 Urinary acidity may enhance the generation and toxicity of reactive oxygen species induced by cardiopulmonary bypass 10,15. Activation of complement during cardiac surgery 16 may also participate in kidney injury. Urinary alkalinization may protect from kidney injury induced by oxidant substances, iron-mediated free radical pathways, complement activation and tubular hemoglobin cast formation 9,17,18. Of note, increasing urinary pH - in combination with N-acetylcysteine 19,20 or without 21 - has recently been reported to attenuate acute kidney injury in patients undergoing contrast-media infusion. 