Local Anesthesia

Question 1

Local anesthesia (LA)

Answer 1

occurs when sensory transmission to CNS is blocked from a local area of the body
○ These reversibly block the voltage gated sodium channels of excitable
nerves, blocking action potential initiation and impulse propagation.

Question 2

Anesthetic solutions are usually _____, accounting for some of the initial pain with injection.

Answer 2

acidic

Question 3

Amides

Answer 3

(lidocaine, bupivacaine, ropivacaine, mepivacaine, prilocaine):
■ Usually more rapid onset of action
■ More commonly used

Question 4

Esters

Answer 4

(Cocaine, procaine (Novocaine), chloroprocaine, and tetracaine
(Altacaine), benzocaine)

Question 5

Local anesthetics belong to either the ___ or ____ classes of medication

Answer 5

ester or amide classes

Question 6

The duration of a local anesthetic is proportional to ______

Answer 6

the amount of time the drug
remains in contact with a given nerve

Question 7

______: A common Vasoconstrictor that is added to many anesthetics

Answer 7

Epinephrine

Question 8

Epinephrine use in anesthesia

Answer 8

A common Vasoconstrictor that is added to many anesthetics
■ Increases duration of anesthesia
■ Decreases the rate of systemic absorption (decreasing risk of toxicity)
■ Helps to control bleeding

Question 9

Topical anesthitics

Answer 9

○ Sprays:
○ Creams/Gels
○ Patches
○ Mucus Membranes

Question 10

Spray anesthetics

Answer 10

■ Benzocaine spray - rapid onset.
■ Ethyl chloride spray - effective to a small area for a short time
● cryo treatment prior to joint injections

Question 11

Creams/Gels anesthetics

Answer 11

■ LET (lidocaine 4%, epinephrine 0.1% and tetracaine 0.5%) apply to cotton and
apply directly to skin, effective in 20 to 30 minutes
■ EMLA (lidocaine 2.5 % and Prilocaine 2.5 %) 5 -10 grams under occlusive
dressing, effective in 50 to 60 minutes

Question 12

Anesthetic patches

Answer 12

■ Lidocaine 5 % apply for 12 hours off for 12 hours. Used to treat chronic pain, also
helps with rib fractures

Question 13

Mucus Membranes

Answer 13

■ Viscous lidocaine gel - for oral lesions, herpes simplex, anal fissures (warn and
use caution not to swallow!). Not used orally in children.
■ Benzocaine spray - rapid onset. Used for procedures in the nose, mouth, and
airways
■ “Magic Mouthwash” - numbs the mouth and throat
● 1:1:1:1 mixture of viscous lidocaine 2%, Mylanta, diphenhydramine, with or
without dexamethasone
■ GI cocktail (or “green goddess”) - numbs the throat, esophagus, and stomach
● Various combinations of an antacid (like Maalox), viscous lidocaine 2%, and an
anticholinergic

Question 14

Peripheral nerve block:

Answer 14

: Injected at or near a specific nerve (single injection or
continuous)
■ Digital nerve block, femoral nerve block, sciatic nerve block, pudendal nerve
block
■ Interfascial plane blocks, abdominal plane blocks: Used frequently for surgical
anesthesia and/or analgesia

Question 15

Neuraxial ansthetic injection

Answer 15

analgesia and anesthesia (single injection or continuous) - Injected at or
near the spinal cord
■ Spinal anesthesia
■ Epidural anesthesia

Question 16

Local Anesthetics - Needle Basics

Answer 16

1. Gauge - Needle Diameter. 16-32G are commonly used
   ● Higher number = smaller diameter of the needle.
   ● Lower number = bigger diameter
2. Syringe - capacity in millimeters (mL) or Cubic centimeters (cc)
   ● May be pre-attached to the needle
3. Length - Needle length usually uses inches

Question 17

Local Anesthetics - Blocks

Answer 17

• Infraorbital nerve block (intraoral
  approach)
• Mental nerve block (infraoral approach)
• Aural Block
• Dorsal penile nerve block
• Fingers and toes – Digital nerve block

Question 18

For children with simple facial or scalp lacerations, ______ is generally effective opposed to subjecting the child to an injection.

Answer 18

topical LET (lidocaine, epinephrine,
tetracaine)

Question 19

______ is much more effective in many body regions (eg, fingers, toes, tongue, sole of foot) than direct infiltration

Answer 19

Regional anesthesia (eg digital blocks)c

Question 20

T/F Toxicity is common with local anesthetic

Answer 20

F

Question 21

LA Systemic Toxicity (LAST) can cause:

Answer 21

▪ Minor symptom: perioral numbness, metallic taste, mental status
changes or anxiety, visual changes
▪ Major LAST events: Convulsions, sedation, respiratory depression,
seizures, or ventricular arrhythmias, asystole, cardiac arrest

Question 22

topical anesthetics, especially benzocaine spray,
are a common cause of

Answer 22

methemoglobinemia

Question 23

Methemoglobinemia

Answer 23

topical anesthetics, especially benzocaine spray, are a common cause of methemoglobinemia
* Abrupt development of symptoms of hypoxia (low tissue oxygen)
* Ferrous (Fe2+) iron in heme is oxidized to the ferric (Fe3+) state

Question 24

AVOID INJECTING MORE THAN ____ ML OF ANESTHESIA AT ANY GIVEN TIME (usually
never go over 3cc, less if cardiac issues)

Answer 24

10