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Table 1 Preoperative and perioperative risk variables associated with KDIGO stages 1-3

From: Validating a scoring tool to predict acute kidney injury (AKI) following cardiac surgery

Risk factors (Total n = 2316) No AKI (N = 1980) KDIGO stage 1 (N = 142) KDIGO stage 2 (N = 60) KDIGO stage 3 (N = 134)  
Preoperative continuous Mean (SD) Mean (SD) Mean (SD) Mean (SD)  
Age (years) 66.75 (11.01) 69.40* (10.96) 70.27 (10.30) 69.81* (12.43)  
BMI 29.74 (7.97) 30.98 (5.87) 30.54 (5.61) 30.23 (5.35)  
Preoperative creatinine (μmol/L) 95.48 (32.16) 101.25 (36.40) 95.28 (20.19) 152.07 (121.10)*,&,#  
Preoperative categorical N (%) N (%) N (%) N (%) p-value
Gender      0.9
Female (n = 585) 494 (24.9%) 39 (27.5%) 17 (28.3%) 35 (26.1%)
Male (n = 1731) 1486 (75.1%) 103 (72.5%) 43 (71.7%) 99 (73.9%)
Preoperative intra-aortic balloon pump      0.02
Yes (n = 27) 18 (0.9%) 3 (2.1%) 1 (1.7%) 5 (3.7%)
No (n = 2289) 1962 (99.1%) 139 (97.9%) 59 (98.3%) 129 (96.3%)
Congestive heart failure      <0.001
Yes (n = 256) 177 (8.9%) 23 (16.2%) 15 (25%) 41 (30.6%)
No (n = 2060) 1803 (91.1%) 119 (83.8%) 45 (75%) 93 (69.4%)
Ejection fraction <35%      0.8
Yes (n = 224) 197 (9.9%) 11 (7.7%) 5 (8.3%) 11 (8.2%)
sNo (n = 2092) 1783 (90.1%) 131 (92.3%) 55 (91.7%) 123 (91.8%)
Type of surgery      <0.001
CABG only (n = 1509) 1344 (67.9%) 77 (54.2%) 25 (41.7%) 63 (47.0%)
Valve only (n = 251) 220 (11.1%) 11 (7.7%) 8 (13.3%) 12 (9.0%)
CABG + valve (n = 468) 341 (17.2%) 48 (33.8%) 24 (40.0%) 55 (41.0%)
Other cardiac surgery(n = 88) 75 (3.8%) 6 (4.2%) 3 (5.0%) 4 (3.0%)
Previous cardiac surgery      <0.001
Yes (n = 178) 131 (6.6%) 21 (14.8%) 8 (13.3%) 18 (13.4%)
No (n = 2138) 1849 (93.4%) 121 (85.2%) 52 (86.7%) 116 (86.6%)
Diabetes mellitus^      0.01
Type 1 (n = 22) 18 (0.9%) 2 (1.4%) 0 2 (1.5%)
Type 2 (n = 698) 569 (28.7%) 50 (35.2%) 28 (46.7%) 51 (38.1%)
None (n = 1596) 1393 (70.4%) 90 (63.4%) 32 (53.3%) 81 (60.4%)
Chronic obstructive pulmonary disease      0.2
Yes (n = 114) 90 (4.5%) 10 (7.0%) 4 (6.7%) 10 (7.5%)
No (n = 2202) 1890 (95.5%) 132 (93.0%) 56 (93.3%) 124 (92.5%)
Total 100% 100% 100% 100%  
Perioperative continuous Mean (SD) Mean (SD) Mean (SD) Mean (SD)  
Cardiopulmonary bypass time (entry to exit minutes) 279.79 (73.91) 314.45* (93.31) 316.45* (92.60) 340.02*,& (109.14)  
Clamp time (minutes) 94.77 (36.63) 111.87* (40.65) 114.72* (48.14) 126.36*,& (55.70)  
Pump time (minutes) 112.55 (47.95) 135.55* (51.30) 141.98* (66.01) 162.98*,& (78.01)  
Number of bypass grafts 5.53 (1.87) 5.44 (2.07) 5.25 (2.49) 5.35 (2.21)  
  1. Abbreviations: AKI acute kidney injury, BMI body mass index, CABG coronary artery bypass graft, KDIGO, kidney disease: improving global outcomes, SD standard deviation.
  2. Note: Conversion factors for units: SCr in to μmol/L to mg/dL x0.0113.
  3. *significantly different from No AKI (p < 0.05, Bonferonni).
  4. &significant different from Stage 1 (p < 0.05, Bonferonni).
  5. #significantly different from Stage 2 (p < 0.05, Bonferonni).
  6. ^p-value with type 1 diabetes only: p = 0.7.