The Role of O2 Transport in the Development of the Transfusion Trigger

The “transfusion trigger” is that event or set of events which result in a patient receiving a red cell transfusion. Excellent recent discussions have been published regarding the transfusion trigger [1’4], and numerous conferences have been held to specify guidelines or algorithms whereby clinicians can make objective decisions about the use of red cells [5,6]. For many years an empirical transfusion trigger was a haemoglobin concentration of 10 g/dl. If the value was less, the patient received at least 2 units of packed red cells or whole blood, in spite of the well known fact that many patients tolerate modest anaemia quite well [7]. The rationale for such transfusions was that an O2 reserve needed to be maintained so that if unexpected (or expected) blood loss occurred during surgery, the patient would be in less danger of suffering deficient O2 delivery to tissue. Guidelines for the transfusion of blood or packed red cells in the face of severe blood loss have been less well defined.