Cumulative fluid accumulation is associated with the development of acute kidney injury and non-recovery of renal function: a retrospective analysis

BACKGROUND: Acute kidney injury (AKI) is common in patients in the intensive care unit (ICU) and may be present on admission or develop during ICU stay. Our objectives were (a) to identify factors independently associated with the development of new AKI during early stay in the ICU and (b) to determine the risk factors for non-recovery of AKI. METHODS: We retrospectively analysed prospectively collected data of patients admitted to a multi-disciplinary ICU in a single tertiary care centre in the UK between January 2014 and December 2016. We identified all patients without AKI or end-stage renal failure on admission to the ICU and compared the outcome and characteristics of patients who developed AKI according to KDIGO criteria after 24 h in the ICU with those who did not develop AKI in the first 7 days in the ICU. Multivariable logistic regression was applied to identify factors associated with the development of new AKI during the 24–72-h period after admission. Among the patients with new AKI, we identified those with full, partial or no renal recovery and assessed factors associated with non-recovery. RESULTS: Among 2525 patients without AKI on admission, the incidence of early ICU-acquired AKI was 33.2% (AKI I 41.2%, AKI II 35%, AKI III 23.4%). Body mass index, Sequential Organ Failure Assessment score on admission, chronic kidney disease (CKD) and cumulative fluid balance (FB) were independently associated with the new development of AKI. By day 7, 69% had fully recovered renal function, 8% had partial recovery and 23% had no renal recovery. Hospital mortality was significantly higher in those without renal recovery. Mechanical ventilation, diuretic use, AKI stage III, CKD, net FB on first day of AKI and cumulative FB 48 h later were independently associated with non-recovery with cumulative fluid balance having a U-shape association. CONCLUSIONS: Early development of AKI in the ICU is common and mortality is highest in patients who do not recover renal function. Extreme negative and positive FB were strong risk factors for AKI non-recovery.