The Lymphedematous Arm, the Hematoma, and the Short-Draw Lavender Tube
A 62-year-old inpatient with a saline-locked 22-gauge IV in the right antecubital fossa needs a STAT basic metabolic panel, CBC, PT/INR, and two sets of blood cultures. Three years ago she had a left mastectomy with axillary lymph node dissection; her left arm is visibly lymphedematous. The right antecubital area carries a 4 cm hematoma from a 6:00 a.m. draw, and the IV was placed 90 minutes ago. No fluids are infusing now, but the line is due for a flush. She is a known difficult stick and the nurse mentions that the last two draws were "below the IV." It is 6:45 a.m.; the ED has called twice for results. On your second attempt a usable vein yields everything except that the lavender tube fills to only about 1 mL of its 4 mL draw volume.
1. Where do you draw, and in what order do you collect the cultures and the four tubes? Justify each site you excluded.
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Excluded sites, with reasoning
- Left arm: axillary node dissection plus visible lymphedema. Venipuncture on that side risks lymphangitis/cellulitis and gives blood that may not reflect systemic values. Not an option for any tube.
- Right antecubital fossa: an active 4 cm hematoma means drawing through a collection of extravasated blood - pain, hemolysis, and unreliable results - and the tissue is already traumatized from a 6:00 draw.
- Right arm proximal to the IV: drawing above a cannulated vein risks dilution/contamination from the infusate and flush solution.
Chosen approach: a vein in the right hand or distal forearm, below both the hematoma and the IV site, using a 23-gauge butterfly. If no vein is accessible, drawing from the IV after stopping the flush, flushing with saline, and discarding 5–10 mL is a documented last resort - line draws carry higher contamination and hemolysis rates and should be noted as such on the requisition.
Order of draw: blood culture sets first (aerobic bottle before anaerobic), each set from a separate venipuncture site; then light blue (PT/INR) - with a winged set, draw and discard a small waste tube first so the dead space in the tubing does not underfill the citrate tube; then serum separator (gold), lithium heparin (green) for the BMP, and EDTA (lavender) last. Blood cultures before everything else protects against contamination of the bottles from tube additives and septa.
2. The lavender tube holds roughly 1 mL of its 4 mL draw volume. The patient is tearful and says she will not do another stick, and the CBC is not flagged STAT. What do you do, and what would reporting that tube do to the results?
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Do not report it. The tube has roughly four times the intended ratio of liquid EDTA to blood. The consequences are predictable and not correctable: dilution of the sample by the anticoagulant solution, osmotic shrinkage/crenation of red cells, falsely reduced MCV and hematocrit, a spuriously elevated MCHC, and unreliable platelet counts and morphology. Underfilled EDTA tubes are rejected for hematologic analysis; there is no valid correction factor to apply.
Sequence: since the CBC is not STAT, do not force a third stick immediately. Explain the problem through the situation - not the technical detail - that the sample cannot be analyzed and that a small additional draw is needed; offer to let her lie down, use a smaller-gauge butterfly, and involve the nurse. If she continues to refuse, document the refusal verbatim, notify the ordering provider and the nurse so the CBC can be redrawn with the next scheduled draw, and note in the record that the previously collected lavender tube is unusable. Do not place the short tube in the analyzer to "see if it works" - a plausible-looking result from a rejected specimen is the most dangerous outcome here.
3. The nurse suggests using the IV line for everything to spare the patient further sticks. How do you respond, and what would change your answer?
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Peripheral venipuncture remains the preferred source, and I would say so plainly: line draws carry a higher blood culture contamination rate and a higher hemolysis rate, and they risk dilution from the infusate and flush, which is precisely the failure mode that produces a falsely low potassium or a falsely low glucose and drives the wrong clinical decision.
What would change my answer: absent peripheral access after a genuine attempt (documented), or an emergency in which delay is the greater harm. In that case: stop the infusion, flush the line with saline, allow a short dwell, discard the first 5–10 mL, then collect - and flag on the requisition and in the LIS that the specimen is line-drawn so the provider interprets it in context. Blood cultures drawn from a line should be paired with a peripheral set wherever possible so a differential time-to-positivity can be interpreted.