As an MD anesthesiologist with a specialty in regional anesthesia and interventional pain management, I have a special interest in veterinary pain management. In my training I was taught regional anesthesia techniques for the head and neck, arms, chest/abdomen and legs along with spinal and epidural/caudal anesthesia. Knowledge of these fundamental regional nerve blocks provided an anesthetic armamentarium for the majority of surgical procedures. These same regional anesthesia techniques certainly have application in veterinary surgical practice as well.

Regional anesthesia is utilized most effectively in surgery when administered preemptively. This means that the regional nerve block has been performed with local anesthesia prior to the surgical incision or surgical stimulus. This has the benefit of blocking nociceptive pathways to reduce the amount of sensory information sent to the central nervous system. In other words, it prevents the establishment of central sensitization caused by a painful incisional stimulus. Preemptive anesthesia provides blockade of nociceptive stimuli during the operative and the early postoperative period. It also has the benefits of decreasing general anesthesia requirements, rapid postoperative recovery from anesthesia and decreased postsurgical analgesic requirements. A fundamental requirement for regional anesthesia; KNOW YOUR ANATOMY.

The following techniques are some basic regional nerve blocks which will provide you with an armamentarium of nerve blocks to cover the Head, Fore Limb, Chest and Abdomen and Hind Limb procedures as well as Lumbar and Caudal Epidural anesthesia. All of these regional blocks should be performed after the patient has been anesthetized.

Regional Blockade of the Head

The most common veterinary procedures performed on the head are dental and oral procedures. The following regional anesthesia techniques will provide analgesia to any oral or circumoral procedures.

Infraorbital Block-

Indications – Regional anesthesia for procedures on the first, second and third molars, incisors, canines, tissue rostral to the upper fourth premolars, upper lip and nasal cavity. Bilateral procedures require bilateral blockade.

Nerve Blocked – Infraorbital nerve

Approach:

• retract the upper lip dorsally
• palpate the infraorbital foramen
• insert the needle through the buccal mucosa adjacent to the maxilla in a caudad direction
• aspirate
• inject 0.3 – 0.5 ml of local anesthesia

Maxillary Block – 

Indications – Regional anesthesia for procedures involving the maxilla, upper lip, palate, maxillary fourth molar, all molars and tissue caudad to the fourth molar

Nerve Blocked – Maxillary nerve

Approach: 

• open the mouth wide
• retract the corner of the upper lip caudally
• identify the depression formed by the caudal aspect of the maxilla, ventral edge of the zygomatic arch and the vertical ramus of the mandible
• advance the needle in the dorsal direction perpendicular to the palate just behind the second molar
• aspirate
• inject 0.3 – 1 ml of local anesthesia

Mental Block –

Indications – Regional anesthesia for procedures involving the first three molars, canines, incisors and mandibular tissues rostral to the mental foramen.

Nerve Blocked – Mental nerve

Approach:

• retract the bottom lip ventrally
• palpate the mental foramen ventral to the second premolar just inside the lower lip
• insert needle into the mucosa aiming caudally
• advance 1 -2 mm into the foramen
• aspirate
• inject 0.3 – 0.6 ml of local anesthesia

Mandibular Block –

Indications – Regional anesthesia for procedures involving the lower lip, mandible and all the teeth in the mandible.

Nerve Blocked – Inferior alveolar nerve

Approach:

•   Extra-oral Approach-

• palpate the notch under the mandible just anterior to the angular process
• the notch is in line with the lateral canthus of the eye
• palpate under the mandible and slide your finger toward the lingual surface of the caudad aspect of the mandible and palpate the foramen
• direct the needle dorsally along the medial aspect of the mandible toward the foramen
• it is sometimes difficult to advance the needle into the foramen, however, advancement to the entrance of the foramen will be sufficient to provide anesthetic blockade of the nerve
• aspirate
• inject 0.5 – 1 ml of local anesthesia

• Intra-oral Approach –

• open the mouth
• palpate the angular process of the mandible extra-orally and the mandibular foramen
• Intra-orally which is located halfway between the last molar and condylar process
• advance the needle along the lingual surface adjacent to the foramen
• aspirate
• inject 0.5 – 1 ml of local anesthesia

Regional Blockade of the Fore Limb

Brachial Plexus Block

Indications – Regional anesthesia for procedures distal to the humerus, elbow, antebrachium and carpus.

