Dear Phlebotomy Guru:

We had a situation where a phlebotomist collected blood from patient A, labeled the tubes and puts them in the rack next to the outpatient drawing chair. Then she drew the next patient, Patient B, and put each tube in the same rack. Before removing the needle from Patient B, she wanted to add more blood to one of the tubes, so she picked it out of the rack and pushed it back into the tube holder to fill further. That's when she discovered the tube she picked up was from Patient A, not Patient B.

Obviously, samples from both patients need to be recollected. But what we're wondering about is the potential for Patient A's blood to backflow into Patient B's vein. The phlebotomist used a tube holder and multi-sample needle. What should we do?

My response:

This was really unfortunate. We're sure the phlebotomist felt terrible about this mistake, and we applaud her for bringing it to your attention. It would have been easy for a phlebotomist of lesser integrity to keep it to herself. But she put the patient's safety ahead of her own concerns. She should be recognized for the courage to speak up.
     Keeping this from happening again is as simple as changing your processes so that tubes from multiple patients are never in the same rack. For outpatients, that could mean two racks, one designated for prior patients and one designated for the patient in the chair. Alternatively, you could require tubes to be taken out of the draw stations between patients and delivered to the processing area or pneumatic tube station. For inpatients, it would require a second rack or other receptacle for previously drawn patients so that the current patient's tubes are not commingled. In this unfortunate case, the fact that Patient A's tubes were labeled was not enough of a distinction to prevent one from being placed into the tube holder being used on Patient B. A better mechanism is required.

Now, on to the more serious issue. Whether or not Patient A's blood backflowed into Patient B's vein, carrying potential pathogens with it, is hard to say. It depends on how Patient A's tube of blood was oriented when it was put into the tube holder being used on Patient B. If the partially filled tube of Patient A was oriented with the cap upward, Patient A's blood would not have come in contact with the stopper, nor the needle that pierced it. However, if the tube was angled downward, the blood in the tube would have come in contact with the stopper, and the needle piercing it could have allowed some of Patient A's blood to reflux into Patient B. We realize the phlebotomist probably has no recollection of how the tube was oriented, though.

But if it was oriented downward, two facts suggest the risk is real.

1) Most manufacturers of blood culture bottles do not recommend their blood culture bottles to be inverted inserted directly into a tube holder/multi-sample needle assembly because of the potential for broth to backflow into the patient. It stands to reason, therefore, that if broth has the potential, so does blood from a blood tube.

2) In Section 2.9.7.1, GP 41 states "If possible, ensure the patient's arm or other venipuncture site remains in a downward position to prevent reflux or "backflow" from the collection tube into the vein." It cites a 1975 article from the Can Med Assoc Journal. It's an old reference though.

So you'll need to weigh these carefully along with all the other ramifications when determining whether to notify the patient.