SS25 Local Anesthetics II (Exam 4) Flashcards
1
Q
What are the pharmacokinetic categories of LAs?
A
- Alkalinization of LA Solutions
- Adjuvant Mixed with LAs
- Combining LAs
- Vasoconstrictor Use
2
Q
General LA uses
A
- Topical
- Local infiltration
- Peripheral Nerve Block (PNB)
- IV
- Epidural
- Spinal
- Tumescent Lipsuction
3
Q
What is the average pKa of LA?
A
8
4
Q
- What is the function of the Alkalinization of LA Solutions?
- What are the benefits of alkalinization?
A
Function: Alkalinization increases the percentage of lipid-soluble or non-ionized form
- Sodium bicarb main buffer (except: not used in spinals)
Benefits:
* Faster onset of action (onset of peripheral and epidural blocks speed up by 3 to 5 mins)
* Enhances the depth
* Increase the spread (i.e., epidural)
5
Q
Cheat sheet for weak bases introduced into soln with normal pH (7.4) to find more ionized form
A
- The higher the pKa = the more non-ionized/unionized it is
6
Q
Regarding weak bases, the pKa is ________ pH.
A
- before
- Ex. pKa 9, pH 7 → 9 - 7 = +2
7
Q
Regarding weak acids, the pKa is ________ pH.
A
- after
- Ex. pKa 9, pH 7 → 7 - 9 = -2
8
Q
Nicely negative numbers are _________.
A
non-ionized
9
Q
If Drug V (weak base) has a pKa of 9.1, will the drug be more ionized or nonionized at physiological pH?
A
pKa - pH
9.1 - 7.4 = +1.7
Drug V will be more ionized at physiological pH.
Weak Bases, pKa before pH
Weak Acids, pKa afterpH
10
Q
If the pKa of LA (a weak base) is at 4.5, will the drug be more ionized or nonionized at physiological pH?
A
pKa - pH
4.5 - 7.4 = -2.9
LA will be more non-ionized at physiological pH.
Weak Bases, pKa before pH
Weak Acids, pKa afterpH
11
Q
LA1’s pKa is 9.2, and LA2’s pKa is 7.5. Which of the following are correct when placed in physiological pH? Select 2 answers.
A. LA2 has more non-ionized components
B. LA1 has more ionized components
C. LA2 has more ionized components
D. LA1 has more non-ionized components
A
B and C
LA1
9.2 - 7.4 = +1.8 (ionized)
LA2
7.5 - 7.4 = +0.1 (ionized)
Weak Bases, pKa before pH
Weak Acids, pKa afterpH
12
Q
What Adjuvant Mixed medications prolong the duration of LAs?
A
- IV Dexmedetomidine: Increased duration of both motor & sensory blocks; first analgesic request after subarachnoid block (SAB: type of spinal)
- Magnesium: Increased duration with SAB w/ or w/o opioids
- Clonidine & Ketamine: Increased duration in peds and regional
- Dexamethasone: Increased duration either IV or mixed with LA
DM - CKD
13
Q
What will be the results of combining LA Chloroprocaine & Bupivacaine?
A
- Produce a rapid onset
- Tachyphylaxis (Bupivacaine)
14
Q
What is added to 30 mL of combo LA to alkalinize the drug?
- How much do you add?
A
- 1 mL of 8.4% Sodium Bicarbonate
- This will increase the non-ionized form of LA
- Make sure the mixture does not contain any precipitate
15
Q
T/F: Combining LAs and getting toxic effects is a synergistic process.
A
- False
- Additive
16
Q
Compare the onset of action between chloroprocaine and bupivacaine.
A
Chloroprocaine: Rapid
Bupivacaine: Slow
17
Q
What vasoconstrictors can be utilized with LA?
A
- Epinephrine
- Phenylephrine
18
Q
Why is it important to use vasoconstrictors with LA?
A
- The duration of action of a LA is proportional to the time the drug is in contact with nerve fibers
- Adding a vasoconstrictor to LA solution, limits systemic absorption and maintains the drug concentration in the vicinity of the nerve fibers to be anesthetized
19
Q
What are the results of using vasoconstrictors with LA?
