Association between postoperative fluid balance and acute kidney injury in patients after cardiac surgery: A retrospective cohort study

Abstract

Purpose: The present study aims to explore appropriate postoperative fluid management in patients after cardiac surgery.

Materials and methods: Data were extracted from an online database. Associations between fluid balance (FB), fluid intake and mortality were investigated.

Results: Compared to zero FB (level 3), more negative FB (level 1, odds ratio (OR): 0.938, 95% CI: 0.631-1.394; level 2, OR: 0.921, 95% CI: 0.709-1.196) could not further decrease AKI incidence while positive FB was associated with higher AKI incidence (level 4, OR: 1.272, 95% CI: 1.028-1.573; level 5, OR: 2.042, 95% CI: 1.652-2.524). Both limited (level 1, OR: 1.354, 95% CI: 1.065-1.699) and increased postoperative fluid intake (level 3, OR: 1.127, 95% CI: 0.890-1.430; to level 5, OR: 1.405, 95% CI: 1.105-1.786) were associated with increased AKI incidence, compared to level 2. Multivariable logistic models using linear spline function showed a similar pattern.

Conclusions: Compared to zero FB, postoperative positive FB was associated with higher AKI incidence. Yet, the association between negative FB and AKI was insignificant. A "U"-shape association between postoperative fluid intake and AKI was detected.

Keywords: Acute kidney injury; Cardiac surgery; Fluid balance; Fluid intake.