A febrile non-hemolytic transfusion reactions (FNHTR) is defined as a temperature increase of 1°C over 37°C occurring during or after the transfusion of blood components. FNHTRs are more common in the transfusion of platelets. Multiply-transfused patients and multiparous women make up the largest populations experiencing this type of reaction.
There are two mechanisms involved in the manifestation of an FNHTR. The first involves the presence of a white cell antibody in the patient's plasma that interacts with the white cells in the blood product. These antibodies may be directed against granulocyte antigens or human leukocyte antigens (HLA).This interaction causes endotoxins to be released, which act on the hypothalamus and stimulate a fever. The second mechanism involves the generation of leukocyte cytokines during product storage. The production of cytokines usually occurs during storage in warmer temperatures, which is why non-leukoreduced platelets are commonly implicated.