Large study also reveals that N-acetylcysteine offers no renal protection.

Sodium bicarbonate may increase the risk of contrast nephropathy (CN), recent findings suggest.

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Researchers at the Mayo Clinic in Rochester, Minn., examined 11,516 cases of contrast exposure in a “real world population” of 7,977 patients. Sodium bicarbonate alone, N-acetylcysteine (NAC) alone, and both of these agents were administered in 268, 616, and 221 cases, respectively. The remaining cases received hydration alone and served as the reference group. CT scans were the most common reason patients were given contrast media. The investigators, led by Aaron M. From, MD, defined CN as a post-exposure creatinine rise of 25% or greater or more than 0.5 mg/dL within seven days.


Compared with patients who received no prophylaxis against CN, those treated with sodium bicarbonate alone had a three times higher risk of CN. An increased risk of CN persisted even when patients were stratified by glomerular filtration rate (GFR). The risk of CN associated with sodium bicarbonate alone was 3.62 times higher among patients with a GFR of 60 mL/min or more and 2.64 times higher in patients with a GFR below 60 mL/min. The risk was not significantly affected by NAC alone or combined with sodium bicarbonate.


“The clinical use of sodium bicarbonate for renal protection should be reconsidered until further investigation can elucidate its proper use,” the authors concluded.


In a separate study of 57 patients with CKD stages 2 to 4 undergoing coronary angiography or angioplasty, Rashidi Saidin, MD, and his colleagues at the National University of Malaysia in Kuala Lumpur, found that sodium bicarbonate was no more effective than normal saline at preventing CN. The condition developed in nine patients in the sodium bicarbonate group (31%) compared with four in the normal saline group (14.3%), but difference in the proportions was not statistically different.


Additionally, a group at Rhode IslandHospital in Providence led by George Bayliss, MD, reported that the volume of contrast dye used in patients undergoing cardiac catheterization does not affect the incidence of CN. “That could be important for patients who require significant angiographic intervention or multiple angiographic interventions requiring large volumes of contrast material,” the investigators concluded.


The study, which examined 513 cardiac catheterizations, demonstrated no significant difference in CN incidence even among a small subset of patients with a pre-procedure glomerular filtration rate less than 60 mL/min, the defining limit for stage 3 CKD.