Contributors: Sheilah Ann Robertson
Species: Feline | Classification: Techniques
- Good sample collection technique is vital to successful biochemical and hematological analysis of blood Standard venipuncture.
- Jugular vein gives rapid, unobstructed flow of blood.
- Peripheral veins, eg cephalic and saphenous, often detrimental → slow blood flow → sample artifacts (hemolysis and microclots).
- Collection of blood for analysis.
- Simple technique (unless difficult animal).
- Difficult to apply sustained pressure to venipuncture site if required.
- Poor technique or sampling from an animal with coagulopathy may result in significant bruising/hemorrhage.
- Cephalic venipuncture (offers no real advantages).
- Placement of jugular catheter Jugular catheterization.
- Success depends on good holding and raising of vein.
- Fast 6-12 hours before sampling, if possible, to avoid sample lipemia.
- Jugular vein - ventral cervical region approximately 2/3 of the way to angle of mandible from thoracic inlet.
- Restrain animal in sitting position.
- Sit near the edge of table.
- Sampler squats in front of cat.
- In some animals it is easier to restrain them in sternal recumbency.
- Tip back head to expose jugular grooves.
Step 1 - Preparation
- Clip the hair over vein.
- Cleanse skin with surgical spirit.
Step 1 - Locate vein
- Sampler applies pressure just cranial to thoracic inlet to occlude venous return and raise vein.
The vein may be located by feel or sight.
- Vein is raised and lowered (left hand), jugular groove palpated with fingers of right hand to locate the vein.
- Vein is more often visualized on release of pressure not when it is filling with blood.
Step 2 - Collect blood sample
- Insert needle into vein directed towards head until blood appears in needle hub.
- Withdraw blood by gentle suction on syringe.
If needle bevel against wall vein - rotate slightly → easier blood flow.
- If using vacutainer connect needle to vacuum once blood appears in hub and allow blood to flow into container until filled to mark.
Vacutainer may collapse vein particularly in small patients.
Step 1 - Remove needle
- If posting, package according to Post Office regulations Transportation of diagnostic specimen.
- Refrigerate prior to despatch or if delay in in-house processing.
- Separate plasma/serum within 30 minutes of sampling (especially for glucose) - if possible.
Reasons for Treatment Failure
- Poor technique may preclude venipuncture.
- Repeated attempts at venipuncture may damage vein sufficiently to prevent further sampling.
- Repeated entry into same site with same needle → introduce tissue proteins → abnormal results.
- Use of too fine a needle.
- Failure to remove needle from syringe prior to placing blood in tube.
- Needle pushed directly through evacuated tube top. Fluid flow under pressure inevitably damages the RBCs. Hence remove bung and gently release blood from syringe.
- Excessive back pressure when withdrawing blood.
- Mailing samples (time related).
- Minimize by separating serum/plasma from clot or heparinized samples before sending sample.
Difficulty in extracting sample
- Excess skin folds.
- Vacutainer in cat → collapsed vein.
- Excess back pressure.