Blood Collection Procedures
What you must understand
Expect questions on sequence and technique. Standard venipuncture: verify identity and orders, prepare supplies, position the arm, apply the tourniquet 3–4 inches above the site for no more than about a minute, palpate, cleanse with 70% isopropyl alcohol in concentric circles and let it dry, then insert bevel up at roughly a 15–30 degree angle. Release the tourniquet before removing the needle, apply gauze with pressure, activate the safety device, and bandage after bleeding stops. Hold pressure longer for patients on anticoagulants.
Needle choice: a 21-gauge is typical for adults, 23-gauge for fragile veins, and butterfly sets for small or difficult veins - remembering that a smaller needle raises hemolysis risk when used with full-vacuum tubes.
Memorize the order of draw: blood culture, light blue (citrate), red/gold serum, green (heparin), lavender (EDTA), gray (fluoride/oxalate). Culture bottles first keeps contaminants out of the needle; citrate second protects the coagulation ratio; EDTA after heparin reduces additive carryover.
Capillary collection: warm the site, cleanse and dry, puncture the lateral side of the distal phalanx of a non-dominant middle or ring finger, perpendicular and deep enough for free flow, and avoid squeezing hard (tissue fluid dilutes the sample). Infants: heel stick on the medial or lateral calcaneus, no deeper than 2 mm, never the arch or posterior heel.
Traps
- Filling a light blue tube only partially - the 9:1 blood-to-additive ratio is invalidated.
- Palpating after cleansing.
- Drawing above an infusing IV line.
Rule of thumb: "Cultures, Citrate, Serum, Sodium heparin, EDTA, Gray" - say it in order until it is automatic.