The new formula not only can save hospital resources and staff time, but also can lead to a more rational allocation of banked blood, according to the researchers.
Before a bypass procedure, blood typically is delivered to the operating room in case it will be needed to replace blood lost during surgery. But not just any blood will do. The reserve blood must be matched with the patient's blood type, and it also must be "cross-matched." In cross-matching, a small amount of the patient's blood is mixed with a small portion of banked blood to test for adverse immunological reactions.
In their study, the Duke researchers found that the patients who are most likely to need the most blood during or immediately following their surgery are those who are over the age of 75, those who have impaired kidney function and those who weigh less than 121 pounds.
"At most U.S. hospitals, four units of typed and cross-matched blood are routinely sent to the operating room at the time of surgery," said George Lappas, M.D., a cardiovascular anesthesiology fellow who presented the Duke team's results on May 1, 2006, at the annual scientific sessions of the Society of Cardiovascular Anesthesiologists. "This is the arbitrary amount that has been used for many years in operating rooms nationwide."
"We thought there needed to be a better way to estimate blood needs, since blood is a scarce commodity that takes staff times and resources to prepare," Lappas said. "Also, with blood being held in operating rooms 'just in case,' it is not available for other patients who might need it."