Acute Kidney Injury Can Predict In-Hospital Mortality in Elderly Patients with COVID-19 in the ICU: A Single-Center Study

Figures & data

Figure 1 Flowchart of the patient inclusion and exclusion process.

Table 1 Comparisons of the Clinical Characteristics of Patients in ICU with Different Severities of Coronavirus Disease 2019

Characteristics	All Patients (n=107)		P-value	Severe Patients		P-value	Critical Patients		P-value
	Non-AKI (59, 55.1)	AKI (48, 44.9)		Non-AKI (30, 81.1)	AKI (7, 18.9)		Non-AKI (29, 55.1)	AKI (41, 44.9)
Age (years)	68 (63–75)	73 (67–81)	0.031	67 (63–78)	78 (71–84)	0.021	68 (63–72)	72 (65–81)	0.170
Male sex	37 (62.7)	32 (66.7)	0.671	18 (60.0)	6 (85.7)	0.174	19 (65.5)	26 (63.4)	0.856
Body mass index (kg/m^2)	22.8±1.9	23.7±2.5	0.033	22.7±1.9	22.7±2.5	0.930	23.0±1.9	23.9±2.5	0.092
Comorbidity
Hypertension	37 (62.7)	36 (75.0)	0.175	20 (66.7)	6 (85.7)	0.294	17 (58.6)	30 (73.2)	0.202
Cardiovascular disease	12 (20.3)	21 (43.8)	0.009	6 (20.0)	4 (57.1)	0.058	6 (20.7)	17 (41.5)	0.068
Chronic obstructive pulmonary disease	12 (20.3)	11 (22.9)	0.747	5 (16.7)	0	0.132	7 (24.1)	11 (26.8)	0.800
Diabetes	10 (16.9)	12 (25.0)	0.305	3 (10.0)	1 (14.3)	0.750	7 (24.1)	11 (26.8)	0.800
Cerebrovascular disease	6 (10.2)	13 (27.1)	0.023	2 (6.7)	3 (42.9)	0.025	4 (13.8)	10 (24.4)	0.275
Chronic kidney disease	0	5 (10.4)	0.004	0	3 (42.9)	0.001	0	2 (4.9)	0.140
Signs and symptoms
Cough	51 (86.4)	38 (79.2)	0.317	26 (86.7)	5 (71.4)	0.353	25 (86.2)	33 (80.5)	0.528
Fever	46 (78.0)	35 (72.9)	0.545	24 (80.0)	4 (57.1)	0.225	22 (75.9)	31 (75.6)	0.981
Dyspnoea	47 (79.7)	30 (62.5)	0.049	47 (79.7)	30 (62.5)	0.049	24 (82.8)	27 (65.9)	0.117
Muscle ache	38 (64.4)	30 (62.5)	0.838	16 (53.3)	2 (28.6)	0.231	22 (75.9)	28 (68.3)	0.490
Fatigue	34 (57.6)	27 (56.3)	0.886	18 (60.0)	3 (42.9)	0.412	16 (55.2)	24 (58.5)	0.779
Chest pain	11 (18.6)	5 (10.4)	0.235	7 (23.3)	0	0.069	4 (13.8)	5 (12.2)	0.844
Chills	11 (18.6)	5 (10.4)	0.235	5 (16.7)	0	0.132	6 (20.7)	5 (12.2)	0.340
Headache	4 (6.8)	2 (4.2)	0.554	3 (10.0)	0	0.251	1 (3.4)	2 (4.9)	0.769
Diarrhoea	1 (1.7)	3 (6.3)	0.212	0	0	–	1 (3.4)	3 (7.3)	0.479
Chest CT findings
Multiple mottling and ground glass opacity	56 (94.9)	44 (91.7)	0.500	28 (93.3)	7 (100.0)	0.352	28 (96.6)	37 (90.2)	0.292
Pneumonia			0.274			0.514			–
Unilateral pneumonia	1 (1.7)	0		1 (3.3)	0		0	0
Bilateral pneumonia	58 (98.3)	48 (100.0)		29 (96.7)	7 (100.0)		29 (100.0)	41 (100.0)
MAP on ICU admission	97±15	95±21	0.633	101±14	95±11	0.268	92±15	95±23	0.495
Laboratory results on ICU admission
Albumin (g/L)	31.9±3.8	31.0±4.5	0.265	31.9±3.3	33.4±5.7	0.559	31.6±4.3	30.5±4.2	0.294
Alanine aminotransferase (U/L)	30.5 (16.4–57.7)	31.4 (17.2–53.3)	0.698	22.6 (12.0–53.9)	21.7 (15.2–30.2)	0.628	35.9 (18.4–62.8)	36.0 (17.3–59.3)	0.981
Aspartate aminotransferase (U/L)	26.9 (16.9–42.0)	29.7 (21.9–63.7)	0.152	24.3 (14.9–39.9)	26.5 (19.7–53.9)	0.698	31.9 (19.1–48.7)	30.2 (22.6–73.1)	0.551
BUN (mmol/L)	6.1 (4.5–8.1)	9.4 (6.2–13.4)	<0.001	5.4 (4.4–6.7)	9.1 (4.1–12.0)	0.103	6.7 (4.7–9.0)	9.5 (6.4–13.6)	0.007
Uric acid (μmol/L)	189.0 (133.0–229.0)	282.5 (187.5–392.3)	<0.001	190.5 (146.5–228.0)	315.0 (229.0–502.0)	0.002	170.0 (116.5–235.0)	261.0 (181.5–387.5)	0.001
