The aim of this randomized controlled study is to investigate the effect of implementing a preoperative nutrition education and fasting protocol prepared in accordance with Enhanced Recovery After Surgery (ERAS) guidelines during the 24-hour preoperative period on postoperative hydration status and the incidence of nausea and vomiting in patients scheduled for total knee arthroplasty. Total knee arthroplasty is a commonly performed surgical procedure, particularly in older adults, and postoperative recovery may be negatively affected by surgical stress, anesthesia-related complications, dehydration, and postoperative nausea and vomiting. ERAS protocols emphasize the optimization of preoperative nutrition and hydration as key components to improve postoperative outcomes. In this study, patients undergoing elective total knee arthroplasty will be randomly assigned to an intervention group or a control group. Patients in the intervention group will receive ERAS-based preoperative nutrition education and a standardized fasting protocol during the 24 hours prior to surgery, while patients in the control group will receive routine standard care. Postoperative hydration status, nausea and vomiting severity, and fluid intake-output balance will be assessed and compared between the two groups. The findings of this study are expected to contribute to improving perioperative nursing care practices and enhancing patient recovery and comfort following total knee arthroplasty.