Table 3.
Pre-, intra-, and postoperative risk factors for acute kidney injury (AKI)
| Variable | n | No AKI | n | AKI | P value |
|---|---|---|---|---|---|
| Preoperative medical status, n (%) | |||||
| Cyanosis (oxygen saturation <85%) | 139 | 34 (24) | 68 | 28 (41) | 0.02 |
| Arrhythmia | 139 | 11 (8) | 68 | 2 (3) | 0.23 |
| Ventilated | 139 | 9 (6) | 68 | 7 (10) | 0.44 |
| Lung collapse | 139 | 5 (4) | 68 | 8 (12) | 0.04 |
| Pulmonary oedema | 139 | 17 (12) | 68 | 3 (4) | 0.09 |
| Infection | 139 | 13 (9) | 68 | 7 (10) | 0.83 |
| Renal dysfunction/failure | 139 | 5 (4) | 68 | 0 (0) | 0.14 |
| Preoperative medications, n (%) | |||||
| Diuretics | 139 | 38 (27) | 68 | 29 (43) | 0.03 |
| ACEi | 139 | 15 (11) | 68 | 5 (7) | 0.62 |
| Antibiotics | 139 | 28 (20) | 68 | 11 (16) | 0.50 |
| Aspirin | 139 | 9 (6) | 68 | 10 (15) | 0.06 |
| Beta-blockers | 139 | 9 (6) | 68 | 5 (7) | 0.78 |
| Digoxin | 139 | 5 (4) | 68 | 0 (0) | 0.18 |
| Iron | 139 | 8 (6) | 68 | 6 (9) | 0.41 |
| Prostaglandin | 139 | 33 (24) | 68 | 6 (9) | 0.01 |
| Blood composition | |||||
| Haemoglobin (g/L), mean ± SD | 139 | 141 ± 26 | 68 | 143 ± 28 | 0.73 |
| Platelet count (×109/L), mean ± SD | 135 | 325 ± 131 | 65 | 347 ± 134 | 0.27 |
| White blood cell count (×109/L), mean ± SD | 139 | 11.1 ± 5.7 | 68 | 10.5 ± 5.1 | 0.49 |
| Neutrophils (×109/L), median (IQR) | 63 | 5.5 (3.8, 7.7) | 30 | 3.1 (2.2, 6.2) | 0.003 |
| Lymphocyte (×109/L), mean ± SD | 63 | 4.5 ± 2.8 | 30 | 5.5 ± 3.2 | 0.15 |
| Blood pH, mean ± SD | 135 | 7.38 ± 0.1 | 67 | 7.38 ± 0.1 | 0.91 |
| Biochemistry, n (%) | |||||
| Elevated alanine transaminase (>2× normal values) | 137 | 1 (1) | 67 | 7 (10) | 0.002 |
| Elevated aspartate transaminase (>3× normal values) | 138 | 15 (11) | 68 | 11 (16) | 0.3 |
| Operative factors | |||||
| Total number of CPB cycles, n (%) | 139 | 68 | 0.19∗ | ||
| One | 100 (72) | 41 (60) | |||
| Two | 24 (17) | 17 (25) | |||
| Three | 8 (6) | 6 (9) | |||
| Four | 7 (5) | 4 (6) | |||
| Total CPB time (min), mean ± SD | 139 | 111 ± 56 | 68 | 154 ± 73 | <0.001 |
| Total number of cross-clamp cycles, n (%) | 139 | 68 | 0.55 | ||
| None | 11 (8) | 6 (9) | |||
| One | 118 (85) | 54 (79) | |||
| Two | 10 (7) | 8 (12) | |||
| Total cross-clamp time (min), mean ± SD | 128 | 76 ± 36 | 62 | 106 ± 58 | <0.001 |
| Deep hypothermic circulatory arrest, n (%) | 139 | 21 (15) | 68 | 13 (19) | 0.47 |
| Circulatory arrest time (min), mean ± SD | 21 | 24 ± 13 | 13 | 18 ± 9 | 0.12 |
| Cerebral perfusion, n (%) | 139 | 12 (9) | 68 | 5 (7) | 1 |
| Modified ultrafiltration, n (%) | 139 | 129 (93) | 68 | 65 (96) | 0.56 |
| Any intraoperative steroids, n (%) | 139 | 41 (30) | 68 | 13 (19) | 0.12 |
| Steroids day before surgery, n (%) | 139 | 29 (21) | 68 | 6 (9) | 0.03 |
| Steroids in CPB prime, n (%) | 139 | 38 (27) | 68 | 9 (13) | 0.03 |
