Patient characteristics stratified by the severity of Covid-19
We included 210 patients with completed data, of whom 131 were males (62.4%). The median age was 64 years (IQR: 56-71). The patient characteristics as stratified by the disease severity are shown in Table E1. 60 patients were categorized as having severe disease and the remaining 150 patients as having critical disease upon admission to ICU. The gender and the age were comparable. Diabetes was more common in critical cases than in severe cases (24.7% vs 11.7%, P=0.037). There were, however, no significant differences for other comorbidities between severe and critical cases.
Overall, the most common respiratory support for severe cases consisted of conventional oxygen therapy (COT) and high-flow nasal cannula (HFNC), A significantly larger proportion of patients with critical disease were initiated with invasive mechanical ventilation（IMV）. There was, however, no significant difference in the use of non-invasive mechanical ventilation (NIV) between severe and critical cases.（Table E1）
Of the 210 patients, 194 patients were from Wuhan JinYinTan Hospital, and 16 patients were from The First Affiliated Hospital of Guangzhou Medical University. Right heart failure,
Hypoxemia , hypercapnia and higher levels of interleukin-6 were more common in patients from Wuhan JinYinTan Hospital (both P<0.05).（Table E2）
The incidence of AKI and use of CRRT, and the Risk factors associated with AKI
Of 92 (43.8%) patients who developed AKI during hospitalization, 13 (14.1%), 15 (16.3%) and 64 (69.6%) patients were classified as having stage 1, 2 and 3 disease, respectively (Table 1). 54 cases (58.7%) received CRRT.
Patients with AKI were significantly more likely to be critical cases (97.8% vs. 50.9%, P<0.001), have malignancy (10.9% vs. 3.4%, P=0.031), develop sepsis (78.3% vs. 33.9%, P<0.001), right heart failure (30.4% vs. 13.6%, P=0.003) and disseminated intravascular coagulation (29.4% vs. 4.2%, P<0.001). Significantly more critical cases than severe cases who received nephrotoxic drugs developed AKI (41.3% vs. 11.9%, P<0.001). Patients with AKI more frequently received IMV (87.0% vs. 32.2%, P<0.001) but less frequently received COT (2.2% vs. 33.1%, P<0.001) and NIV (4.4% vs. 21.2%, P<0.001). Furthermore, patients with AKI had markedly higher levels of serum creatinine (median: 75.5 vs. 67.1 μmol/L, P=0.002), interleukin-6 (median: 17.9 vs. 12.3 pg/ml, P<0.001) and serum ferritin (median: 2001.0 vs. 985.4 ng/ml, P<0.001). Hypoxemia and hypercapnia were also more frequently identified in patients with AKI (both P<0.001). In the multivariate regression model, greater age(OR 1.05,95%CI 1.01-1.09) , sepsis(OR2.82,95%1.14-6.98), Nephrotoxic drug(OR2.67, 95%1.09-6.55), IMV(OR9.72, 95%2.93-32.24) and elevated baseline Scr(OR1.01, 95%1.00-1.02) were associated with AKI occurrence among patients with Covid-19. (Table 2)
Outcomes of renal diseases and impact of AKI on clinic outcomes
Of 92 patients with AKI, the renal function improved during hospitalization among 16 patients (17.4%), who had a significantly shorter time from admission to AKI diagnosis (median: 5 vs. 9 days, P<0.001), lower incidence of right heart failure (56.3% vs. 25.0%, P=0.030) and higher P/F ratio (median: 133.5 vs. 67.0, P<0.001) than their counterparts (Table 3) (Fig 1)
Of 210 patients, 93 patients deceased within 28 days of ICU admission (ICU 28-day mortality: 44.3%), and non-survivors were more likely to be critical cases compared with severe cases (98.9% vs. 1.1%, P<0.001). Significantly more non-survivors had sepsis (77.4% vs. 34.2%, P<0.001) acute kidney injury stage 3 (52.7% vs. 12.8%, P<0.001) and disseminated intravascular coagulation (28.0% s. 5.1%, P<0.001). CRRT was initiated significantly more frequently in non-survivors than in survivors (41.9% vs. 12.8%, P<0.001). IMV was initiated more frequently whereas COT and HFNC were initiated less frequently in critical cases (all P<0.01). Non-survivors had higher levels of interleukin-6 (median: 17.2 vs. 13.6 pg/ml, P=0.031) and serum ferritin (median: 2001.0 vs. 1000.7 ng/ml, P<0.001) compared with survivors. Hypoxemia and hypercapnia were also more common in non-survivors (both P<0.001). However, neither the use of nephrotoxic drugs nor the serum creatinine levels differed between survivors and non-survivors (Table 4). After adjusting for the potential confounding factors, having KDIGO stage 3 (OR:5.33, 95%CI: 1.15-24.65), critical disease (OR: 69.16, 95%CI: 5.86-815.79) , greater age (OR: 1.06, 95%CI: 1.02-1.11) and Min P/F <150mmHg(OR: 15.21 , 95%CI: 4.72-49.07) independently predicted the death within 28 days of ICU admission(Table 5) (Fig 2).