[Correlation between acute kidney injury diagnosed by serum creatinine and urine output criteria and short-term prognosis in critically ill patients following non-cardiac surgery].

OBJECTIVE: To analyze the correlation between acute kidney injury (AKI) diagnosed by elevated serum creatinine (Scr) versus only meeting the urine output (UO) reduction criteria and short-term adverse outcomes in critically ill patients following non-cardiac surgery, and to evaluate the association between even mild elevations in Scr and clinical outcomes furthermore.

METHODS: This study was a secondary analysis of data from a prospective cohort study. A total of 1020 non-cardiac surgery adults admitted to the intensive care unit (ICU) of Peking University First Hospital from May 20, 2019 to March 7, 2022 were included. According to Kidney Disease: Improving Global Outcomes (KDIGO) guideline, AKI patients were classified into two groups: the AKI-Scr group (those meeting the Scr elevation criteria) and the AKI-UO group (those fulfilling only the UO reduction criteria). The primary outcome was in-hospital mortality in patients with AKI, and the secondary outcomes were major renal adverse events, post-operative renal replacement therapy (RRT), postoperative complications, postoperative mechanical ventilation time, ICU stay, postoperative hospital stay, total hospital stay, and total medical costs. Multivariate Logistic regression analysis was used to identify risk factors of hospitalized death in critically ill patients with AKI following non-cardiac surgery.

RESULTS: A total of 1020 non-cardiac surgical patients admitted to the ICU were enrolled, among whom 429 were diagnosed with AKI. There were 91 cases in the AKI-Scr group and 338 cases in the AKI-UO group. The primary study endpoint: no statistically significant difference in in-hospital mortality was observed between the AKI-Scr and AKI-UO groups (5.5% vs. 2.1%, P>0.05). The secondary study endpoints: compared with the AKI-UO group, the patients in the AKI-Scr group had a higher incidence of major renal adverse events (9.8% vs. 4.4%), postoperative RRT (4.4% vs. 0.3%) and postoperative complications (50.5% vs. 24.0%, all P < 0.05), a significantly longer duration of postoperative mechanical ventilation (12.0 d vs. 7.5 d), ICU stay (2 d vs. 1 d), postoperative hospital stay (14 d vs. 9 d) and total hospital stay (21 d vs.17 d, all P < 0.05), and a significantly higher total medical expenditure (112000 yuan vs. 89000 yuan, P<0.001). Multivariate Logistic regression analysis showed that postoperative RRT (OR=33.164, 95%CI: 1.305-842.794, P=0.034) and sepsis during hospitalization (OR=23.096, 95%CI: 4.242-125.175, P < 0.001) were independent risk factors for hospitalized death in the critically ill patients with postoperative AKI. Compared with the ΔScr≤24% patients (Scr increased by less than 24% from baseline within 7 d), even in the patients with only a minor elevation in Scr (ΔScr increase of 25%-49% from baseline but < 26.5μmol/L), the incidence of postoperative complications was significantly higher (48.6% vs. 19.2%, P < 0.001), along with prolonged ICU stay [1(1, 3) d vs. 1(1, 2) d], postoperative hospital stay (13 d vs. 9 d), and total hospital stay (23 d vs. 16 d, all P < 0.05). Compared with the non-AKI group, the incidence of in-hospital mortality (2.1% vs. 0.3%, P < 0.05) and postoperative complications (24.0% vs. 18.3%, P < 0.05) was higher in the AKI-UO group, and the ICU stay [1(1, 3) d vs. 1(1, 2) d, P < 0.001] was longer.

CONCLUSION: In critically ill patients with AKI following non-cardiac surgery, the short-term prognosis of patients with AKI whose diagnosis was mainly based on increased Scr was worse than patients who only met the diagnostic criteria of oliguria. Even a mild elevation in serum creatinine was associated with adverse patient outcomes.