Creatine kinase (U/L)	44.5 (25.1–85.8)	66.3 (36.4–160.6)	0.025	32.1 (19.8–72.3)	66.7 (53.1–75.8)	0.092	52.1 (36.9–101.3)	63.7 (35.9–164.1)	0.489
Lactate dehydrogenase (U/L)	305.2 (225.0–375.3)	467.0 (293.1–755.2)	<0.001	228.3 (198.8–306.2)	251.0 (242.0–578.3)	0.194	354.9 (303.1–469.3)	482.1 (334.0–773.9)	0.031
Creatine kinase isoenzyme (U/L)	11.9 (8.7–16.1)	18.1 (11.1–30.2)	<0.001	9.3 (7.9–11.9)	11.0 (8.8–52.7)	0.181	15.7 (11.4–21.5)	18.6 (12.6–29.8)	0.116
Cystatin C (mg/L)	1.0 (0.9–1.2)	1.4 (1.1–1.8)	<0.001	1.0 (0.9–1.2)	1.6 (1.3–2.2)	<0.001	1.1 (0.9–1.3)	1.3 (1.1–1.7)	0.011
CO2 (mmol/L)	25.0 (23.0–28.0)	22.0 (19.0–25.0)	0.001	24.0 (23.0–27.0)	23.0 (20.0–29.0)	0.656	26.0 (22.0–29.0)	22.0 (19.0–24.0)	0.002
D-dimer (mg/L)	1.8 (1.3–5.4)	5.1 (2.4–7.9)	<0.001	1.7 (0.9–3.2)	4.5 (2.4–8.0)	0.052	2.4 (1.5–6.2)	5.4 (2.3–9.1)	0.028
Haemoglobin (g/L)	114±20	119±20	0.224	110±19	116±20	0.451	118±21	120±21	0.816
Leucocytes (×10^9/L)	9.0 (6.2–13.2)	10.7 (6.1–17.4)	0.261	7.1 (5.6–10.4)	5.0 (4.2–5.6)	0.015	11.2 (7.2–15.7)	11.7 (8.1–18.2)	0.633
Platelets (×10^9/L)	224 (165–276)	153 (60–196)	<0.001	224 (169–260)	163 (79–166)	0.008	224 (101–298)	152 (58–198)	0.005
C-reactive protein (mg/L)	33.2 (8.7–112.4)	91.5 (22.5–150.9)	0.031	22.4 (5.7–86.0)	22.1 (2.0–117.5)	0.816	52.4 (11.8–141.2)	94.1 (28.6–155.4)	0.226
Procalcitonin (ng/mL)	0.1 (0.1–0.4)	0.5 (0.2–1.4)	<0.001	0.1 (0.1–0.2)	0.2 (0.1–3.2)	0.087	0.2 (0.1–0.6)	0.6 (0.2–1.4)	0.022
Blood gas analysis
Lactate (mmol/L)	1.2 (0.7–2.3)	2.1 (1.3–3.7)	0.001	1.0 (0.7–1.3)	1.2 (1.1–1.8)	0.206	1.8 (1.2–2.7)	2.2 (1.5–3.7)	0.170
PH	7.42±0.10	7.39±0.12	0.110	7.43±0.05	7.41±0.03	0.192	7.41±0.13	7.38±0.13	0.402
PaO2 (mmHg)	78.9 (56.7–114.0)	71.3 (57.0–90.4)	0.503	88.9 (74.7–123.4)	81.8 (78.0–121.5)	0.877	59.9 (53.7–83.5)	70.7 (57.0–84.6)	0.238
PaCO2 (mmHg)	38.7 (33.4–45.2)	39.9 (32.9–46.7)	0.558	37.8 (33.4–40.6)	37.6 (32.0–47.5)	0.641	41.9 (33.1–48.0)	40.7 (33.2–46.7)	0.802
Oxygenation index (mmHg)	205.0 (86.0–280.0)	91.0 (64.0–179.0)	0.003	254.5 (203.0–324.0)	233.0 (86.0–281.0)	0.313	86.0 (65.0–203.0)	87.0 (61.0–154.0)	0.616
Proteinuria	13 (22.0)	33 (68.8)	<0.001	5 (16.7)	4 (57.1)	0.035	8 (27.6)	29 (70.7)	<0.001
Hematuria	19 (32.2)	28 (58.3)	0.007	6 (20.0)	3 (42.9)	0.225	13 (44.8)	25 (61.0)	0.182
Kidney function
Baseline Scr (μmol/L)	58.0 (48.0–66.0)	72.0 (62.0–78.0)	<0.001	58 0.0 (48.0–67.0)	81.0 (70.0–100.0)	0.003	56.0 (49.0–67.0)	70 (60–76)	<0.001
Scr on ICU admission (μmol/L)	56.8 (48.6–68.8)	83.3 (67.3–123.8)	<0.001	55.6 (47.9–67.7)	100.2 (70.7–121.9)	0.002	61.0 (48.9–71.5)	82.6 (61.8–124.5)	<0.001
Scr at the time of AKI diagnosis (μmol/L)	56.8 (48.6–68.8)	127.5 (111.3–161.2)	<0.001	55.6 (47.9–67.7)	104.9 (101.1–161.2)	<0.001	61.0 (48.9–71.5)	127.7 (112.2–161.1)	<0.001
Peak Scr (μmol/L)	67.6 (57.6–77.1)	183.6 (126.1–279.5)	<0.001	67.6 (55.8–77.4)	139.4 (104.6–181.7)	<0.001	66.8 (60.4–77.9)	212.5 (129.6–306.7)	<0.001
Oliguria	–	17 (35.4)	<0.001	–	–	–	–	17 (41.5)	<0.001
AKI Stage			<0.001			<0.001			<0.001
1	–	17 (35.4)	–	–	6 (85.7)	–	–	11 (26.8)	–
2	–	9 (18.8)	–	–	1 (14.3)	–	–	8 (19.5)	–
3	–	22 (45.8)	–	–	0	–	–	22 (53.7)	–

