1. Is it indicated?

2. If it is indicated, which red cell preparation should be used?

Practicalities of red cell transfusion

All those involved in the prescription and administration of blood should follow local guidelines with respect to patient identification and the checking of the compatibility and viability of the transfused units. Critical information is contained on the blood bag and the attached compatibility label (Fig 42.1). No discrepancies are permissible. Most serious adverse transfusion reactions are due to transfusion of the wrong blood to the patient (Fig 42.2). Errors can be reduced by newer technologies such as bar coding and radiofrequency chips – these generally rely on machine readable data on patient wristbands.

In shocked patients blood is transfused rapidly, the precise rate dependent on the monitoring of vital signs such as pulse, blood pressure and urine output. Transfusion for correction of anaemia is usually a more elective process. Units of red cells are typically given over 2–4 hours and a rise of around 10 g/L of haemoglobin can be expected from each unit. Red cells are infused via specially designed sterile ‘giving sets’ which contain 170 µm filters. Careful monitoring is particularly important during the first 10 minutes of each unit.

Complications of red cell transfusion

Massive blood transfusion

Massive transfusion is defined as replacement of the patient’s whole blood volume by stored allogeneic blood in less than 24 hours. There have been recent changes in practice driven by the military experience of trauma with increased early use of plasma and platelets. Problems can still arise in part due to the inevitable deficiencies of stored blood. Shortage of clotting factors and platelets in transfused blood may exacerbate haemorrhage. It is important to monitor haemostasis by checking the basic coagulation screen and replacing components accordingly. Metabolic disturbances are less common but include hyperkalaemia, hypocalcaemia, acidosis and citrate toxicity. Rapid transfusion can cause hypothermia; this can be minimised by carefully controlled blood warming.

Alternatives to allogeneic blood transfusion

Use of the patient’s own blood for transfusion rather than allogeneic blood minimises the risk of infection. Selected patients awaiting elective surgery can ‘pre-deposit’ blood in the weeks prior to the operation. An alternative approach, now more favoured, is to use specially designed equipment to ‘salvage’ blood lost during surgery and reinfuse it back into the patient. Other strategies to reduce blood transfusion include the active treatment of anaemia, strict application of transfusion triggers, anaesthetic measures or drugs (e.g. tranexamic acid) to reduce blood loss and biological agents such as erythropoietin. Questions remain regarding optimal transfusion practice and there is a need for more randomized controlled trials. Possible future developments include manufactured haemoglobin solutions and platelet substitutes.

Platelet transfusion

This is used to treat or prevent haemorrhage in patients with significant thrombocytopenia. It is more useful where platelets are low due to underproduction (i.e. marrow failure) or dilution than where thrombocytopenia is due to immune destruction as in immune thrombocytopenia (ITP). Platelets are collected either from routine blood donations or from a single donor by plasmapheresis. They should ideally be matched with the patient for ABO and Rhesus. The standard dose for an adult is either a single plasmapheresis donation or 4–6 pooled standard donations. Where repeated platelet transfusions are given, patients can become sensitised against class I HLA antigens absorbed onto the platelet surface with the result that they derive a lower increment in platelet count than would be predicted (‘platelet refractoriness’). In these cases, platelet donors matched with the recipient’s HLA class I type can be selected. Platelet transfusion can cause non-haemolytic reactions and can transmit infection as for red cells.

Granulocyte (neutrophil) transfusion

Granulocyte transfusion is infrequently used in neutropenia and the indications are uncertain.

 Fresh frozen plasma (FFP). Plasma is collected from whole blood or derived from plasmapheresis prior to rapid freezing. FFP contains the full range of coagulation factors and indications for use are shown in Table 42.2. The normal dose in an adult is one litre. FFP can transmit infection and cause immunological reactions – it is not suitable for volume expansion alone.

 Cryoprecipitate. This is prepared from FFP by slow thawing and separation of the resultant precipitate. It is rich in fibrinogen and may be useful in the treatment of DIC and management of massive blood transfusion.

 Factor VIII and IX concentrate. See pages 72–73.

 Albumin. This is produced by fractionation of pooled plasma. Solutions for clinical use include human albumin 4.5/5%, human albumin 20% and plasma protein fraction (PPF). Albumin solutions are used for the treatment of severe hypoproteinaemia, particularly when associated with a low plasma volume. Concentrated solutions can help produce a diuresis in hypo-albuminaemia (e.g. in hepatic cirrhosis).

 Immunoglobulins. These can be ‘specific’ and used in passive prophylaxis against a range of infections (e.g. varicella zoster, tetanus) or to prevent haemolytic disease of the newborn (anti-Rhesus D). ‘Non-specific’ immunoglobulins are used for passive prophylaxis against hepatitis A, treatment of hypogammaglobulinaemia and in selected autoimmune disorders (e.g. ITP).