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 < or = 400 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 < or = 70 kg (p < 0.001), cardiopulmonary bypass (CPB) time > or = 90 minutes (p = 0.002), CPB cooling < or = 32 degrees C (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.