Fractional Excretion of Sodium as an Early Predictor of Acute Kidney Injury in Term Neonates with Perinatal Asphyxia at a National Referral Hospital in a Low Income Country

Abstract

Background: The kidney is one of the organs most commonly affected in neonates with perinatal asphyxia. Diagnosis of AKI using serum creatinine and urine output has several shortcomings. This study sought to determine whether fractional excretion of sodium (FENa) could be used on the first day of life to identify neonates with birth asphyxia who eventually suffer AKI.

Methods: This was a hospital based cross sectional study. Urine and serum sodium and creatinine were measured on the first day of life, and used to calculate FENa. AKI was diagnosed on 3rd day of life using serum creatinine levels >100 μmol/l. Analysis for associations between deranged FENa on day 1 of life and AKI at three days of life were done.

Results: A total of 79/108 neonates with perinatal asphyxia admitted during the study period were recruited. AKI was diagnosed in 30/79 neonates, with 27/30 having FENa>2.5% (Sensitivity of 90%). Only 26/49 of the neonates without AKI had FENa<2.5% on day 1 of life giving us a specificity of 53%.

Conclusion: FENa has a high sensitivity which makes it a good screening test. Our low sensitivity however means that it can have false positive AKI diagnosis.