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

Table 2 Multivariable logistic regression analyses o postoperative AKI according to hyperchloremia exposure during PODs 0–3

Group	Variable	Multivariable model 1
Group	Variable	Overall AKI: OR (95% CI)	P value
Entire sample (n = 7991)	Hyperchloremia^a on POD 0	1.22 (0.94, 1.58)	0.144
	Hyperchloremia^a on PODs 0–3	1.09 (0.80, 1.49)	0.571
	Interaction of hyperCl on POD 0–3 with eGFR
	≥ 90 mL·min⁻¹·1.73·m^− 2	1	(0.425)
	60–89 mL·min⁻¹·1.73·m^− 2	0.91 (0.62, 1.34)	0.629
	30–60 mL·min⁻¹·1.73·m^− 2	0.96 (0.65, 1.43)	0.840
	< 30 mL·min⁻¹·1.73·m⁻²	0.70 (0.45, 1.08)	0.109
		Multivariable model 2
		≥ Stage 2 AKI: OR (95% CI)	P value
	Hyperchloremia^a on POD 0	1.61 (0.89, 2.93)	0.367
	Hyperchloremia^a on PODs 0–3	0.77 (0.40, 1.49)	0.437
	Interaction of hyperchloremia with eGFR
	≥ 90 mL·min⁻¹·1.73·m⁻²	1	(0.468)
	60–89 mL·min^− 1·1.73·m^− 2	1.40 (0.67, 2.94)	0.367
	30–60 mL·min^− 1·1.73·m^− 2	0.64 (0.24, 1.69)	0.363
	< 30 mL·min^− 1·1.73·m^− 2	0.91 (0.17, 4.94)	0.915

Covariates with P < 0.2 on univariable analysis (see also Additional file 3) were included in the final multivariable model to adjust for potential confounders. Covariates for multivariable model 1 included preoperative American Society of Anesthesiologists (ASA) score, preoperative estimated glomerular filtration rate (eGFR), NaCl 0.9% and balanced crystalloid infused. Covariates for multivariable model 2 included preoperative ASA score, preoperative eGFR, cardiovascular surgery, NaCl 0.45% and hydroxyethyl starch infused. The Hosmer-Lemeshow goodness-of-fit test was performed to investigate the fitness of the multivariable logistic regression model, and revealed no indication of lack of fit (Model 1: Hosmer-Lemeshow statistic 7.09, P = 0.527; Model 2: Hosmer-Lemeshow statistic 6.287, P = 0.615)
AKI acute kidney injury, CI confidence interval, POD postoperative day
^aHyperchloremia was defined as serum chloride levels ≥ 110 mmol·L^− 1
^bPreoperative 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)

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