Interestingly, increased renin concentrations after cardiac surgery were associated with hemodynamic instability and acute kidney injury [35], and, in another series of patients in whom vasopressors were started at anesthesia induction for cardiac surgery, Ang II reduced the circulating renin concentrations compared to norepinephrine, and high renin levels before surgery were associated with higher vasopressor requirements in the norepinephrine group but not in the Ang II group [36]. Here, REN is linked to acute kidney injury.