Necropsy: Taking a Blood Sample
When taking a blood sample for a hematocrit and plasma protein, draw a sample from a live but sedated fish. Use a 1cc tuberculin syringe with 26 guage or larger bore needle (fish size- dependent). Insert needle into Caudal fin at 45 degree angle until you hit the backbone. Pull back a small amount as you pull on the syringe plunger. For hematocrit and serum protein, only 1/10th of a cc is requiered. Blood can be placed into heparinized hematocrit tubes, and the ends sealed with clay.


Taking a Blood Sample

Where to locate the caudal vein with the syringe

 

Centrifuge Procedures

Place the hematocrit tubes, with the clay ends away from the center of the rotor, into the centrifuge. Make sure that the tubes are balanced in the rotor. Cover and spin at 2,000 x g for five minutes.

When the rotor has come to a complete stop, remove the hematocrit tubes. You can seen that the red cells have been separated from the serum. Just at the interface between the red cells and the serum, is the buffy coat, or layer of white cells (not clearly visable in the movie). Use one of the several types of hematocrit readers to determine the packed cell volume.

To determine the concentration of serum, or plasma protein, break the hematocrit tube above the buffy coat layer, and place a drop of serum on the prism of a refractometer. Units of serum protein concentration are in mg/deciliter.

 

 
 
Next