THE ESTIMATION of blood loss in surgical operations is of primary importance in determining the amount of blood replacement needed. While we know of no minutely accurate and practical method for solving this problem, the present study represents our approach to the problem in thoracic surgery.
Blood volume was measured with the Evans blue dye (T-1824) method based on Gregersen's 10-minute technique as modified by Huey and Holmes.1 One hundred ninety-one patients undergoing thoracic surgical procedures were studied. Hematocrit determinations were made on heparinized blood with use of the Wintrobe tube (45 minutes at 2,400 rpm with a 19 cm. radius), and the plasma proteins were determined by the refractive index method of Neuhausen and Rioch.2 In 120 operations on 94 patients, blood volume studies were made one to eight days before operation (80% within four days before operation) and within 24 hours after operation. Two weeks after