Positive Fluid Balance and Association with Post-Traumatic Acute Kidney Injury

BACKGROUND: Acute kidney injury (AKI) is common in severely injured trauma patients and is associated with poor outcomes. A positive fluid balance is associated with AKI and poor long-term renal outcomes among general ICU and cardiac surgery patients. Currently, the optimal endpoint of resuscitation of severely injured trauma patients is unknown, which may result in excess fluid administration. We hypothesized that positive fluid balance is common after severe trauma and is associated with increased AKI development. STUDY DESIGN: A cohort study of adult (≥16 years old) trauma patients requiring ICU admission from January 2017 to June of 2017 was conducted. Patients were excluded for early death, rhabdomyolysis, or previous history of end-stage renal disease or congestive heart failure. Acute kidney injury within 7 days of admission was defined according to Kidney Disease Improving Global Outcomes creatinine-based criteria. Univariate and multivariable analyses were performed. RESULTS: Of 364 patients, 74% were male. The median age was 41 years (interquartile range [IQR] 27 to 59 years), and the median Injury Severity Score (ISS) was 18 (IQR 10 to 29). Positive fluid balance (>2 L) was observed in 49% of patients. Acute kidney injury was diagnosed in 105 (29%) patients. After adjustment, there was an increased risk of AKI with a positive fluid balance >2 L (relative risk [RR] 1.98 [95% CI 1.24 to 3.17]). Additionally, the risk of AKI incrementally increased by 1.22 with each liter fluid positive above a zero balance (95% CI 1.11 to 1.34). CONCLUSIONS: Positive fluid balance in excess of 2 L at 48 hours occurs in half of severely injured trauma patients, and fluid positivity is independently and incrementally associated with AKI development. Fluid responsiveness should be investigated as an end point of post-traumatic resuscitation to prevent unnecessary fluid administration and subsequent AKI.