[Objective] Acute kidney injury (AKI) is one of the postoperative complications of cardiac surgery with cardiopulmonary bypass (CPB). It has been reported that the incidence of AKI is as high as 15-30% and the prognosis is poor.

Chloride (Cl) is a type of electrolyte. Animal studies have shown that Cl itself causes renal vasoconstriction and decreases glomerular filtration rate. However, there are no reports showing the association between Cl dose during CPB management and postoperative AKI.

In this retrospective study, the total Cl dose during CPB management was defined as the total Cl dose from the CPB priming solution, the infusion and blood products used during CPB. The objective of this study was to determine the association between the total Cl dose during CPB management and postoperative AKI.

[Methods] The subjects were 301 patients aged 18 years or older who underwent open-heart surgery with cardiac arrest by aortic cross-clamping and CPB from January 1, 2016 to December 31, 2018. A multivariate logistic regression analysis was performed to evaluate the association between the total Cl dose during CPB management and postoperative AKI. Confounding factors, which were pre-selected based on the previous literature reports, included age, sex, preoperative weight, estimated glomerular filtration rate, perfusion pressure during CPB management, the lowest oxygen delivery index during CPB management, and CPB duration.

[Results] The cutoff value of 18.0 g was obtained for the total Cl dose during CPB management. In the multivariate logistic regression analysis using the cutoff value of 18.0 g, the incidence of postoperative AKI was significantly higher in the category of the total Cl dose >18.0 g compared to the category ≤18.0 g (odds ratio: 2.376, P=0.037), suggesting that the total Cl dose >18.0 g is a statistically significant risk factor for postoperative AKI.

[Conclusion] In terms of the total Cl dose from the CPB priming solution, the infusion and blood products used during CPB, patients managed with the total Cl dose >18.0 g had a higher incidence of postoperative AKI compared to those managed with the total Cl dose ≤18.0 g.