Aspiration of gastric contents during perioperative period is a grave complication with significant morbidity and mortality. Diabetic patients have a higher incidence of autonomic dysfunction, causing gastropathy. They are known to have gastroparesis and the consequent delayed gastric emptying which predisposes them to an increased risk of aspiration than the general population. Furthermore, other common factors can influence the gastric emptying rate, as for example, old age, pain, and the use of opioid analgesics.

In the previous study, evidence of increased pain was reported in patients undergoing staged bilateral total knee arthroplasty, in whom the second operated knee had greater sensitivity (tertiary hyperalgesia) due to the surgical injury to the first operated knee.

In the present study, we will evaluate the effect of old age, diabetes, surgical stress, pain, and the use of analgesics on the residual gastric volume in elderly patients undergoing staged-bilateral total knee arthroplasty.

Inclusion Criteria:

• Patients scheduled for staged bilateral total knee arthroplasty aged 65 to 85 years
• American Society of Anestheiologist physical status classification 1, 2, and 3
• Body mass index < 35 kg/cm2

Exclusion Criteria:

• Previous surgery of the upper gastrointestinal tract
• Achalasia

Study participants will be patients whom are scheduled to undergo staged bilateral total knee arthroplasty requiring preoperative fasting period of at least 8 hours. 40 patients will be recruited in total. One cohort consisting 20 patients will be diabetic. The other cohort consisting of 20 patients will be non-diabetic.