Lecture 17 (Exam 4) - Local Anesthetics Pt. 2

Question 1

Although Chloroprocaine and Bupivacaine have similar potency values… which has a faster onset and why?

Answer 1

Chloroprocaine has a faster onset because it has a more lipid soluble component
Slide 10

Question 2

Which drug has an additive effect with Bupivacaine, increasing the onset of action when given in conjunction?

Answer 2

Chloroprocaine
Slide 10

Question 3

What are the two most common vasoconstrictors used in conjunction with local anesthetics?

Answer 3

Neo and Epi
Slide 11

Question 4

The duration of action of a local anesthetic is proportional to what?

Answer 4

The time the drug is in contact with nerve fibers
Slide 11

Question 5

What are some reasons we use vasoconstrictors with local anesthetics?

Answer 5

• Produce vasoconstriction
• Increased neuronal uptake of LA
• Alpha-adrenergic effects may have some degree of analgesia
• No effect on the onset rate of LA
• Enhanced cardiac irritability with inhaled anesthetics

Slide 11

Question 6

Alpha-adrenergic effects have some degree of ___________ by blocking nerve transmission.

Answer 6

Analgesia

Slide 11

Question 7

Patient A receives plain Lidocaine while Patient B receives Lidocaine with Epi, which patient has a faster rate of plasma absorption?

Answer 7

Patient A

Slide 12

Question 8

No question… Just a graph

Answer 8

Local anesthetics given with Epi have a slower rate of plasma absorption due to vasoconstriction and the drug staying at the site of action for longer durations.

Slide 12

Question 9

Local Anesthetic Strengths:
0.25%
0.5%
1%
2%
4%

Answer 9

0.25% = 2.5 mg/mL
0.5% = 5 mg/mL
1% = 10 mg/mL
2% = 20 mg/mL
4% = 40 mg/mL

Slide 14 (Pack this in your brain)

Question 10

What is the concentration of 1:200,000 Epi?

Answer 10

5 mcg/mL (1,000,000/200,000)

Slide 14

Question 11

What is the concentration of 1:500,000 Epi?

Answer 11

2 mcg/mL
(1 million/500 thousand)

Slide 14

Question 12

What is the concentration of 1:10,000 Epi?

Answer 12

100 mcg/mL (1 million/10 thousand)

Slide 14

Question 13

What is the concentration of 1:1,000 Epi?

Answer 13

1,000 mcg/mL (1 million/1 thousand)
This also equals 1 mg/mL

Slide 14

Question 14

Spinal (Subarachnoid) anesthesia results in blockade in segments, referred to as “segmental block.”

What is the 1st segment that is affected when we do a spinal/epidural block?
2nd?
3rd?

Answer 14

1. SNS
2. Sensory
3. Motor

Slide 35

Question 15

Which fibers are affected in the 1st segment in a segmental blockade?

Which fibers are affected in the 2nd segment in a segmental blockade?

Which fibers are affected in the 3rd segment in a segmental blockade

Answer 15

PREganglionic B (myelinated, fastest) fibers are blocked 1st!!! (THESE ARE NOT BETA!) –> these affect the SNS!

Followed by the sensory fibers (pain, temp) - myelinated A , myelinated B, then unmyelinated, small, C…

Followed by proprioception/motor fibers - myelinated A-delta and unmyelinated C

Recap: (SNS) Preganglionic B > (pain/temp) A, B, C > (motor) A-delta, C

Slide 35

Question 16

With LA in a spinal, what is the 1st sign you will see? and why?

Answer 16

Hypotension from vasodilation 2/2 blocking B fibers (SNS) & tachycardia

Can also be called a “sympathectomy”

Slide 35

Question 17

You are doing an Interscalene Block on one of your patients. You lay them down and scan their neck, and get the image below. Where would you inject the LA?

Answer 17

You would inject the LA into the shaded blue area and let the nerves (Yellow) absorb the LA.

(Slide 30)

Question 18

Lets practice!
Below is an image of a few nerves you want to numb!
Identify which area you would inject the LA into!

Answer 18

You would inject the LA into the blue shaded area and then let the nerve absorb the medication.

(Slide 32)

Question 19

Tell me about IV Regional Anesthesia.
AKA (August) Bier Block.

