Background: The elevation of serum creatinine (SCr), acute kidney injury (AKI), is associated with an increase of mortality in critically ill patients. However, it is uncertain whether a decrease in SCr in the intensive care unit (ICU) has an effect on outcomes.
Methods: In a retrospective study, we enrolled 486 patients who had been admitted to an urban tertiary center ICU between Jan 2014 and Dec 2014. The effect of changes in SCr after ICU admission on 90 day mortality was analyzed. Patients were classified into 3 groups based on change in SCr after ICU admission: a stable SCr group (Δ SCr < 0.3mg/dL during ICU stay), a decreased SCr group (Δ SCr ≥ -0.3 mg/dL during ICU stay) and an increased SCr group with criteria based on the KDIGO AKI criteria.
Results: In total, 486 patients were identified. SCr decreased in 123 (25.3%) patients after ICU admission. AKI developed in 125 (24.4%) patients. The overall 90-day mortality rate was 29.0%. In a Kaplan-Meyer analysis, the mortality of the AKI group was higher than that of other groups (p<0.0001). Patients with a decrease in SCr had a higher mortality rate than those with stable SCr (p<0.0001). A Cox analysis showed that both a decrease in SCR (HR, 3.56; 95% CI, 1.59-7.97; p = 0.002) and an increase in SCr (AKI stage 1, HR, 9.35; 95% CI, 4.18-20.9; p<0.0001; AKI stage 2, HR, 11.82; 95% CI, 3.85-36.28; p<0.0001; AKI stage 3, HR, 17.41; 95% CI, 5.50-55.04; p<0.0001) were independent risk factors for death compared to stable SCr.
Conclusion: Not only an increase in SCr, but also a decrease in SCr was associated with mortality in critically ill patients.