Determination of central blood volume. Comparison of Stewart-Hamilton method with direct measurements in dogs

Abstract

Central blood volume (cardiac output times mean transit time) from right atrium to ascending aorta was determined by the indicator-dilution method in 22 open-chested dogs which had previously had their red blood cells tagged with Cr51. The actual amount of blood in the heart and lungs was calculated from the total radioactivity in the blended homogenate of these organs. The two measurements of central blood volume correlated well ( r = +.88), the indicator-dilution volumes averaging 12% greater. The discrepancy between measurements is probably related to the pulmonary circuit having a lower hematocrit than the large vessels. The results substantiate the use of the Stewart-Hamilton formula (cardiac output times mean transit time) to measure central blood volume.

The Pulmonary Blood Volume in Man*

“…Further theoretical and experimental confirmation of the validity of this volume determination, utilizing the product of the mean transit time of indicator particles and the blood flow, has been given repeatedly (2,(11)(12)(13)(14).…”

Reductions in cardiac output, central blood volume, and stroke volume with thermal stress in normal men during exercise.

“…In addition to elimination of problems cited above, central sampling prevented the large errors in determination of CBV due to gross disparities between aortic and peripheral transit times induced by peripheral vasoconstriction during exercise (7,8). Indeed, Schlant and associates (20) observed a close correlation between a direct measurement of CBV and this volume as determined by the Stewart-Hamilton method with central injection and sampling. However, measurements of CBV could have been distorted by sampling from the aorta at the origin of the left subclavian artery rather than from the root.…”

Observations on the Pulmonary Blood Volume Determined by the Precordial I¹³¹-Albumin Dilution Method Compared with the Blood Content of the Lungs

“…As is the case with dilution methods in general, no comparative studies have been made between the pulmonary blood volume calculated by the dilution method and the actual volume, with the exception of the investigation of Schlant et al (11). In their study they compared in open thorax experiments the heart-lung blood volume calculated on basis of dye dilution and that meas ured with the aid of Cr51-tagged red cells.…”