Cur­rent guide­lines per­mit stor­age of blood for as long as 42 days after col­lec­tion. How­ever, accord­ing to a new study, blood stored for 40–42 days has increased lev­els of biliru­bin, fer­ritin, and non–transferrin-bound iron and enhanced growth of path­o­genic Escherichia coli bac­te­ria. The researchers con­cluded that dur­ing their stor­age, red blood cells undergo changes that are asso­ci­ated with iron release and poten­tially adverse consequences.

Researchers exam­ined the changes that stored blood under­goes by giv­ing stored blood to 14 healthy adult vol­un­teers. Each vol­un­teer donated two leuko­re­duced red blood cell units and was sub­se­quently trans­fused with one unit after it was stored for 3–7 days (fresh) and one unit after it was stored for 40–42 days (older).

The researchers found that the basic meta­bolic para­me­ters were sim­i­lar after trans­fu­sion with fresh or older blood. How­ever, biliru­bin, serum iron, trans­fer­rin, fer­ritin, and cir­cu­lat­ing nontransferrin-​​bound iron lev­els were increased after trans­fu­sion of older ver­sus fresh blood. Serum sam­ples col­lected two to four hours after trans­fu­sion showed that older blood sup­ported enhanced growth of path­o­genic E. coli. The researchers con­cluded that extend­ing stor­age times has improved blood avail­abil­ity but has also raised con­cerns that the qual­ity of blood has suf­fered, which might explain the increased infec­tion rate asso­ci­ated with the trans­fu­sion of older units of blood.

• Hod, E.A., Brit­ten­ham, G.M., Bil­lote, G.B, Fran­cis, R.W., Ginzburg, Y.Z., Hen­drick­son, J.E., . . . Spi­tal­nik, S.L. (2011). Trans­fu­sion of human vol­un­teers with older, stored red blood cells pro­duces extravas­cu­lar hemol­y­sis and cir­cu­lat­ing non-​​transferrin-​​bound iron. Blood, 118, 6675–6682. doi: 10.1182/blood-2011–08-371849