Mean relative creatinine increase was -0.14 % ( interquartile range -15.1 % to 12.0 % ) for withholding hydration and -0.32 % ( interquartile range -9.7 % to 10.1 % ) for sodium bicarbonate ( mean difference 0.19 % , 95 % confidence interval -5.88 % to 6.25 % , P-value non-inferiority < 0.001 ) .