Precautions for measuring blood flow during anemia with the microsphere technique

Publisher Website
Google Scholar
Abstract
Preliminary data from a study of the effects of anemia on organ blood flow [in newborn lambs] showed large discrepancies between cardiac output measured with the microsphere technique and simultaneous values calculated by the Fick principle. The most likely explanation was that the reference sample drawn according to the standard procedure underestimated the microsphere concentration in arterial blood, resulting in erroneously high blood flow values. Here, the usual reference sample, from a small catheter advanced from a peripheral artery into the brachiocephalic artery (withdrawal rate 1.3 ml/min), were compared with a simultaneous sample from a larger catheter withdrawn at the much higher rate (7.89 mg/min). At hematocrits above 32%, microsphere concentrations from the 2 catheters were similar, but below 32% the concentration of microspheres in blood from the larger catheter was 30-50% more than from the smaller. The discrepancy was not altered by changing the injection site from left ventricle to left atrium and thus was probably not the result of poor mixing within the heart. It may have been the result of nonhomogeneous distribution of microspheres within larger vessels, perhaps as a consequence of laminar flow and axial streaming of both red blood cells and microspheres during anemia. Whatever the cause, it was possible to eliminate the difference by withdrawing from the smaller catheter at a more rapid rate (2.46 ml/min).

This publication has 4 references indexed in Scilit: