Length of storage of transfused red cells and postoperative morbidity in patients undergoing coronary artery bypass graft surgery

BACKGROUND: The transfusion of old red cells (RBCs) may be associated with reduced delivery of oxygen to tissues and an increased risk of transfusion complications. The association of postoperative morbidity with the length o f storage of perioperatively transfused RBCs was studied in 268 consecutive patients receiving a blood transfusion for coronary artery bypass graft su rgery. STUDY DESIGN AND METHODS: The postoperative length of hospitalization, the postoperative length of stay in the intensive care unit, and the length of endotracheal intubation after the day of the operation were used as surroga te measures of global postoperative morbidity. The length of storage of the oldest transfused RBC unit, the mean length of storage of the oldest and s econd oldest RBC units, and the mean length of storage of all RBC units tra nsfused to each patient were tested for association with the three outcome variables. Multiple linear regression analysis and Cox proportional-hazard analysis were used to adjust for the effects of confounding factors that pe rtained to each patient's severity of illness and the difficulty of each op eration. RESULTS: There were no significant associations after adjustment for the ef fects of confounding factors. CONCLUSION: This study did not corroborate the previously reported associat ion between transfusion of old RBCs and increased morbidity. However, there is surprisingly little research on the clinical outcomes of the transfusio ns of old RBCs, and this hypothesis should be investigated further.