Table 2.
Imbalance of patient characteristics before and after propensity weighting in the assessment of acute kidney injury
| Variables | Before weighting | After weighting | ||||
|---|---|---|---|---|---|---|
| No exposure to NE (n = 3448) |
Exposure to NE (n = 1605) |
SMD | No exposure to NE (n = 3498) |
Exposure to NE (n = 1581) |
SMD | |
| Age (years) | 68 [60–76] | 70 [61,7] | 0.120 | 69 [61, 76] | 68 [60, 76] | < 0.001 |
| Male gender | 2407 (70) | 1080 (67) | 0.054 | 2429 (69) | 1105 (70) | 0.009 |
| BMI (kg m−2) | 27.48 [24.44–30.72] | 26.83 [23.83–30.42] | 0.017 | 27.53 [24.39, 30.76] | 26.76 [23.72–30.26] | 0.025 |
| Hypertension | 1925 (56) | 890 (56) | 0.008 | 1922 (55) | 868 (55) | 0.001 |
| Coronary disease | 385 (11) | 213 (13) | 0.064 | 404 (12) | 189 (12) | 0.012 |
| Diabetes | 690 (20) | 294 (18) | 0.043 | 672 (19) | 304 (19) | < 0.001 |
| Dyslipidemia | 274 (8) | 107 (7) | 0.049 | 259.5 (7) | 122 (8) | 0.010 |
| Chronic kidney disease | 126 (4) | 98 (6) | 0.114 | 155.9 (5) | 75 (5) | 0.013 |
| Peripheral vascular disease | 188 (6) | 76 (5) | 0.033 | 206 (6) | 74 (5) | 0.055 |
|
Hemoglobin, g dl−1 |
12.5 ± 0.5 | 12.2 ± 0.1 | 0.181 | 12.3 ± 0.7 | 12.3 ± 0.8 | 0.002 |
|
Platelet, 103 mm−3 |
148 ± 34 | 139 ± 35 | 0.111 | 146 ± 34 | 143 ± 36 | 0.004 |
| Creatinine (µ mol l−1) | 77 [64–94] | 82 [67–105] | 0.187 | 79 [65–98.09] | 78 [65–97.34] | 0.013 |
| CPB time (min) | 84 [56–118] | 100 [67, 136] | 0.336 | 88 [58–125] | 91 [61–125] | 0.032 |
| Aortic clamp time (min) | 57 [35–83] | 64 [42–94] | 0.111 | 59 [37–87] | 60 [39–89] | 0.004 |
| Surgery type | ||||||
| CABG | 962 (28) | 468 (29) | 0.185 | 1000 (29) | 461 (29) | 0.012 |
| Valve surgery | 1254 (36) | 620 (39) | 1285 (37) | 576 (36) | ||
| Combined surgery | 336 (10) | 212 (13) | 369 (11) | 166 (11) | ||
| Others | 896 (26) | 305 (19) | 845 (24) | 379 (24) | ||
| SAPS II | 34 [28–40] | 40 [33–48] | 0.595 | 35 [29–43] | 36 [30–43] | 0.026 |
| Inotropes | 0 (0) | 128 (8) | 0.306 | 0 (0) | 87 (6) | 0.226 |
An absolute MSD < 10% was considered to support the assumption of a balance between the groups. SMD: standardized mean differences. Data are presented as medians [interquartile ranges] or as numbers (percentages). NE: norepinephrine, CABG: coronary bypass graft, CPB: coronary bypass, SAPS II: Simplified Acute Physiology Score. BMI, hypertension, and peripheral vascular disease were not selected for the propensity weighting as the P value for their association with acute kidney injury was over 20%