Answer 19

IV injection of LA into an extremity isolated from the rest of the systemic circulation with a tourniquet
Sensation and muscle tone are dependent on tourniquet!

Ester or amide LA can be used
Mepivacaine > Lidocaine, but …
Most commonly used: Lidocaine because of less side effects.

(Slide 33)

Question 20

What are the steps for a Bier Block?

Answer 20

1. IV start
2. Exsanguination
   ➤ Exsanguinate with a rubber (Esmarch) tourniquet, you are trying to wring out as much blood out of the extremity so that there is little amount of blood.
3. Double cuff
   ➤ Apply double cuffs on top of tourniquet. One cuff proximal and one distal.
4. Give LA injection
   ➤ Surgeon does his thing.
5. IV D/C
   ➤Release tourniquets one by one so that the anesthetic goes systemic slowly not fast.

(Slide 34 and Castillo)

Question 21

1. For a Bier Block, how long do you have to stop circulation before giving LA?
2. If you are doing ankle surgery, how long can you keep the tourniquet on that leg?
3. How will you know how much pressure to apply to your tourniquet when doing a Bier Block?

Answer 21

1. Circulation is stopped 30 min to an hour before injection of LA.
2. For a leg procedure using the Bier Block, you can keep the tourniquet for up to 2 hours on that leg,
3. To perform the block will have to be on 100 points higher than the systolic BP of the leg.
   If the blood pressure on the leg Is 150/80 mmHg, the tourniquet must be applied with a pressure of 250 mmHg.
   ➤The leg is not at risk for amputation being at this pressure for 2 hours. The artery is still supplying the leg with blood. It is the vein that is mainly blocked.

(Slide 33)

Question 22

How do we know we are in the spinal (subarachnoid) area?

Answer 22

Aspiration of CSF

Slide 36

Question 23

What is the principle site of action in SAB (spinal anesthesia block)?

Answer 23

Preganglionic fibers

Slide 36

Question 24

Not only do we have time segments, we also have ______ segments with LA’s.

These will have effects below and above the denervation site.

Answer 24

layer/anatomic

Slide 36

Question 25

If you block at T10 (umbilicus), where will you see sensory blockade?

Answer 25

T10 Slide 36-37

Question 26

If you block at T10 (umbilicus), where will you see SNS blockade?

Answer 26

up to T8 (2 levels cephalad of denervation) Slide 36-37

Question 27

If you block at T10 (umbilicus), where will you see motor blockade? What sx is this block useful for?

Answer 27

down to T12 (2 levels below denervation) This block can be useful for an appendectomy. (not for C section) Slide 36-37

Question 28

What dermatomes correlate with our cardiac accelerators? If you block here, what will happen?

Answer 28

T1- T4 ❤️ Can cause bradycardia/asystole 😅 Slide 37

Question 29

What are the 5 most common LA for a SAB (subarachnoid block)? HINT: TLBRB

Answer 29

Slide 38

Question 30

The dosage of SAB LA's is based on what 3 things?

Answer 30

Slide 38

Question 31

_______ is more important than concentration of the drug (%) or the volume (mL) of the solution injection when it comes to SAB's. For 0.75% bupivacaine, you give 1mL if the patient is 5ft. You add _____ ml for every _____ above. So if your patient is 5'5", you will give how many ml's?

Answer 31

Dose (This is bc the drug is the same mg / %...0.75% bupivacaine...) You add 0.1mls for every inch above 5ft... 1.5mls **not really sure where he got the 2cc's total on the slide... Slide 39

Question 32

What is important in determining the spread of the drug?

Answer 32

**Its specific gravity!** Slide 39

Question 33

If you add glucose to the LA, it will _____. This can also be called _______. If you add distilled water to the LA, it will ____. This can also be called ______. If you are using a hypobaric spinal LA, which side will you want your pt lying on if you are operating on the R hip?

Answer 33

Glucose = sinks; hyperbaric (LA sp. gravity > CSF) Distilled water = Float; hypobaric You will want the pt LEFT side-lying bc the drug will float and affect the upper (right) hip. Slide 39

Question 34

112.5 mgs of Bupivacaine with Epi and 250 mgs of Lidocaine with Epi were both given during a plastic surgery case. What are the percentages of each local anesthetic based on the recommended maximum single dose in mgs?

