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Non-haemolytic Immune Transfusion Reactions (NHTR)4. Non-haemolytic Immune Transfusion Reactions (NHTR)NHTR are associated with immunological reaction between antibodies in patient’s plasma and other antigenic constituents e.g. platelets and leucocytes in donor blood.Febrile non-haemolytlc TR (FNHTR) FNHTR is suspected when a temperature rise of 1°C or more occurs during or after the transfusion, and no other cause can be found. These are thought to be due to an immunological reaction against one or more of the transfuse cellular or plasma components, usually leucocytes, though plasma proteins or platelets may be involved. These reactions are more common in patients receiving multiple transfusions or in multiparous women. Endogenous pyrogens released during the antigen-antibody interaction stimulate the thermoregulatory centre to produce fever. Clinical manifestations 1. Fever and chills shortly after the start of transfusion or even after the transfusion is over. Temperature rise may be mild to severe 2. Nausea, vomiting 3. Hypotention and shock. Antibodies associated with FNHTR Leucocyte antibodies have been detected in many cases. They are the result of previous pregnancy or multiple transfusions. The antibodies are directed against antigenic determinants of HLA system (80%) or granulocyte-specific antigen system (5%). In addition, platelet-specific alloantibodies (10%) have also been incriminated in some cases. Management These reactions should be prevented. If mild, the reaction can be managed by slowing of the infusion and antipyretics. Severe reactions, however, require active intervention. The reactions are often self-limiting. Leucocyte poor red cell concentrates should ideally be used in the patients at risk. These can prepared by filtration or centrifugation. Filtration is the most frequently used technique to achieve leucodepletion. Third generation in-line leucocyte filters which remove 99.9% of white cells are now available. Leucocyte depleted products should be given only if the patient has two or more febrile reactions since they are rarely recurrent. Allergic transfusion reactions Allergic reactions occur most commonly due to infusion of plasma proteins. The severity of the reactions is variable and is not necessarily dose-related. a. Mild allergic reaction : Urticaria This is a commonly encountered reaction characterized by a localized swelling of the superficial layers of the skin. The lesions are pruritic, raised, erythematous, sharply-demarcated and transient. The reactions are due to allergy to a product in the donor plasma. IgE in the recipient reacts with antigens on the donor cells. The release of histamine causes the typical clinical features. The reactions are managed by administration of antihistaminics (diphenhydramine 25-50mg). After the reaction has subsided transfusion can be continued at a slow rate as the reaction is not likely to recur. b. Severe allergic reaction. Anaphylactoid reaction This is a rare reaction. The reaction is dramatic and can result in death unless recognized and managed promptly. The symptoms of shock and unconsciousness may occur after transfusion of a few ml of blood. Pathogenesis It occurs in IgA deficient (IgA < 1mg/mi) patients who have developed anti-IgA after previous transfusion or pregnancy. The antibodies can fix complement. On reexposure to minute amounts of lgA, these patients develop anaphylactoid reaction. The incident of IgA deficiency is 1 : 1000. Clinical features The reaction is characterized by * Cough * Respiratory distress * Bronchospasm * Nausea, vomiting, abdominal cramps & diarrhoea * Circulatory collapse * Hypotension & shock Diagnosis Diagnosis can be made by demonstration of antibody to IgA, however, this is not done in most laboratories. Absence of serum lgA may be demonstrated by immunodiffusion. Management 1. Stop the transfusion. 2. Treat hypotension with fluids. 3. Give epinephrine injection (0.5mg) subcutaneously if patient is in shock. 4. Steroids (100-200 mg hydrocortisone) are useful. Prevention 1. Sensitized patients should be given blood and blood deficient in IgA. 2. if red cells are required deglycerolized and washed red cells may be used. 3. Transfusion should be given at a slow rate. Since IgA deficinet donors may be difficult to find, autologous blood may be used.
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