Fresh or stored red cells for transfusion?
A much cited study suggested that transfusion of stored red cells could actually impair regional oxygenation but a recent blinded, randomised, controlled study comparing the effect of fresh versus stored leucocyte-depleted red cells on systemic and regional oxygenation in ICU patients showed no definitive evidence that fresh red cells have better oxygen delivery in critically ill patients (PMID 14758149) (See download at bottom of page). A study of the effect of acute anaemia on cognitive function in healthy subjects detected no difference in the response when haemoglobin concentrations were restored with fresh or stored autologous red cells (PMID 16645441). The TRICC clinical trial (PMID 9971864) suggested that some ICU patients maintained at a lower Hb concentration, and so receiving less transfusion, may have improved outcomes. One interpretation was that this could be associated with some adverse effect of transfusing stored red cells. Randomized trials are in hand to investigate this hypothesis. Large observational studies in cardiac surgery have also suggested poorer outcomes with longer stored red cells. At present, it remains to be conclusively shown in prospective studies whether the use of fresh red cells offers benefits for critically ill patients (PMID 12393351).
Is there a case for single unit transfusion of red cells?
It is often stated that there is no case for giving a single unit transfusion, but in some cases, a single unit may be an appropriate dose. For example in a 40 kg patient with hypoxic signs or symptoms attributed to a Hb concentration of 7g/dl, a single unit of red cells may be quite sufficient to relieve symptoms (and to raise the Hb concentration by 1-2g/dl). Use of a second unit in such a case exposes the patient to additional and unnecessary risks.
Whole blood vs a red cell component?
The concept of blood component therapy (together with the requirement for plasma for fractionation) has encouraged the widespread use of red cell concentrates in most developed countries, although in some other areas of the world, most transfusions are given as red cells (R67). The clinical experience of military surgical teams is that the early administration of plasma with red cells (in approximately equal volumes) appears to be associated with better achievement of haemostasis. Whole blood may be appropriate for a patient with acute bleeding who requires both red cells and expansion of plasma volume. In cases when disseminated intravascular coagulation (DIC) contributes to the blood loss, it may be logical to use whole blood (or leucocytedepleted whole blood) since it contains at least a part of the total dose of fibrinogen and stable clotting factors that the patient requires and could reduce the need for plasma units from other donors.
Is fresh frozen plasma safe?
Worldwide, the largest avoidable risk to patients from transfusion is probably due to the transfusion of fresh frozen plasma (FFP) for unproven clinical indications. Plasma is just as likely as whole blood to transmit viral infections (other than those that are strictly cell associated). In any area where blood safety testing may be unreliable, transfusion of FFP, unless it is pathogen reduced, can be an important source of transmission of these infections.
Is fresh frozen plasma clinically effective?
There is a poor level of evidence to support many of the traditional indications for transfusing FFP (PMID 15198745). This is reflected in the recent clinical guidelines e.g. from Germany and UK. FFP should be used only to replace rare clotting factor deficiencies for which no virus-safe fractionated plasma product is available or when there is a multifactor deficiency due to severe bleeding and DIC. Other indications for FFP are the management of thrombotic thrombocytopenic purpura (TTP) and haemolytic uraemic syndrome (HUS), in which plasma infusion or plasma exchange with FFP is effective (PMID 17266701).
Does Fresh Frozen Plasma have to be used immediately after thawing?
After thawing, the level of factor VIII falls rapidly. Factor V also falls, more slowly, but level of fibrinogen and the other haemostatic proteins is maintained. Guidelines in some countries permit the use of plasma that has been stored in the blood bank for up to 24 hours after thawing. This has the advantage that plasma can be released quickly when required for urgent management of massive bleeding. In some countries, liquid plasma (never frozen) is used.