Chapter 5- Sedation, General Anesthesia, and Analgesia

Question 1

Why is it preferred to use regional anesthesia than general anesthesia in farm animals?

Answer 1

Due to practical and financial reasons

Question 2

Which is the most commonly used local anesthetic solution in farm animals?

Answer 2

Lidocaine

Question 3

What is the analgesic duration of lidocaine in farm animals?

Answer 3

90-180 minutes

Question 4

True/False: Lidocaine is the only local anesthetic solution licensed for use in farm animals in the US

Answer 4

True

Question 5

How soon and for how long can proparacaine hydrochloride desensitize the cornea after application?

Answer 5

Within 30 seconds and for 10-15 minutes

Question 6

Auriculopalpebral block in cows
1. Anatomy
2. Amount
3. Action

Answer 6

1. Palpable along the zygomatic arch, ventral to the zygomaticoauricularis muscle and to the zygomatic process of the temporal bone caudal to the coronoid process
2. Infiltrate 5-15 mL
3. Motor-only desensitization causing akinesia of the corresponding eyelid

Question 7

Peterson block
1. Anatomy
2. Amount
3. Action
4. Notes

Answer 7

1. Using a 3.5 inch 18G needle. In a space delineated by the zygomatic process of the frontal bone, the zygomatic process of the temporal bone, the frontal process of the zygomatic bone, and the rostral edge of the coronoid process of the zygomatic bone. The needle should be advanced to the pterygopalatine fossa toward the foramen orbitorotundum at a depth of 7-10 cm
2. 15 mL of lidocaine
3. Desensitizes the oculomotor, trochlear, and abducens nerves and the 3 branches of the trigeminal nerve (ophthalmic, maxillary, and mandibular). Complete motor and sensory block of the eye, except the eyelid
4. More challenging than the retrobulbar block, but less chances for hemorrhage, penetrating the globe, damage to the optic nerve, or injection into the meninges.

Question 8

Retrobulbar block
1. Anatomy
2. Amount
3. Action
4. Notes

Answer 8

1. Using a 3-4 inch, 18 G needle curved. Penetrate the eyelids at medial and lateral canthus at the dorsal and ventral orbital rims while using the fingers to reflect the globe away. Advance through the conjunctiva in a curve medially to the orbital apex
2. 15 mL of lidocaine divided in the 4 sites
3. Desensitize all ocular muscles and the optic nerve
4. Possible damage to the globe, intraneural meningeal injection, retrobulbar hemorrhage, damage to the optic nerve

Question 9

Anesthesia for dehorning
1. Cattle
2. Goats

Answer 9

1. Anesthesia of the cornual nerve
2. Anesthesia of the cornual nerve, the cornual branch of the zygomaticotemporal nerve, and branches of the infratrochlear nerve

Question 10

Anesthesia for disbudding in cattle
1. Anatomy
2. Amount
3. Action
4. Notes

Answer 10

1. Palpable along the ventrolateral aspect of the frontal ridge, halfway between the lateral canthus and the base of the horn
2. 5-10 mL
3. The cornual nerve is a branch of the zygomaticotemporal nerve, part of the trigeminal nerve
4. In older cattle a hemicircunferential block of the caudal aspect of the horn base might be needed to block the cutaneous branches from the second cervical spinal nerve

Question 11

Anesthesia for disbudding in goats
1. Anatomy
2. Amount
3. Notes

Answer 11

1. A) The cornual branch of the zygomaticotemporal nerve is desensitized at a location half way between the lateral canthus of the eye and the lateral base of the horn, as close as possible to the ridge of the supraorbital process. B) The branches of the infratrochlear nerve are blocked with a line block half way between the medial canthus of the eye and the medial base of the horn, dorsal and parallel to the dorsomedial margin of the orbit.
2. Both with 2-3 mL
3. Use a low amount of lidocaine in goats due to their extreme sensitivity to lidocaine toxicity. Max dose of 10 mg/kg. In kids, divide 1 mL in the four sites to desensitize the bud

Question 12

What are some disadvantages of a line block technique? (5)

Answer 12

1. Increase surgical bleeding
2. Delayed healing
3. Incomplete anesthesia in deeper tissues
4. Risk of toxicity
5. Inability to extend the incision

Question 13

Inverted L infusion technique

Answer 13

First, inject along the last rib and then horizontally just ventral to the transverse processes with multiple subcutaneous injections (1 cm deep) and deeper muscle injections (2-7 cm deep)

Question 14

What region does the paravertebral block provide analgesia to?

