Phlebotomy Principles and Sites

Specimen Collection Principles

• Venipuncture is a medical procedure extracting blood from a vein.
• Veins are preferred for blood extraction due to their superficial location, less nerve density, and lower pressure compared to arteries.
• Patient identification is crucial. Full name and date of birth should be verified from patient ID bands or bracelets.
• When a patient is sleeping or unconscious, gently wake them or ask a relative, nurse, or physician for identification.

Phlebotomy Sites

• Antecubital veins (triangular space in front of the elbow) are the primary sites for venipuncture.

• Median vein is the preferred site due to safety, ease of access, and minimal pain.

• Cephalic vein is a secondary choice, suitable for obese patients.

• Basilic vein is the least preferred due to potential pain.

• Other sites (dorsal veins, leg, ankle, and foot veins) are used only when antecubital veins are unavailable, with caution and physician consent.

• Dorsal veins on the hand are used as a last resort site; they can be painful.

• IV lines should be avoided as venipuncture site

Capillary Puncture

• Used for small blood samples when veins are inaccessible, infants/children, or POCT testing.
• Puncture should be less than 2mm.
• Earlobe and lateral plantar heel are preferred for blood gas analysis in infants and newborns.

Venipuncture Equipment

• Tourniquet: A constriction device used to inflate veins during venipuncture.
• Needles (multi-sample, hypodermic, winged infusion): Sterile single-use needles with varied gauges (diameter). Higher gauge number indicates a smaller diameter.
• Evacuated tube system (ETS): a closed collection system that ensures samples do not contaminate other tubes and prevents blood from leaking out.

Blood Collection Tubes

• Color-coded tubes: Different colors indicate different additives (inhibitors) that prevent clotting or perform specific reactions.
• Anticoagulants: Prevent blood clotting (e.g., EDTA, heparin).
• Clot activators: Used for serum collection where clotting is desired (e.g., red-topped tubes).
• Additives: Specific chemicals for glucose preservation or other tests.

Order of Draw

• A specific sequence for collecting multiple tubes to avoid cross-contamination.
• Crucial for accurate test results and specific sample handling.

Additional Notes

• Gold tubes are not suitable for blood banking (potential interference)