Table 1. Preoperative variables
|
Total
(n=729)
|
Without postoperative AKI (n=541)
|
With postoperative AKI (n=188)
|
P value
|
Preoperative albumin ≥ 37.5g/La (n=456)
|
Preoperative albumin < 37.5g/La (n=273)
|
P value
|
Age (y)
|
67±16
|
66±16
|
71±14
|
<0.001
|
66±15
|
69±14
|
0.056
|
Male sex
|
432 (59.3%)
|
318 (58.8%)
|
114 (60.6%)
|
0.655
|
276 (60.5%)
|
156 (57.1%)
|
0.368
|
BMI (kg/m2)
|
24.1±4.5
|
24.0±4.6
|
24.6±4.4
|
0.139
|
24.7±4.3
|
23.2±4.7
|
<0.001
|
Preoperative comorbidities
|
|
Diabetes mellitus
|
194 (26.6%)
|
136 (25.1%)
|
58 (30.9%)
|
0.127
|
123 (27.0%)
|
71 (26.0%)
|
0.775
|
Hypertension
|
399 (54.7%)
|
287 (53.0%)
|
112 (59.6%)
|
0.122
|
260 (57.0%)
|
139 (50.9%)
|
0.109
|
Coronary heart disease
|
195 (26.7%)
|
138 (25.5%)
|
57 (30.3%)
|
0.199
|
130 (28.5%)
|
65 (23.8%)
|
0.165
|
Congestive heart failure
|
23 (3.2%)
|
14 (2.6%)
|
9 (4.8%)
|
0.133
|
13 (2.9%)
|
10 (3.7%)
|
0.544
|
Cerebrovascular disease
|
140 (19.2%)
|
99 (18.3%)
|
41 (21.8%)
|
0.293
|
94 (20.6%)
|
46 (16.8%)
|
0.212
|
Chronic kidney disease
|
23 (3.2%)
|
9 (1.7%)
|
14 (7.4%)
|
<0.001
|
8 (1.8%)
|
15 (5.5%)
|
0.005
|
Lung disease b
|
68 (9.3%)
|
51 (9.4%)
|
17 (9.0%)
|
0.876
|
41 (9.0%)
|
27 (9.9%)
|
0.686
|
Liver disease c
|
20 (2.7%)
|
16 (3.0%)
|
4 (2.1%)
|
0.548
|
10 (2.2%)
|
10 (3.7%)
|
0.240
|
Malignant neoplasm
|
474 (65.0%)
|
349 (64.5%)
|
125 (66.5%)
|
0.624
|
247 (65.1%)
|
177 (64.8%)
|
0.935
|
Peripheral vascular disease
|
37 (5.1%)
|
24 (4.4%)
|
13 (6.9%)
|
0.182
|
21 (4.6%)
|
16 (5.9%)
|
0.455
|
ASA classification
|
|
<0.001
|
|
<0.001
|
I
|
12 (1.6%)
|
12 (2.2%)
|
0 (0.0%)
|
|
7 (1.5%)
|
5 (1.8%)
|
|
II
|
275 (37.7%)
|
224 (41.4%)
|
51 (27.1%)
|
|
202 (44.3%)
|
73 (26.7%)
|
|
III
|
404 (55.4%)
|
284 (52.5%)
|
120 (63.8%)
|
|
238 (52.2%)
|
166 (60.8%)
|
|
IV
|
38 (5.2%)
|
21 (3.9%)
|
17 (9.0%)
|
|
9 (2.0%)
|
29 (10.6%)
|
|
Preoperative Hb (g/L) d
|
124±23
|
125±22
|
119±26
|
0.007
|
133±18
|
108±23
|
<0.001
|
Preoperative albumin (g/L) d
|
38.6±6.2
|
39.3±6.0
|
36.7±6.3
|
<0.001
|
42.5±3.0
|
32.1±4.2
|
<0.001
|
Preoperative albumin < 37.5g/L
|
273 (37.4%)
|
175 (32.3%)
|
98 (52.1%)
|
<0.001
|
__
|
__
|
__
|
Baseline serum creatinine (umol/L) e
|
80.4±26.3
|
78.2±22.2
|
86.7±35.1
|
0.002
|
81.5±23.6
|
78.5±30.4
|
0.163
|
Preoperative BNP (pg/ml) f
|
98 (43, 190)
|
84 (38, 166)
|
126 (61, 220)
|
0.001
|
66 (31, 133)
|
140 (72, 257)
|
<0.001
|
Radiocontrast exposure g
|
76 (10.4%)
|
48 (8.9%)
|
28 (14.9%)
|
0.020
|
44 (9.6%)
|
32 (11.7%)
|
0.375
|
On ACEI/ARB
|
62 (8.5%)
|
48 (8.9%)
|
14 (7.4%)
|
0.546
|
38 (8.3%)
|
24 (8.8%)
|
0.830
|
Smoke h
|
136 (18.7%)
|
108 (20.0%)
|
28 (14.9%)
|
0.124
|
94 (20.6%)
|
42 (15.4%)
|
0.079
|
Data are presented as mean ± SD, number of patients (percentage), or median (interquartile range), unless otherwise indicated.
