30 Minutes or Less

How many people have heard of the 30 minute rule for units of returned blood? If you haven’t there is folklore that says once a unit of blood leaves the blood bank it is ok to return it to inventory if they get it back before 30 minutes are up. We even have a place on the documentation that accompanies the unit of blood to write down the time that we can accept a return. It was recommended to us that we get an infrared temperature meter so we could actually take the temperature of units when they are returned. One day I decided to play with my new toy and figure out how long a unit could really be out and still be ok to return. Our policy states a unit can be returned if the temperature is 10 degrees Celsius or colder.

I split my little experiment into two parts. Using an expired unit of blood, I left the unit on the counter and took the temperature every minute for 30 minutes. For the second part, I held an expired unit in my hand (simulating a nurse or transporter carrying the unit) and took the temperature every 2 minutes. In the first experiment the unit of blood reached 10°C in 19 minutes; at 30 minutes I recorded a temperature of 14°C. As expected, holding a unit in my hand sped up the rise in temperature; it took 12 minutes for the unit to reach 10°C. After 30 minutes the same unit was 17°C.  In both experiments I mixed the blood before rolling the unit of blood around the thermometer.

This very informal experiment confirmed my suspicion that the temperature of a unit of blood is environment dependent. Put the unit in a warm room and it will warm up faster than if it were in a cold room. When we dispense units we place the unit in a thin plastic bag; the plastic on the blood units themselves is thin as well. There is no insulation from the unit and our warm hands.

So what do you do with this information? If you have a policy or use the 30 minute rule, I recommend suspending it immediately. There is no way of knowing what happens to that blood once it leaves your blood bank. If you do not have an infrared temperature meter, put it on the capital wish list for 2014. They will save you from taking back blood that is not safe and it will put a finite cut off point for taking units back. Once we started using the meter we found that the majority of blood that comes back is not suitable for reissue and ends up being disposed. While we do waste blood, I feel much better knowing that the blood that we do take back is suitable for transfusion and is ultimately better for the patient.

It is performing little experiments like the one outlines above that keeps us all interested in the laboratory field. What other career can you have a question about something, know how to figure out an experiment to find the answer, and then carry it out to see if you were right or not?  Now the real question I have is: when I order the pizza for lab week what are the chances it gets here in 30 minutes or less?


Tommy Transfusion is the pseudonym of a blood bank supervisor in the midwest.

6 thoughts on “30 Minutes or Less”

  1. First of all, who is gonna leave the unit of blood at the room temp the whole time? The blood bank personnel should tell nurses how to handle (leave it in the control cooler) prior to issue in first place. Second of all, who is gonna be holding the blood on their hand the whole time if they don’t need to transfuse? Finally, I totally disagree with your experiment.

  2. We validated ours so they can be out 45 minutes before they reach 10C. Suggest each place do their own validation for it.

    1. Tony, that is pretty extreme but that definitely saves you from having to determine whether you can re-use a unit or not. We will only reject a unit from return if it has been spiked or if it is over the 10C. Thanks for the comment!

  3. LB: I’m curious as to how you validated 45 minutes, equipment used, etc. I love hearing how different labs do it.

    “Welcome:” I’m sorry that you didn’t agree with my experiment but there are many times that people become distracted and a unit of blood is left siting at a nurse’s station. Not to mention all of the steps it takes to get the blood and patient ready to transfuse. Have you ever received an ammonia that was very high more than likely caused by it not being placed on ice quick enough? Also if you have a large facility it may take 10 minutes or more to travel to a floor and do the necessary checks at the nurse’s station only to realize that the blood needs to be sent back. We all know that nurses are human and we can tell them how to do things exactly but deviations still happen. You may have a process at your facility but across the country there may be hundreds of different policies and procedures that technologists follow. Your world may be very different from everyone else.

    Thank you for the comments and please look for future articles!

  4. Everyone should keep in mind that production of that unit of blood also uses the 30 minute rule after it has been in the fridge. HOWEVER: Let’s keep an open mind and be realistic about how long blood is initially out of the fridge. Once it is drawn from the donor and brought immediately to the components lab we are allowed to process that blood in a controlled temperature room for up to 8 HOURS WITHOUT putting it into the fridge. Just keeping things in perspective here!!!!!.

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