Subzygomatic and infraorbital approaches for maxillary nerve blockade in cats’ cadaver

Abstract

This study compared the accuracy of dye placement on the maxillary nerve by using the percutaneous subzigomatic (SBZ) and infraorbitary (IO) approaches in cats’ cadavers. A second aim was to compare the accuracy of dye placement on the maxillary nerve between different untrained anesthetists. This was a prospective, randomized, blinded study, performed in 40 heads obtained from feline cadavers. Three veterinarians (A, B and C) with no previous experience with the IO approach performed the experiments. The SBZ approach was randomly performed on one side of the head and the IO approach was performed in the contralateral side of the same head. For each approach, 0.2ml of 1% methylene blue dye was injected. Scores for length of nerve staining were as follows: 0 (failure), no staining; 1 (moderate), <6mm of nerve stained; and 2 (ideal), ≥6mm of nerve stained. Median scores (interquartile range) for the SBZ and IO approaches were 2.0 (0.3-2.0) and 1.0 (0.0-2.0), respectively. Scores for length of nerve staining were higher with the SBZ approach than the IO approach (P=0.016). Considering the scores for both the SBZ and IO approaches, there was a significant difference among the three veterinarians (P=0.002). Results of this study do not support the IO approach to perform a maxillary nerve block in cats. A greater accuracy of methylene blue dye placement was observed with the SBZ approach. A variable accuracy may exist between different veterinarians when performing a maxillary nerve block employing the SBZ and IO techniques in cats.

Cadaveric Evaluation of Injectate Distribution for Two Maxillary Nerve Block Techniques in Cats

“…However, in one of the PC injections the injectate missed the targeted area completely, and there was no dye staining associated with the nerve. Interestingly, these findings are different than those found by Becerra et al ( 12 ). In the Becerra study, a catheter was used to perform the IFR technique.…”

“…When comparing the infraorbital foramen and percutaneous injection techniques in dogs, the infraorbital foramen technique had significantly greater maxillary nerve staining when a dye was used to simulate an injectate ( 11 ). Another similar study performed in cat cadavers, did not demonstrate the same difference ( 12 ).…”

“…Previous descriptions of how to perform the IFR technique involve catheter placement into the infraorbital canal ( 10 , 12 ). The length of the infraorbital canal in feline mesaticephalic skulls is roughly 4–5 mm: therefore, a catheter was deemed unnecessary for this study.…”

Accidental arterial catheterisation during a maxillary nerve block using a modified infraorbital approach in a dog

“…However, Fizzano et al performed the MNB using the modified approach on live animals and did not report on the occurrence of intravascular injection. Another possible factor is catheter size, as previous studies describing the technique have used catheter sizes ranging from 20 to 22‐G 9 16 17. The use of a 24‐G catheter with a length of 19 mm (BD Insyte) in the present case may have increased the risk of intravascular catheterisation.…”