Answer 34

Max dose of Bupivacaine is 225mg with Epi, so 112.5mg is 50% of the max dose of Bupivacaine. Max dose of Lidocaine is 500mg with Epi, so 50% of max dose for lidocaine. So, 50% of lidocaine and 50% of Bupivacaine totals to 100% of LA. You cannot give LA anymore as you have already given max of 100% LA and they have additive effect. Slide after 21clinical scenario. (use other adjunct like, ketamine, magnesium, propofol etc)

Question 35

What are single Max recommended maximum dose for lidocaine with Topical, Infiltration, IVRA, PNB, Epidural, and spinal usages?

Answer 35

Topical 300mg IVRA 300mg Infiltration, PNB, and Epidural 300 or 500mg with Epi Spinal 100mg Slide 21

Question 36

What are single max recommended maximum dose for Mepivacaine with clinical usage of infiltration, PNB, Epidural, Spinal?

Answer 36

Infiltration, PNB, and Epidural 400 or 500mg with epi Spinal 100mg Slide 21

Question 37

What are the single max recommended dosages for Prilocaine with clinical usages of infiltration, IVRA, PNB, Epidural?

Answer 37

Infiltration, IVRA, PNB, and Epidural → 600mg Slide 21

Question 38

What are the single max recommended dosages for Bupivacaine with clinical usages of infiltration, PNB, Epidural, and spinal?

Answer 38

Infiltration, PNB, and Epidural → 175 or 225mg with epi. Spinal 20mg Slide 21

Question 39

Topical Anesthesia is applicable on _____.

Answer 39

Mucous membranes of the nose, mouth, tracheobronchial tree, esophagus, or GU tract. Slide 22

Question 40

What are the most common LA seen in clinical practice?

Answer 40

Tetracaine (1% to 2%) Lidocaine (2% to 4%) Cocaine (4% to 10%) Slide 22

Question 41

What are two LA that are not effective as Topical anesthesia?

Answer 41

Procaine and Chloroprocaine (They do not penetrate mucous membranes as much as cocaine, tetracaine, and lidocaine) Slide 22

Question 42

Cocaine produces localized ___________, hence it ______blood loss and ______surgical visualization.

Answer 42

Cocaine produces localized VASOCONSTRICTION, hence it DECREASES blood loss and IMPROVES surgical visualization. Slide 22 (A lot of ENT surgeons especially sinus procedures use cocaine by applying on Qtips.)

Question 43

T/F. Lidocaine is great with surface anesthesia.

Answer 43

True Slide 22

Question 44

T/F. Inhalation of lidocaine alter airway resistance.

Answer 44

False, It does not alter airway resistance but it causes vasodilation. Slide. 22

Question 45

Would you use lidocaine gel in oral airway or nasal airway and why?

Answer 45

Nasal airway as you are just suppressing the sneezing reflex of the upper airway. You do not want to use in the oral airway because you want to keep your lower respiratory reflexes intact, like Pharyngeal, and laryngeal (swallowing, gaging, and coughing). Slide 22

Question 46

What are the two ways you can give topical lidocaine to the patient?

Answer 46

Inhalation and topical lidocaine gel. Slide 23

Question 47

When do you use lidocaine inhalation?

Answer 47

4% lidocaine is used before bronchoscopy and EGD to prevent airway reflexes when pt is not intubated. Slide 23

Question 48

LTA (Lidocaine tracheal anesthesia or Localized tracheal anesthesia) is used for _____.

Answer 48

Especially used in patients with reactive airway diseases (asthma and COPD) and smokers (marijuana, Vape and cigarettes) Slide 23

Question 49

What LA does EMLA (Eutectic Mixture of LA) contains?

Answer 49

Lidocaine 2.5% and Prilocaine 2.5% = 5% LA in cream Slide 24

Question 50

What is the dosage EMLA and the onset of action?

Answer 50

1 to 2 gms/10cm square area Onset of action: 45 minutes but can be used in 10 minutes for Cautery of genital warts venipuncture, lumbar puncture Arterial cannulation (nitroglycerine) Myringotomy (ear tube placement) With skin grafting, you need to wait at least 2 hours for onset of action. Slide 24

Question 51

What is the average pKa of LA? Are they weak acids of bases?

Answer 51

8 Alkalotic- weak bases (slide 5)

Question 52

What is the function of Alkalinization of LA?

