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Table 2 Summary of patients’ characteristics at baseline, preoperative and intraoperative measures

From: Fluid balance, change in serum creatinine and urine output as markers of acute kidney injury post cardiac surgery: an observational study

  All (n = 111) SCr-, UO-, FOL- (n = 43) SCr-, UO-, FOL + (n = 32) SCr-, UO+, FOL- (n = 11) SCr-, UO+, FOL + (n = 15) SCr + (n = 10) P-value
Demographics        
Age (years) 69 ± 10 69 ± 9 73 ± 8 60 ± 14 68 ± 11 69 ± 11 0.03
Male 84 (76%) 36 (84%) 21 (66%) 9 (82%) 11 (73%) 7 (70%) 0.43
Diabetes 31 (28%) 10 (23%) 4 (12%) 5 (45%) 6 (40%) 6 (60%) 0.01
Preoperative Measures        
Weight (kg) 80 (68, 91) 80 (71, 92) 69 (64, 84) 84 (78, 111) 85 (79, 93) 92 (68, 107) 0.01
Height (cm) 170 ± 10 170 ± 10 169 ± 11 172 ± 8 171 ± 10 170 ± 12 0.94
Creatinine (μmol/L) 85 (71, 103) 87 (69, 101) 80 (71, 93) 81 (70, 103) 88 (70, 96) 117 (90, 144) 0.01
eGFR (mL/min/1.73 m2) 72 ± 17 77 ± 23 73 ± 19 81 ± 23 63 ± 28 52 ± 18 0.01
eGFR <60 mL/min/1.73 m2 28 (25%) 8 (19%) 7 (23%) 2 (18%) 4 (27%) 7 (70%) 0.03
Recent IV Contrast 57 (51%) 15 (35%) 21 (64%) 5 (45%) 9 (60%) 7 (70%) 0.05
Pre-op ACE/ARB 73 (66%) 27 (63%) 20 (62%) 9 (82%) 11 (73%) 6 (60%) 0.72
Pre-op Diuretics 31 (28%) 11 (25%) 6 (19%) 3 (27%) 5 (33%) 6 (60%) 0.16
Surgery Type        
MVR Only/AVR Only 35 (32%) 12 (28%) 13 (41%) 2 (18%) 4 (27%) 4 (40%) 0.17
CABG Only 59 (53%) 28 (65%) 13 (41%) 8 (73%) 6 (40%) 4 (40%)  
CABG + MVR/AVR 17 (15%) 3 (7%) 6 (18%) 1 (9%) 5 (33%) 2 (20%)  
Intraoperative Measures        
Duration of Surgery (mins) 177 (146, 209) 188 (150, 209) 156 (122, 190) 176 (117, 200) 186 (151, 233) 200 (173, 243) 0.007
CPB Time (mins) 92 (72, 108) 92 (77, 105) 75 (62, 96) 84 (46, 100) 103 (88, 148) 103 (95, 140) 0.01
Intraoperative pRBC 24 (22%) 6 (12%) 9 (25%) 1 (0%) 7 (40%) 6 (50%) 0.007
Intraoperative Crystalloid (cc) 1260 (875, 1727) 1200 (900, 1780) 1350 (900, 1663) 850 (700, 1260) 1050 (845, 1650) 1386 (1000, 1880) 0.43
Intraoperative Colloid (cc) 500 (500, 500) 500 (500, 650) 500 (500, 600) 500 (500, 500) 500 (500, 500) 500 (500, 500) 0.54
Total Fluid Administered (cc) 1850 (1485, 2380) 1820 (1500, 2380) 1901 (1715, 2398) 1350 (1100, 1960) 1730 (1520, 2404) 2165 (1600, 3412) 0.08
Total Urine Output (cc) 250 (160, 400) 325 (175, 500) 250 (187, 470) 220 (150, 350) 260 (125, 400) 125 (70, 225) 0.07
Total Fluid Balance (cc) 129 (846, 1700) 1350 (900, 1720) 1147 (875, 1519) 1240 (515, 1825) 1200 (−686, 1650) 1765 (105, 2003) 0.68
Negative Fluid Balance at Completion of Surgery 8 (7%) 1 (2%) 0 (0%) 0 (0%) 5 (33%) 2 (20%) <0.001
Postoperative Medications       
Vasopressors 85 (77%) 29 (67%) 27 (84%) 6 (54%) 13 (87%) 10 (100%) 0.04
Number of Vasopressors 1 (1, 2) 1 (0, 1) 1.5 (1, 2) 1 (0, 2) 2 (1, 2) 2.5 (2, 4) <0.001
  1. Vasopressors used were: Adrenaline, noradrenaline, dobutamine, milirinone and vasopressin.
  2. SCr+: Meeting the criteria of Change in SCr ≥ 26.5 µmol/L ; SCr -: Not meeting the Change in SCr criteria.
  3. UO+: Meeting the criteria of Urine Output ≤0.5 cc/kg/hour for greater than 6 hours; UO-: Not meeting the Urine Output criteria.
  4. FOL+: Meeting the criteria of Fluid Overload, defined as fluid balance ≥ 6.5 cc/kg; FOL-: Not meeting the Fluid Overload criteria.
  5. Continuous variables are presented in mean ± standard deviation or median with interquartile range. Categorical variables are presented in count with percentage. One-way ANOVA or Kruskal-Wallis test were used to compare among groups for the continuous variables; Chi-Square test or Fisher’s Exact test were used for the categorical variables.
  6. eGFR was calculated using the MDRD equation.