1 Clinical Anesthesia-Nerve Blocks in VCS 878

• Clinical Anesthesia-Nerve Blocks is covered in VCS 878-Junior Surgery by Dr. Miesner.

Nerve Block Procedures

• Paralumbar fossa (Flank) anesthesia includes several methods.
• Epidurals include Caudal and Lumbosacral.
• Other nerve blocks are Pudendal Nerve block, Baer Block for Limb anesthesia, Anesthesia of the eye and orbit, and Cornual Anesthesia.

Flank Anesthesia - Laparotomy

• Procedures include Cesarean Section, GI-Surgery, and Exploratory
• Techniques include Proximal Paravertebral, Distal Paravertebral, Thoraco-Lumbar, Inverted L, and Line.

Proximal Paravertebral Block

• Landmarks are the 13th rib, L-1, L-2, L-3, and occasionally L-4.
• Nerves blocked are T-13, L-1, and L-2.

Proximal Paravertebral Procedure

• Palpable landmarks determine the location of the needle to nerve location.
• Find landmarks, L-5 is the most posterior palpable transverse process.
• Find the apex of L-1 process by following the last rib up.
• Blocking nerves requires a guide needle and a long spinal needle.
• 5 ml of Lidocaine is used per dorsal and ventral branch (10ml/per nerve).

Proximal Paravertebral Efficacy

• Scoliosis, heat, and sensation can be monitored to check if it worked.

Proximal Paravertebral Pros and Cons

• Benefits include that a small amount of lidocaine is used, scoliosis widens the surgical field, and that there is no lidocaine directly in surgical incision.
• Downfalls include scoliosis makes the animal a little unstable for a few hours, and that it can be difficult to palpate transverse processes in fat cattle.

Segmental Thoracolumbar Block

• Epidural deposition of 2% lidocaine occurs at a rate of 1ml/500lb.
• Spinal needle is used with a hanging drop technique.
• Potentially, it can be performed accidentally during Proximal Paravertebral block (note the small volume above).

Distal Paravertebral Block

• Landmarks: L-1, L-2 and L-4
• Nerves blocked are the same as proximal block

Distal Paravertebral Procedure

• Find the "apex” of transverse process.
• Deposit 10-15 ml of lidocaine dorsal and ventral to process, using an 18 gauge 1 ½ inch needle and fat cattle may require 3 inch.

Distal Paravertebral Efficacy

• Check for minimal Scoliosis, Heat and Sensation for efficacy.

Inverted L

• Involves a Large volume of lidocaine (toxic dose?..10mg/kg).

Epidural Anesthesia

• Used for posterior procedures.

Caudal Epidurals "Tail Block"

• Used for Dystocia, perineal surgery, castration, etc
• Lidocaine (2%) is dosed at 1cc per 200 pounds bw.
• Lidocaine + Xylazine dose is 0.02mg/kg.
• Xylazine alone dose is 0.02-0.04 mg/kg diluted in 1cc per 100lbs of saline, and provides flank anesthesia without motor blockade.
• Use an 18 ga to 20 ga 1" to 1½" needle
• Administer at the Sacro-coccygeal space or Cx 1-Cx2 space using “Hanging Drop” technique.

Caudal Epidural Efficacy

• A flaccid tail occurs within 1 minute.
• Decreased sensation to vulva is within 5 minutes.
• Too much dosage (ie 8 to 10 ml to 1000 pound cow) causes the animal to start to go down in about 5 minutes.
• Remember that the block does not completely wear off immediately, so, apply hobbles and good traction to prevent slipping.

Lumbo-Sacral Epidural Anesthesia "Rostral epidural"

• Used for anesthesia of the caudal half of the animal
• Restraint
• Cesarean (pigs, Sm. Ruminants, midline in cattle) Udder amputation, etc.

Lumbo-Sacral Epidural Anesthesia Dose

• Dose: 2% Lidocaine: Muir et al, pp 71
• Small Ruminants: 1ml/10lbs of bw and if subarachnoid injection * 0.5 ml/10lbs.
• Pigs: Standing 4ml/200lb, 6ml/400lb, 8ml/600lb or Recumbency (cesarean) 10ml/200lb, 15ml/400lb, 20ml/600lb.

Lumbo-Sacral Epidural Anesthesia Complications

• Complications include overdose, rapid administration, and subarachnoid injection.
• Other complications are loss of consciousness, convulsions, respiratory paralysis, hypotension, and hypothermia.

Pudendal Nerve Block

• Nerves blocked include (internal pudendal-fibers of S3 & S4), Caudal rectal (S4 & S5), and pelvic Splanchnic nn.
• It anesthetizes the retractor penis muscle, and rectal vaginal tone.

Pudendal Block Procedure

• Rectal exam and locate sacrosciatic ligament at lesser sciatic foramen, internal pudendal artery.
• Insert needle peri-rectal and advance.
• Inject 10-15ml 2% lidocaine ( internal pudendal nerve).
• Reposition ~ 2-3 cm caudal dorsally and inject another 10ml (caudal rectal and pelvic splanchnic nerves).
• Repeat procedure on other side.

Anesthesia of the Limb

• Three methods are available.
• Intravenous Regional Anesthesia, "Bier"
• Selective Regional Anesthesia

Selective Regional Anesthesia

• See: Greenough, et al; Lameness in Cattle

IV Regional Anesthesia/"Bier"

• See images provided.

I.V. Regional Anesthesia

• Use 20-25 ml of 2% Lidocaine IV to the Dorsal digital vein.

IV Regional Anesthesia-Localizing Lameness

• See image

Anesthesia of the Eye

• Methods include Local "Four Point" Infiltration and Peterson Eye Block.

Local Anesthesia

• 60-80 ml of 2% lidocaine.
• Use a 3 ½ inch needle.
• Retrobulbar, SQ, and auriculopalpebral.

Peterson Eye Block

• Supplies:
  • Use a 14ga. 1 ½ in. guide needle and an 18ga 4 ½ in. needle.
  • 20 ml of Lidocaine, 10ml to the foramen and 10ml to the auriculopalpebral nerve.
  • Requires good restraint.

Peterson Eye Block Landmarks

• The "Notch is made by the zygomatic and temporal processes.
• Target the Coronoid process of the mandible.

Peterson Eye Block Blocking the Nerve

• Block auriculopalpebral nerve

Cornual Block - Cattle

• See image

Cornual Anesthesia (Goats)

• Goats have: 2 branches, cattle 1 primary also some braches of cervical nerves to posterior horn (ring block for cosmetic).
• Goats: Lidocaine toxicity occurs at >5mg/kg.