Rationalizing blood transfusion in cardiac surgery: preliminary findings with a red cell volume-based model.

BACKGROUND AND OBJECTIVES: Cardiac surgery, utilizing extracorporeal circulation, is associated with a heavy fluid load that may significantly depress haemoglobin concentration. Thus, considering haemoglobin alone may be an inaccurate method of replacing red cell volume loss. This study was designed to examine the impact on red cell transfusion of a red cell volume-based guideline. MATERIALS AND METHODS: Patients were randomized to receive red cells as dictated by the red cell volume-based guideline or a haemoglobin-based protocol. End-points considered were red cell transfusion and clinical outcome. RESULTS: Patients transfused as per the red cell volume-based guideline received significantly less red cells with no associated difference in clinical outcome. CONCLUSION: Considering haemoglobin concentration alone may significantly overestimate the requirement for red cell transfusion in elective cardiac surgery patients.

Factors predicting loss and gain of red cell volume in cardiac surgery patients.

Haemoglobin may be a poor indicator of changes in red cell volume (RCV) because of factors such as haemodilution. This study has been designed to analyse what peri-operative variables may be associated with loss or gain in RCV due to bleeding or transfusion. Prospective observational study. Single centre study based in a regional cardiac surgery centre. Twenty-nine elective adult cardiac surgery patients. Loss and gain of RCV were measured in theatre and for the first 24 h post-operatively. Patient and operative factors analysed were age, sex, height, weight, body surface area (BSA), induction haematocrit (Hct), estimated pre-operative RCV and antiplatelet therapy taken less than 7 days before operation, cardiopulmonary bypass (CPB) time, aortic occlusion time, minimum and maximum CPB temperatures and fluid administered. Age, sex, height, weight, BSA and induction Hct were found to predict red cell transfusion but not RCV loss. The total number of red cells transfused was significantly associated with RCV lost when expressed as a percentage reduction in the estimated pre-operative RCV but not the absolute RCV lost. Pre-operative RCV, as predicted by the variables outlined above, is more important than RCV lost in triggering red cell transfusion.