Filterability of ACD-stored red cells

Anaemia and red blood cell transfusion in the critically ill patient

Anaemia is a common finding in critically ill patients. There are often multiple causes. Obvious causes include surgical bleeding and gastrointestinal haemorrhage but many patients have no overt bleeding episodes. Phlebotomy can be a significant source of blood loss. In addition, critically ill patients have impaired erythropoiesis as a consequence of blunted erythropoietin production and direct inhibitory effects of inflammatory cytokines. The ability of a patient to tolerate anaemia depends on their clinical condition and the presence of any significant co-morbidity; maintenance of circulating volume is of paramount importance. There is no universal transfusion trigger. Current guidelines for critically ill and perioperative patients advise that at Hb values <70 g/L red blood cell transfusion is strongly indicated and at Hb values >100 g/L transfusion is unjustified. For patients with Hb values in the range 70 to 100 g/L the transfusion trigger should be based on clinical indicators. Most stable critically ill patients can probably be managed with a Hb concentration between 70 and 90 g/L. Uncertainties exist concerning the most appropriate Hb concentration for patients with significant cardio-respiratory disease.

Influence of prestorage leucocyte depletion and storage time on rheologic properties of erythrocyte concentrates

BACKGROUND AND OBJECTIVES

Rheological blood properties were studied during storage.

MATERIALS AND METHODS

Blood viscosity, erythrocyte morphology and ATP levels were determined in filtered samples (Leukotrap WB filter system) and their unfiltered counterparts during storage with saline-adenine-glucose-mannitol (SAG-M) for 42 days.

RESULTS

Prestorage leucocyte depletion decreased blood viscosity at a high shear rate and reduced the degree of anisocytosis of erythrocytes. During storage, erythrocytes underwent a time-dependent echinocytic shape transformation, which increased the suspension viscosity at high and low shear rates. On day 42, high shear viscosity in filtered units remained lower than in unfiltered counterparts, the mean cellular volume and red blood cell distribution width (RDW) were lower and erythrocytic ATP levels were higher.

CONCLUSIONS

Prestorage leucocyte depletion by Leukotrap WB filters improves biophysical properties of erythrocyte concentrates throughout storage, which is, however, outweighed by a time-dependent echinocytic shape transformation and deterioration of these properties.

Red cell membrane changes during storage

A great deal is known about the red cell membrane and its abnormalities in various pathologic states. During red cell storage there is a progressive development of spheroechniocytosis with eventual production of irreversibly nondeformable red cells. The loss of membrane function is most likely related to some abnormality in maintenance of the cytoskeleton of the red cell. These changes appear to occur independent of ATP levels. Despite the increasing knowledge of the structure and function of the red cell membrane very little as yet is known about the specific abnormality in the red cell membrane that occurs during storage in the blood bank. Recent evidence for abnormal spectrin-actin interaction and abnormal spectrin oxidation has been the most promising. Areas of interest for research include studies of the specific mechanisms by which the plasticizer DEHP interacts with the membrane, specific definition of the molecular defect in membrane proteins that occurs during storage, and means to prevent these. If such deterioration and membrane stiffening could be prevented then the quality of the red cells that are transfused would be improved both in their function and ability to survive in the microcirculation. A final need, while not of specific value to the red cell itself, is the development of media and additives that will allow for increased plasma and Factor VIII yields, one of the driving forces in the blood transfusion system.