As I understand it, the vacutainer system used in modern phlebotomy should never result in air bubbles “glugging” into the vacutainer tube when blood is drawn from a patient.

However, today I learned that it does happen because it happened while my blood was being drawn. I was so surprised I didn’t know what to say. I’ve had my blood drawn many times and never experienced it. What are the circumstances in which this could occur? I also assume that the movement of air which causes the gurgling is air entering the vacutainer tube, not leaving it. Is there a circumstance in which air could leave the tube and enter the bloodstream during the blood draw?

I found a couple of articles — first is about results being skewed due to gas entering blood samples in pneumatic tube based: Air bubbles and hemolysis of blood samples during transport by pneumatic tube systems

Second article was about venous air embolism, which can also occur very rarely when blood is drawn. Historically this would be when it’s done with a needle and syringe — the point of the vacutainer system is that it should not be possible for air to enter the blood stream because the vial has a vacuum in it that “sucks” the blood out.

Interestingly, in my case, the glugging occurred with the first vial — I had two vials drawn — but the second vial filled as normal. So I’m wondering if the vacutainer system can fail in unexpected ways.

I suppose there’s also the Rumsfeldian “failure of imagination” scenario where one could pressurize a vacutainer tube with a gas and force the gas into someone’s bloodstream, but that’s clearly off topic. I’m more interested in the safety and efficacy of the vacutainer system in general and/or if blood test results can become unreliable even with the vacutainer system.

  • I would suspect one of two possibilities: the phlebotomist made an error or it was a defective tube, and I always rank pilot error as the most likely cause. The error I imagine might have been made was not attaching the Vacutainer to the catheter tightly, so it was able to suck air through the loose coupling.
    – Carey Gregory
    Feb 20 at 23:57
  • What sort of defect in the tube are you thinking of? Feb 21 at 1:57
  • I have no idea; it's just that a product defect always has to be on the list of possibilities. But I doubt that's the explanation. As I said, pilot error is the most likely explanation.
    – Carey Gregory
    Feb 21 at 2:46


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