Blood Volume Determinations in the Operative Period

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THE function of anesthesiology has been extended beyond the time of operation to involve preoperative evaluation and immediate postoperative management. The increasing magnitude of modern surgical procedures and the trend toward accepting for operation patients who are poor surgical risks place larger demands on the anesthesiologist’s capacity to assess and to support the vital systems of the body. Blood volume is a major, determinable factor in this evaluation. Among the methods for its determination, those that use radioactive iodinated human serum albumin (I131) are rapid and accurate and can be frequently repeated.

The normal average blood volume by this procedure is about 85 ml. per kilogram of body weight, of which blood cells make up some 40 ml. and plasma the remaining 45 ml. There is variation around this mean. Total blood volume is proportioned to the mass of metabolically active tissue. A lean, muscular person has a greater blood volume per unit of body weight than does an obese person. The aged tend to have smaller total blood volumes than the young. Determinations of hemoglobin content, red cell count, hematocrit ratio or plasma protein levels are made from a unit of the total volume. They give quantitative expressions of these components in relation to that volume, but they do not indicate what that volume may be. Hence, they do not substitute for direct determinations of total circulating volume (Table 1).

This report presents observations made with a simplified, isotopic technic that enables blood volume determinations to be made in. . .



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