The effect of postoperative normovolaemic anaemia and autotransfusion on blood saving after internal mammary artery bypass surgery

Abstract

The efficacy of two blood conservation techniques in decreasing and in preventing the use of homologus blood products was retrospectively studied in 150 patients undergoing internal mammary artery bypass surgery. Patients were matched according to prebypass blood haemoglobin (Hb) content and body surface area and were allocated to one of three groups: in the patients of group 1 (n = 50), normovolaemic anaemia (NA) was accepted postoperatively (haematocrit [Hct] was accepted to a minimum level of 25%); the patients of group 2 (n = 50) were treated with postoperative autotransfusion (AT) of mediastinal shed blood and acceptance of NA. Group 3 (n = 50) contained control patients, not treated with NA or with AT (Hct was accepted to a minimum level of 30%). Patients of group 1 required 3.0 ± 0.3 units of homologous blood products, but the patients of groups 2 and 3 received significantly more (p <0.01 ) units: 3.9 ± 0.2 and 4.5 ± 0.3 units. No donor blood products were needed in 36%, 9% and 5% of the patients in groups 1, 2 and 3 respectively. The net postoperative blood loss was similar in the groups: 1229 ± 92 ml in group 1, 1098 ± 74 ml in group 2 and 1243 ± 72 ml in group 3. However, total blood loss (1982 ± 135 ml), including the retransfused part (954 ± 89 ml), was significantly larger (p <0.01) in group 2, than in groups 1 and 3. We conclude that NA alone is more effective than the combination of NA and AT of large amounts of shed blood in reducing and in preventing the need for homologous blood products in internal mammary artery bypass surgery. When AT of a large amount of shed blood is employed in addition to NA, increased bleeding is observed.