Griffin BR, Bronsert M, Reece TB, et al. - Given the established predictive value of baseline kidney function for postoperative morbidity and mortality, researchers here evaluated if an increased creatinine at the time of surgery, compared with the lowest creatinine in the 3 months before surgery, is linked with poor outcomes. The difference between the immediate presurgical creatinine value and the lowest creatinine value within 3 months preceding surgery defined “change in creatinine from baseline”. Among 1,486 included patients who underwent cardiac surgery at the University of Colorado Hospital between January 2011 and May 2016, association was observed between elevations in creatinine at the time of surgery above the “baseline” level and increased postoperative morbidity. Findings emphasize establishing baseline creatinine before surgery, and heightened vigilance in the postoperative period in cases with small changes in creatinine.