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Table 1 Characteristics of patients with and without perioperative hyperchloremia (Cl− ≥ 110 mmol·L− 1)

From: Hyperchloremia and postoperative acute kidney injury: a retrospective analysis of data from the surgical intensive care unit

Variables Perioperative hyperchloremia (n = 1876, 23.5%) No perioperative hyperchloremia (n = 6115, 76.5%) P value
Preoperative characteristics
 Male sex 1091 (58.2%) 3636 (59.5%) 0.315
 Age, years 58.0 (15.7) 62.1 (15.6) <0.001
 Body mass index, kg m−2 23.5 (3.6) 23.6 (3.8) 0.240
 Surgery time, min 268.8 (150.9) 220.1 (147.6) <0.001
 ASA class    <0.001
  1 433 (23.1%) 975 (15.9%)  
  2 892 (47.5%) 3191 (52.2%)
   ≥ 3 551 (29.4%) 1949 (31.9%)
 Cancer 405 (21.6%) 1840 (30.1%) <0.001
 eGFR*a, mL·min− 1·1.73·m−2    0.313
   ≥ 90 841 (44.8%) 2596 (42.5%)  
  60–89 528 (28.1%) 1825 (29.8%)  
  30–60 310 (16.5%) 1029 (16.8%)  
   < 30 197 (10.5%) 665 (10.9%)  
Intraoperative characteristics
 Type of operation    <0.001
  Non-cardiovascular surgery 1567 (83.5%) 4786 (78.3%)  
  Cardiovascular surgery 309 (16.5%) 1329 (21.7%)  
 Emergency surgery 329 (17.5%) 781 (12.8%) <0.001
 Intraoperative hypotensionb 455 (24.3%) 1659 (27.1%) 0.013
 Type of anesthesia    <0.001
  General anesthesia 1823 (97.5%) 5474 (89.9%)  
  Regional anesthesia 23 (1.2%) 278 (4.6%)  
  Monitored anesthesia care 24 (1.3%) 335 (5.5%)  
Patient management (PODs 0–3)
 NaCl 0.9% infused, mL kg−1 12.3 (13.2) 8.4 (9.5) <0.001
 NaCl 0.45% infused, mL kg− 1 6.5 (20.3) 2.9 (12.9) <0.001
 Balanced electrolyte solution infused, mL kg−1 41.9 (37.1) 49.7 (40.7) <0.001
 Free water containing dextrose, mL kg−1 47.2 (62.5) 59.3 (56.9) <0.001
 Hydroxyethyl starch infused, mL kg−1 22.1 (21.5) 13.4 (16.5) <0.001
 Intraoperative fluid balance, %c 1.8 (3.6) 1.7 (2.8) 0.321
 RRT (without RRT history) 51 (2.7%) 135 (2.2%) 0.199
 Use of inotropes/vasopressorsd 1635 (87.2%) 4286 (70.1%) <0.001
 Use of diureticse 1300 (69.3%) 3423 (56.0%) <0.001
 Use of radiocontrast 991 (52.8%) 1738 (28.4%) <0.001
 Use of nephrotoxic antibioticsf 377 (20.1%) 1147 (18.8%) 0.197
 Use of NSAIDs 754 (40.2%) 2194 (35.9%) 0.001
Postoperative laboratory (PODs 0–3) and clinical outcomes
 Maximum Cl−, mmol/L* 112.3 (2.9) 104.8 (3.3) <0.001
 Increase in Cl−, mmol/L** 5.6 (4.4) 3.5 (3.2) <0.001
 Postoperative metabolic acidosis (PODs 0–3) 262 (14.0%) 615 (10.1%) <0.001
 AKI occurrence 289 (15.4%) 898 (14.7%) 0.443
   AKI stage ≥ 2 occurrence 51 (2.7%) 135 (2.2%) 0.199
  1. Values are expressed as the mean (standard deviation) or number (percentage)
  2. ASA American Society of Anesthesiologists classification, eGFR estimated glomerular filtration rate, RRT renal replacement therapy, POD postoperative day, NSAID nonsteroidal anti-inflammatory drug; AKI, acute kidney injury
  3. *Laboratory values within 3 days after operation
  4. **The increase in Cl− or serum sodium levels was calculated as the difference between the preoperative value and the maximum value noted during PODs 0–3
  5. aeGFR (mL·min− 1·1.73·m− 2) = 186 × (Creatinine)-1.154 × (Age)-0.203 (× 0.742 if female)
  6. bIntraoperative hypotension was defined as mean blood pressure < 60 mmHg for > 1 min
  7. cIntraoperative fluid balance (%) = {[Total input fluid (L) – Total output fluid (L)] × 100} × weight on admission− 1 (kg)
  8. dInotropes/vasopressors include norepinephrine, epinephrine, vasopressin, dobutamine, and dopamine
  9. eDiuretics include mannitol and furosemide
  10. fNephrotoxic antibiotics include aminoglycoside, cephalosporin, vancomycin, and sulfonamide
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