JVlore than 12 million units of packed erythrocytes are transfused annually (1, 2). Because blood products be-came widely used after World War II, hundreds of mil-lions of units have been given (1-4). Major textbooks state that an increase of 10 g/L (1 g/dL) of hemoglobin is expected per unit of blood transfused (5-10). Authors (5, 8, 11) have implied that after transfusion, the rate at which the hemoglobin concentration equilibrates takes about 24 hours, but the supporting evidence is scant. The ability to rapidly determine the increase in hemoglobin levels after transfusion is important in managing outpa-tients and acutely ill patients. A standard time to measure the hemoglobin levels would save unnecessary blood draws. To clarify these issues, we did a prospective study of medical inpatients at a tertiary care medical center to determine the amount of increase in hemoglobin levels after transfusion and the rapidity of equilibration. Hemo-globin levels rather than hematocrit levels were chosen because they are directly measured, not calculated (12).
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Andrew R. Wiesen (1994) studied this question.