BMI, Body Mass Index; ASA, American Society of Anesthesiologists; Hb, hemoglobin; BNP, B-type natriuretic peptide; cTNI, cardio-troponin; ACEI, angiotensin converting enzyme inhibitor; ARB, angiotensin receptor blocker.
a The cutoff value of preoperative albumin for postoperative AKI was determined by Yuden index of ROC curve (Supplemental Digital Content 3).
b Including chronic obstructive pulmonary disease (COPD), asthma and pulmonary fibrosis.
c Including any kind of chronic hepatitis and liver cirrhosis.
d Measured within 3 days before surgery.
e Determined by the minimal value of serum creatinine measured within 3 months before admission and in hospital before surgery; if neither value were available, MDRD (Modification of diet in renal disease) formula was adopted to estimate the baseline serum creatinine according to KDIGO guideline.
f Measured in 366 patients before surgery.
g Including patients who had radiocontrast exposure within 7 days before surgery.
h Smoking for more than 10 cigarettes per day for more than 1 year, including current or past smokers.
Table 2. Intra- and postoperative variables
|
Total
(n=729)
|
Without postoperative AKI (n=541)
|
With postoperative AKI (n=188)
|
P value
|
Preoperative albumin ≥ 37.5g/La (n=456)
|
Preoperative albumin < 37.5g/La (n=273)
|
P value
|
Duration of anesthesia (min)
|
258 (174, 338)
|
253 (169, 337)
|
277 (192, 347)
|
0.053
|
243 (167, 330)
|
272 (201, 364)
|
0.002
|
Duration of surgery (min)
|
171 (97, 249)
|
165 (92, 245)
|
192 (110, 256)
|
0.062
|
158 (88, 242)
|
189 (121, 272)
|
0.002
|
Emergency surgery
|
64 (8.8%)
|
37 (6.8%)
|
27 (14.4%)
|
0.002
|
17 (3.7%)
|
47 (17.2%)
|
<0.001
|
Open surgery b
|
288 (53.9%)
|
193 (50.0%)
|
95 (64.2%)
|
0.003
|
147 (45.1%)
|
141 (67.8%)
|
<0.001
|
Type of surgery
|
|
General surgery
|
330 (45.3%)
|
229 (42.3%)
|
101 (53.7%)
|
0.007
|
180 (39.5%)
|
150 (54.9%)
|
<0.001
|
Neurosurgery
|
18 (2.5%)
|
15 (2.8%)
|
3 (1.6%)
|
0.585
|
10 (2.2%)
|
8 (2.9%)
|
0.535
|
Thoracic surgery
|
52 (7.1%)
|
38 (7.0%)
|
14 (7.4%)
|
0.846
|
33 (7.2%)
|
19 (7.0%)
|
0.888
|
Urologic surgery
|
195 (26.7%)
|
162 (29.9%)
|
33 (17.6%)
|
0.001
|
160 (35.1%)
|
35 (12.8%)
|
<0.001
|
Gynecological surgery
|
25 (3.4%)
|
17 (3.1%)
|
8 (4.3%)
|
0.470
|
6 (1.3%)
|
19 (7.0%)
