A Simple Radioactive Microsphere Method for Measuring Regional Flow and Cardiac Output

The determination of regional blood flow and cardiac output with radioactively labeled microspheres and a reference arterial sample has been assessed in the rabbit. Paired determinations of cardiac output with the microsphere and indocyanine green dye dilution methods correlated well (F=236; p<< 0.001; N=98). A simple method for administering microspheres with a 1.5% accuracy has been developed. Paired samples drawn simultaneously revealed mixing and streaming errors of 5.3%. Regional flows to several organs determined by the method were in accord with published data. The advantages of microsphere-reference sample method include: simplicity, accuracy, the provision of regional flows without simultaneously determining cardiac output, and applicability to small laboratory animals and low flow states.