Venipuncture and order of draw

Principle

• Collection of venous blood into evacuated tubes in a set sequence (CLSI GP41) so additives are not carried over from one tube to the next.

Specimen

• Venous blood, most often from the median cubital vein; the cephalic vein is the next choice; the basilic vein is last because of nearby nerves and the brachial artery.

Reagents and equipment

• Gloves, tourniquet, 70% isopropyl alcohol, gauze, needles (typically 21 gauge; 22–23 gauge or butterfly for small veins), holders, tubes, sharps container, labels.

Procedure

• Identify the patient with at least two identifiers and match to the request; check fasting or timing requirements.
• Apply the tourniquet about 7.5–10 cm (3–4 inches) above the site for no longer than 1 minute.
• Clean the site with alcohol and let it air-dry.
• Anchor the vein and insert the needle bevel up at about 15–30°.
• Order of draw: blood culture (sterile) tubes/bottles, sodium citrate (light blue), serum tubes with or without clot activator or gel (red, gold), heparin (green), EDTA (lavender/pink), sodium fluoride/potassium oxalate (gray).
• With a butterfly, draw a discard tube before the citrate tube if it is the first tube, to fill the tubing dead space.
• Invert tubes gently right after filling (commonly citrate 3–4 times, serum 5 times, heparin, EDTA and fluoride 8–10 times; follow the manufacturer).
• Release the tourniquet as blood flows into the last tube, remove the needle, activate the safety device and apply pressure with gauze.
• Label tubes at the bedside in the patient's presence.

Quality control and pitfalls

• Citrate tubes must be filled to the fill line (9:1 blood to anticoagulant).
• EDTA carryover falsely raises potassium and lowers calcium and ALP.
• Hemolysis: small needle with forceful draw, vigorous mixing, wet alcohol, prolonged tourniquet.
• Avoid arms with IV infusions, the side of a mastectomy (per policy), fistulas, hematomas and edema.
• Complications: hematoma, fainting, nerve injury and accidental arterial puncture.
• Cap colors can vary by manufacturer; the additive defines the order.

Clinical use

• Routine blood collection for chemistry, hematology, coagulation, immunology and blood bank testing.