|
<0.001
|
Orthopedic surgery
|
52 (7.1%)
|
38 (7.0%)
|
14 (7.4%)
|
0.846
|
29 (6.4%)
|
23 (8.4%)
|
0.294
|
Vascular surgery
|
15 (2.1%)
|
10 (1.8%)
|
5 (2.7%)
|
0.552
|
11 (2.4%)
|
4 (1.5%)
|
0.383
|
ENT surgery
|
8 (1.1%)
|
6 (1.1%)
|
2 (1.1%)
|
>0.999
|
3 (0.7%)
|
5 (1.8%)
|
0.158
|
Other c
|
24 (3.3%)
|
18 (3.3%)
|
6 (3.2%)
|
0.928
|
18 (3.9%)
|
6 (2.2%)
|
0.200
|
Intraoperative maximal lactate (mmol/L) d
|
1.1 (0.8, 1.5)
|
1.1 (0.8, 1.5)
|
1.1 (0.8, 1.6)
|
0.995
|
1.1 (0.8, 1.5)
|
1.1 (0.8, 1.5)
|
0.421
|
Intraoperative minimal Hb (g/L) d
|
112 ± 26
|
113 ± 26
|
111 ± 27
|
0.568
|
118 ± 25
|
104 ± 25
|
<0.001
|
Intraoperative management
|
|
Use of vasopressors e
|
175 (24.1%)
|
116 (21.6%)
|
59 (31.4%)
|
0.007
|
116 (21.6%)
|
59 (31.4%)
|
0.007
|
Volume of artificial colloid infusion (ml)
|
500 (500, 1000)
|
500 (500, 1000)
|
500 (500, 1000)
|
0.858
|
500 (500, 1000)
|
500 (500, 1000)
|
0.618
|
Estimated blood loss (ml)
|
100 (10, 300)
|
100 (10, 300)
|
100 (10, 300)
|
0.138
|
100 (10, 300)
|
100 (10, 400)
|
0.034
|
Positive fluid balance (ml)
|
2202 ± 1605
|
2201 ± 1579
|
2204 ± 1679
|
0.982
|
2093 ± 1516
|
2382 ± 1731
|
0.023
|
Postoperative variables before AKI f
|
|
Nephrotoxin exposure
|
|
Glycopeptides
|
46 (6.3%)
|
35 (6.5%)
|
11 (5.9%)
|
0.764
|
17 (3.7%)
|
29 (10.6%)
|
<0.001
|
Aminoglycoside
|
0 (0.0%)
|
0 (0.0%)
|
0 (0.0%)
|
--
|
0 (0.0%)
|
0 (0.0%)
|
--
|
NSAIDs
|
387 (53.1%)
|
292 (54.0%)
|
95 (50.5%)
|
0.415
|
265 (58.1%)
|
122 (44.7%)
|
<0.001
|
Hemolysis
|
1 (0.1%)
|
1 (0.2%)
|
0 (0.0%)
|
>0.999
|
0 (0.0%)
|
1 (0.4%)
|
0.374
|
Rhabdomyolysis
|
1 (0.1%)
|
1 (0.2%)
|
0 (0.0%)
|
>0.999
|
0 (0.0%)
|
1 (0.4%)
|
0.374
|
Sepsis
|
47 (6.4%)
|
29 (5.4%)
|
18 (9.6%)
|
0.043
|
12 (2.6%)
|
35 (12.8%)
|
<0.001
|
Use of vasopressors e
|
77 (10.6%)
|
53 (9.8%)
|
24 (12.8%)
|
0.254
|
41 (9.0%)
|
36 (13.2%)
|
0.074
|
Minimal Hb (g/L)
|
103 ± 25
|
105 ± 26
|
99 ± 21
|
0.008
|
109 ± 27
|
94 ± 18
|
<0.001
|
Maximal BNP (pg/ml)
|
247 (130, 456)
|
244 (128, 443)
|
264 (142, 513)
|
0.265
|
209 (115, 373)
|
322 (188, 564)
|
<0.001
|
Maximal lactate (mmol/L)
|
1.9 (1.3, 2.7)
|
1.9 (1.3, 2.7)
|
1.8 (1.3, 2.8)
|
0.751
|
1.4 (1.9, 2.7)
|
1.8 (1.3, 2.7)
|
0.377
|
Perioperative blood transfusion g
|
186 (25.5%)
|
131 (24.2%)
|
55 (29.3%)
|
