Randomization and blinding
Patients were randomly divided into an intravenous low-dose NE group (NE Group) and a control group (C Group) using a computer-generated randomization list with a block size of 30 and a 1:1 allocation ratio. The patients were registered by a dedicated investigator and assigned sealed, unique, randomly numbered, opaque envelopes in which the allocation was concealed. Before surgery, an anesthesiologist who did not perform the surgery prepared the trial drugs (low-dose NE or saline solution) according to the allocation noted in the envelope. The remaining investigators, surgeons, anesthesiologists, and patients were blinded to allocation.