Association of perioperative fluid balance and acute kidney injury in patients undergoing elective colorectal surgery: A pre-planned secondary analysis of a multicentre prospective observational study

BACKGROUND – Acute kidney injury (AKI) is a common complication after surgery. Greater fluid administration has been related to an increased incidence in patients undergoing major surgery but there are no large series of patients in specific perioperative settings showing relationship between fluid balance and the occurrence of AKI. OBJECTIVE – This study tested the hypothesis that higher perioperative fluid balance was associated with an increased risk of postoperative AKI. DESIGN – Prospective observational study. Predefined secondary sub-study of the Postoperative Outcomes Within Enhanced Recovery After Surgery (POWER) study SETTING – A pre-planned secondary analysis of a multicentre study in 80 hospitals in Spain during a single period of 2 months of recruitment between September and December 2017.PATIENTS – Patients undergoing elective primary colorectal surgery with a planned overnight stay were included if they had complete data regarding postoperative fluid balance. Patients who underwent urgent or emergency surgery or with estimated glomerular filtration rate less than 30 ml min−1 were excluded. MAIN OUTCOMES MEASURES – The primary outcome was the occurrence of AKI (mild, moderate, or severe) at 30.days following surgery. AKI was defined according to KDIGO and EPCO guidelines, incorporating serum creatinine and urine output criteria.RESULTS – A total of 1139 patients were included in the study. Of these, 73 patients (6.4%) developed acute kidney injury in the postoperative period. The adjusted relative risks (RR) that compared the quartile with the lowest perioperative fluid balance (Q1) with other quartiles were 4.10 [95% confidence interval (CI), 1.60 to 10.51] for Q3 and 4.81 (95% CI, 1.91 to 12.11) for Q4. In the Poisson loglinear model after adjusting by sex, ASA grade, Enhanced Recovery After Surgery (ERAS) adherence and intraoperative bleeding, RR for AKI were higher with a higher positive perioperative fluid balance (quadratic nonlinear P<0.01)CONCLUSIONS – In this secondary analysis, we found that higher positive perioperative fluid balance during the first 24 h was associated with an increased risk of postoperative acute kidney injury in patients undergoing elective colorectal surgery. TRIAL REGISTRATION – Clinicaltrials.com identifier: NCT03012802.