Note: Values are n (%), mean ± SD or median (interquartile range).

Abbreviations: AKI, acute kidney injury; MAP, mean arterial pressure, 1 mmHg=0.133 kPa; ICU, intensive care unit; Scr, serum creatinine; BUN, blood urea nitrogen.

Table 2 Complications, Treatments and Outcomes of Patients Between AKI and Non-AKI with Different Severities of Coronavirus Disease 2019

Characteristics	All Patients (n=107)		P-value	Severe Patients		P-value	Critical Patients		P-value
	Non-AKI (59, 55.1)	AKI (48, 44.9)		Non-AKI (30, 81.1)	AKI (7, 18.9)		Non-AKI (29, 55.1)	AKI (41, 44.9)
Complications
Acute respiratory distress syndrome	19 (32.2)	29 (60.4)	0.004	3 (10.0)	1 (14.3)	0.750	16 (55.2)	28 (68.3)	0.263
Hypoproteinemia	22 (37.3)	19 (39.6)	0.808	8 (26.7)	3 (42.9)	0.410	14 (48.3)	16 (39.0)	0.441
Septic shock	9 (15.3)	29 (60.4)	<0.001	0	0	–	9 (31.0)	29 (70.7)	0.001
Disseminated intravascular coagulation	3 (5.1)	6 (12.5)	0.169	0	0	–	3 (10.3)	6 (14.6)	0.594
Treatment
Antibiotic therapy	55 (93.2)	46 (95.8)	0.554	26 (86.7)	5 (71.4)	0.353	29 (100.0)	41 (100.0)	–
Glucocorticoids	51 (86.4)	40 (83.3)	0.654	25 (83.3)	3 (42.9)	0.035	26 (89.7)	37 (90.2)	0.936
Intravenous immunoglobulin therapy	32 (54.2)	29 (60.4)	0.521	16 (53.3)	2 (28.6)	0.231	16 (55.2)	27 (65.9)	0.366
Need for vasopressors	9 (15.3)	29 (60.4)	<0.001	1 (3.3)	1 (14.3)	0.305	8 (27.6)	28 (68.3)	0.001
Oxygen therapy	57 (96.6)	42 (87.5)	0.072	29 (96.7)	6 (85.7)	0.305	28 (96.6)	36 (87.8)	0.174
Non-invasive Mechanical ventilation	26 (44.1)	41 (85.4)	<0.001	3 (10.0)	2 (28.6)	0.232	23 (79.3)	39 (95.1)	0.040
Invasive Mechanical ventilation	16 (27.1)	39 (81.3)	<0.001	0	1 (14.3)	0.063	16 (55.2)	38 (92.7)	<0.001
Continuous renal replacement therapy	3 (5.1)	17 (35.4)	<0.001	0	1 (14.3)	0.063	3 (10.3)	16 (39.0)	0.008
Extracorporeal membrane oxygenation	1 (1.7)	3 (6.3)	0.212	0	0	–	1 (3.4)	3 (7.3)	0.479
Time from symptom onset to hospital admission (days)	16 (12–26)	14 (8–20)	0.010	18 (13–26)	9 (7–22)	0.010	16 (12–35)	14 (8–20)	0.055
Time from symptom onset to ICU admission (days)	21 (14–36)	19 (14–28)	0.219	21 (14–38)	17 (9–32)	0.219	21 (14–41)	19 (14–26)	0.269
Length of hospital stay (days)	26 (16–40)	14 (9–29)	0.001	30 (18–44)	12 (10–22)	0.001	25 (14–38)	14 (7–30)	0.064
Length of ICU stay (days)	9 (5–15)	7 (3–13)	0.442	7 (4–9)	4 (3–10)	0.442	13 (7–18)	9 (4–23)	0.201
In-hospital mortality	11 (18.6)	40 (83.3)	<0.001	0	2 (28.6)	0.007	11 (37.9)	38 (92.7)	<0.001

