Ultrasound assessment of residual gastric volume in older adults undergoing staged-bilateral total knee arthroplasty after consuming carbohydrate-containing fluids: a prospective observational study

Background We compared preoperative residual gastric volume (GV) between the first and second stages of total knee arthroplasty (TKA) in older adults after drinking carbohydrate-containing fluid 2 h prior to surgery. Methods In this study, 36 patients, aged > 65 years, scheduled for staged bilateral TKA with one-week interval, were enrolled. The patients consumed 400 ml of carbohydrate-containing fluid 2 h prior to surgery. Before the induction of spinal anesthesia, the gastric antral cross-sectional area was measured at the first and second TKA using ultrasound, and the residual GV was calculated. The primary outcome was the residual GV. Qualitative GV (grades 0, 1, and 2) and analgesic consumption after the first TKA were assessed as secondary outcomes. Results The GV (median [Q1, Q3]) was greater in the second-stage TKA (41.1 [22.5, 62.8] ml) than in the first-stage TKA (10.3 [0.0, 27.1] ml) (P < 0.001). In the qualitative assessment, the distribution was not different between the two stages of TKA (P = 0.219) and only one patient showed grade 2 gastric content in the second TKA. When opioid consumption was converted to an equivalent dose of morphine, an average of 53.9 mg of morphine was required after the first TKA. Conclusions Residual GV after drinking carbohydrate-containing fluid differed according to the stage of TKA, showing a larger residual GV in the second TKA than in the first one. In older adults scheduled to undergo bilateral staged TKA, caution is required in preoperative fasting practice, especially in second-stage surgery.