Answer 14

Entire flank region potentially

Question 15

Which spinal nerves are blocked?

Answer 15

Last thoracic (T13) and first two lumbar (L1-L2)

Question 16

Dorsal approach technique for the paravertebral block

Answer 16

Palpate the ends of the tranverse processes, the puncture site is abaxial to the transverse process between T13-L1, L1-L2, and L2-L3. Inser a 3.5 inch needle ventrally until the transverse process is encountered (~5-7 cm), then walk the needle off the cranial edge of the process and advance ventrally to penetrate the costotransverse ligament and intercostal membrane. After penetration, usually palpable as a pop, inject 10-15 mL of lidocaine per site.

Question 17

A What is an alternative to the dorsal paralumbar block?

Answer 17

A distal paravertebral block can be performed by inserting the needles parallel to the tip of transverse processes dorsally and ventrally at the processes of L1-L2 and L4

Question 18

What should you consider when performing epidural anesthesia in cattle to avoid damage to the inner thigh musculature?

Answer 18

Have excellent footing and hobble the hind legs

Question 19

What are the common approaches for epidural anesthesia in cattle?

Answer 19

1. Sacrococcygeal (S5-Cx1)
2. First coccygeal (Cx1-Cx2)

Question 20

Epidural anesthesia procedure

Answer 20

The location is located by palpating the dorsal spinous process of the sacrum and coccygeal vertebrae while moving the tail up and down. A 22g, 2 inch needle is inserted directly on midline with the bevel cranially until a pop is felt.

Question 21

Which space would be more straightforward for an epidural injection since it is usually larger?

Answer 21

Intercoccygeal

Question 22

What are some indicatives of penetrating the epidural space?

Answer 22

1. Hanging drop
2. Loss of resistance

Question 23

Recommended lidocaine dose, Onset time and duration of the effect

Answer 23

1. 10 mL/ 100 kg (0.2 mg/kg)
2. 10-20 minutes
3. 30-150 minutes

Question 24

What combination of medications has shown to potentiate the duration of the epidural?

Answer 24

Xilazine 0.03 + Lidocaine 0.2 mg/kg diluted to 5 mL of sterile saline

Question 25

What is the onset of action and duration of xylazine + lidocaine combination?

Answer 25

Onset of 3-4 minutes and duration of ~100 minutes

Question 26

What is the Bier block?

Answer 26

Is IV regional anesthesia

Question 27

The regional anesthesia using the Bier block will last as long as ____

Answer 27

The tourniquet is in place

Question 28

Which vessels can be used for the Bier block and how much should you infuse?

Answer 28

Can infuse up to 30 mL of 2% lidocaine
1. Dorsal metacarpal/metatarsal
2. Palmar/plantar digital vein
3. Dorsal digital vein
4. Lateral saphenous vein

Question 29

For how long can the tourniquet be safely left in place for regional IV anesthesia?

Answer 29

For up to 90 minutes

Question 30

What branches provide innervation to the udder?

Answer 30

Branches originating from L3-L4 (Caudal aspect of the udder); Branches originating from L1-L2 (Cranial aspect)

Question 31

What blocks should you perform to provide anesthesia to the udder?

Answer 31

A paravertebral block and epidural block

Question 32

What can be a consequence of performing a paravertebral block and an epidural block?

Answer 32

Weakness of the pelvic limbs

Question 33

True/False: For procedures that involve the external teat surface a ring block or IV anesthesia is usually adequate

Answer 33

True

Question 34

For procedures affecting the cistern, what block can be sufficient?

Answer 34

Infiltration of anesthetic solution directly to the cistern

Question 35

What do you need to do when applying the anesthetic to the cistern to prevent any milk during the infusion?

Answer 35

A tourniquet can be placed to the base of the teat