title: Perioperative fluid balance affects staging of acute kidney injury in postsurgical patients: a retrospective case-control study.
abstract: BACKGROUND
  Although Acute Kidney Injury Network (AKIN) staging is widely used, it has been suggested that classification using serum creatinine levels, which fluctuate because of fluid balance, is not always appropriate for acute kidney injury (AKI) detection. We hypothesized that some patients are misdiagnosed as having no AKI due to dilution resulting from intraoperative infusion, and have worse outcomes than typical patients with no AKI.
  
  
  METHODS
  We retrospectively selected patients who did not fulfill the AKI criteria from those who underwent cardiac surgery and remained in an intensive care unit (ICU) for ≥7 days. The patients were divided into two groups: those with AKI (AKI group) and those without AKI (no-AKI group), classified using serum creatinine levels adjusted for fluid balance during the perioperative period. We compared the characteristics and outcomes of the two groups.
  
  
  RESULTS
  After adjustment for serum creatinine, 7 of 26 patients were categorized as having AKI. The AKI group had significantly fewer ventilator-free days during a 28-day period and significantly longer ICU stays than the no-AKI group (5.86 ± 10.0 days vs. 15.6 ± 9.71 days, respectively, P = 0.050; 36.4 ± 20.6 days vs. 14.9 ± 10.7 days, respectively, P = 0.033).
  
  
  CONCLUSIONS
  Adjustment of creatinine level for perioperative fluid balance could improve the accuracy of AKI diagnosis after cardiac surgery.
authors.affiliation: Intensive Care Unit, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka, 565-0871 Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Horiguchi
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871 Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Uchiyama
authors.affiliation: Intensive Care Unit, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka, 565-0871 Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Iguchi
authors.affiliation: Intensive Care Unit, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka, 565-0871 Japan.
authors.forename: Kanaki
authors.initials: K
authors.lastname: Sakai
authors.affiliation: Intensive Care Unit, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka, 565-0871 Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Hiramatsu
authors.affiliation: Intensive Care Unit, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka, 565-0871 Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Ueta
authors.affiliation: Intensive Care Unit, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka, 565-0871 Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Ohta
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871 Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Fujino
keywords: Acute kidney injury; Perioperative fluid management; Serum creatinine levels