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Transfusion of Red Cells2. Transfusion of Red CellsAs transfusion began with the use of unmodified whole blood, this association has remained strong in the minds of many clinicians. The term ‘blood transfusion’ is rather loosely used by doctors and what they really mean is the transfusion of red cells. Blood is often transfused without sufficient thought either to the specific need of the patient or to the potential harmful effects of the transfusion.Aim The aim of this subsection is to apprise the medical officers of the different type of red cell preparations available, the advantages and disadvantages of using vrious red cells preparations and the indications of red cell transfusion. Red Cell Preparations a. Whole blood (unmodified, stored) Whole blood is the complete single donated unit of 350/450ml of blood in anticagulant solution. The whole blood contains antigenic granulocytes and platelets an addition to the red cells, and also the plasma proteins. Approximate volume of each bag is either 400m1 (350m1) of blood +49 ml of anticoagulant) or 500m1 (450m1 of blood +63 ml of anticoagulant). Stored whole blood should be used only where both plasma proteins restoration and red cells are necessary eg. * Moderate (>40%) or major blood loss Stored blood is deficient in labile coagulation factors, F VIII and V. Functional platelets and granulocytes are not present however their antigenic potential remains. b. Freshly drawn blood Freshly collected blood defined as the collected blood within proceeding 24 hours, provides volume red blood cells with 100% oxygen carrying capacity, coagulation factors and platelets. Freshly drawn blood should not be used for transfusion due to the risk of transfusion transmitted diseases in untested or incompletely tested blood. Efforts should be made to find out the indication for fresh blood transfusion for all the requests received for fresh blood. In a bleeding patient, try to ascertain the cause of bleeding and manage with fresh frozen plasma or platelets than fresh blood. If the requirement is for transfUsion of red cells with maximum oxygen carrying capacity, use any red cells preparation less than 5 days which has 100% oxygen carrying capacity. c. Red cell concentrate These may have approximate volume of 200m1 (350m1 bag) or 300ml (450m1 bag) and a haematocrit of 60%-70%. A red cell concentrate comprises a unit from a single donor from which most of the plasma has been seperated by centrifugation or sedimentation. d. Optimal additive red cell suspension These are red cell concentrate, to which lOOmI of nutrient preservative solution has been added. The most commonly used solution is Sag-man (SAG-M). Their lower haematocrit permits a better flow rate. This preparation should not be used for neonates and for exchange transfusion, due to lack of plasma proteins. e. Washed red cells Washed red cells are rarely used, however have the plasma proteins as well as leucocytes and platelets removed. There is reduced risk of post-transfusion hepatitis with washed red cells. The development of automated cell washing machines has made washed red cells are viable proposition for therapeutic purposes. These are given to patients with proxysmal noctural haemoglobinuria (PNH) and those which are immunized against plasma proteins e.g. patient deficient in igA who have developed anti-IgA. f. Leucodepleted red cells The leucodepleted red cell components have had most of the leucocytes and platelets removed. These are given to patients. a. who are already sensitized to HLA, granulocyte, and platelet antigens e.g., those who have had multiple transfusions and have had febrile reactions or b. those to whom exposure to these antigens is contraindicated such as patients undergoing renal or bone marrow tansplantation. Various approaches have been used to prepare leucodepleted blood components such as washing, freezing and thawing, filteration, centrifigation, etc. Filteration is the most commonly used approach for leucodepletion. Different types of leucodepletion filters are available which can either be used in the laboratory or at the bed side as inline filters. The 3rd generation leucodepletion filters remove 99% of leucocytes and about 60-70% of platelets. g. Frozen red cells concentrates Frozen red cell are of value in special situations such as a. Long term storage of rare blood gfroups b. Transfusion requirement for patients with antibodies against high frequency antigens. c. Storage of autologous donations in patients with rare blood groups or multiple ailontibodies. Any component that requires an open procedure for preparation such as filtering, washing and freezkng is at risk of bacterial contamination. Such• components should be used within 24 hours or preferrably within 6 hours of preparation, and if not used within the specified period, these must be discarded. Indications of Red Cell Transufuslon The only true indication for transfusion of red cell is the need to improve the delivery of oxygen to the tissues within a short time. In addition to a low Hb concentration, patients general state, age and the rate of fall of haemoglobin are important factors to decide the need of a patient for red cell transfusion. A rise of about ig/dI of haemoglobin may be expected from each unit of red cells tranfused. Single unit red cell transfusion should therefore be avoided as it only provides an insignificant increase in Hb. Medical audit in red cell transfusion Based on the preoperative haemoglobin value, crossmatch transfusion ratio and the indication of red cell transfusion, a review can be done to find out the necessity of red cell transfusion in a particular patient. Each blood transfusion service should regularly review the usage of blood components in the associated hospitals for a medical audit.
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Preservation Storage Transportation of Blood / 2. Transfusion of Red Cells
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