Randomization and grouping
Patients, data collectors, sample collectors and data analysts were not aware of the grouping. The patients were randomly divided into four groups with the help of Excel. The medication regimen of each patient was saved in an opaque envelope marked with the corresponding number by the research assistant who was not involved in data collection and anesthesia management. On the day of the operation, the assistant opened the envelope and filled the syringe with the drug or the same amount of physiological saline. Although the drug and physiological saline were transparent, they were still covered with an opaque label. According to the grouping, the corresponding drug/physiological saline was injected or continuously pumped at the corresponding time (10 min before anesthesia induction, after induction to the end of the operation, and at the beginning of CPB). Preoperative and postoperative assessments, perioperative data collection, and blood sampling were performed by another assistant who was not aware of the allocation scheme and was not involved in anesthesia management. The data were submitted to statisticians who did not participate in the experiment.The patients were randomly divided into the following four groups: (1) penehyclidine hydrochloride group (group P): intravenous injection of 0.02 mg/kg of penehyclidine hydrochloride 10 min before anesthesia induction and at the beginning of CPB, with a total dose of 0.04 mg/kg; (2) dexmedetomidine group (group D): after induction of anesthesia, dexmedetomidine 0.5 μg/kg/h was pumped intravenously until the end of anesthesia; (3) penehyclidine hydrochloride plus dexmedetomidine group (group PD): penehyclidine hydrochloride 0.02 mg/kg was injected intravenously 10 min before anesthesia induction and at the beginning of CPB, with a total dose of 0.04 mg/kg; and dexmedetomidine 0.5 μg/kg/h was pumped intravenously after induction of anesthesia until the end of anesthesia; and (4) control group (group C): the same amount of normal saline was given 10 min before and after anesthesia induction to the end of anesthesia, and at the beginning of CPB.