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Utility of temperature-sensitive indicators for temperature monitoring of red-blood-cell units

Mikyoung Park, Mina Hur, Ahram Yi, Hanah Kim, Hyun Kyung Lee, Eun Young Jeon, Kyung-Mi Oh, and Mark Hong Lee. Vox Sanguinis 2019; 114; 487-494.

Reviewed by Mary Berg, MD

There has been much debate about the ‘30-minute-rule’ with regard to the transport and storage of red blood cell (RBC) units.  The authors of this study performed two well-controlled experiments to get a better understanding of the factors that affect RBC unit temperature.  First, they applied two different temperature sensitive indicators to 50 RBC units that were then issued for transfusion and recorded how long it took for the indicators to achieve a color change indicative of the unit reaching 10 degrees celsius.  The temperature indicators used were the SafetyVue10 (STV10, Temptime Corporation, Morris Plains, NJ) and the Timestrip Blood Temp 10 (BT10, Timestrip UK Ltd, Cambridge, UK).  Factors that were controlled for this study included when the temperature indicators were applied (at the time of issue), where on each unit of blood the indicators were applied (lower portion, near the ports), the age of the units (25-27 days), the type of unit (CPDA-1), where the units were transfused (for consistent transport time and environmental conditions during transfusion), and duration of the transfusion (92-113 minutes, median 100.5 minutes).

One author was responsible for reading the temperature indicators (for consistency) and another author verified the first author’s finding in five cases.  What was described for this experiment is that the BT10 changed color much earlier than the STV10 (median 5.6 minutes versus 19.0) minutes.  The STV10 had great variability as to when the color changed (interquartile range 10.1 to 23.0 minutes) compared to the BT10 (interquartile range 4.9 minutes to 7.5 minutes).  In addition, the authors indicate that 4% of the STV10 and 18% of BT10 showed initial color change during transport; 94% of STV10 and 100% of BT10 showed the color change within 30 minutes of being issued.  In addition to the variability of time for the color change, the authors commented on the difficulty in interpreting the color change. (Was it partially red or pink or completely red?)

The second part of the experiment involved 18 RBC units that were intended to be discarded, usually due to an elevated ALT measurement in the donor.  A type K thermocouple was inserted into each unit and the BT10 and STV10 temperature indicators were applied to the surface, similar to the units in the other experiment.  These units were then transported similar to the units in the first experiment to simulate transfusions.  Also similar to the first experiment, a second observer verified the reading of the temperature indicators for five units.

For this second experiment, the time to reach 10 degrees C was 24.4 + 7.4 minutes for the STV10, 14.3 + 6.4 minutes for the BT10, and 20.6 + 7.6 minutes for the core temperature reading.  With continuous reading of the core temperature, they found the median to be 10.1 C at 20 minutes, 11.0 C at 25 minutes, and 12.0 C at 30 minutes.

Although this was a small study, it was well-controlled and did a good job to demonstrate the variability of temperature indicators available for clinical use.  In addition to the debate of whether the ’30 minute rule’ is appropriate, the authors ask if the ’10 C’ rule is appropriate. (Is a unit more likely to be contaminated at 10.2 C than it might be at 9.8C?)  Reaching a consensus on these questions will require future debate, more data, and the ability to more consistently measure the temperature of units of blood.

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