Introduction
Methods
Patients
Outcome variables and data collection
Sample collection
Patient allocation according to urinary NGAL/hepcidin-25 ratio- and AKI-status
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KDIGO-based AKI-negative and NGAL/hepcidin-25 ratio-negative (no AKI)
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KDIGO-based AKI-negative and NGAL/hepcidin-25 ratio-positive (subclinical AKI)
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KDIGO-based AKI-positive and NGAL/hepcidin-25 ratio-negative (clinical AKI)
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KDIGO-based AKI-positive and NGAL/hepcidin-25 ratio-positive (combined AKI)
Patient follow-up
Statistical analysis
Results
Patient characteristics according to AKI subtypes
Variable | No AKI n = 127 (64.1%) | Subclinical AKI n = 13 (6.6%) | Clinical AKI n = 40 (20.2%) | Combined AKI n = 18 (9.1%) | p |
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Demographic data | |||||
Age (year) | 68.0 (56.0–73.0) | 74.0 (64.0–80.0) | 70.5 (64.0–74.8) | 75.0 (68.8–77.3) | 0.002 |
Female | 39 (30.7%) | 5 (38.5%) | 7 (17.5%) | 8 (44.4%) | 0.154 |
Body mass index (kg/m2) | 26.4 (23.5–29.0) | 26.5 (23.1–29.2) | 27.1 (24.6–30.3) | 25.6 (24.5–31.3) | 0.537 |
Comorbidities | |||||
Insulin-dependent diabetes mellitus | 6 (5.4%) | 0 (0%) | 3 (7.5%) | 0 (0%) | 0.514 |
Arterial hypertension | 94 (74.0%) | 10 (76.9%) | 33 (82.5%) | 16 (89.9%) | 0.428 |
Chronic kidney disease | 31 (24.4%) | 4 (30.8%) | 21 (52.5%) | 11 (61.1%) | 0.001 |
Congestive heart failure | 21 (16.5%) | 3 (23.1%) | 13 (32.5%) | 3 (16.7%) | 0.170 |
Chronic obstructive pulmonary disease | 17 (13.4%) | 2 (15.4%) | 8 (20.0%) | 5 (27.8%) | 0.399 |
Peripheral artery occlusive disease | 35 (27.6%) | 2 (15.4%) | 13 (32.5%) | 2 (11.1%) | 0.279 |
EuroScore (points) | 6.0 (3.0–7.0) | 6.0 (3.5–10.0) | 7.0 (5.0–9.8) | 8.0 (5.0–10.3) | 0.009 |
Pre-operative medication | |||||
Renin–angiotensin–aldosterone system inhibitors | 70 (55.1%) | 8 (61.5%) | 23 (57.5%) | 13 (72.2%) | 0.577 |
Betablockers | 91 (71.7%) | 11 (84.6%) | 30 (75.0%) | 13 (72.2%) | 0.779 |
Calcium channel blockers | 30 (23.6%) | 4 (30.8%) | 18 (45.0%) | 5 (27.8%) | 0.075 |
Statins | 72 (56.7%) | 6 (46.2%) | 28 (70.0%) | 10 (55.6%) | 0.357 |
Variable | No AKI n = 127 (64.1%) | Subclinical AKI n = 13 (6.6%) | Clinical AKI n = 40 (20.2%) | Combined AKI n = 18 (9.1%) | p |
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Intraoperative characteristics | |||||
Valve | 58 (45.7%) | 6 (46.2%) | 15 (37.5%) | 10 (55.6%) | 0.626 |
Coronary artery bypass graft | 23 (18.1%) | 1 (7.7%) | 9 (22.5%) | 2 (11.1%) | 0.556 |
Combined cardiac surgery | 35 (27.6%) | 5 (38.5%) | 10 (25.0%) | 4 (22.2%) | 0.755 |
Past cardiac surgery | 27 (21.3%) | 5 (38.5%) | 15 (37.5%) | 5 (27.8%) | 0.153 |
Aortic cross-clamp time (min) | 72 (55–89) | 78 (72–135) | 59 (46–96) | 120 (65–158) | 0.007 |
Drain output (mL) | 150 (50–200) | 200 (0–250) | 10 (0–200) | 0 (0–250) | 0.042 |
Packed red blood cells | 0 (0–500) | 0 (0–600) | 500 (0–750) | 750 (400–1000) | < 0.001 |
Urine output (mL) | 1600 (1200–2200) | 1500 (900–1800) | 1300 (900–1700) | 1200 (700–1500) | 0.005 |
Fluid balance (mL) | 1300 (400–2200) | 800 (200–1600) | 1000 (600–2000) | 600 (100–2100) | 0.333 |
Furosemide dose, mg | 0 (0–0) | 0 (0–0) | 0 (0–20) | 5 (0–25) | 0.007 |
Lowest mean arterial pressure (mmHg) | 35 (31–40) | 35 (29–42) | 33 (28–40) | 31 (22–40) | 0.145 |
Vasoconstrictive medication | 85 (66.9%) | 10 (76.9%) | 32 (80.0%) | 14 (77.8%) | 0.358 |
Lowest cardiac index (L/min/m2) | 2.3 (1.8–2.6) | 2.1 (2.1–4.5) | 2.4 (1.8–2.9) | 2.5 (1.8–3.4) | 0.448 |
Laboratory values at ICU admission | |||||
Urinary NGAL/hepcidin-25 ratio | 0.009 (0.001–0.030) | 0.740 (0.581–1.667) | 0.032 (0.004–0.143) | 1.010 (0.629–2.690) | < 0.001 |
Plasma lactate (mmol/L) | 1.5 (1.1–3.6) | 2.5 (1.9–5.7) | 2.0 (1.3–5.0) | 3.8 (2.6–7.2) | 0.001 |
Plasma B-type natriuretic peptide (pg/mL) | 129.4 (68.1–280.1) | 182.3 (43.0–460.0) | 242.7 (128.2–381.6) | 202.6 (71.6–385.0) | 0.301 |
Plasma C-reactive protein (mg/L) | 3.3 (1.9–6.3) | 1.5 (0.9–2.9) | 3.8 (2.2–9.8) | 2.4 (1.9–7.5) | 0.547 |
Postoperative outcomes | |||||
AKI stagea | |||||
1 | 0 (0%) | 0 (0%) | 33 (82.5%) | 5 (27.8%) | < 0.001 |
2 | 0 (0%) | 0 (0%) | 3 (7.5%) | 3 (16.7%) | |
3 | 0 (0%) | 0 (0%) | 4 (10.0%) | 10 (55.6%) | |
Renal replacement therapy | 0 (0%) | 0 (0%) | 3 (7.5%) | 10 (55.6%) | < 0.001 |
Length of intubation and ventilation (hrs) | 18 (12–26) | 28 (19–77) | 26 (15–520) | 74 (34–700) | < 0.001 |
Length of stay in ICU (h) | 25.0 (22.0–46.0) | 45.0 (21.0–140.0) | 67 (28–270) | 155 (46–355) | < 0.001 |