Association of intra-operative muscular tissue oxygen saturation with postoperative acute kidney injury in older patients undergoing major abdominal surgery: A prospective cohort study

Abstract

Abstract Purpose Acute kidney injury (AKI) is frequently associated with poor postoperative prognoses. Intra-operative renal ischaemia and hypoxia may contribute to the pathogenesis of postoperative AKI. However, direct monitoring of this condition is difficult. Although near-infrared spectroscopy (NIRS) measurements of muscle tissue oxygen saturation (SmtO2) can predict some postoperative adverse outcomes, their association with AKI in older patients undergoing major abdominal surgery is unclear. Methods This prospective observational study recruited a total of 253 patients aged ≥65 years undergoing ≥2-h-long elective abdominal surgeries from September 2021 to August 2022. NIRS monitoring of bilateral flank, quadriceps, and brachioradialis muscles was performed throughout the surgery. The primary outcome was the incidence of AKI , diagnosed using the Kidney Disease: Improving Global Outcomes criteria, within 7 days postoperatively. Results AKI occurred in 44/240 patients (18.3%) and was associated with worse secondary outcomes. SmtO2 decline >10% of the baseline values at the right flank (OR, 6.98; 95% CI 1.36 to 35.83; P=0.020), left flank (OR, 6.69; 95% CI 1.55 to 28.9; P=0.011), quadriceps (OR, 2.99; 95% CI 1.36 to 6.55; P=0.006) was associated with AKI. The standard deviation values of SmtO2 at the right flank (OR, 3.32; 95% CI 1.72 to 6.41; P<0.001) and left flank (OR, 1.37; 95% CI 1.01 to 1.86; P=0.048) were also associated with an increased risk of AKI. The area under the curve for SmtO2 measurements 10%, and 5% below the baseline at the right flank and quadriceps were associated with an increased risk of AKI. Conclusion SmtO2 is associated with postoperative AKI and may facilitate prevention of AKI.