| Extubated in OR, n (%) | 139 | 35 (25) | 68 | 9 (13) | <0.05 |
| Total time with chest open (h), median (IQR) | 139 | 4 (2.9, 5.7) | 68 | 4.1 (4.1, 9.1) | <0.001 |
| Chest left open in ICU, n (%) | 139 | 25 (18) | 68 | 14 (12) | 0.66 |
| Total time intubated (h), median (IQR) | 139 | 27.4 (7.0, 96.4) | 68 | 56.8 (21, 129.2) | 0.004 |
| Catheter reintervention, n (%) | 136 | 3 (2) | 68 | 5 (7) | 0.12 |
| Postoperative ECMO, n (%) | 138 | 3 (2) | 67 | 6 (9) | 0.07 |
| Surgical reoperation, n (%) | 139 | 9 (6) | 68 | 7 (10) | 0.34 |
| Length of ICU stay (h), median (IQR) | 138 | 3.0 (1.1, 7.0) | 67 | 5.6 (2.9, 12.8) | <0.001 |
| Length of hospital stay (d), median (IQR) | 137 | 7.9 (4.9, 15.1) | 67 | 11.1 (7.2, 29.8) | <0.001 |
| Postoperative RBC transfusions, n (%) | 139 | (22) | 68 | 3 (5) | 0.04 |
| Elevated preoperative lactate (mmol/L), median (IQR) | 136 | 2.8 (2.4, 4.3) | 68 | 3.3 (2.3, 5.1) | 0.67 |
| Postoperative outcomes, n (%) | |||||
| Low cardiac output syndrome | 139 | 5 (4) | 68 | 6 (9) | 0.18 |
| Cardiorespiratory insufficiency | 139 | 11 (8) | 68 | 11 (16) | 0.07 |
| Cardiogenic shock | 139 | 0 (0) | 68 | 1 (1) | 0.33 |
| Pulmonary hypertension | 139 | 4 (3) | 68 | 2 (3) | 1 |
| Cardiac arrest | 139 | 3 (2) | 68 | 5 (7) | 0.12 |
| Arrhythmia | 139 | 31 (22) | 68 | 19 (28) | 0.4 |
| Pneumothorax | 139 | 4 (3) | 68 | 0 (0) | 0.31 |
| Chylothorax | 139 | 13 (9) | 68 | 16 (24) | 0.006 |
| Lung collapse | 139 | 11 (8) | 68 | 11 (16) | 0.07 |
| Cardiac tamponade | 139 | 1 (1) | 68 | 0 (0) | 1 |
| Pleural effusion | 139 | 7 (5) | 68 | 6 (9) | 0.29 |
| Pericarditis | 139 | 9 (6) | 68 | 6 (9) | 0.54 |
| Pericardial effusion | 139 | 1 (1) | 68 | 0 (0) | 1 |
| Pulmonary oedema | 139 | 8 (6) | 68 | 4 (6) | 1 |
| Anaemia | 139 | 2 (1) | 68 | 1 (1) | 1 |
| Bleeding | 139 | 9 (4) | 68 | 4 (6) | 0.74 |
| Pulmonary haemorrhage | 139 | 3 (2) | 68 | 3 (4) | 0.4 |
| Renal failure | 139 | 1 (1) | 68 | 1 (1) | 0.56 |
| Dialysis | 139 | 0 (0) | 68 | 3 (4) | 0.04 |
| Phrenic nerve/neurological injury | 139 | 3 (2) | 68 | 6 (9) | 0.07 |
| Necrotizing enterocolitis | 139 | 0 (0) | 68 | 1 (1) | 0.33 |
| Endocarditis | 139 | 1 (1) | 68 | 0 (0) | 1 |
| Infection | 139 | 20 (14) | 68 | 19 (28) | 0.02 |
| Sepsis | 139 | 3 (2) | 68 | 4 (6) | 0.23 |
| Upper respiratory tract infection | 139 | 7 (5) | 68 | 5 (7) | 0.51 |
| Urinary tract infection | 139 | 2 (1) | 68 | 1 (1) | 1 |
| Wound infection | 139 | 7 (5) | 68 | 2 (3) | 0.73 |
| Catheter infection | 139 | 1 (1) | 68 | 0 (0) | 1 |
ACEi, angiotensin converting enzyme inhibitor; CPB, cardiopulmonary bypass; ECMO, extracorporeal membrane oxygenation; ICU, intensive care unit; IQR, interquartile range; OR, operating room; pH, potential of hydrogen; SD, standard deviation.
Numbers apply unless otherwise indicated by numbers in rows of the table.
∗
Mantel-Haenszel statistic.