Urinary Strong Ion Difference as a Marker of Renal Dysfunction. A Retrospective Analysis.
BACKGROUND
The kidneys play a crucial role in the regulation of electrolytes and acid-base homeostasis. Urinary Strong Ion Difference (SIDu = NaU + KU-ClU) represents an important aspect of renal acid-base regulation. We evaluated the role of SIDu as a marker of renal dysfunction in critically ill patients.


METHODS
Patients admitted to the Medical Intensive Care Unit with a diagnosis of AKI for whom concomitant urinary samples available for SIDu calculation were retrospectively reviewed and staged according to KDIGO criteria for 3 days from inclusion. Patients were classified as Recovered (R-AKI) or Persistent-AKI (P-AKI) whether they exited KDIGO criteria within the 3-day observation period or not. A control group with normal renal function and normal serum acid-base and electrolytes was prospectively recruited in order to identify reference SIDu values.


RESULTS
One-hundred-and-forty-three patients with a diagnosis of AKI were included: 77 with R-AKI, and 66 with P-AKI. Thirty-six controls were recruited. Patients with P-AKI had more severe renal dysfunction and higher mortality than patients with R-AKI (SCr 2.23(IQR:1.68-3.45) and 1.81(IQR1.5-2.5) mg/dl respectively, p<0.001; 24-h UO 1297(950) and 2100(1094) ml respectively, p = 0.003); 30-d mortality, 39% and 13% respectively; p<0.001). SIDu significantly differed between groups, with rising values from controls to P-AKI groups (16.4(12), 30(24) and 47.3(21.5) mEq/l respectively, p<0.001).


CONCLUSIONS
SIDu may be a simple and inexpensive tool in AKI patients' evaluation. Further research is needed to evaluate the ability of SIDu to identify patients with renal dysfunction before derangements in serum creatinine or urine output are observed.
Department of Health Sciences, Section of Anaesthesiology, Intensive Care and Pain medicine, University of Florence, Florence, Italy.
Paolo
P
Balsorano
Department of Health Sciences, Section of Anaesthesiology, Intensive Care and Pain medicine, University of Florence, Florence, Italy.
Stefano
S
Romagnoli
Department of Pulmonary and Critical Care Medicine, Rhode Island Hospital, Providence, United States of America.
Samuel Kagan
SK
Evans
Department of Cardiology and Cardiac Surgery, Pediatric Cardiac Intensive Care Unit, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.
Zaccaria
Z
Ricci
Department of Health Sciences, Section of Anaesthesiology, Intensive Care and Pain medicine, University of Florence, Florence, Italy.
Angelo Raffaele
AR
De Gaudio
D058186:Acute Kidney Injury / Q000652:urine*; D000368:Aged; D015415:Biomarkers / Q000652:urine*; D002118:Calcium / Q000652:urine; D002712:Chlorides / Q000652:urine; D003404:Creatinine / Q000652:urine; D016638:Critical Illness; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007477:Ions / Q000097:blood / Q000652:urine*; D007668:Kidney / Q000473:pathology / Q000503:physiopathology; D019344:Lactic Acid / Q000097:blood; D008274:Magnesium / Q000652:urine; D008297:Male; D008875:Middle Aged; D010710:Phosphates / Q000652:urine; D011188:Potassium / Q000652:urine; D012372:ROC Curve; D012189:Retrospective Studies; D012964:Sodium / Q000652:urine; D014508:Urea / Q000097:blood
D015415:Biomarkers; D002712:Chlorides; D007477:Ions; D010710:Phosphates; D019344:Lactic Acid; D014508:Urea; D012964:Sodium; D003404:Creatinine; D008274:Magnesium; D011188:Potassium; D002118:Calcium