Local Anesthesia Flashcards
Local anesthesia (LA)
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.
Anesthetic solutions are usually _____, accounting for some of the initial pain with injection.
acidic
Amides
(lidocaine, bupivacaine, ropivacaine, mepivacaine, prilocaine):
■ Usually more rapid onset of action
■ More commonly used
Esters
(Cocaine, procaine (Novocaine), chloroprocaine, and tetracaine
(Altacaine), benzocaine)
Local anesthetics belong to either the ___ or ____ classes of medication
ester or amide classes
The duration of a local anesthetic is proportional to ______
the amount of time the drug
remains in contact with a given nerve
______: A common Vasoconstrictor that is added to many anesthetics
Epinephrine
Epinephrine use in anesthesia
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
Topical anesthitics
○ Sprays:
○ Creams/Gels
○ Patches
○ Mucus Membranes
Spray anesthetics
■ Benzocaine spray - rapid onset.
■ Ethyl chloride spray - effective to a small area for a short time
● cryo treatment prior to joint injections
Creams/Gels anesthetics
■ 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
Anesthetic patches
■ Lidocaine 5 % apply for 12 hours off for 12 hours. Used to treat chronic pain, also
helps with rib fractures
Mucus Membranes
■ 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
Peripheral nerve block:
: 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
Neuraxial ansthetic injection
analgesia and anesthesia (single injection or continuous) - Injected at or
near the spinal cord
■ Spinal anesthesia
■ Epidural anesthesia
Local Anesthetics - Needle Basics
- Gauge - Needle Diameter. 16-32G are commonly used
● Higher number = smaller diameter of the needle.
● Lower number = bigger diameter - Syringe - capacity in millimeters (mL) or Cubic centimeters (cc)
● May be pre-attached to the needle - Length - Needle length usually uses inches
Local Anesthetics - Blocks
- Infraorbital nerve block (intraoral
approach) - Mental nerve block (infraoral approach)
- Aural Block
- Dorsal penile nerve block
- Fingers and toes – Digital nerve block
For children with simple facial or scalp lacerations, ______ is generally effective opposed to subjecting the child to an injection.
topical LET (lidocaine, epinephrine,
tetracaine)
______ is much more effective in many body regions (eg, fingers, toes, tongue, sole of foot) than direct infiltration
Regional anesthesia (eg digital blocks)c
T/F Toxicity is common with local anesthetic
F
LA Systemic Toxicity (LAST) can cause:
▪ 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
topical anesthetics, especially benzocaine spray,
are a common cause of
methemoglobinemia
Methemoglobinemia
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
AVOID INJECTING MORE THAN ____ ML OF ANESTHESIA AT ANY GIVEN TIME (usually
never go over 3cc, less if cardiac issues)
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