent at once?
The effects are compounded by one another
62
What type of local anesthetic is tetracaine?
Ester and considered more toxic
63
When is tetracaine typically utilized?
Spinal anesthesia when a long duration is required and topical preparations such as eye drops
64
What is the most versatile local anesthetic agent?
Lidocaine
65
What local anesthetic has a similar profile as lidocaine but has lost favor with the exception of peripheral nerve blocks?
Mepivacaine (Carbocaine)
66
What is the most common local anesthetic used for post op pain control?
Bupivacaine
67
What type of local anesthetic is Bupivacaine?
Amide
68
If a patient gets LAST from bupivacaine what is the best option for survival?
Cardiac Bypass
69
What type of local anesthetic is Ropivacaine?
Amide
70
How do lower concentrations of Ropivacaine compare to Bupivacaine?
Ropivacaine is slightly less potent in producing anesthesia when used in lower concentrations
71
Where are opioid receptors present in the spinal cord?
Substantia gelatinosa
72
Why don't opioids have a significant clinical role in peripheral nerve blockade?
There are no peripheral receptors, or the effects are negligible
73
What type of drug is Clonidine?
Centrally acting selective alpha 2 agonist
74
What is the benefit to using Clonidine in an epidural or spinal compared to opioids?
Does not produce depression of ventilation, pruritus, nausea and vomiting
75
What factors should be considered when selecting a local anesthetic?
Length of surgery
Speed of onset LA
Need of post-op pain control
Patient-related factors
76
How does the pKa affect the onset of a local anesthetic?
The lower the pKa, the shorter the onset of action (exception chloroprocaine)
77
What factors enhance the toxicity of bupivacaine?
Pregnancy
Use of CCB
Acidosis
Hypercarbia
78
What is the most common cause of toxic plasma concentrations of local anesthetic?
Administration of LA directly into a vessel
79
How does Lidocaine effect ventilatory response to hypoxia?
Depresses the response (remember local anesthetics are still anesthetics)
80
What percentage of Lidocaine is typically used in a bier block?
0.5%
81
What form of a local anesthetics has the most effect of blocking sodium channels?
The charged form
82
What type of local anesthetics are more likely to cross the placenta?
Amide
