Local anesthesia for standing sinusotomy in the horse is commonly performed using an incisional line block. Based on local innervation, blockade of the frontal and infra-trochlear nerves should desensitize the skin at the location of a frontonasal sinusotomy. We hypothesized that anesthesia of the frontal and infra-trochlear nerves would desensitize skin along a proposed frontonasal sinusotomy and that a skin/periosteal incision could be performed following these nerve blocks. For phase 1, a randomized cross-over study was performed using 6 horses, with order of line block or targeted nerve blocks randomly assigned. Mechanical nociceptive thresholds (MNT) were taken at 5 sites along a proposed frontonasal sinusotomy at baseline (pre- and post-sedation) and 10 minutes, 1 hour, and 2 hours post-blocking. For phase 2, following targeted nerve blocks (frontal and infra-trochlear), 6 horses had skin/periosteal incisions created; the ability to create the incision (yes/no) and the final incision size were recorded. Data from phase 1 were analyzed using mixed-model ANOVA with P<0.05. There was a significant increase in MNTs following both line and targeted blocks, as compared to baseline (P<0.05). For Phase 2, skin incisions could be created in five out of six horses; however, skin sensation returned at the rostral-abaxial aspect of the proposed sinusotomy site. A slightly smaller than intended sinusotomy incision could be created. Results indicate that frontal and infra-trochlear nerve blocks can be used to create a smaller frontonasal sinusotomy in the majority of horses; however, a larger sinusotomy may require anesthesia of additional nerves.
