Measurement of cardiac output in rats by 125I dilution

A simple, rapid, indicator-dilution method of estimating cardiac output in small animals using 125 I human serum albumin has been developed. The variation of repeat determinations in a single animal was ±10%. The cardiac output in normotensive 250–350 g Wistar male rats was 217 ± 28 (±S.D.) ml/kg min −1 . These results agree with others derived by more tedious methods. After the mean arterial blood pressure was reduced to 50 mm Hg for 60 min by hemorrhage the cardiac output declined to 104 ± 40 ml/kg min −1 . With this method it is possible to repeat determinations of cardiac output during shock.