0.172
|
89 (19.5%)
|
97 (35.5%)
|
<0.001
|
Non-renal SOFA within 24h ICU admission
|
2 (1, 3)
|
2 (1, 3)
|
2 (2, 4)
|
0.005
|
2 (1, 3)
|
3 (1, 4)
|
0.001
|
Postoperative AKI
|
188 (25.8%)
|
—
|
—
|
—
|
90 (19.7%)
|
98 (35.9%)
|
<0.001
|
Data are presented as mean ± SD, number of patients (percentage), or median (interquartile range), unless otherwise indicated.
ENT, ear, nose and throat; Hb, hemoglobin; NSAIDs, non-steroidal anti-inflammatory drugs, BNP, B-type natriuretic peptide; SOFA, sequential organ failure assessment score.
a The cutoff value of preoperative albumin for postoperative AKI was determined by Yuden index of ROC curve (Supplemental Digital Content 3).
b Open or laparoscopic surgery referred to 534 patients.
c Referred to thyroid or breast surgery.
d Measured by arterial blood gas analysis.
e Including use of phenylephrine, norepinephrine, epinephrine and dopamine.
f Occurred before start of AKI.
g Perioperative blood products transfusion, including packed red blood cell, plasma and platelet.
Table 3. Independent risk factors for postoperative AKI
|
Univariate Logistic model a
|
Multivariate Logistic model b
|
OR (95% CI)
|
P value
|
OR (95% CI)
|
P value
|
Age (y)
|
1.022 (1.010-1.034)
|
<0.001
|
1.018 (1.004-1.033)
|
0.013
|
History of chronic kidney disease
|
4.756 (2.023-11.180)
|
<0.001
|
—
|
—
|
Sepsis
|
1.869 (1.013-3.451)
|
0.046
|
—
|
—
|
Radiocontrast exposure c
|
1.797 (1.091-2.961)
|
0.021
|
1.843 (1.031-3.293)
|
0.039
|
Baseline creatinine (umol/L) d
|
1.011 (1.005-1.017)
|
<0.001
|
1.016 (1.008-1.025)
|
<0.001
|
Preoperative Hb (g/L) e
|
0.990 (0.983-0.997)
|
0.004
|
—
|
—
|
Preoperative albumin < 37.5g/L e
|
2.277 (1.624-3.194)
|
<0.001
|
1.892 (1.238-2.891)
|
0.003
|
ASA classification
|
1.966 (1.472-2.625)
|
<0.001
|
1.719 (1.193-2.477)
|
0.004
|
Open surgery
|
1.792 (1.213-2.650)
|
0.003
|
—
|
—
|
Emergency surgery
|
2.284 (1.349-3.869)
|
0.002
|
|
|
General surgery
|
1.582 (1.133-2.208)
|
0.007
|
—
|
—
|
Duration of surgery (every 1 hour increase)
|
1.047 (0.976-1.124)
|
0.202
|
—
|
—
|
Intraoperative use of vasopressors f
|
1.660 (1.146-2.404)
|
0.007
|
1.680 (1.065-2.648)
|
0.026
|
Non-renal SOFA within 24h ICU admission
|
1.133 (1.044-1.230)
|
0.003
|
—
|
—
|
OR, odds ratio; CI, confidence interval.
