General Medical Information

Transfusions

David M. Barrs

Rapid correction of hematologic deficiencies usually depends on blood transfusions. Whole blood is rarely used; it is separated into its components for safety and efficiency. The broadest coverage for urgent coagulation abnormalities is fresh frozen plasma, which contains all the clotting factors, although there are no platelets and the fibrinogen level is low. For elective surgery, the patient can be an autologous donor with a maximum of 1 U donated every 72 hours, up to 72 hours before surgery, as long as the patient maintains a hematocrit of greater than 33%. Fibrinogen transfusion is no longer used because of the high risk of viral transmission; cryoprecipitate is used to treat low fibrinogen levels.

Mild hypersensitivity reactions are relatively common and can be controlled by administration of antihistamines and temporary discontinuation of the transfusion. Febrile reactions usually respond to simple discontinuation of the transfusion. Of specific concern is the patient who has undergone massive transfusion. Volume overload may be minimized by using packed red blood cells. Hyperkalemia, hypokalemia, hyperammonemia, and acidosis do not require specific treatment other than monitoring of blood levels. Platelets survive poorly in banked blood, and massive transfusions may lead to significant thrombocytopenia. Hypothermia can be minimized by warming blood and crystalline replacement. Citrate toxicity can cause a decrease in ionized calcium. Replacement with either calcium gluconate or calcium chloride is reserved for symptomatic hypocalcemia and is not given prophylactically. Clotting studies such as prothrombin time (PT) and activated partial thromboplastin time (aPTT) should be monitored for any sign of coagulopathy.