Winged Set, Short Citrate, and a Patient Who Faints
It is 23:10 in the emergency department and you have an order set for a 58-year-old woman: PT/INR, aPTT, basic metabolic panel, and CBC. Her antecubital veins are scarred and barely palpable after years of IV drug use; the only usable vessel is a thin dorsal hand vein, so you plan a 23-gauge winged collection set with 12 inches of tubing. She tells you she fainted during her last blood draw and asks you to "just get it over with quickly." Her right forearm has a saline lock that has not been accessed in eight hours. Laid out in front of you are two light blue 3.2% sodium citrate tubes, one gold serum separator tube, and one lavender EDTA tube.
1. State the order of draw for these four tubes and explain what you must do first because you are using a winged set with tubing.
Read the worked answer
Order of draw:
- Light blue (citrate) - PT/INR
- Light blue (citrate) - aPTT
- Gold serum separator
- Lavender EDTA
This follows the standard sequence: coagulation tubes before serum tubes, then heparin, EDTA, and glycolytic-inhibitor tubes last. Within the same additive type, tubes are grouped together.
The winged-set step: draw a discard tube first. With a butterfly and 12 inches of tubing, the dead space contains air. If the first analytic tube is a citrate tube, that air transfers into it and shortens the fill, changing the blood-to-additive ratio. The result is falsely prolonged clotting times from a specimen that looks perfectly adequate.
Practical points:
- The discard may be a non-additive waste tube or an extra citrate tube that is thrown away. A second citrate tube is the safe substitute when no plain tube is on the cart.
- Only the first tube needs the discard - once the tubing is primed, subsequent tubes fill correctly.
- Draw from the left arm or the hand; avoid the extremity with the saline lock, and never draw above an infusing line.
2. The first light blue tube stops at 2.0 mL against a 2.7 mL draw volume. The vein has collapsed. What do you do, and why can't you just send it?
Read the worked answer
Do not send it. 2.0 mL of 2.7 mL is about 74% of nominal, well below the roughly 90% minimum. The tube is underfilled and the result is not interpretable.
Why the ratio matters: citrate tubes contain a fixed amount of liquid sodium citrate calibrated to the draw volume. Too little blood means proportionally too much citrate, which chelates calcium beyond what the clotting cascade can overcome - clotting times come out falsely prolonged. A clinician acting on that could adjust anticoagulation on the strength of a collection artifact.
What to do:
- Discard the short tube and recollect, from a different site or with a larger, more suitable vessel.
- Do not pour blood between tubes, do not top up from a second tube, and do not "adjust" the result.
- Anticipate the short draw before you start: for a fragile dorsal vein, consider whether a 23-gauge winged set can actually deliver 2.7 mL before the vessel collapses, and choose the largest vessel the patient can tolerate.
- If recollection is delayed, tell the ordering provider rather than letting the result sit unreported, and document what happened.
Single exception worth knowing: an underfilled citrate tube is only acceptable in rare situations where the patient's hematocrit is markedly elevated and the tube is filled to the volume specified by the laboratory for that condition - that is a laboratory-directed decision, not a bedside workaround.
3. Mid-draw, she turns pale and diaphoretic and says she feels warm. What are your immediate actions, and what happens to the specimens you have already collected?
Read the worked answer
Immediate actions, in order:
- Release the tourniquet.
- Remove the needle and apply firm pressure with gauze - do not leave the needle in place while she goes down.
- Lower her head relative to her heart - supine or a reclined position with legs elevated if she is on a chair - and protect her from falling.
- Stay with her. Call for help; do not leave the patient to file paperwork or carry specimens.
- Cool cloth, loosen tight clothing, monitor until she is conscious, oriented, and has color back. If she does not recover promptly, escalate as a medical emergency.
Specimens already drawn: they are still usable if they were collected correctly and mixed. Tubes with additive should be inverted per policy. Label at the bedside once she is stable and can be identified - labeling is done in the patient's presence, and a fainting episode does not change the identity requirements.
Afterwards: document the vasovagal episode, the position you used, and the recovery. Flag her record so the next collector draws her supine, and tell her before she leaves that she should ask to lie down for future draws - that is the intervention that prevents the next event.