[Impact of oliguria during lung surgery on postoperative acute kidney injury].

OBJECTIVE: To explore the influence of intraoperative urine volume on postoperative acute kidney injury (AKI) and the independent risk factors of AKI.
METHODS: This was a retrospective cohort study recruiting patients who received selective pulmonary resection under general anesthesia in Peking University First Hospital from July, 2017 to June, 2019. The patients were divided into the AKI group and the control group according to whether they developed postoperative AKI or not. Firstly, univariate analysis was used to analyze the relationship between perioperative variables and postoperative AKI. Secondly, receiver operating characteristic (ROC) curve was used to explore the predictive value of intraoperative urine output for postoperative AKI. The nearest four cutoff values [with the interval of 0.1 mL/(kg·h)] at maximum Youden index were used as cutoff values of oliguria. Then univariate analysis was used to explore the relationship between oliguria defined by these four cutoff values and the risk of AKI. And the cutoff value with maximum OR was chosen as the threshold of oliguria in this study. Lastly, the variables with P < 0.10 in the univariate analysis were selected for inclusion in a multivariate Logistic model to analyze the independent predictors of postoperative AKI.
RESULTS: A total of 1 393 patients were enrolled in the study. The incidence of postoperative AKI was 2.2%. ROC curve analysis showed that the area under curve (AUC) of intraoperative urine volume used for predicting postoperative AKI was 0.636 (P=0.009), and the cutoff value of oliguria was 0.785 mL/(kg·h) when Youden index was maximum (Youden index =0.234, sensitivity =48.4%, specificity =75.0%). Furthermore, 0.7, 0.8, 0.9, 1.0 mL/(kg·h) and the traditional cutoff value of 0.5 mL/(kg·h) were used to analyze the influence of oliguria on postoperative AKI. Univariate analysis showed that, when 0.8 mL/(kg·h) was selected as the threshold of oliguria, the patients with oliguria had the most significantly increased risk of AKI (AKI group 48.4% vs. control group 25.3%, OR=2.774, 95%CI 1.357－5.671, P=0.004). Multivariate regression analysis showed that intraoperative urine output < 0.8 mL/(kg·h) was one of the independent risk factors of postoperative AKI (OR=2.698, 95%CI 1.260－5.778, P=0.011). The other two were preoperative hemoglobin ≤120.0 g/L (OR=3.605, 95%CI 1.545－8.412, P=0.003) and preoperative estimated glomerular filtration rate < 30 mL/(min·1.73 m2) (OR=11.009, 95%CI 1.813－66.843, P=0.009).
CONCLUSION: Oliguria is an independent risk fact or of postoperative AKI after pulmonary resection, and urine volume < 0.8 mL/(kg·h) is a possible screening criterium.