Background and Aims This study was aimed to evaluate and compare the preoperative fasting gastric volume (GV) in diabetic and non-diabetic older adults undergoing staged bilateral total knee arthroplasty (TKA) using ultrasonography.

Methods This was a prospective non-randomized and comparative study of 38 older adults aged over 65 years who were scheduled for staged bilateral TKA. All participants were fasted from midnight. Patients diagnosed with diabetes mellitus (DM group, n=19) or not (non-DM group, n=19) were matched forage, sex, and body mass index. The primary outcome was residual GV assessed by ultrasonography.

Results The GV was significantly different between the DM group [75.1 (43.2) mL] and the non-DM group [35.9 (25.9) mL] at second TKA (P=0.002), but not at first one (P=0.096). In the comparison of GV within the group, GV was larger in the second TKA compared with first operation, in both DM (P<0.001) and non-DM (P=0.018) groups. The mean difference of GV amount within two sequential TKAs was greater in the DM group (42.5 mL; 95% confidence interval [CI], 26.6 to 58.5) than non-DM group (20.0 mL; 95% CI, 3.8 to 36.2; P=0.044).

Conclusions The preoperative fasting GV measured at the second TKA was larger in diabetic older adults than in non-diabetic ones. Furthermore, the residual GV was different according to the stage of TKA, showing greater volume in second than first operation, in both diabetic and non-diabetic group. Hence, a caution is required for preoperative fasting practice in the elderly undergoing staged bilateral TKA, especially in diabetic patients undergoing second stage operation.