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Table 4 Multivariable logistic regression analyses for postoperative AKI stage ≥ 2 according to Cl increase

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

Group Variable Multivariable model 4
Odds ratio (95% CI) P value
Entire sample (n = 8157) Increase in Cl, mmol L− 1*
 Q1: ≤1 mmol L− 1 1 (0.802)
 Q2: 1–3 mmol L− 1 1.22 (0.65, 2.28) 0.542
 Q3: 3–6 mmol L− 1 0.86 (0.46, 1.62) 0.642
 Q4: > 6 mmol L− 1 1.00 (0.53, 1.89) 0.992
Interaction of Cl increase with eGFRa
 Increase in Cl: Q1 * eGFR: ≥ 90 1 (0.960)
 Increase in Cl: Q2 * eGFR: 60–89 0.62 (0.23, 1.67) 0.348
 Increase in Cl: Q2 * eGFR: 30–60 1.01 (0.31, 3.30) 0.990
 Increase in Cl: Q2 * eGFR: < 30 0.00 (0.00) 0.996
 Increase in Cl: Q3 * eGFR: 60–89 1.14 (0.46, 2.79) 0.780
 Increase in Cl: Q3 * eGFR: 30–60 1.44 (0.48, 4.37) 0.518
 Increase in Cl: Q3 * eGFR: < 30 2.52 (0.38, 16.95) 0.342
 Increase in Cl: Q4 * eGFR: 60–89 0.96 (0.38, 2.44) 0.937
 Increase in Cl: Q4 * eGFR: 30–60 1.52 (0.50, 4.62) 0.460
 Increase in Cl: Q4 * eGFR: < 30 2.53 (0.38, 17.01) 0.341
  1. Covariates with P < 0.2 on univariable analysis (see also Additional file 4) were included in the final multivariable model to adjust for potential confounders. Covariates for multivariable model 4 included preoperative American Society of Anesthesiologists (ASA) score, preoperative estimated glomerular filtration rate (eGFR), cardiovascular surgery, NaCl 0.45% and hydroxyethyl starch infused
  2. *The increase in Cl was calculated as the difference between the preoperative value and the maximum value noted during postoperative days (PODs) 0–3. The following quartiles were obtained: Q1, 2535 patients (31.7%); Q2, 1593 patients (20.0%); Q3, 2075 patients (26.0%); and Q4, 1788 patients (22.4%). The Hosmer-Lemeshow goodness-of-fit test was performed to investigate the fitness of the multivariable logistic regression models, and revealed no indication of lack of fit. For the entire sample, the Hosmer-Lemeshow statistic was 5.76 and the P value was 0.674
  3. AKI acute kidney injury, CI confidence interval, Cl serum chloride levels
  4. aPreoperative eGFR (mL·min− 1·1.73·m− 2) was calculated using the Modification of Diet in Renal Disease formula: 186 × (preoperative serum Creatinine)-1.154 × (Age)-0.203 (× 0.742 if female)