Nerve Blocks for Oral Surgery in Dogs

Not only do nerve blocks provide a basis for pain management in the immediate postoperative period, they also allow for decreased minimum alveolar concentration of inhalant anesthetic, resulting in a safer procedure.

The maximum dose of bupivacaine is determined by patient weight; a safe target maximum dose is 2 mg/kg.¹ The volume range of anesthetic infused per site based on patient weight varies (Table, below).

Several types of nerve blocks can be used in oral surgery:

• Rostral maxillary (infraorbital) blocks affect bone, teeth, and intraoral soft tissue from the maxillary third premolar rostral to the midline.
• Caudal maxillary blocks affect bone, teeth, and intraoral soft tissue from the last molar rostral to the midline, including the ipsilateral soft and hard palatal mucosa and bone.
• Rostral mandibular (mental) blocks affect bone, teeth, and intraoral soft tissue from the mandibular second to third premolar rostral to the midline.
• Caudal mandibular (inferior alveolar) blocks affect bone, teeth, and intraoral soft tissue from the mandibular third molar rostral to the midline.

Care should always be taken not to inject a vessel. Although rare, resistance when depressing the syringe plunger indicates that the needle may be in the nerve; the needle should be withdrawn and redirected. Extravascular placement can be ensured by aspirating the needle before injection.

Exact placement of the anesthetic agent is not required. Extravasation of the agent throughout the tissue allows minor deviations in needle placement. However, the more accurate the placement of medication, the less agent required to achieve effect. A canine skull is convenient to have on hand for reviewing anatomic landmarks. Keeping the patient at a light anesthetic plane can enhance safety and allow the surgeon to confirm effectiveness of the nerve block. If the block was not performed correctly or if the full anesthetic effect has not been achieved, the patient will physio­­logically react to the initial surgical incision. Provided the volume of bupivacaine administered is within the maximum recommended volume for the patient’s weight, additional agents can be administered if a particular block is ineffective. Small- to medium-sized brachycephalic patients do not require a caudal maxillary block. Their short infraorbital canals allow the agent to be placed via the rostral maxillary block to reach nerves before entry into the infraorbital foramen and maxillary bone.

• Syringe (tuberculin to 6 mL, depending on patient size and infusion volume)
• Needle (for patients ≤15 kg, 25 gauge, 5/8 inch [0.5 x 16 mm]; for patients >15 kg: 22 gauge, 3/4 inch [0.70 x 19 mm])
• 0.5% bupivacaine
• Optional: canine skull to visualize anatomic landmarks