Mechanisms behind operating room blood transfusions in coronary artery bypass graft surgery patients with insignificant bleeding

Objective: To investigate situations in cardiac surgery when transfusions are sometimes used for indications other than to compensate for surgical bleeding. Design: Retrospective study. Setting: Cardiac surgery unit at a university teaching hospital. Participants: Patients scheduled for coronary artery bypass graft surgery (n = 2,469). Interventions: A subgroup of patients with surgical bleeding of less than or equal to400 mL (n = 982) was selected to identify mechanisms leading to perioperative erythrocyte transfusion. Measurements and Main Results. Bleeding of >400 mL triggered transfusion. At less than this bleeding volume, other indications were noted: unstable angina, use of blood cardioplegia, and bad surgical outcome, such as inotropic support. After exclusion of these predictors and anemic patients, the strongest predictors were female gender (p < 0.001), weight less than or equal to70 kg (p < 0.001), cardiopulmonary bypass (CPB) time greater than or equal to90 minutes (p = 0.002), CPB cooling less than or equal to32degreesC (p = 0.038), and advanced age (p < 0.001). Results from a more detailed study of medical records showed that within its normal concentration range, the operating room-transfused patients had lower hemoglobin levels. When followed postoperatively in the intensive care unit and ward, these patients continued to receive more transfusions (p < 0.05) even though their bleeding in the intensive care unit did not differ from the control subjects. Conclusion: Some patients are transfused because of institutional bias of an anticipated need rather than for true surgical bleeding. A concern of hemodilution from standard CPB circuits suggests a possible advantage with low-priming volume for smaller adult female patients. Copyright 2002, Elsevier Science (USA). All rights reserved.