Abstract
A variety of sites have been described for the purposes of blood collection and intravenous drug administration in chelonians, including the heart, jugular vein, brachial vein, ventral coccygeal vein, dorsal coccygeal vein, and the post-occipital sinus.1,2 However, another large vessel that is positioned in a supravertebral position, just below the carapace, is available for blood collection and injection.3
This vertebral vessel may be approached with either the head extended from, or retracted into, the coelom. For example, in the red-eared slider (Trachemys scripta elegans) a 22-ga, 1-inch needle is positioned dorsal to the head and neck, on the midline close to where the skin attaches to the cranial rim of the carapace. The needle is advanced caudally at an angle (to the horizontal) of 0° to 60° incline and the vessel is located just dorsal to the spine.
This vein is particularly useful for blood collection from, or intravenous injection in:
1. Small or dehydrated individuals where peripheral vessels may be very small.
2. Those species that possess a front plastron hinge (e.g., Terrapene spp.).
3. Strong individuals that are capable of resisting head extraction for jugular sampling.
4. Individuals where the jugular or associated areas have been damaged or diseased.
5. Individuals where the jugular vessel is catheterized or is being reserved for catheterization.
6. Blood donor chelonians, where large volumes of blood are required quickly and easily.
Contrast radiography was performed by injecting iohexol (Omnipaque, Sanofi Winthrop Pharmaceuticals, New York, NY, USA) at 500–580 mg/kg IV into the aforementioned vessel of two red-eared sliders (Trachemys scripta elegans) via the previously described technique. A distinct line of radio-opaque material was noted coursing along the midline in both cases. Iohexol was also injected into the equivalent vessel of an eastern box turtle (Terrapene carolina) and fluoroscopic radiography performed. Within 10 sec, the contrast material was identified in the heart. This suggests that the contrast material drained from a vertebral vessel to the junction of the external jugular vein into the heart. Anatomic dissections to further describe the position and utility of this vessel are underway.
This vessel has been utilized by the veterinary coauthors for blood collection and injection of anesthetic drugs, such as propofol, without any untoward effects. Therefore, it is recommended as a potentially valuable IV access site in chelonians.
Literature Cited
1. Murray, M. 2000. Reptilian blood sampling and artifact considerations. In: Fudge, A.M. (ed.). Laboratory Medicine: Avian and Exotic Pets. WB Saunders Co., Philadelphia, Pennsylvania. Pp. 185–192.
2. Olson, G.A., J.R. Hessler, and R.E. Faith. 1975. Techniques for blood collection and intravascular infusion in reptiles. Lab. Anim. Sci. 25:783–786.
3. Divers, S.J. 2000. Diagnostic techniques in reptiles. Proceedings of the North American Veterinary Conference, Vol 14, Orlando, Florida, Pp. 932–935.