Nerve Blocks for Oral Surgery in Cats

See the companion article, Nerve Blocks for Oral Surgery in Dogs

Nerve blocks for oral surgical procedures in cats provide a complete sodium channel blockade, preventing ascending pain signals that are created during surgical manipulation to reach the cerebral cortex. Because of their high surface area to body ratio, cats are particularly susceptible to hypothermia. Nerve blocks not only provide perioperative analgesia but allow inhalant anesthetic concentrations to be minimized. Doing so maximizes cardiac output, blood pressure, and overall perfusion, resulting in warmer patients.

Bupivacaine is the anesthetic of choice for oral nerve blocks because of its long duration of action (6–10 hours). Its maximum extravascular dose is determined by patient weight; a safe target maximum dose is 2 mg/kg (Table), but this dose is not commonly reached.

Related Article:Peripheral Nerve Block Techniques: Dental Blocks

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

• Rostral maxillary (infraorbital) blocks affect the entire maxillary arcade on the ipsilateral side, adjacent bone, tooth, soft tissue, hard and soft palatal mucosa, and palatal bone.
• Rostral mandibular (mental) blocks affect bone, teeth, and intraoral soft tissue from the mandibular canine to the mandibular symphysis.
• Caudal mandibular (inferior alveolar) blocks affect bone, teeth, and intraoral soft tissue from the mandibular molar rostral to the midline.

Care should be taken not to inject a vessel. Extravascular placement can be ensured by aspirating the needle before injection.

What You Will Need

• Tuberculin syringe
• 25-gauge, 5/8-inch needle
• 0.5% bupivacaine
• Optional: feline skull to visualize anatomic landmarks

In small cats, multiple quadrant blocks may approach or exceed the recommended maximum per patient volume of anesthetic agent. It is important to pay careful attention so as not to exceed the total volume. Cats are more susceptible to lidocaine and bupivacaine toxicity than are dogs.

If the volume of agent is less than 0.1 mL per site based on the calculated maximum dose, saline can be added to the agent to dilute it to a ratio of up to 1:1 without compromising the effectiveness of the block.

Some patients chew and/or macerate their tongue following regional oral nerve blocks. Sternal recumbency can prevent lateral deviation of the tongue between the carnassial teeth where damage can occur. As long as the patient is monitored carefully after surgery until it is sternally recumbent, such damage cannot occur.

BRETT BECKMAN, DVM, FAVD, DAVDC, DAAPM, owns a teaching center in Orlando, Florida, dedicated to advancing the dentistry and oral surgery education needs of veterinarians and veterinary technicians. He also accepts dentistry and oral surgery cases in Atlanta, Georgia; Orlando, Florida; and Punta Gorda, Florida. Dr. Beckman was Distinguished Fellow of the Year, 2010, for the Academy of Veterinary Dentistry and received the Miltex Award for Excellence in Veterinary Dentistry, 2012. He earned his DVM from Mississippi State University.