Effects of fluid resuscitation on CO in the three groups. The trial program and case grouping were carried out according to the design indicated in Methods. CO was measured by Doppler echocardiography. There were no differences in CO among the three groups at all the six time points. Comparing the CO variables in the same group, CO at T120 and T8h was significantly higher than at T0 in the Ns group; the parameter at T8h was higher than at T0 in the Hs group; and CO at T60, T90, T120 and T8h were higher than that at T0 in the Sb group (*p < 0.05). CO improved earlier in the Sb group than in the Ns and Hs groups.