A
- Produce vasoconstriction
- Increased neuronal uptake of LA
- α-adrenergic effects may have some degree of analgesia
- No effect on the onset rate of LA
- Enhanced cardiac irritability with inhaled anesthetics
- Systemic absorption → HTN (tachycardia?)
20
Q
Explain effects of LA when Epinephrine is added to LA solution.
A
- Will have a decrease in plasma levels of LA because Epinephrine prolongs duration of LA at the actual primary site
21
Q
What is epinephrine 1:200,000 mean?
- Convert that to mcg/mL
A
- 1:200,000 means 1 gram of epinephrine is dissolved in 200,000 mL of solvent
- Shortcut: 1,000,000 / 200,000 = 5 mcg / mL
OR - 1g/200,000 mL
- 1000mg/200,000 mL
- 1 mg/200 mL
- 1000 mcg/200 mL
- 10 mcg/2 mL
- 5 mcg/mL
22
Q
Compute 1:500,000 to mcg/mL
A
- 1:500,000 means 1 gram of compound is dissolved in 200,000 mL of solvent
- Short cut: 1,000,000 / 500,000 = 2 mcg / mL
OR - 1 g/500,000 mL
- 1000 mg/500,000 mL
- 1 mg /500 mL
- 1000 mcg/500 mL
- 10 mcg/5 mL
- 2 mcg/mL
23
Q
How much epinephrine or phenylephrine is given with bupivacaine or lidocaine for a subarachnoid block (SAB)?
A
- 0.2 mg Epi
- 2 mg Phenylephrine
24
Q
Compute 1:500,000 Epi to mcg/mL
A
1,000,000/ 500,000 = 2
2 mcg/mL
25
Compute 1:10,000 Epi to mcg/mL
1,000,000/ 10,000 = 100
**100 mcg/mL**
26
Compute 1:1000 Epi to mcg/mL
1,000,000/ 1000 = 1000
**1000 mcg/mL** or **1 mg/mL**
27
LA strength of 0.25% equates to how many mg per mL ?
2.5 mg/mL
28
LA strength of 0.5% equates to how many mg per mL?
5 mg/mL
29
1% equates to how many mg per mL ?
10 mg/mL
30
2% equates to how many mg per mL ?
20 mg/mL
- 2% lidocaine is the **most common concentration** used in the OR
31
4% equates to how many mg per mL ?
40 mg/mL
32
Your surgeon injected 20 mLs of Bupivacaine 0.25% with 1:200,000 of Epi.
What are the total mgs for Bupivacaine and the total mcgs for Epinephrine?
Bupivacaine:
0.25% = 2.5 mgs/mL
2.5 mgs x 20 mLs = **50 mgs total**
Epinephrine:
1:200,000 = 5 mcg/mL
5 mcg x 20 mLs = **100 mcg total**
33
Lidocaine max single **PLAIN** dose & **onset**:
- Topical
- Infiltration
- IVRA
- PNB
- Epidural
- **Plain 300 mg**
- Fast
34
Lidocaine max single **PLAIN** for **Spinal** & onset:
- **100 mg**
- Fast
35
Which clinical uses can you use Epi with?
- Infiltration
- Epidural
- PNB
36
Lidocaine max single dose **w/ Epinephrine**:
- Infiltration
- PNB
- Epidural
- **300 or 500 mg**
37
Mepivacaine max single dose **with or w/o Epi** & **onset**:
- Infiltration
- PNB
- Epidural
- **400 mg Plain & 500 mg w/ Epi**
- Fast
38
Mepivacaine max single dose for spinal & **onset**?
- **100 mg**
- Fast
39
Prilocaine:
- Max Single Dose?
- Clinical uses?
- Do we use Epi?
- Onset?
- **600 mg**
- Clincal uses: **Infiltration; IVRA; PNB; Epidural**
- **No Epi**
- Fast
40
Bupivacaine max single dose **with or w/o Epi** and **onset**:
- Infiltration
- PNB
- Epidural
- **175 mg or 225 w/ Epi**
- Infiltration: **Fast**
- PNB: **Slow**
- Epidural: **Moderate**
41
Bupivacaine max single **spinal** dose & **onset**:
- Spinal (plain only): **20 mg**
- Onset: **Fast**
42
112.5 mg of Bupivacaine with Epi and 250 mg of Lidocaine with Epi were given during surgery.
