Remimazolam Versus Propofol for Painless Abortion

The goal of this clinical trial is to compare the efficacy and safety of propofol vs. remimazolam in combine use of esketamine in women with early pregnancy undergoing painless abortion. The main questions it aims to answer are: * whether remimazolam plus esketamine (R+E) has a better sedative and analgesic effectiveness than propofol plus esketamine (P+E). * whether R+E has less adverse events than P+E. Participants will be randomly allocated to two groups: R+E and P+E group. * For those in group R+E: they will be administered with 0.3mg/kg remimazolam and 0.3mg/kg esketamine before the abortion surgery. * For those in group P+E: they will be administered with 2mg/kg propofol and 0.3mg/kg esketamine before the abortion surgery. We will compare R+E with P+E to see if the time to loss of conscious and time to recover from the sedation will be shorter and if there will be less severe adverse events in R+E.