Fractional excretion of sodium and potassium and urinary strong ion difference in the evaluation of persistent AKI in sepsis

Nicolás Contrera Rolón; Joaquín Cantos; Iván Huespe; Eduardo Prado; Griselda I Bratti; Carlos Schreck; Sergio Giannasi; Guillermo Rosa Diez; Carlos F Varela

doi:10.1016/j.medine.2024.02.003

Fractional excretion of sodium and potassium and urinary strong ion difference in the evaluation of persistent AKI in sepsis

Med Intensiva (Engl Ed). 2024 Feb 24:S2173-5727(24)00027-4. doi: 10.1016/j.medine.2024.02.003. Online ahead of print.

Authors

Nicolás Contrera Rolón¹, Joaquín Cantos², Iván Huespe², Eduardo Prado², Griselda I Bratti³, Carlos Schreck³, Sergio Giannasi², Guillermo Rosa Diez³, Carlos F Varela³

Affiliations

¹ Critical Care Department, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina; Nephrology Department, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina. Electronic address: nicolas.contrerarolon@hospitalitaliano.org.ar.
² Critical Care Department, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina.
³ Nephrology Department, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina.

PMID: 38403531
DOI: 10.1016/j.medine.2024.02.003

Abstract

Objective: To evaluate the diagnostic performance of FENa (Fractional excretion of sodium), FEK (fractional excretion of potassium) and uSID (urinary strong ion difference) in predicting pAKI in sepsis and septic shock.

Design: Retrospective cohort study.

Setting: Two intensive care units in Argentina.

Patients: Adult patients with a confirmed diagnosis of sepsis or septic shock and AKI, and had a urinary biochemistry within 24h of the AKI diagnosis.

Interventions: None.

Main variables of interest: We evaluated the diagnostic accuracy of FENa, FEK and uSID through a ROC (Receiver Operating Characteristic) curve analysis.

Results: 80 patients were included. 40 patients presented pAKI. pAKI group had higher APACHE, SOFA score, and mortality rate. In the ROC curve analysis, uSID had no diagnostic utility (AUC=0.52, p=0.69). FENa presented moderate accuracy showing an AUC of 0.71 (95% CI 0.60-0.83; p=0.001), while FEK presented low accuracy with an AUC of 0.69 (95% CI 0.57-0.80; p=0.04). The optimal Youden point for identifying pAKI was at a FENa higher than 0.51 % with a specificity of 72.5% and a sensitivity of 65.0%. In the case of FEK, a value higher than 21.9 % presented the best relation, with a specificity of 67.5% and a sensitivity of 65.0%.

Conclusions: urine biochemistry interpretation in septic patients must be revised. FENa and FEK are related to the severity of AKI and could be helpful complementary tools for diagnosing pAKI.

Keywords: Acute kidney injury; Diferencia de aniones fuertes urinaria; Fracción excretada de potasio; Fracción excretada de sodio; Fractional excretion of potassium; Fractional excretion of sodium; IRA asociada a la sepsis; IRA persistente; Injuria renal aguda; Persistent AKI; Sepsis; Sepsis-associated AKI; Urinary strong ion difference.