Hb, hemoglobin; ASA, American Society of Anesthesiologists; SOFA, sequential organ failure assessment score.
a Perioperative variables with P < 0.10 in univariate analyses by independent samples t test, Mann-Whitney U test, chi-square test or Fisher's exact test were included except preoperative BNP, duration of anesthesia and postoperative minimal Hb before AKI because of collinearity.
b Backward: LR.
c Including patients who had radiocontrast exposure within 7 days before surgery.
d Determined by the minimal value of serum creatinine measured within 3 months before admission and in hospital before surgery; if neither value were available, MDRD (Modification of diet in renal disease) formula was adopted to estimate the baseline serum creatinine according to KDIGO guideline.
e Measured within 3 days before surgery.
f Including use of phenylephrine, norepinephrine, epinephrine and dopamine.
Table 4. Postoperative outcomes
|
Total (n=729)
|
All patients (n=729)
|
P value
|
AKI patients (n=188)
|
P value
|
Without postoperative AKI (n=541)
|
With postoperative AKI (n=188)
|
Preoperative albumin ≥ 37.5g/L (n=90)
|
Preoperative albumin < 37.5g/L (n=98)
|
On MV in ICU
|
390 (53.6%)
|
268 (49.6%)
|
122 (64.9%)
|
<0.001
|
51 (56.7%)
|
71 (72.4%)
|
0.024
|
Duration of MV (h) a
|
26.9 (19.8, 34.0)
|
14.7 (11.1, 18.3)
|
53.4 (33.0, 73.8)
|
<0.001
|
55.4 (21.5, 89.4)
|
51.9 (26.5, 77.4)
|
0.835
|
Length of ICU stay (d) b
|
2.5 (2.3, 2.8)
|
2.0 (1.8, 2.3)
|
4.0 (3.1, 4.9)
|
<0.001
|
3.4 (2.1, 4.8)
|
4.5 (3.3, 5.7)
|
0.027
|
Number of postoperative complications except AKI c
|
0 (0, 1)
|
0 (0, 0)
|
0 (0, 2)
|
<0.001
|
0 (0, 1)
|
1 (0, 3)
|
<0.001
|
Postoperative hospital stay (d) d
|
13.7 (12.6, 14.8)
|
12.3 (11.3, 13.3)
|
17.8 (14.8, 20.9)
|
<0.001
|
16.9 (11.8, 22.0)
|
18.7 (15.2, 22.2)
|
0.158
|
In-hospital mortality
|
14 (1.9%)
|
1 (0.2%)
|
13 (6.9%)
|
<0.001
|
2 (2.2%)
|
11 (11.2%)
|
0.020
|
Total cost (10,000 yuan)
|
7.8 (4.5, 11.5)
|
7.5 (4.2, 10.9)
|
8.9 (5.6, 13.2)
|
<0.001
|
8.0 (4.1, 11.8)
|
10.0 (6.8, 14.7)
|
0.011
|
Data were presented as number of patients (percentage), or median (interquartile range), unless otherwise indicated.
ICU, intensive care unit; MV, mechanical ventilation.
a Results of patients requiring postoperative mechanical ventilation. Data were analyzed by Kaplan-Meier analysis and compared by log-rank test; results were presented as average (95% confidence interval);
b Result of patients admitted to ICU. Data were analyzed by Kaplan-Meier analysis and compared by log-rank test; results were presented as average (95% confidence interval).
c Including pulmonary infection, pleural effusion, atelectasis, respiratory failure, acute myocardial infarction, congestive heart failure, new onset arrhythmia, hemodynamic insufficiency, stroke, venous thromboembolism, ileus, intra-abdominal abscess, wound infection, urinary tract infection, sepsis, surgical bleeding, digestive tract bleeding , acute liver injury, disseminated intravascular coagulation, anastomotic leakage and wound dehiscence (Supplemental Digital Content 2);
d Data were analyzed by Kaplan-Meier analysis and compared by log-rank test; results were presented as average (95% confidence interval).