Etiology of preoperative anemia in patients undergoing scheduled cardiac surgery

Ten percent of our cardiac surgical patients have preoperative anemia. Anemia diagnosed before scheduled cardiac surgery is a strong predictor of the need for homologous blood transfusion (RBC) perioperatively but the cause of this preoperative anemia is not known. The purpose of this study was to evaluate the etiology of preoperative anemia.

Seventy-five consecutive anemic cardiosurgical patients (Hb = < 120 g x L(-1) the day before surgery) were studied prospectively. All had multiple diagnostic blood tests done in the preoperative period to diagnose the cause of the anemia and subsequently underwent non-emergency cardiac surgery. Anesthesia and RBC transfusion were standardized according to the protocol. Data in respect to operation, RBC and other blood product transfusion during operation and hospital stay were recorded.

Hospital-acquired anemia was present in 37.3% of anemic patients (hemoglobin decrease during hospitalization before surgery > or =9 g x l(-1)). The second most common diagnosis was iron deficiency anemia (29.3% patients) followed by anemia of chronic renal disease (10.7% patients). When coronary angiography was performed close to operation time, patients had a higher decrease in hemoglobin concentration during hospitalization --suggesting that blood loss during angiography was, in part, responsible for anemia. Seventy-five percent of anemic patients were transfused with RBC perioperatively compared with our overall transfusion rate of 30% of cardiac surgery patients.

In the majority of patients, preoperative anemia is potentially preventable. Investigation and treatment of anemia before cardiac surgery should be a priority in preparing the patient for surgery.