The correlation of intraoperative oliguria with acute kidney injury after noncardiac surgery: a systematic review and meta-analysis

BACKGROUND: Acute kidney injury (AKI) occurs commonly after major surgery and is correlated with increased in-hospital morbidity and mortality. There is no consensus on whether intraoperative oliguria affects postoperative AKI. We conducted a meta-analysis to systematically assess the correlation of intraoperative oliguria with postoperative AKI. METHODS: PubMed, Embase, Web of Science, and Cochrane Library databases were searched to identify reports on the relationship between intraoperative oliguria and postoperative AKI. Quality was assessed using the Newcastle-Ottawa Scale. The primary outcomes were the unadjusted and multivariate-adjusted odds ratios (ORs) for intraoperative oliguria to correlate with postoperative AKI. The secondary outcomes included intraoperative urine output in the AKI and non-AKI groups, the demand for postoperative renal replacement therapy (RRT), in-hospital mortality, and length of hospital stay in the oliguria and non-oliguria groups. RESULTS: Nine eligible studies with 18 473 patients were included. The meta-analysis revealed that patients with intraoperative oliguria had a considerably greater risk of postoperative AKI (unadjusted OR: 2.03, 95% CI: 1.60-2.58, I2 =63%, P <0.00001; multivariate-adjusted OR: 2.00, 95% CI: 1.64-2.44, I2 =40%, P <0.00001). Further subgroup analysis did not find differences between different oliguria criteria or surgical types. Furthermore, the AKI group's pooled intraoperative urine output was less (mean differences: -0.16, 95% CI: -0.26 to -0.07, P <0.001). Intraoperative oliguria was associated with increased demand for postoperative RRT (risk ratios: 4.71, 95% CI: 2.83-7.84, P <0.001) and in-hospital mortality (risk ratios: 1.83, 95% CI: 1.24-2.69, P =0.002), but not with prolonged length of hospital stay (mean differences: 0.55, 95% CI: -0.27 to 1.38, P =0.19). CONCLUSIONS: Intraoperative oliguria was significantly associated with a higher incidence of postoperative AKI, as well as increased in-hospital mortality and demand for postoperative RRT, but not with prolonged hospitalization.