Acute changes in fluid status affect the incidence, associative clinical outcomes, and urine biomarker performance in premature infants with acute kidney injury

Background During the first postnatal weeks, infants have abrupt changes in fluid weight that alter serum creatinine (SCr) concentration, and possibly, the evaluation for acute kidney injury (AKI). Methods We performed a prospective study on 122 premature infants to determine how fluid adjustment (FA) to SCr alters the incidence of AKI, demographics, outcomes, and performance of candidate urine biomarkers. FA-SCr values were estimated using changes in total body water (TBW) from birth; FA-SCR = SCr x [TBW + (current wt. - BW)]/ TBW; where TBW = 0.8 x wt in kg). SCr-AKI and FA-SCr AKI were defined if values increased by >= 0.3 mg/dl from previous lowest value. Results AKI incidence was lower using the FA-SCr vs. SCr definition [(23/122 (18.8 %) vs. (34/122 (27.9 %); p < 0.05)], with concordance in 105/122 (86 %) and discordance in 17/122 (14 %). Discordant subjects tended to have similar demographics and outcomes to those who were negative by both definitions. Candidate urine AKI biomarkers performed better under the FA-SCr than SCr definition, especially on day 4 and days 12-14. Conclusions Adjusting SCr for acute change in fluid weight may help differentiate SCr rise from true change in renal function from acute concentration due to abrupt weight change.