Objective:To investigate the effect of slow intravenous infusion of low-dose mannitol on the hemodynamics of patients after cardiopulmonary bypass.Methods:Prospective, continuous inclusion of 62 patients after cardiac surgery under cardiopulmonary bypass. By random number method, they were divided into normal treatment group(group C) with 29 cases and mannitol treatment group(group M) with 33 cases. Group C was treated according to the postoperative routine treatment measures. On the basis of conventional treatment, group M received intravenous infusion of 20% mannitol injection 0.25 g/kg at 1、8、24 hours after operation, and the intravenous infusion time was 60 minutes each time. According to the hemodynamic changes during the two groups of treatment, the effect of slow intravenous infusion of low-dose mannitol on patients after cardiopulmonary bypass under cardiopulmonary bypass was analyzed.Results:In group M, CI and SVI were significantly increased after use of mannitol than before, with statistical significance( P<0.01). SVRI showed a downward trend, and the changes were statistically significant after use of mannitol( P<0.01). PAWP increased first and then decreased after operation, and the changes were statistically significant after mannitol use than before( P<0.05). RAP and MPAP had no significant changes after the first use of mannitol, but the changes after the latter two use mannitol were statistically significant than before( P<0.05). Repeated-measurement data analysis of variance was performed on the hemodynamic parameters of each group, and the results were all P<0.01. Conclusion:Postoperative slow intravenous infusion of low-dose mannitol optimizes hemodynamic status, increases stroke volume, reduces cardiac preload, improves systemic and pulmonary circulation resistance, and promotes recovery of postoperative cardiopulmonary function.