Incidence of Acute Kidney Injury and Mortality in Critically Ill Patients: Urinary Chloride as a Prognostic Marker

Acute kidney injury (AKI) is characterized by a rapid decrease in renal function. It is frequent in hospitalized patients and its incidence is higher in critically ill patients. It is associated with high rates of morbidity and mortality.

AKI affects over 13 million people per year globally, and results in 1.7 million deaths. It is diagnosed in up to 20% of hospitalized patients and in 30- 60% of critically ill patients. It is the most frequent cause of organ dysfunction in intensive care units and the occurrence of even mild AKI is associated with a 50% higher risk of death. AKI has been associated with longer hospital stays, in-hospital mortality, cardiovascular events, progression to chronic kidney disease and long-term mortality. It results in a significant burden for the society in terms of health resource use during the acute phase and the potential long-term sequelae including development of chronic kidney disease and kidney failure. Yunos et al. have focused on chloride, which is the most abundant strong anion in extracellular fluid. Progression of hyperchloremia in the ICU was identified as a predictor of increased mortality in a large retrospective cohort study of critically ill septic patients. Sadan et al. have shown associations between hyperchloremia and an increased incidence of AKI in patients with subarachnoid hemorrhage, as well as in patients who have undergone abdominal surgery. Abnormal blood chloride concentrations were associated with metabolic acidosis, which may worsen patient outcomes. Moreover, hyperchloremia may be caused by inappropriate fluid management with chloride-rich solutions.

Importantly, chloride-rich solutions were reportedly associated with hyperchloremia and major adverse kidney disease, including death, in intensive care settings. Urine samples are relatively easy to collect in ICU, and real-time urinary electrolyte monitoring device is available for clinical use. In addition, recent development of urinary AKI biomarkers has enabled clinical evaluation of kidney function. Komaru et al. examined associations among urinary chloride, mortality, and AKI incidence in ICU patients and concluded that lower urinary chloride concentration was associated with increased mortality and incidence of AKI in the ICU.