The 30-minute rule for reissuing blood: are we needlessly discarding units?

The standards of the American Association of Blood Banks require that blood for reissue must be maintained continuously between 1 and 10 degrees C. To comply with this standard, most transfusion services have set a 30-minute limit on the time that a unit of blood can be out of a monitored refrigerator before it must be discarded. The primary reason for such a time limit is to reduce the risk that small numbers of contaminating bacteria could grow to lethal numbers before the blood is administered. An extensive review of the pertinent literature revealed that the organisms that may survive refrigeration (i.e., psychrophilic bacteria) are unable to begin logarithmic phase growth for several hours after returning to room temperature. This is due to alterations in bacterial enzyme systems and membrane lipids that occur during growth at refrigerator temperatures and that must be repaired before rapid growth may occur. On the basis of this information, it appears that the 30-minute limit could be extended to 2 hours without any increased risk to the recipient. Such a policy change could save 18,000 units of blood per year in the United States.