In a retrospective analysis of records of 321 patients who underwent a repeat coronary artery bypass or valve replacement procedure during 1995 to 2001, investigators here found that transfusions of older stored blood were linked with an increased risk of kidney failure
In a retrospective analysis of records of 321 patients who underwent a repeat coronary artery bypass or valve replacement procedure during 1995 to 2001, investigators here found that transfusions of older stored blood were linked with an increased risk of kidney failure.
For example, the in-hospital mortality rate for patients who received the "freshest" blood (1 to 19 days old) was 4%, compared with 25% for patients who received the oldest blood (31 to 42 days old), said Sukhjeewan Basran, M.D., and colleagues at Columbia.
Surprisingly, older blood was also linked to increased mortality risk in these patients years later, Dr. Basram and colleagues said in the July issue of Anesthesia & Analgesia.
The researchers grouped the patients into quartiles based on the age of the oldest unit of blood they received: 1 to 19 days, 20 to 26 days, 27 to 30 days, and 31 to 42 days.
Compared with patients who received the freshest blood, those who received the oldest were 15% more likely to die in the hospital (hazard ratio=1.15; P<.0001).
The rate of acute renal dysfunction in those receiving the newest blood was 7%, compared with nearly 45% for those receiving the oldest (HR=1.44; P<.001).
Those who received the oldest blood were 11% more likely to die out of the hospital during follow-up, which ranged from three to eight years (HR=1.11; P<.0001).
Age of blood was also significantly linked to length of stay in the intensive care unit and in the hospital. Patients in the freshest blood quartile stayed an average of 3.5 days in the ICU, compared with about seven days for those in the oldest blood group (P=.002). Similarly, patients in the freshest group spent an average of about 12 days in the hospital, compared with 17 days for the oldest group (P=.05).
The study did not address the biological mechanisms underlying the findings, but the investigators noted that previous research showed that red blood cells tend to become rigid and abnormally shaped during storage. These abnormal cells are thought to lead to decreased microcirculatory blood flow, tissue hypoxia, and possible death, they said.
Another study suggested the abnormal red blood cells might serve as thrombogenic surfaces for platelet activity and therefore could lead to increased risk for stroke or pulmonary embolism, they added.
The current study's findings likely apply not to cardiac surgery alone, but to any type of surgery or medical procedure involving transfusion of stored blood, said co-author Ervant Nishanian, M.D., Ph.D., also of Columbia.
But inquiring about the age of blood you will receive before going into surgery is not likely to do much good. "The answer depends on the demand for blood that day in your geographic region," so the surgeon can not know, Dr. Nishanian said.
Because stored blood tends to be scarce, not much of it is allowed to sit in storage long, so the problem of old blood is unlikely to be an issue for most hospitals, he said. Dr. Nishanian also pointed out that in some cases, an older unit of blood that is well-matched to a patient will probably be safer than a fresher unit of blood that is not as well matched.
However, patients who may be concerned about receiving older blood during surgery have the option of giving their own blood beforehand and having it set aside for them, Dr. Nishanian said.
The authors pointed out that "a significant limitation of our study is that patients who received red blood cells stored for a prolonged duration were also more likely to have received a larger number of total red blood cell transfusions. Our statistical analysis included multivariate analyses that controlled for many of the potential confounders; however, we cannot exclude the potential effect of confounders."
