Blood transfusion as a cause of leucocytosis in critically ill patients.

The diagnosis of infection in the intensive care unit is confounded by the presence of non-infectious causes of leucocytosis. Unless such causes are recognised, time and effort will be spent on unnecessary investigations and treatments. In a prospective study we have shown that the transfusion of blood frequently (45/50 patients) causes an acute leucocytosis in such patients. This effect was not seen in 8 patients who received plasma. Blood transfusion should be added to the list of non-infectious causes of leucocytosis in the critically ill.