The effect of postoperative fluid balance on the occurrence and progression of acute kidney injury after cardiac surgery

Abstract Objections : In addition to the association between positive fluid balance (FB) and acute kidney injury (AKI) after cardiac surgery reported by former studies, this study emphasized on the relationship between FB and progressive AKI. Design : A retrospective, observational study. Setting : In a university teaching, grade A tertiary hospital in Shanghai. Participants : Adult patients after cardiac surgery from July to December 2016. Interventions : Perioperative data was collected relating to postoperative fluid intake and output. AKI progression was defined as a worsening of AKI stage. FB was calculated as (fluid intake(L)-fluid output(L)/body weight(kg)*100%. Measurements and Main Results : 1522 patients were enrolled in the study. The incidence of AKI and progressive AKI was 33.1% (n=504) and 18.1% (n=91), respectively. There was an exponential increase between 24h FB and AKI occurrence, and an approximate “U”-shape association between 48h FB and the AKI progression. Multivariate logistic regression showed 24h FB ≥5% was an independent risk factor for AKI incidence (OR=3.976, P Conclusions : We found an exponential increase between 24h FB and AKI occurrence, and a “U”-shape association between 48h FB and AKI progression. Both excessively negative and positive accumulative 48h FB increased the risk of AKI progression, suggesting cautious monitoring and appliance of fluid load in clinical practice.