Minimizing Hemolysis

Drawing blood from animals without causing hemolysis requires careful technique and consideration of the species.

1. Choose the Right Equipment: Use an appropriately sized needle and syringe or a vacuum blood collection system. For most animals, a 20–22-gauge needle is suitable, but smaller animals may require finer needles.

2. Select the Vein Carefully: Common sites include the jugular vein (for larger animals like dogs, cats, or livestock), cephalic vein (forelimb), or saphenous vein (hindlimb). For rodents, the tail vein or retro-orbital sinus may be used.

3. Minimize Stress: Manage the animal gently but securely to reduce stress, which can affect blood quality. Use proper restraint techniques or sedation if necessary.

4. Prepare the Site: Clip the fur around the puncture site if needed and clean it with minimal alcohol. Allow the site to air dry completely to avoid damaging red blood cells.

5. Draw Blood Gently: Insert the needle at the correct angle for the vein being used. Avoid excessive suction or rapid withdrawal, as this can cause hemolysis.

6. Manage the Sample Properly: If using a syringe, remove the needle before transferring blood into collection tubes to prevent cell damage. Use the correct “Order of Draw” and gently invert the tubes 8-10 times to mix. (See Order of Draw below)

7. Prevent Clotting: Use anticoagulant-treated tubes if required and ensure the correct blood-to-anticoagulant ratio. Avoid overfilling or underfilling the tubes.

8. Store Samples Correctly: Label the tubes immediately and store them as per the test requirements. Refrigerate or process the sample promptly to maintain quality.

9. Species-Specific Considerations: Different animals may have unique anatomical or physiological factors. For example, birds often require blood collection from the basilic vein or jugular vein, and care must be taken to avoid excessive blood loss.

By following these steps, you can ensure a high-quality blood sample while minimizing stress on the animal and hemolysis of the sample.

The "Order of Draw" is a guideline followed during blood collection to prevent cross-contamination between additives in blood tubes and ensure accurate test results. Here is the general order recommended by the Clinical and Laboratory Standards Institute (CLSI):

1. Blood Culture Tubes (or bottles) – Used for microbiology tests to detect infections.

2. Light Blue – Contain citrate for coagulation studies.

3. Red or Gold (SST) – Serum tubes, with or without clot activators, used for chemistry tests.

4. Green – Contain heparin for plasma chemistry and some specialty tests.

5. Lavender or Pink – Contain EDTA for hematology tests or blood typing.

6. Gray – Contain fluoride/oxalate for glucose and lactate measurements.

For certain animals, species-specific needs may adjust this order, but these guidelines apply broadly to most veterinary samples.