Regional blood flows measured in conscious rats by combined Fick and microsphere methods

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Abstract
Regional blood flow measurements made by the radioactive microsphere technique were studied in conscious rats. A femoral arterial reference sample blood flow was measured directly and, at the same time, indirectly by the combined use of direct Fick cardiac output and microsphere techniques. A significant correlation (r = .81, P < .01) was obtained between direct and indirect blood flow values when 200-400 microspheres were trapped in the reference sample. When 100-200 microspheres were trapped, regional blood flow was 32% below true flow (P < .01); and cardiac output, calculated by the reference sample method, was 57% greater than Fick cardiac output (P < .01). When 3 consecutive Fick determinations and microsphere injections (20,000/injection, 15 .mu.m diameter) were made in conscious rats, significant correlations were obtained among the 1st, 2nd and 3rd regional blood flow measurements (r = .95, P < .01). Cardiac output and reference blood flow can be measured with accuracy and precision in the conscious rat by the radioactive microsphere procedure.