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Table 1 Demographic and clinical characteristics of the cohort

From: Effects of preoperative high-oral protein loading on short- and long-term renal outcomes following cardiac surgery: a cohort study

  Control group
(n = 214)
Protein-loading group
(n = 110)
p-value
Demographics    
 Age, years 63 (54 – 71) 62 (54 – 71) 0.693
 Male sex, n (%) 151 (71%) 78 (71%) 0.948
 Race/ethnicity, n (%)    0.856
  White 210 (98.1%) 108 (98.2%)  
  Black 4 (1.9%) 3 (1.8%)  
  Weight, kg 76 (65 – 85) 77 (68 – 84) 0.431
Body mass index, kg/m2 24.6 (22.2 – 28.3) 25.5 (23.5 – 28.2) 0.134
Comorbidities, n (%)    
 Hypertension 142 (66.4%) 72 (65.5%) 0.871
 Atrial fibrillation 29 (13.6%) 24 (21.8%) 0.057
 Peripheral vasculopathy 19 (8.5%) 8 (7.3%) 0.620
 Type 2 diabetes mellitus 15 (7.0%) 7 (6.4%) 0.827
 Smoking status (former smoker or current smoker) 76 (35.5%) 40 (36.4%) 0.745
 Dyslipidemia 65 (30.4%) 25 (22.7%) 0.146
Medication, n (%)    
 Antiplatelet 38 (17.8%) 18 (16.4%) 0.753
 Beta-blocker 108 (50.5%) 41 (37.3%) 0.024
 ACEi or ARB 99 (46.3%) 50 (45.5%) 0.890
 Statin 50 (23.4%) 39 (35.5%) 0.021
 Diuretica 57 (26.6%) 27 (24.5%) 0.684
Baseline clinical data    
 Leucocytes, × 109/L 6.40 (5.30 – 7.40) 6.35 (5.43 – 7.62) 0.727
 Hemoglobin, g/dL 14.2 (13.2 – 15.2) 14.0 (13.1 – 14.8) 0.198
 Platelets, × 109/L 204 (176 – 241) 212 (184 – 246) 0.186
 Albumin, g/dL 4.0 (3.8 – 4.1) 3.9 (3.8 – 4.1) 0.445
 eGFR, mL/min/1.73 m2 b 90 (80 − 98) 91 (82 − 100) 0.886
 Urea, mg/dLc 35.0 (30.0 – 41.3) 36.0 (29.0 – 43.0) 0.392
 Troponin I, μg/L 0.01 (0.01 – 0.01) 0.01 (0.01 – 0.01) 0.328
 NYHA classification, n (%)    0.697
  1 75 (35.4%) 43 (39.1%)  
  2 133 (62.1%) 65 (59.1%)  
  3 6 (2.8%) 2 (1.8%)  
 Left ventricular ejection fraction, % 62.9 (58.0 – 68.0) 61.0 (58.0 – 66.0) 0.449
 Systolic pulmonary arterial pressure, mm Hg 30.0 (28.0 − 37.0) 30.0 (22.3 − 38.0) 0.334
 EuroSCORE II for operative risk, %d 1.17 (0.85 − 1.99) 1.03 (0.69 − 1.83) 0.294
 STS risk score, %e    
  Risk of mortality 0.64 (0.34 – 1.13) 0.60 (0.41 – 1.36) 0.423
  Risk of morbidity or mortality 8.55 (6.50 − 10.87) 8.47 (6.66 − 12.25) 0.389
  Risk of renal failure 1.34 (0.90 − 2.22) 1.29 (0.90 − 2.07) 0.847
 Thakar scoref    0.326
  0.4 165 (77.1%) 90 (81.8%)  
  1.8 49 (22.9%) 20 (18.2%)  
Operative data    
 Aortic cross-clamp, min 79.5 (59.0 − 97.0) 79.5 (60.0 − 104.5) 0.445
 Cardiopulmonary bypass time, min 112.5 (90.0 − 138.0) 115.0 (98.0 − 149.8) 0.182
 Procedure, n (%)    
  Coronary artery bypass graft only 8 (3.8%) 4 (3.6%) 0.507
   Valve only 107 (50.5%) 58 (52.7%) 0.457
   Combined or other 97 (45.8%) 48 (43.6%) 0.142
  Minimally invasive 141 (66%) 72 (65%) 0.468
  Intraoperative diuresis, mL 1000 (550 − 1377) 800 (552 − 1200) 0.252
  Surgery fluid balance, mL 3650 (2880 − 4327) 3815 (2892 − 4537) 0.378
  Lowest mean arterial pressure, mmHg 66.7 (63.3 − 66.7) 66.7 (63.3 − 73.3) 0.007