**What are the percentages of each LA based on the recommended max single dose?**
Max single dose of Bupivacaine with Epi: 225 mg
112.5/225 = **50%**
Max single dose of Lidocaine with Epi: 500 mg
250/500 = **50%**
43
Where are topical anesthetics applicable?
- Applicable on the **mucous membranes** of the **nose, mouth, tracheobronchial tree, esophagus, or GU tract**
44
- Which LA are used topically?
- Cocaine 4 - 10% (most effective)
- Tetracaine 1 - 2%
- Lidocaine 2 - 4 %
45
Which anesthetic has localized vasoconstriction that will **decrease blood loss and improve surgical visualization?**
- Include LA concentration
Cocaine (4% - 10%)
46
Which anesthetic is great with surface anesthesia?
- Include LA concentration
Lidocaine (2 - 4%)
47
Lidocaine inhalation does not alter airway resistance, but does cause ______.
Vasodilation
48
Which local anesthetics are not effective for topical anesthesia?
**Procaine and Chloroprocaine**
49
What is does LTA stand for?
- Lidocaine tracheal anesthesia
50
What does black mark indicate?
-Vocal cord level
51
**Bonus**: What is the total amount in mgs of a pre-filled syringe with 4 mL of 4% Lidocaine?
- 40 mg/mL w/ 4 mL in tube (total 160 mg total of Lidocaine)
52
**Eutectic Mixture of LA (EMLA)** contains what two local anesthetics?
- Dose:
- Onset (when will it be ready for surgery):
- **Lidocaine 2.5% + Prilocaine 2.5%** = 5% LA
- Dose: **1 to 2 g/ 10 cm2 area**
- Readiness: **45 mins**
53
EMLA has to be applied for ____ hours before **skin graft**.
**2 hours**
54
EMLA can be applied for 10 minutes before any of these procedures:
- Cautery of genital warts
- Venipuncture, lumbar puncture
- Arterial cannulation (also can use NTG?)
- Myringotomy - recurrent ear infxns
55
What is the main adverse effect of EMLA?
- Why?
- **Methemoglobinemia**
- Contains Prilocaine
56
Contraindications for EMLA?
* No open skin wounds/infxns
* No amide allergy patients
57
Other Topical Anesthesia Preparations besides EMLA
* Amethocaine (EMLA-like)
* Tetracaine 4% Gel
* Lidocaine 7%
* Tetracaine 7%
58
What is considered **local infiltration with LA**?
- **Extravascular** placement of LA (**Subcutaneous injection**)
- IV starts, hiatel hernia site, lap chole closures
59
For Infiltration use, what LAs are used on **Inguinal operative sites**?
- duration of action?
* Lidocaine 1% or 2%
* Ropivacaine 0.25%
* Bupivacaine 0.25%
- Duration: **doubled by adding Epi 1:200,000**
60
Why is Epinephrine contraindicated in LA infiltrations at end arteries?
- What is considered end artery tissues?
* **Not intracutaneously or into tissues at end arteries**
* Includes **fingers, toes, ears, nose, & penis**
* **Vasonstriction → ischemia → necrosis**
61
How is Peripheral Nerve Block achieved?
- MOA?
- **LA injection into tissues surrounding individual peripheral nerves or nerve plexuses**
- MOA: Diffusion from **outer mantle to central core of nerve** along a concentration gradient.
62
Smallest ________ and _______ fibers first, then _____ motor and proprioceptive axons.
So the patient with feel ______ prior to _________.
- Blank 1: sensory
- Blank 2: ANS (or sympathetic nervous system)
- Blank 3: Large
- Blank 4: numb
- Blank 5: paralysis (or no movement)
63
What **area (*proximal or distal*) is affected first** with local anesthetic administration?
