Part of the ICU Emergencies Hub — browse every related guide in one place.
The order of draw exists to prevent cross-contamination between tube additives. Drawing a coagulation tube (citrate) after a lavender tube (EDTA) without following the correct sequence can contaminate the citrate sample with EDTA — causing false coagulation results. The CLSI order of draw standard:
| Order | Tube Color (US) | Additive | Tests |
|---|---|---|---|
| 1 | Yellow (SPS) or Blood Culture bottles | Sodium polyanethol sulfonate (SPS) | Blood cultures — always first to minimize contamination |
| 2 | Light Blue | Sodium citrate (1:9 ratio with blood — must fill to line) | PT/INR, PTT, coagulation studies |
| 3 | Red (or Gold/SST) | None (red) or gel separator with clot activator (gold/SST) | Chemistry panels, serology, blood bank (crossmatch uses plain red) |
| 4 | Green | Heparin (lithium or sodium) | Stat chemistry, ionized calcium, ammonia |
| 5 | Lavender (Purple) | EDTA | CBC, blood bank (some facilities), HbA1c |
| 6 | Pink | EDTA | Blood bank/type and screen (facility-specific) |
| 7 | Gray | Sodium fluoride + potassium oxalate | Glucose, lactate (preserves glucose; inhibits glycolysis) |
Site selection: Antecubital fossa (median cubital, cephalic, or basilic veins) is the preferred primary site for most adults. Avoid: arm with IV infusion running (dilutes specimen — if unavoidable, stop infusion for 2 minutes first and discard the first 5 mL drawn); arm with lymph node dissection or fistula (lymphedema risk, fistula damage); arm with phlebitis or active infection. Dorsal hand veins are acceptable secondary sites. Do not draw from a central line without specific order and training — risk of catheter damage and altered specimen quality.
Tourniquet time: Apply 3–4 inches above the intended draw site. Tourniquet must be released within 1 minute of application — prolonged tourniquet causes hemoconcentration (falsely elevated potassium, protein, hemoglobin) and hemolysis. If still setting up after 1 minute, release and reapply after 2 minutes.
Insertion angle: 15–30 degrees bevel up. Shallower angle for superficial veins; steeper for deeper veins. Feel the needle enter the vein — a slight "pop" or give signals entry. Advance slightly after entry to ensure the full bevel is inside the vein before attaching tubes.
Tube changes: Keep the needle and arm still while switching tubes — movement causes the needle to move within or out of the vein. Hold the tube holder steady and use the other hand to push tubes in and pull them out.
| Cause | Prevention |
|---|---|
| Drawing through a small gauge needle too forcefully | Use the largest gauge tolerated; use gentle vacuum pressure; avoid forceful syringe aspiration |
| Excessive tourniquet time | Release tourniquet within 1 minute; release before withdrawing needle |
| Mixing tubes too vigorously | Gently invert (do not shake) the required number of times per tube type |
| Transferring blood from syringe to tube too forcefully | Remove needle from syringe before transfer; allow blood to flow gently into tube via gravity or gentle push |
| Drawing from a hematoma site | Select a different vein; damaged cells lyse easily |
| Specimen exposed to heat or cold extremes | Transport at room temperature; do not refrigerate most specimens unless specifically required |
Blood cultures must be drawn before antibiotics are given whenever possible — antibiotics reduce bacterial yield and can cause false-negative results. The standard is two sets from two different sites (reduces contamination interpretation — a contaminant like coagulase-negative staph typically grows in only 1 of 2 sets; a true bacteremia grows in both). Each set consists of an aerobic bottle and an anaerobic bottle.
Skin prep for blood cultures is stricter than routine phlebotomy: Clean the skin with 70% isopropyl alcohol and allow to dry fully, then apply chlorhexidine gluconate (or povidone-iodine) in a concentric circle outward and allow to dry 30–60 seconds before puncturing. Do not repalpate the site after prepping without re-gloving or using a sterile finger. Inject blood into aerobic bottle first (oxygen in the syringe enriches aerobic culture). Fill each bottle to the marked volume line (typically 8–10 mL per bottle for adults). Label bottles at the bedside immediately — never pre-label.
Warm the arm — heat vasodilates superficial veins and significantly improves venous prominence. Apply a warm compress for 5–10 minutes before attempting. Gravity-dependent positioning: lower the arm below heart level to increase venous filling. Hydration: dehydrated patients have collapsed veins — if non-urgent, consider oral or IV hydration first. Butterfly needles (winged infusion sets) provide better control for small, rolling, or fragile veins (elderly, pediatric, oncology patients). After two failed attempts by the same nurse, call for assistance rather than continuing to traumatize the patient's veins.
Related guides: IV complications | Central line care | Medical abbreviations
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