When should blood (autologous or allogeneic) be transfused?
Blood components should be transfused only when they are needed. However, objective indications for the transfusion of blood components are difficult to establish. The decision to transfuse RBC’s is ideally based on the prevention of tissue hypoxia due to an oxygen transport deficit. No specific method to measure or anticipate a clinically significant deficit exists. In awake patients, symptoms of oxygen deficiency such as headache, lightheadedness, tinnitus, and faintness are nonspecific and do not lend themselves to the avoidance of symptomatic hypoxia. If available, base excess, the oxygen extraction ratio, serum lactate, and cardiac index can be used as surrogate markers. The hemoglobin and hematocrit are easily obtained laboratory values, but are far less likely to reflect the degree of oxygen deficiency in a patient because many other factors affect oxygen transport, such as underlying cardiac or pulmonary disease, cardiac output, and hemoglobin’s affinity for oxygen. Practice gu
