In a previous issue of Critical Care, Heringlake and

colleagues [1] report important results of a cohort analysis of use of bicarbonate to prevent cardiac surgery-associated acute kidney injury (CSA-AKI). Acute kidney injury (AKI) is common in hospitalized patients and is associated with increased morbidity and mortality. Cardiac surgery with cardiopulmonary bypass (CPB) is the second leading cause of AKI in the ICU, just after sepsis [2]. CSA-AKI incidence varies widely in the litera-ture, usually in between 3 % and 50 % of patients under-going CPB [3,4]. Its occurrence depends on several procedure-related (type of cardiac surgery, duration of aortic cross-clamping, CPB time) and patient-dependent factors (age, chronic kidney disease, low left ventricular ejection fraction, peripheral vascular disease, diabetes). Th e incidence of CSA-AKI is only 2.3 % in isolated coronary artery bypass graft procedures in patients without comorbidities but its incidence rises up to 15 % in patients also with chronic kidney disease [5]. Due to its signifi cant incidence and infl uence on resource utiliza-tion and potentially on mortality, the prevention and/or treatment of CSA-AKI is a relevant issue. Pathophysiology of CPB-AKI is complex, mainly rely-ing on hemodynamic and infl ammatory disturbances [3,6]. CPB is associated with ischemia-reperfusion injury but also with signifi cant release of free hemoglobin and iron. Nevertheless, the respective importance of the diff erent pathophysiological processes in CSA-AKI remains unclear. In addition, nephrotoxic drugs, anemia and blood transfusions may further exacerbate CSA-AKI. Experimental data have shown that higher tubular pH could be protective in the presence of hemoglobinuria or myoglobinuria [7], especially through inhibition of hydroxyl radical generation and lipid peroxidation, which could be central in AKI [8-10]. In analogy with the bene-fi cial eff ects of urine alkalinization after rhabdomyolysis [11], urine alkalinization after intravenous bicarbonate was thought to prevent CSA-AKI. In a pilot randomized study including 100 patients submitted to cardiac surgery with CPB, perioperative bicarbonate administration decreased the proportion of patients experiencing an increase in creatinine from 52 to 32 % (P = 0.043) [12]. In addition, bicarbonate blunted the increase in biomarker