Are anesthetics generally vasoconstrictors or vasodilators?
- Anesthetics are generally vasodilators
- Cocaine is a vasoconstrictor!
What are the four most widely used local anesthetic agents today?
- Procaine (novocaine)
- Tetracaine (pontocaine)
- Lidocaine (xylocaine)
- Bupivacaine (marcaine)
Which of the four most widely used local anesthetic agents are esters and which are amides?
Esters
- Procaine
- Tetracaine
Amides
- Lidocaine
- Bupivacaine
Which type (esters or amides) of local anesthetic agents are most likely to cause allergies?
- Esters
What are the mechanisms of action of local anesthetics?
- Prevent or relieve pain by preventing the generation and conduction of nerve impulses
Which nerve fibers are most sensitive to actions of local anesthetics?
- Small nerve fibers
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?
- Yes, and yes
What can be added to tetracaine and lidocaine when used for topical anesthesia to produce vasoconstriction?
- Epinephrine
What are the benefits of adding epinephrine to local anesthetics?
- 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
What are the potential side/bad effects of local epinephrine injection?
- 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
How quickly will epinephrine in a local anesthetic produce its full effect?
- 5-10 minutes for the full vasoconstriction, even though the anesthetic itself may only take 1-2 minutes
**Which type(s) of preparations of local anesthetics have preservatives, and which do not?
**- Epinephrine, multi-dose vials
In general, with the administration of local anesthetics, which sensation or function disappears first, and which follow in what order?
- Sensation of pain
- Sense of cold and warmth
- Sense of touch
- Deep pressure
- Motor function
In what order do which sensations and functions return as a local anesthetic wears off?
- Reverse order
- Motor function
- Deep pressure
- Sense of touch
- Sense of cold and warmth
- Sensation of pain
What are some of the major drug interactions/bad effects with local anesthetics?
- 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
What is the most frequent CNS action of local anesthetics?
- Sedation
Into which tissues is it not safe to inject local anesthetics containing epinephrine?
- Fingers
- Toes
- Nose
- Penis
- Female genitalia
What is the purpose of adding sodium bicarbonate to local anesthetics?
- 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
Can sodium bicarbonate be safely added to local anesthetic products containing epinephrine? Why/why not?
- 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
What are the effects of adding sodium bicarbonate to local anesthetic products containing epinephrine?
- Decreases the overall activity of epinephrine
What is “infiltration anesthesia?”
- Injection of local anesthetic directly into tissue without considering the course of cutaneous tissue
What are the “two” definitions of a field block?
- 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
What are the two advantages of a field block over an infiltration anesthesia?
- 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
**What are the various routes of administration of local anesthetics?
- Injection
- Topical
- Intravenous regional anesthesia
- Spinal anesthesia
- Epidural anesthesia
