A 25-year-old man involved in a motorcycle accident incurs a laceration to his thigh. The bleeding is stabilized en route to the hospital, but on arrival, he is noted to have orthostatic hypotension and his hematocrit is 21%. He receives 2 units of PRBCs. As the first unit is nearly finished transfusing, he becomes febrile and hypotensive. Urine output ceases. The serum above the clot in a red top phlebotomy tube is pink. Which of the following complications of transfusion has most likely occurred in this man?

The findings are those of a hemolytic (ABO) transfusion reaction, virtually all of which result from clerical errors. You learned that proper phlebotomy procedure requires labeling the tubes just after drawing the blood, not handing the tubes to someone else for labeling, and possible mix-up. This is not consistent with a transfusion-related acute lung injury (TRALI) in which there are donor-derived HLA or granulocyte-specific antibodies in the recipient's blood product that is directed against antigens on the recipient WBCs. Though hepatitis C infection is still possible, but uncommon, from transfused blood, this infection has an incubation period of months. The two units of packed RBCs in a young person are very unlikely to lead to circulatory overload. He does not have transfusion-associated graft-versus-host disease, which is a rare but untreatable condition with a very high mortality rate.