Estimated blood volume loss, hemoglobin concentration measurements, and consideration
of the patient’s clinical status are standard methods for assessing transfusion needs in
acutely bleeding patients. It should be noted that these approaches carry limitations
because anesthetic agents may mask some signs and symptoms of anemia, making
assessment of the amount of blood lost difficult. Hemoglobin measurements are usually
artifactually low in patients who have received large volumes of fluids that temporarily
expand plasma volume.