Postoperative cognitive dysfunction (POCD) is more common in older patients, and increased insulin resistance is an important factor for POCD. Fasting before surgery is performed to reduce the incidence of pulmonary aspiration after anesthesia. However, prolonged fasting increases insulin resistance. Recently, it is recommended to minimize fasting times and consume carbohydrate drinks before surgery. Therefore, the investigators investigate whether preoperative carbohydrate drinks can reduce insulin resistance in the elderly patients. Fifty patients (age>65 years) scheduled for arthroplasty will be divided into carbohydrate (n=28) and control (n=28) groups. Randomly selected patients of the carbohydrate group are given 400ml of 12.8 g/100 ml carbohydrate beverage 2-3 hours before their scheduled operation. In contrast, patients in the control group are fasted from water 2 h before surgery according to standard protocol.

Inclusion Criteria:

1. Patients undergoing arthroplasty
2. age>65 years

Exclusion Criteria:

1. The subject is a foreigner or illiterate
2. Patients with gastroesophageal reflux disease, gastric emptying disorders, inflammatory bowel disease, or previous treatment for intra-abdominal cancer
3. Patients with chronic renal disease or severe cardiovascular disease
4. HbA1c >69 mmol/mol or BMI >30 kg/m2
5. A duration of ≥5 h between consumption of CHO and initiation of surgery.

Investigator and outcomes assessor are blinded to group assignment.