HP and acute kidney injury: Taken together, the results of this study suggest that 1) although acetaminophen attenuates intraoperative plasma isofuran concentrations, the contribution of hemeprotein-mediated lipid peroxidation to systemic oxidative stress during CPB may be limited, 2) the effect of acetaminophen on hemeprotein-mediated lipid peroxidation may be obscured by plasma haptoglobin, and 3) free hemoglobin-mediated lipid peroxidation may play a minor role in the mechanism of postoperative AKI following CPB, particularly when plasma haptoglobin is not depleted.