The indication for perioperative transfusion of red blood cells

Today, about 50% of all blood transfusions are given perioperatively. Although transfusion-associated complications have been reduced by quality management measures, a non-negligible risk remains. Moreover, the increasing numbers of elderly patients undergoing major surgery, and the decreasing numbers of blood donors will appreciably increase both the need for transfusions and their cost. Against this background, a rational indication for blood transfusion with the aim of reducing allogeneic blood exposure and costs is mandatory. The therapeutic goal of RBC transfusion is the avoidance and/or treatment of anaemic hypoxia. Hence, a knowledge of the physiological mechanisms compensating for anaemia (increased cardiac output and oxygen extraction, homogenisation of microvascular perfusion) and the factors modifying this compensation (e.g. coronary artery disease, congestive heart failure, anaesthesia, hypothermia, hyperoxia) is essential. Clinical symptoms indicative of anaemic hypoxia are known as "physiological transfusion triggers". If they are present, RBC-transfusion is mandatory. In haemorrhagic shock and persistent massive bleeding, RBC have often to be transfused before the occurrence of physiological transfusion triggers. Normovolaemic young healthy adults tolerate haemoglobin concentrations of 6 g/dl and - under certain conditions - less without the need for RBC transfusion. Pregnant women and children compensate anaemia well. Stable patients with a cardiovascular risk should be transfused at haemoglobin concentrations of between 8 and 10 g/dl. The decision to transfuse should continue to be based on haemoglobin concentration, pre-existing risk factors, the individual ability to compensate for anaemia, and the expected rapidity and amount of further blood loss.