Phlebotomy Techniques in Crocodilians
Assoc Reptilian Amphibian Vet 9[3]:12-13 Fall'99 Review Article 12 Refs

The goal of this article is to demonstrate venipuncture sites in crocodilians for blood collection as well as intravenous fluid and drug administration. Equipment: Depending on the size of the crocodilian, an 18 to 22 ga x 25 to 40 mm (1 to 1.5 in) needle may be adequate. Spinal needles however, may be required for animals over one meter snout-vent-length, particularly for cardiopuncture and caudal venipuncture. Syringe sizes will vary from 1 ml to 10 ml based on the sample volume required and as appropriate for the crocodilian size. An anticoagulant-coated syringe may be useful to prevent clotting with prolonged aspiration or to acquire an adequate volume. Many hemocytologists recommend heparin for reptiles to minimize cellular artifacts. Citrate may be preferred for clotting profiles, fibrinogen, live cell collection/storage, or transfusion. Techniques/Anatomic Location: 1. Occipital venous sinus [Immediately caudal to the occiput, on the dorsovertebral midline - Place the animal in sternal recumbency on a flat surface. Palpate the caudal occiput. Insert the needle caudal to the occiput into the midline dorsal venous sinus angling the needle perpendicular or 30 degrees caudad. Gentle ventroflexion of the neck may be used to widen the approach site at cervical vertebrae l, 2 and 3. Depending on the species and size, a palpable depression may exist between the caudal occipital margin and the first cervical osteoderm. 2. Caudal vein - The animal may be placed in dorsal recumbency to access the ventrum of the tail or the tail may be lifted vertically with the torso sternal. On the ventral caudal midline, insert a needle 60 degrees craniad and advance to the caudal vertebrae. The needle often contacts the ventral vertebral body prior to blood collection using this technique. The vein runs through the chevron bones ventral to the coccygeal vertebrae. This vessel may also be reached laterally by insertion at the longitudinal lateral groove where the dorsal and lateral epaxial muscles meet. The authors have not found this approach to be advantageous, but some prefer it in very large or obese animals. 3. Cardiac puncture [ventral midline immediately caudal to the xyphoid - With the animal in dorsal recumbency the heart is located on the midline, at the level of the 11th and 12th row of ventral scutes, caudad from the broad band just cranial to the forelimbs. For larger animals, over one meter, spinal needles as long as 7.5 to 15 cm are required to penetrate to the level of the ventricular lumen. An abrupt penetrating rapid insertion may be required to penetrate the mobile heart and tough ventricular myocardial wall of larger crocodilians. A slow smooth insertion may simply push the heart dorsally and no sample will be obtained even at the correct location. Risk of cardiac injury can be minimized by linear needle insertion. Myocardial damage is more likely with any lateral movement of the needle. Cardiac venipuncture can cause significant pathology and due care should be observed.