Nerve Blocks in Veterinary Medicine

Nerve Blocks

• Nerve blocks temporarily interrupt nerve impulses.
• Local anesthetic solutions are injected to desensitize and temporarily paralyze the region controlled by the nerve.
• Indications include pain relief and improving animal function.
• Chronic conditions like splints, ringbone, navicular disease, and laminitis in horses are treated with nerve blocks.

Radial Nerve Block

• The radial nerve is the largest branch of the brachial plexus.
• Indications include fracture reduction, elbow joint dislocation, and surgical procedures.
• The site of the block is along the musculospiral groove of the humerus, between the triceps muscle heads.

Median Nerve Block

• The median nerve runs below the elbow, then down the forearm between the radius and flexor carpi radialis muscle.
• It supplies muscles involved in pronation and digital flexion.
• The block site is below the medial tuberosity of the radius, in the groove between the radius and flexor carpi radialis.

Ulnar Nerve Block and Neurectomy

• The ulnar nerve is relatively superficial in the lower third of the forearm.
• It lies between the flexor carpi ulnaris and the ulnaris lateralis muscle.
• It provides sensation and motor function to muscles related to the wrist and fingers.
• The block site is a few inches above the accessory carpal.

Volar Nerve Block and Neurectomy

• The volar/metacarpal nerves are branches of the median nerve.
• High volar block involves injecting 5-7 cm above the fetlock joint, in the depression between the suspensory ligament and deep flexor tendon.
• Low volar block is performed midway between the fetlock and coronet, between the deep and superficial digital flexors.

Peroneal Nerve Block

• The peroneal nerve innervates the tibialis anterior, long and lateral digital extensors, and peroneus muscles.
• Its block desensitizes the anterolateral part of the leg and foot, and the anteromedial part of the fetlock joint.
• Indications include lameness diagnosis.
• The site of the peroneal nerve block in cattle is immediately behind the lateral condyle of the tibia.

Tibial Nerve Block

• The tibial nerve innervates the gastrocnemius, superficial and deep digital flexors, popliteus, and tibialis posteromedial and posterolateral muscles of the pes.
• Indications include lameness diagnosis and tibial neurectomy.
• The block site in horses is approximately 10 cm above the hock, between the tendo-achilles and digital extensor muscles, on the medial aspect of the limb.

Pudic Nerve Block

• The pudic nerve branches from the sacral spinal nerves.
• It is crucial for procedures involving the penis and prepuce.
• The internal pudic artery is palpated rectally to locate the nerve.
• The nerve is situated just cranial to the lesser sciatic foramen.
• The block site is within the ischiorectal fossa (between the anal orifice and ischial tuberosities).

Site for Collection of Bone Marrow

• Indications for bone marrow collection include disease investigation.
• Collection sites vary by species:
  • Cattle, horses, sheep, goats: ribs and tuber coxae
  • Dogs, cats, pigs: iliac crest and proximal femur

Site for Collection of Cerebrospinal Fluid (CSF)

• Cerebrospinal fluid (CSF) is a plasma filtrate, surrounding the brain and spinal cord.
• CSF collection in horses involves puncturing the cisterna magna (suboccipital site).
• In cattle, sheep, and goats, a lumbar puncture is used.

Liver Biopsy

• The usual liver biopsy site in most animals is the 12th intercostal space on the right.
• This area is along a line running from the tuber coxae to the point of the shoulder.
• In cattle, the biopsy area is at the junction of the upper and middle thirds of the 10th or 11th intercostal space on the right side.

Gall Bladder Biopsy

• The gall bladder biopsy site is often at the ventral aspect of the 11th intercostal space on the right.