Clinical presentation of haemolytic transfusion reactions.

Haemolytic transfusion reactions can be defined as the occurrence after transfusion of measurably increased destruction of red cells, of donor or recipient, by alloantibodies. They may be acute (occurring within 24 hours of transfusion) or delayed (when signs of red cell destruction do not occur until 4 to 10 days after transfusion). The severest signs and symptoms of acute reactions follow intravascular red cell lysis and progress to anaemia, fever, haemoglobinuria and jaundice. The subjective responses of pain, restlessness, nausea, skin flushing, dyspnoea and shock are mediated by cleavage products of complement (C3a, C5a) activated by red cell antigen-antibody reaction. The bleeding and renal failure complications that follow are multi-factoral in aetiology but also stem from the activation of intravascular clotting and from the vasomotor disturbances following histamine and kinin release.