RED-CELL TRANSFUSION THERAPY IN THE CRITICAL CARE SETTING

According to our own experience and published reports the frequency of red cell transfusion in intensive care units is in the range of 0.2 t o 0.4 units per patient per day and is dependent upon the local strate gy, the patients involved and the kind of surgery performed. The ratio nale for red cell transfusion is to maintain or restore the oxygen car rying capacity of the blood to avoid tissue hypoxia which occurs when oxygen delivery drops below a certain critical value. Besides bleeding , phlebotomy is also a significant source of blood loss in critically ill patients. According to several recent reviews and consensus articl es there is no basis for a fixed indicator for transfusion, such as a haemoglobin concentration of <100gL(-1). The decision to transfuse has to be made according to the patients individual status. The major ada ptive mechanism in response to acute anaemia is an increase in cardiac output and hence blood flow to tissues. As a consequence even moderat e degrees of acute anaemia may not be tolerated by patients with cardi ac disease, whilst marked anaemia carries a considerable risk of ischa emia in patients with brain lesions or cerebral arterial stenoses. In critically ill patients it has been postulated that supply dependency of oxygen consumption occurs over a wide range of oxygen delivery, far above the critical values of oxygen delivery seen under normal condit ions. Maximising oxygen delivery was therefore formulated as a goal in these patients. However, whether pathological supply dependency of ox ygen delivery really exists in critically ill patients is still under discussion and recent studies found no benefit in maximising oxygen de livery to this patient group. However, individualised triggers for red blood cell transfusion are adequate for critically ill patients consi dering their co-morbidities and severity of disease. Finally, the deci sion to transfuse must also take into account the potential risks (inf ectious and noninfectious), as well as benefits for the individual pat ient. In the future, the level of transfusions may be reduced by using blood sparring techniques such as blood withdrawal in closed systems, bedside microchemistry, intravascular monitors, or autotransfusion of drainage blood in intensive care units. (C) 1997 Elsevier Science Ltd .