- Proximal area (site of LA administration) is affected first and then distal
- proximal → distal
64
When the **peripheral nerve block is wearing off**, what comes back first *(proximal or distal)* ?
- Proximal comes back first & then distal
- proximal → distal
65
Peripheral Nerve Block onset of action is dependent on the local anesthetic's _________.
**pK**
- **lower pk = faster onset**
- Example: Lidocaine 7.9 (3 mins) v Bupivacaine 8.1 = 15 mins
66
The duration of a peripheral nerve block depends on the _____ of the local anesthetic.
**dose**
- Ex: Bupivacaine w/ Epi + Fent & Clondine will last 12- 18hrs
67
What are the benefits of a **continuous infusion block**?
* Improved pain control
* Less nausea
* Greater satisfaction
* Additives are used with continuous infusion blocks (Exparel ER common with additives)
68
Examples of PNBs?
- Interscalene
- Axillary
- Femoral
- Sciatic
-Nerve stimulator (mA 0.1 - 1); pinpoint needles
- US guided (in-plane v out-of-place)
69
What is a Regional (August) Bier Block?
- IV Regional Anesthesia
- IV injection of LA **into an extremity isolated from the rest of the systemic circulation with a tourniquet**.
70
Bier Block: Sensation and muscle tone are dependent on ________ release
**tourniquet**
71
What LA is commonly used in Bier Block?
- Why?
Lidocaine
- Vasodilates = more comfort
72
Which LA is the drug of choice for Bier Block?
-why?
Mepivacaine
- Vasoconstrictive properties
73
T/F: You can only use Amides LA for Bier Blocks.
False
- Esters can be used as well
74
What are the steps to performing a Bier Block?
1. IV start
2. Exsanguination
3. Double cuff (**deflate proximal cuff 1st then distal cuff**)
4. LA injection
5. IV D/C
75
What is the sequence of blockades for a segmental block in Neuraxial Anesthesia?
1. SNS (**Myelinated preganglionic B** fibers) = ↓ BP & ↑ HR
2. **Sensory**, (**Myelinated A** & **B** fibers, **Unmyelinated C fibers**) = loss of sensory
3. **Motor** (**Myelinated A-δ and Unmyelinated C** fibers) = loss of motor
76
Which of the following will be the last sign associated with injection of an anesthetic for neuraxial blockade?
A. NIBP
B. Heart Rate
C. Cold Alcohol Pad
D. Leg Movement
D. Leg Movement
77
How is a Spinal Anesthesia Block (SAB) produced?
- By direct injection of LA into Subarachnoid
78
What is used for confirmation of a Spinal Anesthesia Block (SAB)?
**CSF**
79
What is the principal site of action for subarachnoid block?
**Preganglionic fibers**
80
For SAB, the _______ effect is on the same level of denervation.
**sensory**
81
For SAB, the _______ effect is 2 spinal segments _______ of the sensory block.
For SAB, the _____ effect is 2 spinal segments **below** the sensory block.
- **SNS, cephalad** (up towards head)
- **Motor**
82
If the sensory block is at T5, where is the SNS block?
- What will be triggered?
- T3
- SNS effect goes 2 levels cephalad (up towarda head)
- This SNS block will trigger an **asystole** event by blocking cardiac accelerators
83
What dermatomes correspond with our cardiac accelerator?
**T1 to T4**
84
What dermatomes correspond to the following:
- Nipple line
- Edge of Xiphoid process
- Lowest rib cage anteriorly
- Umbilical
- Nipple line **T4**
- Edge of Xiphoid process **T6**
- Lowest rib cage anteriorly **T8**
- Umbilical **T10**
## Footnote
Factor by 2 in anatomical order
85
If the assessed sensory level after SAB is T6 (Top of Xiphoid Process), what are the blocked SNS and motor levels?
- Sensory level T6
- SNS Block: T4
- Motor Block: T8
- 6 - 2 = 4 & 6 + 2 = 8
86
What are the most common local anesthetics used in SABs ?
Most common: Tetracaine, Lidocaine, Bupivacaine, Ropivacaine, and Levobupivacaine
87
What factors affect SAB dosage?