  Lowest hemoglobin, g/dL 10.5 (8.9 − 10.9) 9.6 (8.7 − 10.8) 0.329
  Red blood cell transfusion, n (%) 6 (2.8%) 11 (10.0%)a 0.012
ICU data    
 Mechanical ventilation, days 1.0 (1.0 − 1.0) 1.0 (1.0 − 1.0) 0.445
 Intra-aortic balloon pump, n (%) 5 (2.3%) 3 (2.7%) 0.830
 Extra-corporeal membrane oxygenation, n (%) 2 (0.9%) 1 (0.9%) 0.982
 Myocardial infarction, n (%) 0 (0%) 1 (0.9%) 0.501
 Stroke, n (%) 1 (0.5%) 3 (2.7%) 0.081
 Re-intervention, n (%) 6 (2.8%) 2 (1.8%) 0.588
 Day 1 fluid balance, mL  − 718 (− 1274 to − 117)  − 150 (− 640 to 301) 0.305
 Day 2 fluid balance, mL  − 150 (− 640 to 301)  − 270 (− 1020 to 115) 0.022
 Weight difference, kgg  − 1.50 (− 3.00 to − 0.10) - 2.05 (− 3.40 to − 0.02) 0.170
 ACEi or ARB use, n (%) 53 (24.8%) 22 (20.0%) 0.335
 Aminoglycoside use, n (%) 2 (0.9%) 0 (0%) 0.309
 Vancomycin use, n (%) 3 (1.4%) 0 (0%) 0.212
 NSAID drug use, n (%) 4 (1.9%) 0 (0%) 0.149
 Mean arterial pressure < 65 mmHg
within the first 24 h, n (%)
83 (38.8%) 35 (31.8%) 0.217
 Inotropes, n (%) 67 (31.3%) 41 (37.3%) 0.281
 ICU stay, h 57 (41 − 87) 51 (41 − 71) 0.569
 Hospital stay, days 6 (6 − 8) 5 (4 − 6)  < 0.001
3-month follow-up data    
 ACEi or ARB 125 (58.4%) 65 (59.6%) 0.435
 Readmission, n (%) 4 (1.9%) 5 (4.5%) 0.165
 3-month mortality, n (%) 0 (0%) 1 (0.9%) 0.162
1-year follow-up data    
 ACEi or ARB 112 (52.8%) 59 (54.1%) 0.392
 1-year mortality, n (%) 2 (0.9%) 1 (0.9%) 0.982
  1. Covariates used in the propensity score analysis (age, gender, race, cardiac disease, baseline eGFR) did not show significant differences between the protein loading and control groups
  2. ACEi angiotensin-converting enzyme inhibitor, ARB angiotensin II receptor blocker, ICU intensive care unit, IQR interquartile range, NSAID non-steroidal anti-inflammatory drug; NYHA New York Heart Association, STS Society of Thoracic Surgeons
  3. Summaries of quantitative variables are presented as median and interquartile range (in parentheses). For categorical variables, the absolute and relative frequencies (as %, in parentheses) for the categories are presented
  4. aDiuretics include loop diuretics and thiazides
  5. bThe eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation [15]
  6. cTo convert the value for urea to blood urea nitrogen, it was multiplied by 0.467
  7. dThe European System for Cardiac Operative Risk Evaluation (EuroSCORE) score is calculated using a logistic-regression equation and ranges from 0 to 100%, with higher scores indicating greater risk
  8. eThe STS risk score is calculated using a logistic-regression equation; it estimates the risk of morbidity and mortality and the risk of renal failure, and ranges from 0 to 100% (higher scores indicate greater risk)
  9. fThe Thakar score is calculated using a logistic-regression equation; it estimates the risk of dialysis for patients undergoing cardiac surgery, and ranges from 0% to 21.5% (higher scores indicate greater risk)
  10. gICU discharge − hospital admission