Anesthetic blockade of the maxillary and pterygopalatine nerves provides analgesia to the nose, palate, maxilla, and upper lip and teeth. This prospective, randomized, blinded, controlled study compared 2 approaches. In the percutaneous method, a needle is inserted percutaneously and advanced into the pterygopalatine fossa, toward the maxillary foramen. In the intraoral deep infraorbital block, a needle is advanced into the infraorbital canal to the level of the first maxillary molar; in this modification an IV catheter (not needle) was used.
Four veterinarians without experience were given written explanations of both approaches. The percutaneous approach used 23-gauge × 1-inch needles, whereas the infraorbital approach used catheters ranging from 22 gauge × 25 mm to 20 gauge × 48 mm. Using methylene blue dye, both techniques were performed on 37 canine cadavers. Dissections were performed and evaluated for accuracy of dye placement and potential for complications.
The infraorbital approach resulted in complete staining of both nerves in 56.7% of cases (compared with 21.6% for the percutaneous approach) with no potentially dangerous dye distributions observed. Thus, the infraorbital method may be safe and more successful for regional maxillary nerve blocks. Further research is needed to evaluate whether dye study can accurately predict real outcomes.
When using a catheter supported by an infraorbital approach, if the appropriate length of maxillary nerve was affected, the pterygopalatine nerve was also stained, widening the area of efficacy of the block. Although distribution of local anesthetic in an anesthetized patient may differ from that of the dye at the volume used in this study, the results suggested that the infraorbital approach to blocking the maxillary nerve may be more effective. No complications were noted in this study, but potential for neural and vascular trauma is possible during catheter advancement in a living patient.—Khursheed Mama, DVM, DACVAA
A cadaver study comparing two approaches for performing maxillary nerve block in dogs. Viscasillas J, Seymour CJ, Brodbelt DC. VET ANAESTH ANALG 40:212-219, 2013.