Chloride Variation as an Independent Risk Factor for AKI Development and In-Hospital Mortality in Patients with Rhabdomyolysis

Background: Rhabdomyolysis (RB) is considered as an important cause for acute kidney injury (AKI) and mortality. Studies have suggested that acidosis is a risk factor for AKI. We alternatively hypothesized that serum chloride variation (SCV) might be associated with AKI and mortality in RB patients. Methods: We studied a retrospective cohort of RB (>5x reference values of CPK) patients admitted in a tertiary hospital during a year. Demographic, clinical and laboratorial data were assessed and a regression analysis (RA) was performed in order to identify the independent variables associated with AKI and 28d mortality, including SCV. Results: We included 291 patients admitted with RB due to diverse causes, from which 67% developed AKI. AKI patients were older, had more comorbidities and were sicker during admission (shock 35 vs 13%; p < 0.0001, mechanical ventilation, MV 49 vs 29%; p= 0.0015; sepsis 11 vs 3%; p=0.03). Peak CPK levels were higher in the AKI group (4218 IQR 2316-8968 vs 3221 IQR 1940-6206 U/L; p=0.04). Serum bicarbonate (SBic) and chloride did not differ between AKI and non-AKI at admission (21.0 IQR 18-24 vs 21.5 IQR 20-24 mEq/L, p=0.3; and 107 IQR 102-111 vs 107 IQR 113-111 mEq/L, p=0.5, respectively). During hospitalization, SCV was higher in the AKI group (2 IQR 0-10 vs 0 IQR 0-10 mEq/L, p=0.0003), and SBic was lower (18 IQR 14-21 vs 21 IQR 19-24 mEq/L, p< 0.0001). After RA, SCV remained as an independent variable associated with AKI (OR 1.09 CI 1.01-1.16, p=0.020), along with baseline hypertension (p=0.024) and SBic (p<0.001). AKI patients had higher mortality (39 vs 3.5%, p<0.0001) and RA showed that SCV was associated with mortality in the entire cohort (OR 1.082 CI 1.006-1.163, p=0.035), along with increased age, use of MV, AKI, use of renal replacement therapy, trauma and higher serum lactate. Conclusion: Higher serum chloride variation was an independent risk factor for AKI and death in hospitalized patients with RB.