Abstract
Hyperphosphatemia is associated with mortality in patients with chronic kidney disease, and is common in critically ill patients with acute kidney injury (AKI); however, its clinical implication in these patients is unknown. We conducted an observational study in 1144 patients (mean age, 63.2 years; male, 705 [61.6%]) with AKI who received continuous renal replacement therapy (CRRT) between January 2009 and September 2016. Phosphate levels were measured before (0 h) and 24 h after CRRT initiation. We assessed disease severity using various clinical parameters. Phosphate at 0 h positively correlated with the Acute Physiology and Chronic Health Evaluation II (APACHE II; P < 0.001) and Sequential Organ Failure Assessment (SOFA; P < 0.001) scores, and inversely with mean arterial pressure (MAP; P = 0.02) and urine output (UO; P = 0.01). In a fully adjusted linear regression analysis for age, sex, Charlson comorbidity index (CCI), MAP, and estimated glomerular filtration rate (eGFR), higher 0 h phosphate level was significantly associated with high APACHE II (P < 0.001) and SOFA (P = 0.04) scores, suggesting that phosphate represents disease severity. A multivariable Cox model also showed that hyperphosphatemia was significantly associated with increased 28-day (HR 1.05, 95% CI 1.02–1.08, P = 0.001) and 90-day (HR 1.05, 95% CI 1.02–1.08, P = 0.001) mortality. Furthermore, patients with increased phosphate level during 24 h were at higher risk of death than those with stable or decreased phosphate levels. Finally, c-statistics significantly increased when phosphate was added to a model that included age, sex, CCI, body mass index, eGFR, MAP, hemoglobin, serum albumin, C-reactive protein, and APACHE II score. This study shows that phosphate is a potential biomarker that can reflect disease severity and predict mortality in critically ill patients receiving CRRT.
Highlights
Acute kidney injury (AKI) is common in critically ill patients
We investigated whether phosphate can serve as a biomarker of disease severity and a predictor of mortality in critically ill patients receiving continuous renal replacement therapy (CRRT)
We found that phosphate level well correlates with APACHE II and Sequential Organ Failure Assessment (SOFA) scores, which are two representative scoring systems that can reflect a life-threatening condition in patients in the intensive care unit (ICU)
Summary
Acute kidney injury (AKI) is common in critically ill patients. 5% of patients with AKI in the intensive care unit (ICU) require renal replacement therapy (RRT), [1] and these patients are more likely to have higher mortality and to progress to chronic kidney disease (CKD) [2] than those without AKI [3,4,5]. Identification of risk factors is important for predicting adverse outcomes. Disturbances in the regulatory mechanisms can result in significant consequences, especially in critically ill patients [6]. Hyperphosphatemia is a common condition in patients with AKI. It is likely due to decreased phosphate removal and secondary hyperparathyroidism as a result of reduced kidney function [10, 11]
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