Saline
OtherPatients in the experimental group were given a loading dose of 0.6 μg/kg of saline intravenously after 10 minutes of intubation, followed by a continuous infusion at a rate of 0.4 μg/kg/h until 30 min before the end of the surgery.continuous infusion at a rate of 0.4 μg/kg/h until 30 min before the end of the surgery.