Simple blood and urinary parameters measured at ICU admission may sign for AKI development in the early postoperative period: a retrospective, exploratory study

Abstract

Recent studies have suggested that some blood physicochemical and urinary biochemical parameters have a standardized behavior during acute kidney injury (AKI) development. The changes in these parameters frequently begin to occur before significant rises in serum creatinine (sCr) and may help in identifying patients with more subtle decreases in glomerular filtration rate (GFR). Surgical patients have an increased risk of AKI but renal impairment is usually not evident at ICU admission. We hypothesized that the surgical patients who have AKI diagnosed in the early postoperative period have an impaired GFR since ICU admission, indirectly inferred by alterations in these blood physicochemical and urinary biochemical parameters even in the presence of a still normal sCr. We retrospectively evaluated 112 surgical patients who were categorized according to AKI development during the first 3 ICU days. Twenty-eight patients developed AKI, most of them in the first day (D1) after ICU admission (D0). AKI patients had, at D0, lower serum pH and albumin, higher C - reactive protein (CRP), lower urine sodium (NaU) and fractional excretion of urea (FEUr). Fractional excretion of potassium (FEK) was high in both groups at D0 but remained high in the subsequent days only in AKI patients. Very low CRP and high serum albumin, high NaU and FEUr values at ICU admission had a significant negative predictive value for AKI. We concluded that some easily assessed parameters in blood and urine may help to identify patients with indirect signs of increased inflammatory response and decreased GFR at ICU admission, which could help to predict the risk of postoperative AKI development.

Keywords: Acute kidney injury; inflammation; physicochemical approach; postoperative; urine biochemistry.