Remimazolam Total Intravenous Anesthesia Under Analgesia Nociception Index-guidance

The investigators hypothesized that intraoperative opioid consumption would be different between remimazolam and propofol if the ANI-guided remifentanil continuous infusion rate was adjusted when the depth of anesthesia was maintained at similar depths with remimazolam or propofol under total intravenous anesthesia. The purpose of this study is to compare the intraoperative remifentanil requirement in patients undergoing total knee arthroplasty when the intraoperative remifentanil dose adjustment was performed under the ANI guidance while maintaining a similar depth of anesthesia with remimazolam or propofol.