Week Four - Questions

Question 1

Are anesthetics generally vasoconstrictors or vasodilators?

Answer 1

• Anesthetics are generally vasodilators

- Cocaine is a vasoconstrictor!

Question 2

What are the four most widely used local anesthetic agents today?

Answer 2

• Procaine (novocaine)
• Tetracaine (pontocaine)
• Lidocaine (xylocaine)
• Bupivacaine (marcaine)

Question 3

Which of the four most widely used local anesthetic agents are esters and which are amides?

Answer 3

Esters

• Procaine
• Tetracaine

Amides

• Lidocaine
• Bupivacaine

Question 4

Which type (esters or amides) of local anesthetic agents are most likely to cause allergies?

Answer 4

• Esters

Question 5

What are the mechanisms of action of local anesthetics?

Answer 5

• Prevent or relieve pain by preventing the generation and conduction of nerve impulses

Question 6

Which nerve fibers are most sensitive to actions of local anesthetics?

Answer 6

• Small nerve fibers

Question 7

Do local anesthetics used at typical rates and concentrations wear off with time, and is there typically a complete recovery in nerve function with no damage to nerve cells or fibers?

Answer 7

• Yes, and yes

Question 8

What can be added to tetracaine and lidocaine when used for topical anesthesia to produce vasoconstriction?

Answer 8

• Epinephrine

Question 9

What are the benefits of adding epinephrine to local anesthetics?

Answer 9

• Decreases bleeding, making surgery easier
• Prolongs the duration of the anesthesia by retarding absorption at the site of the injection
• Minimizes the amount of anesthesia needed
• Less anesthesia = decreased systemic toxicity

Question 10

What are the potential side/bad effects of local epinephrine injection?

Answer 10

• May induce hypoxic damage if used in areas of the body where there is limited circulation
• Category C - do not use in pregnancy: may cause premature labor

Question 11

How quickly will epinephrine in a local anesthetic produce its full effect?

Answer 11

• 5-10 minutes for the full vasoconstriction, even though the anesthetic itself may only take 1-2 minutes

Question 12

**Which type(s) of preparations of local anesthetics have preservatives, and which do not?

Answer 12

**- Epinephrine, multi-dose vials

Question 13

In general, with the administration of local anesthetics, which sensation or function disappears first, and which follow in what order?

Answer 13

1. Sensation of pain
2. Sense of cold and warmth
3. Sense of touch
4. Deep pressure
5. Motor function

Question 14

In what order do which sensations and functions return as a local anesthetic wears off?

Answer 14

• Reverse order

1. Motor function
2. Deep pressure
3. Sense of touch
4. Sense of cold and warmth
5. Sensation of pain

Question 15

What are some of the major drug interactions/bad effects with local anesthetics?

Answer 15

• Bradycardia
• Hypotension
• Sedation
• Muscle twitching
• Fatigue
• Indigestion and constipation
• Dermatitis
• MAOIs –> HTN crisis
• Carbamazepine/Cyclobenzaprine - potentiate effects of drug
• Tricyclic and tetracyclic antidepressants→ in the presence of exogenous epi can produce prolonged HTN crisis and dysrhythmia
• Phenothiazines→ When combined w/ vasodilator effects of all local anesthetics can cause profound hypotension
• Hypersensitivity reactions
• True allergic response in < 1% of people

Question 16

What is the most frequent CNS action of local anesthetics?

Answer 16

• Sedation

Question 17

Into which tissues is it not safe to inject local anesthetics containing epinephrine?

Answer 17

• Fingers
• Toes
• Nose
• Penis
• Female genitalia

Question 18

What is the purpose of adding sodium bicarbonate to local anesthetics?

Answer 18

• Buffering with sodium bicarbonate makes the anesthetic’s pH closer to physiological pH, which reduces pain on infiltration
• For nerve blocks, alkalization makes it more readily cross the nerve membrane, which leads to a faster onset of action

Question 19

Can sodium bicarbonate be safely added to local anesthetic products containing epinephrine? Why/why not?

Answer 19

• It can be added, but needs to be added just immediately before use because epinephrine is chemically unstable in anesthetic solutions alkalinized by sodium carbonate

Question 20

What are the effects of adding sodium bicarbonate to local anesthetic products containing epinephrine?

Answer 20

• Decreases the overall activity of epinephrine

Question 21

What is “infiltration anesthesia?”

Answer 21

• Injection of local anesthetic directly into tissue without considering the course of cutaneous tissue

Question 22

What are the “two” definitions of a field block?

Answer 22

• Injection in an inverted V just proximal to and to each side of the lesion (not into the lesion) with no attempt to locate specific nerves –> anesthetizing the region distal to the site of injection
  > Blocks nerve transmission from the injected site to the brain
• Injection completely around the boundaries of the lesion, with no attempt to locate specific nerves –> an anesthetized “field” inside of the boundaries of the anesthesia

Question 23

What are the two advantages of a field block over an infiltration anesthesia?

Answer 23

• Less drug can be used to provide a greater area of anesthesia
• Not injecting anesthetic directly into the lesion avoids distortion of the anatomy of the lesion and allows the pathologist to correctly interpret the biopsy specimen

Question 24

**What are the various routes of administration of local anesthetics?

Answer 24

• Injection
• Topical
• Intravenous regional anesthesia
• Spinal anesthesia
• Epidural anesthesia

Question 25

**What are the considerations when choosing an infiltration anesthetic?

Answer 25

- Adding epinephrine doubles the duration of the action > Decrease the total amounts used by 33% - Be cautious using lidocaine 2% since it is stronger and you could end up using more than necessary - Side effect profile - History of use (stick to what pt has had good results with in the past) - Length of procedure - Will there be significant post-procedure pain

Question 26

What are the maximum allowable safe single doses of plain 1% lidocaine and 0.25% bupivacaine alone and with epinephrine?

Answer 26

- 1% Lidocaine: 4.5 mg/kg - 1% Lidocaine with epinephrine: 7 mg/kg - 0.25% bupivacaine: 3 mg/kg - 0.25% bupivacaine with epinephrine: 3.5 mg/kg

Question 27

What alternatives to local anesthesia are available when a patient is apparently allergic to the ones commonly used?

Answer 27

- Do skin testing if possible - If the allergen is an ester, use an aminde - Injecting Benadryl in place of a local anesthetic may reduce most or all of the pain - Local ethyl chloride - Place ice directly over the wound for a short period of decreased pain sensation - Don't use anesthetic for small lacerations

Question 28

What are the advantages and disadvantages of vertical mattress sutures?

Answer 28

Advantages - Everts the edges better than other stitches - Helps to close a large area of dead space in a wound - Strong stitch provides added support to a wound under stress - Can be used as a "stay" suture > Use initially to align and approximate wound edges, then remove after other sutures were used to close it Disadvantages - Time consuming to place properly - Can result in "railroad tracking" scars if tied too tight or left in place for too long