“Old Blood” Linked to Infection

“Previous data indicate that the average age of transfused blood is around 17 days old,” said Nahra. “In our study, the average age of blood was 26 days, and 70 percent of all the blood transfused was older than 21 days, suggesting that a large pool of available blood is old blood with higher levels of cytokines and more potential for an immunosuppressive effect.”

The analysis showed that 11 percent of patients died, while 57 patients (13.5 percent) developed nosocomial infections: 32 patients developed one nosocomial infection, 21 developed two nosocomial infections, and four developed three nosocomial infections. Patients who developed nosocomial infections had a significantly higher OL (28.5 days vs. 32 days), and a significantly greater number of units of blood (2 U vs. 3 U). Patients who received transfusions with blood that was 29 days or older were twice as likely to develop nosocomial infections as those receiving transfusions with blood stored for 28 days or less. When the outcome of “at least one infection” was analyzed, a higher number of units of blood (>5 U) was found to be an independent predictor of infection. Furthermore, while the age of the first unit of blood transfused appeared to be associated with the development of infection, the age of the oldest unit showed the strongest relationship. Many institutions, including Nahra’s, use the oldest available blood first, to ensure that it does not go to waste. Researchers speculate that if strict regulation of blood storage were to occur (i.e., shorter maximum storage allowance), the overall blood supply may decrease.