Note: Values are n (%) or median (interquartile range).

Abbreviations: AKI, acute kidney injury; ICU, intensive care unit.

Table 3 Univariable and Multivariable Logistic Regression Analyses for In-Hospital Mortality with Coronavirus Disease 2019

Charcteristics	Univariable Analysis		Multivariable Analysis
	OR (95% CI)	P	OR (95% CI)	P
AKI	21.81 (8.00–59.46)	<0.001	33.74 (3.34–341.29)	0.003
Invasive mechanical ventilation	112.00 (27.35–458.68)	<0.001	18.44 (2.35–144.69)	0.006
Septic shock	64.80 (13.97–300.61)	<0.001	15.58 (2.08–116.78)	0.008
Oxygenation index	0.99 (0.98–0.99)	<0.001	0.99 (0.98–1.00)	0.014
Body mass index	1.36 (1.11–1.68)	0.004
Diabetes mellitus	2.92 (1.08–7.89)	0.035
Muscle ache	3.03 (1.32–6.96)	0.009
Critical vs severe	40.83 (8.99–185.56)	<0.001
Albumin	0.85 (0.76–0.94)	0.002
Aspartate aminotransferase	1.02 (1.00–1.04)	0.012
BUN	1.22 (1.08–1.37)	0.001
Creatine kinase	1.00 (1.00–1.01)	0.035
Lactate dehydrogenase	1.01 (1.00–1.01)	<0.001
Creatine kinase isoenzyme	1.18 (1.09–1.28)	<0.001
CO2 (mmol/L)	0.89 (0.81–0.97)	0.011
D-dimer (mg/L)	1.11 (1.02–1.21)	0.013
Leucocytes	1.08 (1.01–1.15)	0.015
Platelets	0.99 (0.99–1.00)	0.003
C-reactive protein	1.01 (1.01–1.02)	<0.001
Lactate	2.47 (1.58–3.87)	<0.001
PH	0.00 (0.00–0.17)	0.007
PaCO2	1.05 (1.02–1.09)	0.006
PaO2	0.98 (0.97–0.99)	0.003
Baseline Scr	1.04 (1.01–1.07)	0.013
Scr on ICU	1.02 (1.00–1.03)	0.018
Peak Scr	1.02 (1.01–1.03)	<0.001
Acute respiratory distress syndrome	7.24 (3.07–17.05)	<0.001
Disseminated intravascular coagulation	10.23 (1.23–84.98)	0.031
Oxygen therapy	0.11 (0.01–0.96)	0.046
Need for vasopressors	38.64 (10.48–142.49)	<0.001
Non-invasive mechanical ventilation	51.72 (11.30–236.74)	<0.001

Abbreviations: AKI, acute kidney injury; BUN, blood urea nitrogen; ICU, intensive care unit; Scr, serum creatinine; OR, odds ratio; CI, confidence interval.

Figure 2 Kaplan–Meier survival curves for patients with severe to critical COVID-19 with and without AKI during the time from hospital admission (Log rank test P < 0.001).

Figure 3 Prediction nomogram for predicting the AKI onset probability of patients with coronavirus disease 2019. Prediction of the patient’s value is located on each variable axis, and a line is drawn upward to determine the number of nomogram points for predicting the AKI probability of patients with COVID-19. The sum of these numbers is located on the total points axis, and a line is drawn downward to the predicted axes to determine the likelihood of AKI (C-index: 0.935; 95% CI, 0.892–0.978).