As a matter of principle, a patient who is subjected to an operation should have normal values for blood volume, hemoglobin, and serum protein and, as far as possible, should be kept in such balance during and after the operation, compensation being made for the lost blood by blood transfusions. Endeavors have been made to achieve this by preoperative control of the hemoglobin percentage, the serum protein concentration, and the fluid balance and, possibly, by supplying blood by transfusion.
The loss of blood is measured during the operation, and as much blood is supplied as the amount lost according to the rule of Wangensteen, which is the weighed loss of blood plus 20% to cover the amount of blood which escapes the weighing. It is endeavored to keep the patient in fluid balance postoperatively, and using estimates based on controls of hemoglobin percentage, to give the number of blood transfusions
FRETHEIM B. Blood Values in Gastric CarcinomaPreoperative and Postoperative Blood Volume, Total Circulating Hemoglobin, and Serum Protein in Patients with Gastric Carcinoma. AMA Arch Surg. 1955;71(1):14-23. doi:10.1001/archsurg.1955.01270130016004