The relationship between trajectories of renal oxygen saturation and acute kidney injury: a prospective cohort study with a secondary analysis

Background Acute kidney injury (AKI) is a major postoperative consequence, affecting prognosis of older patients. Effective prediction or intervention to predict or prevent the incidence of AKI is currently unavailable. Aims Dynamic changes of renal tissue oxygen saturation (RSO 2 ) during surgery process are understudied and we intended to explore the distinct trajectories and associations with postoperative AKI. Methods This was a secondary analysis including data for older patients who underwent open hepatectomy surgery with informed consent. Latent class mixed models (LCMM) method was conducted to generate trajectories of intraoperative renal tissue RSO 2 through different time points. The primary outcome was postoperative 7-day AKI. The univariate and multivariate regression analysis were performed to identify the relationship between distinct trajectories of renal tissue RSO 2 and the risk of AKI. Meanwhile, the prediction efficacy of renal tissue RSO 2 at different time points was compared to find potential intervention timing. Results Postoperative AKI occurred in 14 (15.2%) of 92 patients. There are two distinct renal tissue RSO 2 trajectories, with 44.6% generating "high-downwards" trajectory and 55.4% generating "consistently-high" trajectory. Patients with "high-downwards" trajectory had significantly higher risk of postoperative AKI than another group (Unadjusted OR [Odds Ratio] = 3.790, 95% CI [Confidence Interval]: 1.091–13.164, p = 0.036; Adjusted OR = 3.973, 95% CI 1.020–15.478, p = 0.047, respectively). Predictive performance was 71.4% sensitivity and 60.3% specificity for "high-downwards" trajectory of renal tissue RSO 2 to identify AKI. Furthermore, the renal tissue RSO 2 exhibited the lowest level and the best results in terms of the sensitivity during the hepatic occlusion period, may be considered as a "time of concern". Conclusions Older patients undergoing hepatectomy may show high-downwards trajectory of renal tissue RSO 2 , indicating a higher risk of AKI, and the lowest level was identified during the hepatic occlusion period. These findings may help to provide potential candidates for future early recognition of deterioration of kidney function and guide interventions.