In our institution, many patients undergo staged bilateral total knee arthroplasty at weekly intervals, and most of the patients are older adults with degenerative arthritis. As recommended, the older adult patients who undergoing total knee arthroplasty drink carbohydrate-containing fluid (400 ml) 2 hours prior to surgery. In this type of surgery, there are additional points to consider when applying the fasting guidelines. This is because, in addition to the factor of advanced age, which can affect gastric emptying time, the patient's physical, medical, and psychological conditions at the first and the second operation may be different. For example, the effect of the acute pain that occurs after the first total knee arthroplasty and subsequent opioids administered on gastric motility cannot be ignored. However, to date, there have been no studies examining the association of stress (emotional and surgical) and residual gastric volume of older adult patients with staged bilateral total knee arthroplasty and whether there is a difference according to the stage when carbohydrate-containing fluid is ingested.

In the present study, the investigators will evaluate the effect of emotional stress, surgical stress, pain, and the use of opioids on the residual gastric volume in older adults undergoing staged-bilateral total knee arthroplasty.

Inclusion Criteria:

• Patients scheduled for staged bilateral total knee arthroplasty aged ≥ 65
• American Society of Anesthesiologists physical status classification 1, 2, and 3
• Body mass index < 35 kg/cm2
• Patients administered carbohydrate-containing fluid 2 hours prior to surgery

Exclusion Criteria:

• Previous surgery of the upper gastrointestinal tract
• Achalasia
• Diabetes

Study participants will be patients who are scheduled to undergo staged bilateral total knee arthroplasty requiring administration of carbohydrate-containing fluid 2 hours prior to surgery.