Basic data and general information of the AKI patients
A total of 8,106 patients were admitted to the ICUs of the three hospitals. Of the 3019 patients excluded, the reasons were as follows: 517 patients were <18 years old, 1831 patients were admitted to the ICU for <24 hours, 482 patients had chronic kidney disease, 16 patients had nephrectomy, 5 patients underwent kidney transplantation within 3 months before admission to the ICU, 52 patients were re-admitted to the ICU during the same hospital stay, and 116 patients had missing needed data for the study (Fig. 1). The characteristics of the AKI patients are shown in Table 1.
Incidence of AKI
According to the KIDGO criteria, a total of 890 ICU patients developed AKI, with an incidence of 17.5% (890/5087).
According to the KIDGO criteria, AKI can be divided into KIDGO stages (I, II, III), as shown Table 2; this study included 22.02% (196/890) stage I cases, 31.01% (276/890) stage II cases, and 46.97% (418/890) stage III cases.
Etiology of AKI
To clarify the etiology of AKI, the AKI patients were divided into three categories according to etiology: prerenal, renal substantive and postrenal, among which 64% (570/890) had pre-renal failure. The main causes included 255 cases of sepsis and septic shock, accounting for 44.7%; 130 cases of reduced cardiac output, accounting for 22.8%; 113 cases of fluid loss from various causes, accounting for 19.8%. A total of 33% (294/890) had renal substantial renal failure; 16.3% (48) had renal vascular and glomerular diseases, 75.9% (223) had renal tubular and interstitial diseases, 7.8% (23) had other unknown renal injury sites, and 2.7% (24) had postrenal failure. The main causes were 37.5% (9) cases of urinary tract stones, 25% (6) cases of urinary tract tumors, and 29.2% (9) cases of ureteral strictures, followed by prostate disease and neurogenic bladder.
Continuous renal replacement therapy
Currently, the main treatment methods for AKI include identifying and removing causes and risk factors, treating the primary disease, improving renal insufficiency, providing kidney-preserving drugs, and administering continuous renal replacement therapy (CRRT). CRRT has been an important supportive therapy for patients with AKI, and there are multiple treatment models available based on different mechanisms. Of the 890 AKI patients, 35.8% (319/890) received CRRT, including 6.3% (20/319) stage I patients, 21.6% (69/319 stage II patients), and 72.1% (230/319) stage III patients. The higher the AKI stage was, the more patients received CRRT.
Outcomes of AKI
The AKI patients were divided into two groups according to outcome: the survival group and the non-survival group. Of the patients with AKI hospitalized in the ICU, there are 368 deaths during hospitalization, and the mortality rate was 41.3% overall, 16% (59) for stage I AKI, 31.5% (116) for stage II AKI, and 52.4% (193) for stage III AKI; the higher the AKI stage was, the worse the prognosis. (Table 2) The mortality of patients without RRT was 37.1% (212), and 48.9% (156) of patients with RRT died (p=0.001). Further analysis showed that patients treated with RRT had a higher AKI stage and more severe disease than those without RRT.
Risk factors for death in AKI patients
- Univariate analysis
Univariate logistic regression analysis showed that male sex, old age, high AKI stage, RRT, infection, cardio-pulmonary resuscitation, reduced cardiac output, mechanical ventilation, diuretics, and reduced white blood cells, platelets, blood urea nitrogen, serum albumin prothrombin time (PT) and activated partial thromboplastin time (APTT) were significantly correlated with death in AKI patients (all P values were less than 0.05). (Table 3)
- Multivariate analysis
Multivariate logistic regression analysis showed that old age, male sex, high AKI stage, reduced cardiac output, mechanical ventilation, RRT, elevated leucocyte count, reduced platelet count, and reduced serum albumin were all independent risk factors for AKI death. (Table 4)
Sepsis and septic shock were the most common causes of AKI in critically ill patients. Among the AKI patients enrolled in this study, 28.7% (255/890) had AKI caused by sepsis and septic shock, which were the major causes of AKI. The main infection sites were the lung, abdomen, urinary system, skin and soft tissue. Among the patients with AKI caused by sepsis and septic shock, 92 patients received RRT, accounting for 28.8% of the total patients treated with RRT. A total of 136 patients with sepsis and septic shock AKI died, leading to a mortality of 53.3%.