Local Anesthetics

Question 1

Types of regional anesthesia

Answer 1

Nerve pathway
- neuroaxial = epidural or spinal
- perinerual = brachial plexus block

Question 2

Types of general anesthesia

Answer 2

Systemic /full body effect
Volatile (inhalants or injectables)

Question 3

Types of local anesthetics

Answer 3

Topical - skin, mucosa (surface)
Infiltrative - line block, testicular (below surface)

Question 4

Indications for LA and SA

Answer 4

LA - common w heavy sedation
SA - normally combined w general anesthesia
Monitor patients & provide oxygen

Question 5

Goals for using local anesthesia

Answer 5

Reduces anesthesia requirements when combined w GA, reducing the GA side effects
^ cardio function
Better pain control

Question 6

Sodium channel blockers

Answer 6

Not specific for pain pathways
Block transduction & transmission at site, regional or local
Affect modulation
Differential block - temp, sharp, light touch, motor

Question 7

Forms of anesthetics targeting initial perception

Question 8

Forms of anesthesia that block modulation of spinal pathway

Question 9

Forms of anesthesia for blocking transmission

Question 10

Forms of anesthesia for blocking transduction

Question 11

Chemical compounds of local anesthetics

Answer 11

Benzene ring & hydrophilic amine group
- linked by amide or ester bond
Weak bases

Question 12

Examples of aminoamides

Answer 12

Lidocaine, bupivacaine, mepivacaine, ropicavaine, prilocaine

Question 13

Examples of aminoesters

Answer 13

Propaganda in, procaine, (novacaine) tetracain, benzocaine

Question 14

Lidocaine common use

Answer 14

Most widely used in VM, small & large, short onset & duration of action, moderate tissue irritating

Question 15

Bupivacaine common use

Answer 15

Longer onset & duration of action, most cardio toxic !! Second most commonly used
-consider post op analgesia effects

Question 16

Mepivacaine common use

Answer 16

Common in horses, joint blocks, less irritating to tissues

Question 17

Proparacaine common use

Answer 17

Ophthalmic preparations, short onset & duration

Question 18

Factors effecting activity

Answer 18

PH at site of admin - low pH = low efficacious (cannot be in non ionized form, lower form of action)
Dose administered - better to ^ concentration than volume for prolonged action

Question 19

Additives to local anesthetics

Answer 19

Sodium bicarbonate - reduces pain of injection
Vasoconstrictors - epinephrine- increased duration
Analgesics - opioids, alpha-2s

Question 20

Toxicity of local anesthetics on cardio system

Answer 20

= high systemic contraction
Hypotension, arrhythmias (may be refractory) cardiac arrest

Question 21

Toxicity of LA on rest p

Answer 21

Hypoventilation to point of apnea or resp t arrest

Question 22

Toxicity of LA on CNS

Answer 22

Tremors or ataxia, sedation to coma, seizures

Question 23

Species sensitive to LA toxicity

Answer 23

Cats are more sensitive than dogs
Sheep are most sensitive in general

Question 24

Drugs to care for seizures from LA tox

Answer 24

Benzodiazepines

Question 25

Drugs to care for cardio from LA tox

Answer 25

IV fluids for hypotension,vasodilation, positive into ropes, anti cholinergic, vasopressors

Question 26

Ways to care for respt from LA tox

Answer 26

Supplemental ox, ventilation support

Question 27

Use & function of lidocaine

Answer 27

Can be given IV for systemic analgesia, given as CRI - may decreased anesthetic requirements Most commonly used in horses - concern for sedation & ataxia in recovery Prokinetic GI, anti-endotoxemic, anti inflammatory -not recommended in cats bc of cardio depression

Question 28

Why is lidocaine a good option for a collcing horse?

Question 29

why is lidocaine IV not recommend for cats?

Answer 29

Very negative ionotropic effect in cats = decreased cardiovascular function

Question 30

Why are spinal needles preferred when performing an epidural ?

Question 31

What types of nerves are blocked in an epidural & spinal blocks

Answer 31

Sensory, motor and autonomic Blocks motor function of both legs Spinal /sciatic blocks - singular /effected legs

Question 32

Locations for epidurals

Answer 32

Lumbosacral or sacrococcygeal

Question 33

Lumbosacral block

Answer 33

Common in SA Anesthesia of caudal ab, pelvic limb, perineum, tail

Question 34

Sacrococcygeal block

Answer 34

Common in LA could be SA Avoids anesthesia of caudal Ab and pelvic limb Want to avoid LA losing function of pelvic limbs

Question 35

Spinal cord ends in dogs & what block is common

Answer 35

L5-L6 Lumbosacral

Question 36

Spinal cord ends in cats & what block is common

Answer 36

S1-S2 Sacrococcygeal

Question 37

Spinal cord ends in pigs & what block is common

Answer 37

L6-S1 Sacrococcygeal

Question 38

Spinal cord ends in ruminants & what block is common

Answer 38

S3-S4 Sacrococcygeal

Question 39

Spinal cord ends in EQ & what block is common

Answer 39

S3-S4 Sacrococcygeal

Question 40

Areas effected with 0.1mL/kg of local

Answer 40

Perineum, tail

Question 41

Area effected by 0.2mL/kg of local

Answer 41

Pelvic limbs, perineum, tail

Question 42

Area effected with 0.3mL/kg

Answer 42

Caudal ab, pelvic limb, perineum, tail

Question 43

Risks w spinal

Answer 43

Spinal requires reduces dosage, (typically half of original) if volume is too high could lead to sympathetic blockage, vasoconstriction =hypotension

Question 44

CHAINS

Answer 44

Coagulopathy Hypovolemia Abnormal anatomy Infection Neoplasia Sepsis

Question 45

Epidural tech

Answer 45

LA - standing SA - recumbent, sternal (easier) or lateral Clip & prepare area Palpate wings of ilium to locate space between L7 and S1 Pierce skin, bevel faces cranially, “pop” or loss of resistance - enter space ASPIRATE Deliver slow

Question 46

hanging drop aspiration

Answer 46

Sucked if enters epidural space

Question 47

Complications encountered

Answer 47

Blood during aspiration - withdraw entirely & restart CSF during aspiration - remove/restart OR reduce injection volume 50% When sternal pull hind limbs cranially, aligns pelvis

Question 48

Additional pharmacologics

Answer 48

Analgesics- opioids, alpha 2 agonists Prolonged compared to systemic admin Lower doses, less side effects Morphine is most common - alpha2 agonists more common in equine

Question 49

Other types of blocks & species commonly used

Answer 49

Dental blocks TAP (transverse abdominis plane) ab body wall Bier block - distal limb, more La than Sa Teat block - cattle, sheep Retrobulbar block - enucleation Lidocaine topical - feline/swine larynx prior to intubation Proparacaine - ocular procedure, nasal tube passage (small animal)