Activation of complement by blood transfusion filters

[Effect of leukocyte depletion on preservation of erythrocyte and platelet concentrates]

Early leukocyte depletion suppresses metabolic or cellular changes which they involve during red blood cell or platelet concentrates storage. The evolution of the cellular alteration control parameters and of the storage media content is modified by leukocyte concentration of blood products.

The role of blood microfilters in clinical practice

Blood filters have been available since the 1930s. In this review we evaluate the role of microaggregate filters (MF) in certain transfusion complications, namely non-haemolytic febrile transfusion reactions (NHFTR), pulmonary injury, thrombocytopenia, fibronectin depletion and histamine release. We review the latest generation of leucocyte depleting filters and discuss their role in preventing alloimmunisation, immunosuppression and CMV transmission. Finally, we provide a rationale for the role of blood microfiltration in the present day practice of intensive care medicine.

[Technical constraints in rapid vascular fluid replacement]

Rapid fluid infusion remains the cornerstone for therapy of hypovolaemic shock. The principal limitations of flow rate are governed by the four variables of Poiseuille's law: tube internal diameter and length, viscosity of the fluid passing through the tube, and the pressure gradient between the two ends of the tube. Conventional transfusion systems, with wide bore tubing (up to 5.0 mm internal diameter), large bore cannulas (8.5 French introducer catheters), high pressure (up to 300 mmHg) and diluted blood, can result in a maximum flow rate of about 1,000 ml.min-1 (for crystalloid solutions). Specific apparatus for rapid infusion can increase this to 1,500 ml.min-1 (Rapid Infusion System, Haemonetics). Dry-heat warming devices and microfiltration, to remove microaggregates and prevent non haemolytic febrile transfusion reactions, seem necessary when carrying out rapid transfusions. However, the use of microaggregate filters could be avoided by the routine production of leukocyte-poor red blood cell concentrates.