Local Anesthesia

Question 1

The most commonly used local anesthetic is:

Answer 1

2% Lidocaine

Question 2

Lidocaine takes effect within ______ minutes and the duration of action is:

Answer 2

3-5 minutes
1-2 hours

Question 3

In contrast to Lidocaine, Mepivacaine (Carbocaine) and Bupivacaine last (respectively):

Answer 3

1-2 hours
4-6 hours

Question 4

What is the onset and duration of Proparacaine when using topical anesthesia of the eye?

Answer 4

Onset: 15 sec
Duration: 15-30 min

Question 5

The most important motor nerve block of the eye is the:

Answer 5

Auriculopalpebral
(25 gauge, 1 in needle; 1-2 mL)

Question 6

The auriculopalpebral nerve block paralyzes:

Answer 6

Eyelids (motor)

Question 7

What is the technique for auriculopalpebral blocks?

Answer 7

Infiltrate the caudal aspect of the zygomatic arch

Question 8

What structures does the supraorbital block target, and what is the technique for this block?

Answer 8

Sensory to most of the upper eyelid;
Inject in and over supraorbital foramen (palpate foramen)

Question 9

Lacrimal nerve block targets:

Answer 9

Sensory to the temporal canthus; 25% upper lid

Question 10

Infratrochlear nerve block targets:

Answer 10

Nasal canthus

Question 11

Zygomaticofacial nerve block targets:

Answer 11

Temporal 75% of lower lid

Question 12

The Infraorbital I nerve block gives analgesia to:

Answer 12

Upper lip and nose

Question 13

Infraorbital II nerve block desensitizes:

Answer 13

Teeth up to 1st molar
Maxillary sinus
Roof of nasal cavity
Skin to medial canthus

Question 14

How to perform infraorbital II block?

Answer 14

Thread your needle into the infraorbital foramen
standing horses do not tolerate well

Question 15

The maxillary nerve blocks what structures and what is the technique for this block?

Answer 15

-All of the upper teeth, sinuses, and nasal cavity
-Insert 3.5” needle ventral to zygomatic process, dorsal to vessels, caudal 1/3 of eye - @90 degrees

Question 16

The mandibular nerve blocks what structures and what is the technique for this block?

Answer 16

-All mandibular structures (lateral canthus, mandibular cheek teeth)
-20 gauge, 6” needle ~10-15cm rostral to angle of the mandible

Question 17

The Mental I nerve block desensitizes what structures and what is the technique for this block?

Answer 17

Analgesia of the lower lip
Inject 5mL over the mental foramen

Question 18

The Mental II nerve block desensitizes what structures and what is the technique for this block?

Answer 18

Analgesia of lower incisors and caudal to the 3rd premolar
Thread needle into the mental foramen

Question 19

What are the indications for an epidural?

Answer 19

-Procedures involving rectum, vagina, perineum, urethra and bladder
-Obstetric manipulations
-Analgesia of stifles and hocks
-Intraoperative

Question 20

Contraindications for epidural?

Answer 20

-Infection at puncture site
-Sepsis
-Uncorrected hypovolemia
-Anticoagulant prescriptions
-Anatomic abnormalities

Question 21

Which is preferred for horses: Lumbosacral or caudal epidural? Why?

Answer 21

Caudal: preserves locomotor function of hindlimbs

Question 22

What is the landmark for lumbosacral subarachnoid epidural?

Answer 22

1 to 2 cm caudal to a line drawn from the cranial edge of tuber sacrale and dorsal midline

Question 23

What are the two techniques for caudal epidural anesthesia?

Answer 23

1: Enter center of space between Co1 and Co2 perpendicular to the skin (may feel popping of interarcuate ligament)

2: Insert needle at the caudal part of the interspace at about 30 degrees parallel to the horizontal plane

Question 24

What are the pros/cons to using epidural catheters?

Answer 24

Pro: Repeat dosing
Con: Localized inflammation and fibrosis

Question 25

What is the maximum amount of lidocaine/mepivacaine that can be given with epidurals?

Answer 25

No more than 10-15 mL *when combined with saline

Question 26

Increasing the volume of the epidural also increases:

Answer 26

The area of the hindquarters that is desensitized

Question 27

When alpha-2 agonists are combined with local anesthetic, what is the result?

Answer 27

Work synergistically to prolong anesthesia

Question 28

What is the mechanism of opioids for epidurals?

Answer 28

Inhibition of pain transmission in the dorsal horn of the spinal cord

Question 29

Benefits of using opioids for epidural anesthesia?

Answer 29

-Epidural dose lower than systemic dose
-Provide analgesia without motor blockade
-Usually used for intra- and post-op analgesia of perineum and hind limb

Question 30

Onset and duration of morphine as local anesthetic?

Answer 30

Onset: 1-5h
Duration: 6-16 h

Question 31

Morphine reduces the MAC of halothane for hindlimb surgeries by:

Answer 31

14%

Question 32

Onset and duration of Ketamine in local anesthesia?

Answer 32

Onset: 10 min
Duration: 30-75 min

Question 33

Benefits of using drug combinations:

Answer 33

1. Can synergistically prolong anesthesia
2. Provide better analgesia than one agent alone
3. Minimize side effects of individual agents!

Question 34

If giving alpha-2 in combination with a local, you need to decrease the dose of the local by:

Answer 34

30%
Can cause excessive ataxia if not decreased

Question 35

Complications of local anesthesia/epidural with drug combinations?

Answer 35

1. Failure to achieve analgesia
2. Hypoventilation
3. Bradycardia
4. Pruritis (after morphine)
5. Upward fixation of patella
6. Sepsis
7. Recumbency