Post hoc subgroup analyses for the primary composite and secondary acute kidney injury (AKI) outcomes. The results are shown as relative risk of increased primary composite or more severe postoperative AKI comparing lactated Ringer’s (LR) versus saline. Displayed P value is an interaction P value for each of six subgroup analyses; overall P values are corresponding to the relative risk of the primary composite outcome and the relative risk of more severe AKI for LR versus saline. The box represents the estimate of the relative risk, and the line represents the confidence intervals. Intraop, intraoperative; Preop, preoperative.