The Terrapin Journal
Summer 2003

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Blood Sample Collection — Comparison of Two Collection Sites

By Luu Canh Trung



Luu Canh Trung and Dr. Ralph Warner draw
blood sample from a diamondback terrapin.
This summer the Terrapin Project started to carry out studies on the biochemical and molecular aspects and the health status of chelonians.  These are recognized as essential components of the conservation program.  Blood has obviously been one of the best choices of tissues to study.

However, the lymphatic system in turtles is often in close proximity to superficial veins, and when performing venipunctures for blood samples it is possible for lymph to mix with venous blood and dilute the sample.  Because diluted blood samples can skew research results, it is necessary for researchers to look for better methods of collecting accurate blood samples without harming or sacrificing the animal.



Drawing blood sample from the coccygeal vein

The aim of this study was to find out what site is better to collect blood in a diamondback terrapin — the dorsal caudal vein or the femoral vein.

The general procedure applied for this technique is as follows: With the turtle immobilized as much as possible, insert the needle slowly, while maintaining a slight negative pressure in the syringe, until you get a flash of blood in the syringe. Once blood is observed in your syringe, stabilize the needle and continue with a slight negative pressure in the syringe.

For this study, blood was collected in a 1 ml syringe with a 26-gauge 5/8" needle attached.  The volume of each blood sample taken from either vein in the study was 0.3 ml or less.  The first sample was taken from the dorsal coccygeal vein followed immediately by a sample taken from the femoral vein of the same terrapin. 


Drawing blood sample from the femoral vein
A heparinized microhematocrit tube was filled for packed cell volume (PCV) determination by centrifuging.  A drop of blood was then placed in a hemoglobinometer chamber, hemolyzed with an applicator stick, and the hemoglobin concentration was then measured.

Initial results of the experiment reveal that blood collected from femoral vein is slightly better in terms of lymph contamination than blood collected from the dorsal coccygeal vein.  Average percentages of packed cell volume from the dorsal coccygeal vein were 24.32% compared with 32.56% from the femoral vein.  The femoral samples therefore contain 8.24% less lymph than those collected from the coccygeal vein.  Blood collected from the femoral vein is higher quality and will reflect the health status of the turtle more accurately, making this collection site practical.  It is, however, more difficult to collect blood from from the femoral vein and requires considerable practice.


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