Answer 52

alkalinization increases the % of lipid-soluble or non-ionized form (slide 5)

Question 53

What is the benefits of Alkalinization of LAs?

Answer 53

Faster onset of action - Peripheral and epidural blocks by 3 to 5 mins. Enhances the depth Increase the spread (i.e., epidural)

Question 54

How can we find the ionization vs non-ionization? (Dr. Kane's way)

Answer 54

Question 55

If the weak base drug V has a pKa of 9.1, is the drug more ionized or nonionized in the blood with a pH of 7.4?

Answer 55

ionized (+) 9.1-7.4= +1.7 (slide 6)

Question 56

If the weak base drug W has a pKa of 4.5, is the drug more ionized or nonionized in the blood with a pH of 7.4?

Answer 56

nonionized (-) 4.5 - 7.4= -2.9 (slide 6)

Question 57

Answer 57

2 correct answers. Both LAs will have a more ionized components

Question 58

what 5 drugs discussed in class are given as adjuvant therapies with LA to either increase/prolongs DOA of LAs? (And which drugs do what?)

Answer 58

Dexmedetomidine IV- Increases duration Magnesium- increases duration Clonidine- prolongs Ketamine- prolongs Dexamethasone- increases (slide 8)

Question 59

If you are in the OR mixing your concoction of LA drugs to give to your patient and you notice the medications produce precipitate, what do you do?

Answer 59

Do not give!! Yeet it to the waste bend (slide 9)

Question 60

For combinations of LA, which 2 drugs added together can produce a rapid onset BUT can also cause tachyphylaxis?

Answer 60

Chloroprocaine & Bupivacaine (sldie 9)

Question 61

For combinations of LA, what drug can be added in a very small amount? what is that amount? And what other combination of LA can this also be added to?

Answer 61

8.4% Sodium Bicarbonate (1mL added to 30mL of LA) Chloroprocaine & Bupivacaine combo (slide 9)

Question 62

What’s the most commonly used drug for epidural anesthesia with our local anesthetics?

Answer 62

Lidocaine! It has good diffusion and is safest. (Slide 41)

Question 63

Which is safer for use in the epidural space, bupivacaine, ropivacaine, or levobupivicaine? (pick 2)

Answer 63

Levobupivicaine and ropivacaine - less toxic cardiac and CNS effects. (Slide 41)

Question 64

Epidural anesthesia onset is usually?

Answer 64

15 - 30 min. This slower onset is due to the drug having to diffuse across the epidural space before reaching the nerve fibers. (slide 41)

Question 65

In the epidural space, will mixing epi with bupivicaine increase the duration of the local anesthetic?

Answer 65

NO! Not in this instance. (Slide 41)

Question 66

Epidural doses are generally larger or smaller than spinal doses?

Answer 66

Larger! (Slide 42)

Question 67

What can be added to an epidural anesthetic dose to cause a synergistic effect for pain control?

Answer 67

Opioids! (Slide 42)

Question 68

Local anesthetics in the epidural space can have an effect on the fetus at this time frame:

Answer 68

Between 24 - 48 hrs. (Slide 42)

Question 69

Is there a segmental blockade in epidural anesthesia like with spinal anesthesia?

Answer 69

No! There is no differential zone of SNS, sensory, or motor like with spinal anesthesia. (Slide 42)

Question 70

Between lidocaine and bupivicaine, which is least likely to cross placenta?

Answer 70

The answer depends on the clinical practitioner! - Lidocaine has less protein binding —> washed out of system sooner and less likely to lead to toxic effects in baby and mom. -Bupivicaine has more protein binding, so less likely to cross placenta and affect baby. (No slide, this is based off a question near end of lecture)

Question 71

Tumescent liposuction involves giving how much local anesthetic?

Answer 71

SQ infiltration of a LARGE amount of local anesthetics! 5L or more! (Slide 43)

Question 72

What is the concentration of local anesthetics that is used for tumescent liposuction? What is the concentration of typical vasoconstrictor additive?

Answer 72

Diluted lidocaine of 0.05% to 0.10%. Epinephrine 1: 100,000 (Slide 43)

Question 73

Where is tumescent local anesthetic given?

Answer 73

Typically the thigh, abdomen, hips, booty. (Slide 44)

Question 74

The local anesthetic used in tumescent liposuction peaks around what time frame?