Nerves Blocked – Musculocutaneous, axillary, radial, median and ulnar

Approach:

• place the patient in lateral recumbency
• insert the needle into the axilla just medial to and at the level of the shoulder joint
• direct the needle parallel to the vertebral column
• the needle tip should now be caudad to the spine of the scapula
• a nerve stimulator at 2 mA is helpful in locating the brachial plexus
• aspirate
• inject 0.1 ml/Kg of local anesthetic

Regional Blockade of the Chest and Upper Abdomen

Intercostal Nerve Blocks

Indications – Regional anesthesia for procedures of the chest and upper abdomen

Nerves Blocked – the intercostal nerves innervating the area of surgery or injury and two intercostal spaces cranial and caudad to the procedural area

Approach:

• palpate the caudad edge of the rib three finger breadths from the lateral spine
• place the needle perpendicular to the skin and direct the needle tip toward the caudad edge of the rib
• aspirate
• inject 0.5 – 1 ml of local anesthesia
• repeat these steps for intercostal nerves innervating the area of interest and two intercostal spaces craniad and caudad to the area of interest

Regional Blockade of the Hind Limb

For complete regional blockade of the hind limb, blockade of the femoral, saphenous and sciatic nerves is necessary.

Femoral/Saphenous Nerve Block

Indications – Regional anesthesia of the distal femur, stifle and distal limb (used in combination with the sciatic nerve block)

Nerves Blocked – femoral nerve and its terminal branch, the saphenous nerve

Approach:

• place the patent in the lateral recumbent position
• abduct the hind limb caudally and palpate the femoral artery
• anatomically the femoral nerve is lateral (near the femur) to the femoral artery and the femoral vein is medial to the femoral artery
• direct the needle tip to the anatomic lateral aspect of the artery with a nerve stimulator at 2 mA to identify the femoral nerve
• aspirate
• inject 0.2 ml/Kg of local anesthetic

Sciatic Nerve Block

Indications – Regional anesthesia of the distal femur, stifle and distal limb (used in combination with the femoral/saphenous nerve block)

Nerves Blocked – Sciatic nerve with the common peroneal and tibial branches

Approach:

• place the patient in lateral recumbency
• draw a line between the greater trochanter and the iliac tubercle
• place your needle at a point 1/3 of the distance from the greater trochanter
• direct the needle perpendicularly to the skin
• continue the perpendicular trajectory with a nerve stimulator at 2 mA to locate and stimulate the sciatica nerve and its branches.
• aspirate
• inject 0.05 - .1 ml/Kg of local anesthetic

Epidural Anesthesia – Lumbar and Caudal

Epidural anesthesia is a very versatile regional anesthesia technique that can be used for thoracic to lower extremity procedures dependent on epidural needle placement and the volume of local anesthetic used. The epidural space is located between the ligamentum flavum and the outer layer of the dura mater.

Lumbar Epidural 

Indications – Regional anesthesia for abdominal, thoracic, hindlimb, perineal, tail procedures and C-sections dependent on the location of needle placement and volume of local anesthetic used.

Nerves Blocked – Nerves caudad to the spread of local anesthetic in the epidural space. This is dependent on the location of needle placement in the lumbar region, the volume of local anesthetic used and the position of the patient.

Approach:

• the patient is placed in sternal recumbency
• palpate the iliac wings on either side of the spine
• locate the L7 – S1 interspace
• insert the styleted epidural needle with a craniad pointing bevel just caudad to L7 in the midline
• advance the needle utilizing a loss of resistance technique with an air or saline filled syringe or a hanging drop technique until a popping sensation is noted
• there should be no flow of blood or CSF from the needle
• inject 0.2 ml/Kg of local anesthesia

Caudal Epidural 

Indications – Regional anesthesia for urethral, tail, perineal and dystocia procedures

Nerves Blocked – Nerves caudad to the spread of local anesthesia in the caudal epidural space. The degree of spread is dependent on the volume of local anesthetic used.

Approach:

• place the patient in sternal recumbency
• palpate the sacral hiatus which is a U-shaped depression between the sacral cornua just craniad to the tail
• insert a beveled epidural needle at a 45-degree angle into the sacral hiatus
• advance the needle until you feel a “pop” indicating that you have entered the caudal epidural space
• reduce the needle’s angle to about 20 degrees and advance about 1 – 2 mm into the caudal canal
• there should be no flow of blood or CSF
• inject 0.2 ml/Kg of local anesthesia

A working knowledge of the anatomy of your patient is fundamental in providing effective regional anesthesia. Utilizing your anatomical knowledge along with procedural dexterity will provide you with an excellent armamentarium of skills to provide highly effective regional anesthesia for the majority of veterinary surgical procedures.

Patient Positioning

Warming Systems

Thermal Blankets