Fifty-two patients who underwent CVS with CPB were included. pAKI occurred in 18 (34.6%) of those patients.
Patient demographic characteristics
Table 1 shows a comparison of the demographic data of the patients with and without pAKI. There were more male patients with pAKI than female patients (P=0.01), and patients with AKI had a lower preoperative eGFR (P=0.02) than did those without pAKI. There were no significant differences between the two groups with respect to the other demographic parameters.
Table 1. Characteristics of patients with and without postoperative AKI
|
with pAKI
(n=18)
|
without pAKI
(n=34)
|
P value
|
age (years)
|
72〔63 to 78〕
|
74〔68 to 82〕
|
0.33
|
male, n (%)
|
16(88.9)
|
17(50)
|
0.01
|
height (cm)
|
159.8 ± 11.4
|
161.8 ± 8.8
|
0.51
|
weight (kg)
|
63.5〔56.1 to 69.8〕
|
53.6〔47.8 to 66.3〕
|
0.07
|
ASA-PS
|
3〔2 to 3〕
|
3〔2 to 3〕
|
0.69
|
EuroSCORE II
|
3.55〔1.68 to 5.15〕
|
3.00〔2.04 to 4.61〕
|
0.33
|
hypertension, n (%)
|
11(61.1)
|
21(61.8)
|
1.00
|
diabetes mellitus, n (%)
|
5(27.8)
|
3(8.8)
|
0.11
|
preoperative eGFR
(ml min-1 1.73m2 -1)
|
57.5 ± 13.0
|
67.5 ± 14.9
|
0.02
|
LVEF(%)
|
60.2 ± 13.5
|
62.4 ± 9.5
|
0.50
|
operation time (min)
|
290〔259 to 409〕
|
328〔266 to 403〕
|
0.57
|
aortic cross-clamp time (min)
|
112〔89 to 166〕
|
116〔90 to 147〕
|
0.97
|
duration of CPB (min)
|
166〔140 to 247〕
|
182〔134 to 222〕
|
0.86
|
transfusion (RCC) (unit)
|
6〔4 to 10〕
|
6(0 to 11)
|
0.44
|
transfusion (FFP) (unit)
|
8(4 to 10)
|
8〔4 to 8〕
|
0.72
|
type of procedure, n. (%)
|
|
|
0.39
|
total arch replacement
|
4(22.2)
|
9(26.5)
|
|
valve surgery
|
13(72.2)
|
19(55.9)
|
|
total arch replacement +valve surgery
|
1(5.6)
|
6(17.6)
|
|
pAKI: postoperative acute kidney injury, EuroSCOREⅡ: European System for Cardiac Operative Risk Evaluation II, eGFR: estimated glomerular filtration rate, LVEF: left ventricular ejection fraction, RCC: red cell concentrate, FFP: fresh frozen plasma
Changes in the serum syndecan-1 concentration
Figure 2 shows the perioperative changes in the serum syndecan-1 concentration. Six patients with a CPB duration of less than 2 hours did not have a serum syndecan-1 measurement at T3. It began to increase with the initiation of CPB and then reached a bimodal peak value. The serum syndecan-1 concentration at all time points was significantly elevated compared to that at T1.
Comparison of the serum syndecan-1 concentration between patients with and without pAKI
Figure 3 shows a comparison of perioperative serum syndecan-1 concentrations between patients with and without pAKI. Before and after weaning from CPB, the serum syndecan-1 concentration was not significantly different between the two groups, whereas there was a significant difference at T6 (patients with pAKI 97.1 〔73.5 to 127.2〕 ng ml-1 and patients without pAKI 53.3 〔38.7 to 74.4〕 ng ml-1 (P<0.01)). Table 2 shows the ORs and 95% CIs from the single logistic regressions of pAKI occurrence according to the serum syndecan-1 concentration at each time point. Serum syndecan-1 concentrations at T4 and T6 were associated with an increased risk of pAKI (T4: OR=1.10 [1.01 to 1.21, P=0.03]; T6: OR=1.16 [1.01 to 1.34, P=0.04]). To calculate the cutoff value for the occurrence of pAKI, ROC analysis was performed for the serum syndecan-1 concentrations at T4 and T6. The estimated cutoff value was 101.0 ng ml-1 (sensitivity: 0.71; specificity: 0.62; area under the curve (AUC)=0.67 (0.51 to 0.83)) at T4 and 57.1 ng ml-1 (sensitivity: 0.82; specificity: 0.56; AUC=0.71 (0.57 to 0.86)) at T6 (Figure 4). To analyze whether this cutoff value was significantly associated with the development of AKI, a χ2 test was performed. The cutoff value at T4 was not significantly associated with the occurrence of pAKI (χ2 (1)=0.34, P=0.56), whereas the cutoff value at T6 was significantly associated with the occurrence of pAKI (χ2 (1)=4.55, P=0.03). Finally, to evaluate the association between the serum syndecan-1 concentration at T6 and the occurrence of pAKI, multivariable logistic regression was conducted to control for the potentially confounding effects that are thought to be associated with pAKI (age, CPB duration, preoperative estimated glomerular filtration rate (eGFR)) and the serum syndecan-1 concentration at T6. Table 3 shows the ORs and 95% CIs from logistic regressions of pAKI occurrence adjusted for patient and setting characteristics, as described above. A high serum syndecan-1 concentration at T6 was associated with the occurrence of pAKI (OR=1.02 (1.00 to 1.03), P=0.03).
Table 2: Single logistic regressions of pAKI incidence according to the serum syndecan-1 concentration
|
OR
|
95%CI
|
P value
|
T1
|
1.18
|
(0.90 to 1.55)
|
0.24
|
T2
|
0.98
|
(0.92 to 1.05)
|
0.61
|
T3
|
0.98
|
(0.92 to 1.05)
|
0.60
|
T4
|
1.10
|
(1.01 to 1.21)
|
0.03
|
T5
|
1.02
|
(0.98 to 1.05)
|
0.36
|
T6
|
1.16
|
(1.01 to 1.34)
|
0.04
|
(T1) After induction of anesthesia, (T2) 1 h after initiation of CPB, (T3) 2 h after initiation of CPB, (T4) 30 min after weaning from CPB, (T5) 2 h after weaning from CPB, (T6) postoperative day 1
Table 3: Logistic regressions of pAKI occurrence adjusted for patient and setting characteristics
|
OR
|
95% CI
|
P value
|
age
|
1.01
|
0.95 to 1.07
|
0.87
|
CPB duration
|
0.99
|
0.98 to 1.00
|
0.22
|
preoperative eGFR
|
0.93
|
0.88 to 0.99
|
0.03
|
syndecan-1 at T6
|
1.02
|
1.00 to 1.03
|
0.03
|
CPB: cardiopulmonary bypass, eGFR: estimated glomerular filtration rate