A morphometric study of the canine skull and periorbita and its implications for regional ocular anesthesia.

OBJECTIVE: A hypothetical relationship between canine cranial length and the length of the periorbita could be used for intraconal anesthetic volume estimation. STUDY SUBJECTS: Forty-one canine cadaver heads and one macerated dog skull. PROCEDURES: Inion and nasion points were recognized in the macerated skull and used as landmarks for cranial length measure. Thirty cadavers classified as dolichocephalic, mesaticephalic and brachycephalic were distributed in three study groups. Anatomic references of the skull shapes were recognized and parameters measured: body weight (BW), cranial length (Lcr ) and length of the periorbita (Lpo ). Results were compared and statistical analyses were performed to find correlations between BW and the skull parameters. Contrast medium was injected in another 11 cadavers with a total volume calculated based on Lcr (10 cadavers) or BW (one cadaver) and then submitted to computerized tomography examination to compare techniques, estimate the capacity of the intraconal space of the periorbita and to illustrate practical implications. RESULTS: There is a positive correlation between BW and Lpo (P < 0.001) as well as between Lcr and Lpo (P < 0.0001). Linear regression of the variable BW predicts only 71% of the variable Lpo (r2 = 0.71), whereas the variable Lcr predicts 88% (r2 = 0.88) of Lpo . CONCLUSIONS: This study demonstrated a mathematical relation between Lcr and Lpo . A method for calculating anesthetic solution volumes based on canine morphometric features is presented. The formula 0.1 mL/cm Lcr to calculate total intraconal anesthetic volume is suggested.

Supplemental vibrissal extensions as an alternative to improve the tactile sensitivity of blind dogs - a preliminary approach investigation.

OBJECTIVE: This preliminary study suggests a way to artificially extend vibrissae of blind dogs to assist ambulation and avoiding facial contact with obstacles. PROCEDURES: Fourteen irreversibly blind dogs had 5-6 mystacial vibrissae on each side of the face supplementally extended by attaching carefully chosen adult pig hairs to them and were subjected to a maze test before and after the procedure. In three of these dogs the test was repeated one more time after all the extensions had fallen off. Collision counts and course times with and without extensions were analyzed and compared. A p-value > 0.05 was considered significant. RESULTS: Median number of collisions was significantly higher post-extensions (5 IQR 2.25) and after extensions had fallen off (4 IQR 7.50) compared to pre-extensions (1 IQR 1), p = 0.021. Median times were significantly higher pre-extension (25.6 IQR 8.98) and after the extensions had fallen off, compared to the post-extension performance (22.8 IQR 8.55), p = 0.04. CONCLUSION: Vibrissae play an important role in the tactile perception of blind dogs, and our preliminary results suggest that extending this sensory organ possibly improves obstacle location and their quality of life.