Local Anesthesia Flashcards
What is the basic chemical structure of local anesthetics?
Lipophilic and hydrophilic portion joined by a hydrocarbon chain
Order of nerve blockade
- Beta fibers: preganglionic sympathetic
- A-delta and C fibers: Pain
- A-gamma: Proprioception
- A-Beta: Touch, pressure
- A-Alpha: Motor
What is the pH of local anesthetics?
Weak bases
What kind of tissue will increase ionized portion of local anesthetics?
Acidic tissue
What are potency, onset, and duration affected by?
pK
Protein binding
Lipid solubility
Higher protein binding
longer duration of action
Higher lipid solubility
higher potency
What are the commonly used amides?
Lidocaine Bupivacaine Mepivacaine Ropivacaine Prilocaine
What is the only local anesthetic that may be given IV?
Lidocaine
What are the systemic Lidocaine effects?
Anti-arrhythmic Decreases MAC Analgesic Free radical scavenger Improves GI motility
What is the local anesthetic with the highest cardiovascular toxicity?
Bupivacaine
What are the uses for Mepivacaine?
Nerve blocks
Intra-articular
What local anesthetic is safer to use than Bupivacaine?
Ropivacaine
What are commonly used esters?
Procaine
Tetracaine
Proparacaine
Benzocaine
What are tetracaine and proparacaine used for?
Ophthalmic procedures
What is used for a laryngeal spray for intubation?
Benzocaine
PABA
Paraaminobenzoic acid
What causes allergic reactions?
PABA
What local anesthetic is associated with PABA?
Penicillin G
Which is more likely to accumulate esters or amides?
Amides
Why is epinephrine used in local anesthetics?
prolongs the duration of block
What does epinephrine cause?
Vasoconstriction
Why is bicarbonate added to local anesthetics?
Faster onset
prolonged duration
What causes methemoglobinemia?
Benzocaine
prilocaine
Benzocaine
tetracaine
What causes methemoglobinemia in cats?
Benzocaine
Tetracaine
What local anesthetic causes chondrotoxicity?
Bupivacaine
What local anesthetic is used for equine lameness diagnosis?
Mepivacaine
What are the clinical signs of Lidocaine systemic toxicity?
Depression/sedation
twitching
seizures
cardiovascular signs
Bier Block
Limb wrapped tightly from distal to proximal and tourniquet is places
Local anesthesia is injected into peripheral vein and diffuses into target tissues
When is epidural anesthesia used?
Tail/perineum
Hindlimb
abdominal/thoracic
Epidural contraindications
Coagulopathy Hypovolemia Infection at injection site Neoplasia at injection site Inability to palpate landmarks Sepsis
What are the adverse effects of local anesthesia?
Hypotension Motor Block/paralysis Hematoma Infection neurotoxicity
