In the past, some guidelines advised no oral intake for at least 8 hours before any surgery. However, research has shown risks associated with excessive fasting, such as postoperative insulin resistance, and advantages in shorter fasting protocols, such as reduced postoperative nausea and vomiting.

The perioperative fasting guidelines of the European Society of Anaesthesiology focus on preoperative carbohydrates. They hold that it is safe for patients to drink carbohydrate-rich fluids up to 2 hours before elective surgery and that drinking carbohydrate-rich fluids improves subjective well-being, reduces thirst and hunger, and reduces postoperative insulin resistance at an evidence level of 1++. Nevertheless, data on drinking carbohydrate fluids before surgery in elderly patients are limited.

In our institution, there are two clinical pathways for total knee arthroplasty according to the surgeons. One difference is whether carbohydrate fluids drink or not before surgery. The purpose of this study, therefore, is to assess gastric volume in fasted elderly patients using ultrasound after they drank carbohydrate fluids 2 hours before surgery and to compare with matched patients using age, body mass index, and comorbidity, who did not drink carbohydrate fluids before surgery.

Inclusion Criteria:

• Patients undergoing total knee arthroplasty
• Age: 65~85 yeas
• ASA 1~3

Exclusion Criteria:

• Age < 65 years
• ASA >= 4
• Diabetes mellitus
• Chronic kidney disease

Patients undergoing total knee arthroplasty