Answer 74

12 - 14 hrs later! Make sure pt has someone watching them at home! (Slide 44)

Question 75

What is the recommended dosing for local anesthetics with tumescent liposuction?

Answer 75

Regional anesthesia lido with epi: 7mg/kg Highly diluted lido with epi tumescent: 35 - 55 mg/kg Theory: 1g of SQ can absorb up to 1 mg of lido (Slide 44)

Question 76

Is EMLA cream recommended for skin wounds? What caution should a provider be cognizant of when dealing with EMLA cream? What allergies are contraindicated with EMLA?

Answer 76

No - do not place on skin wounds Caution with methemoglobinemia when absorbed systemically EMLA C/I w/ Amide allergies (slide 25)

Question 77

Name some other preparations of EMLA. (4)

Answer 77

Amethocaine (EMLA-like) Tetracaine 4% gel Lidocaine 7% Tetracaine 7% (slide 25)

Question 78

Answer 78

(slide 15 and 16)

Question 79

Local Infiltration (extravascular placement) of an LA is ____ (SQ or IM)? What would the addition of Epi 1:200,000 do to the duration of action of the LA? What anatomical sites would Epi be C/I in? What would happen if you were to inject Epi into one of these sites?

Answer 79

SQ the addition of Epi 1:200,000 would DOUBLE the duration of action of the LA Anatomical sites to avoid injecting with Epi: intracutaneously or into tissues with end-arteries; i.e. Fingers, toes, ears, nose, and penis (ouch) vasoconstriction --> ischemia --> necrosis (slide 26)

Question 80

Give an example per lecture of common operative sites where Local Infiltration is used? What med and what strength? (3)

Answer 80

Inguinal operative sites: - Lidocaine 1-2% - Ropivacaine 0.25% - Bupivacaine 0.25% (slide 26)

Question 81

How is a Peripheral Nerve Block achieved? MOA of a peripheral nerve block: _________ from outer mantle to central core of _____ along a concentration ________.

Answer 81

Achieved by LA injection into tissues surrounding individual peripheral nerves or nerve plexuses diffusion from outer mantle to central core of nerve along a concentration gradient (slide 27)

Question 82

Peripheral nerve block was just administered to your patient. You tell them to expect ________ to be affected first and then ______. A period of time passes and now the block should be wearing off. You tell the patient to expect ________ to return first followed by ______.

Answer 82

proximal; distal proximal; distal (slide 27)

Question 83

Which nerve fiber types would be affected first by a peripheral nerve block? What nerve fibers are affected following those?

Answer 83

smallest sensory and ANS fibers first, followed by larger motor and proprioceptive axons (slide 27)

Question 84

OOA of Peripheral Nerve Block is dependent on what? OOA for Lidocaine? OOA for Buvicaine?

Answer 84

dependent on the pK of the LA 3 mins (faster) 15 mins (slower) (slide 28)

Question 85

Continuous Infusion blocks yield ________ pain control, _____ nausea, and _______ satisfaction. Besides pK of a chosen LA, what other factors would affect its DOA? (2 more)

Answer 85

Improved pain control, less nausea, and greater satisfaction. Dose and additives will change the DOA for a LA (slide 28)

Question 86

What are the 7 uses of LA's discussed in lecture?

Answer 86

Topical Local infiltration Peripheral nerve block IV Epidural Spinal Tumescent Liposuction

Question 87

What additives might be good for a LA in a pt who is due to be discharged home immediately following surgery?

Answer 87

Ketorolac/Toradol (good choice in pain management and will not cause sedation) Decadron/Dexamethasone (clinical pearl)

Question 88

Give 4 examples of types of Peripheral Nerve Blocks.

Answer 88

Interscalene Axillary Femoral Sciatic (slide 29)

Question 89

what two types of block injection verification techniques do we have at our disposal? Which one is preferred and why?

Answer 89

Ultrasound-guided and Nerve stimulator (never seen this before) US-guided is preferred as it is less noxious to the patient (slide 29)

Question 90

State any 1-2 details about Nerve Stimulator guided blocks. State any 1-2 details about US-guided blocked.

Answer 90

Nerve stimulator: - mA 0.1-1 - pinpoint needles US-guided: - in-plane - out-of-plane (slide 29)