A 60 year old man with a history of intermittent rectal bleeding for several months is admitted after his hemoglobin level is found to be 5.5 g/dL. He is not bleeding at the time of admission.

A single unit of packed red cells is transfused cautiously over 4 hours, with a single dose of furosemide administered mid-transfusion.

Half an hour after the transfusion he started to complain of breathlessness, fever and profuse sweating.