Sodium Bicarbonate vs Sodium Chloride in Preventing Contrast Medium–Induced Nephropathy—Reply

In Reply: In response to Dr Burgess and colleagues, the formulation of sodium bicarbonate used in our study (and commonly used in clinical practice because of ease of preparation) was identical to that used by Merten et al¹ in the registry phase of their study, reportedly with excellent results. The formulation used in the trial phase of their study had a slightly higher sodium bicarbonate concentration, which would result in a 70-kg patient receiving an additional 15 mEq of sodium bicarbonate over the study period. This small difference did not appear to alter the outcomes between the trial and registry phases of their study, and we believe is unlikely to account for the lack of observed benefit in our study. Although measures of urine pH may have been informative, the optimal timing of testing and degree of change in urinary pH to confer a protective effect, if any, remains unknown. In the study by Recio-Mayoral et al,² the group receiving sodium bicarbonate was hydrated at a higher rate and received intravenous N-acetylcysteine while the control group received less hydration before and after the procedure, confounding the results.