Patterns of blood usage in adult patients after cardiac surgery

Abstract

Towards the end of 2005, routine intra-operative cell salvage for cardiac surgery was introduced in our unit. Audit found that the proportion of patients undergoing coronary artery bypass grafting that required transfusion peri-operatively decreased from 58% to 43%; despite this 38% who received cell salvage were transfused. The aim of this audit was to compare transfusion within the first 24 h postoperatively against our unit's guidelines. We prospectively collected clinical and operative data, including blood transfusions, over 6 weeks. Actual practice was compared with the unit's protocol that has transfusion thresholds of < 8.0 g.dl−1 in the first 4 h postoperatively and < 9.0 g.dl−1 after this time. One hundred and ten patients were audited. A total of 118 cardiac operations were carried out on 115 patients; five patients were excluded because they had insufficient datasets available. Mean (IQR) age was 63 (57–71) years and pre-operative haemoglobin concentration was 13.4 (12.3–14.9) g.dl−1. Cell salvage was used in 65 (59%) cases. Aprotinin and tranexamic acid were used in 64 (58%) and 30 (27%) cases, respectively; two patients received both drugs. Postoperative transfusions within 24 h of arrival in the intensive care unit occurred in 38 (35%) cases. Median (IQR (range)) haemoglobin concentration before transfusion was 7.9 (7.6–8.6 (6.2–10.0)) g.dl−1. Median (IQR) number of units transfused was 2 (1–3) and time to transfusion was 4.2 (1.9–8.5) h. Haemoglobin level after transfusion was 9.4 (9.2–9.9 (8.3–11.1)) g.dl−1. The use of cell salvage, aprotinin and tranexamic acid (respectively p = 0.159, 0.652 and 0.536) was not significantly associated with the incidence of transfusion. Regression analysis showed that the dose of aprotonin (r2 3.7%) and tranexamic acid (r2 0.2%) did not correlate with the number of units of blood transfused postoperatively. The unitary transfusion protocol within 4 h of surgery was adhered to in 12 (66.7%) patients, with six transfusions occurring out with this protocol. Non-protocol transfusion cases had a postoperative haemoglobin concentration of 9.6 (7.6–8.6) g.dl−1. Adherence to the protocol beyond 4 h was 100% during the initial 24 h. Despite the significant decrease in blood usage associated with cell salvage systems in our unit, poor adherence to the unit's transfusion protocol may have perpetuated high rates of transfusion, which were likely to be unnecessary. Education and rigorous adherence to transfusion protocols is needed to reduce the transfusion rates in our unit, to avoid unnecessary postoperative transfusions.