Venipuncture Technique of the Occipital Venous Sinus in Freshwater Aquatic Turtles
J Herpe Med Surg 12[4]:31-32 Winter'02 Clinical Techniques 7 Refs

The occipital sinus has been described as a good method for blood sampling in sea turtles and some tortoises, such as the desert tortoise, Gopherus agassizii, box turtle, Terrapene carolina, Burmese brown tortoise, Manouria emys, and pancake tortoise, Malacochersus tornieri. In these species, the supraoccipital crest is small and not prominent, and an approach to the sinus with the neck extended is feasible. However, in freshwater aquatic turtles, this technique has not been described, probably because the supraoccipital crest is larger than in tortoises, which makes it difficult to insert the needle into the venous sinus. Technique - Position the turtle vertically with the head up. Gentle traction of the head with the dominant hand is used to completely extend the neck. With your nondominant hand, hold the carapace and plastron, leaving the index finger free. Next, direct the head ventrally so that it rests at 90 degrees to the carapace and hold in place with the free index finger of the nondominant hand. The supraoccipital and dorsal horn of the hyoid apparatus must be easily palpable with the free (dominant) hand. A 25 ga needle is inserted into the occipital sinus, in the dorsal midline of the neck, just below the hyoid. A 23 ga needle may be necessary in larger turtles. In our clinical observations and dissections, we found the occipital venous sinus to be larger than other veins, so that the risk of aspiration of interstitial or lymphatic fluid is minimal. Moreover, we observe clinically that this is a good site position for delivery of barbiturates in the euthanasia of turtles, with more rapid effects than the dorsal coccygeal vein. However, because of the proximity of the foramen magnum, care must be taken not to extend the needle into the central nervous system. For safety, a 23 ga needle should never be inserted completely. This approach has proved successful in turtles of the genus Trachemys, Pseudemys, Chrysemys and Graptemys. In conclusion, this technique is easy to perform and appears suitable for hematology and blood chemistry analysis, and for the injection of intravenous drugs for anesthesia and euthanasia. Additionally, this method requires only one person to perform. The authors consider the occipital sinus as the preferred site for venipuncture in freshwater aquatic turtles.