Measuring blood volume with fluorescent-labeled hydroxyethyl starch

Objectives To develop and evaluate a method for measuring brood volume usin g the dilution of a fluorescent-labeled hydroxyethyl starch. Design: Laboratory and clinical investigation. Setting: Biochemistry laboratory at the University of Cardiff, Hematology c linic, surgical ward and intensive care unit of the University Hospital of Wales. Patients: Seventeen patients with suspected polycythemia. Eight patients wh o had undergone major surgery and/or were receiving intensive postoperative care. Interventions: All surgical and postoperative care was provided by clinicia ns not involved in the study. Patients with suspected polycythemia were ref erred for blood volume measurement using labeled albumin and red blood cell s. Measurement and Main Results:A proprietary brand of hydroxyethyl starch (El ohaes) was labeled with fluorescein isothiocyanate. Dilution of this compou nd in vivo was used for measuring blood volume, and the results were compar ed with those obtained using radiolabeIed albumin and the considered criter ion, radiolabeled red cells. The elimination of the labeled starch follows the same progress as that of the parent compound, indicating that the fluor escent tag is stable in vivo. The volume of distribution of the labeled sta rch is 2.5 mL/kg lower than that for labeled albumin (p =.05), Brood volume , measured from the dilution of fluorescent starch, is lower (4.9 mL/kg) th an that measured with albumin (p =.048) but higher (6.61 mL/kg) than that m easured with red blood cells (p =.0007). This latter difference may be even smaller at marginally higher doses of the fluorescent starch. Conclusion: These data support the view that hydroxyethyl starch provides a valid alternative to red cell labels as a means of calculating blood volum e in patients. Labeling the starch with a fluorescent marker makes the assa y procedure more sensitive and infinitely easier. The dose required is not high enough to affect the hemodynamic status of the patient.