* Height of patient
* Segmental level of anesthesia desired
* Duration of anesthesia desired
88
What does the height of the patient associated with in terms of SAB dosing:
- volume of subarachnoid space
89
For SAB, _____ is more important than _______ of drug or the volume of the solution injection.
Dose; Concentration
90
What is the dose of bupivacaine for the scenario below?
- 5 ft tall patient = _____mL of 0.75% Bupivacaine
- + ______ mL for every inch above…. 2 cc total ( 1½ hours to 2 hours)
- What would be the dose for a 5'5" patient?
- **1 mL**
- **0.1 mL**
- Give 1.5 mL of 0.75% Bupivacaine for a SAB*
[ 1 mL + (0.1 mL * 5 in) ] =1.5
91
What is the max Bupivacaine dose for Neuraxial Spinal/SAB?
- duration of action?
- **2 mL** for 1.5 - 2 hrs
## Footnote
6' or more will get 2 mL + probabky additives
92
For SAB, the _________ of LA is important in determining the spread of the drug.
**specific gravity**
93
What can be added to LA so that its specific gravity can increase?
What can be added to LA so that its specific gravity can decrease?
Glucose added → Hyperbaric solution (**LA S.G > CSF**)
Distilled water added → Hypobaric solution
94
**Review:** Which side will you want to position a right-hip arthroplasty patient on if they receive a hyperbaric LA solution?
Right side lying, the hyperbaric solution will "sink."
95
**Review:** Which side will you want to position a right-hip arthroplasty patient on if they receive a hypobaric LA solution?
Left side lying, the hypobaric solution will "float".
96
The most common LA used in Epidural Anesthesia.
Lidocaine
- Good diffusion through tissue and safer
- Great with loading dose & intermittent/ boluses
97
Order of efficacy for following :
- Bupivacaine
- Ropivacaine
- Lidocaine
- Levobupivacaine
- Lidocaine >
- Bupivacaine > Levobupivacaine & Ropivacaine: highly protein binding →cardiac & CNS toxicity risk → need cardiac bypass
98
What is the onset of epidural anesthesia?
- Onset: 15 to 30 minutes (slow diffusion)
99
Epi 1:200,000 with ___________ offers no advantage in an epidural block.
- Bupivacaine
(people still use it)
100
Can epidural anesthesia cross the placental-blood barrier (PBB) with OB and C-section patients?
- How long?
- Yes; Imaginary space has veins so can go intravascularly & cross PBB
- **can effect fetus up 24 - 48 hrs**
101
Does Bupivacaine or Lidocaine cross more?
- Lidocaine d/t rapid onset
- AE: Ion trapping
102
What is the difference between spinals (SAB) and epidurals?
- What does the effect?
- **Epidurals have no differential zone of SNS, sensory, and motor blockade**
- Just one level
- Effects dose requirement: **Epidurals require larger doses**
103
What is considered an acceptable additive to both epidural and SAB to produce a synergistic effect?
Opioids
104
What is Tumescent Liposuction?
- **Subcutaneous infiltration of large volume (5L or more)**
105
What makes up the tumescent solution?
* Diluted Lidocaine (0.05% to 0.1%)
* Epinephrine 1:100,000
106
What causes the tumescent effect?
- **The taunt stretching of overlying blanched skin d/t large volume & vasoconstriction**→ Tumescent Effect
## Footnote
Indicates it's safe to start liposuction
107
Advantage of Tumescent Effect?
- **Fat can be aspirated without blood loss and provide prolonged post-op analgesia**
108
Where is tumescent usually administered?
* Thigh
* Abdomen
* Hips
* Buttocks
## Footnote
**BBL mami**
109
When is the plasma peak for tumescent anesthesia?
**12 to 14 hours s/p injection**
- re-absorption of LA → risk for LA toxicity
110
What is the normal dose for Regional Anesthesia Lidocaine with Epi?
**7 mg/kg**
111
**Highly diluted** Lidocaine with Epi Tumescent dose.
**35 to 55 mg/kg**
112
What is the theory of the **Tissue Buffering System**?
- **1 gram of SQ tissue can absorb up to 1 mg of Lidocaine**
