Phlebotomy Principles and Sites

Study Notes

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.

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

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.

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.

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.