Contrast-induced nephropathy accounts for more than 10% of hospital-acquired renal failure, senior author Dr. Thomas P. Kennedy, formerly of the Carolinas Medical Center, Charlotte, North Carolina, and his colleagues note. Moreover, animal studies have shown that the bicarbonate anion is better than the chloride anion at preventing renal failure from ischemia or doxorubicin. They theorize that increases urinary pH reduces oxidative injury in the kidney.

The investigators therefore prospectively followed patients undergoing diagnostic or interventional procedures using the contrast agent iopamidol. The patients, who had stable renal insufficiency and creatinine levels between 1.1 and 8 mg/dL, were randomly assigned to sodium bicarbonate (n = 60) or sodium chloride (n = 59) hydration for 1 hour prior to a procedure lasting until 6 hours afterward.

Contrast-induced nephropathy, defined as an increased in serum creatinine of 25% or more within 2 days, occurred in 1.7% of those in the bicarbonate group and 13.6% of those in the sodium chloride group. The absolute risk reduction was 11.9%.

The randomized trial had been stopped early when the benefits of bicarbonate became apparent. Dr. Kennedy's group then enrolled 191 patients in a follow-up registry who underwent similar procedures with bicarbonate hydration. Again, the incidence of contrast-induced nephropathy was low, occurring in 1.6% of patients.

In a JAMA editorial, Dr. Glenn M. Chertow points out that sodium bicarbonate is far more practical than using N-acetylcysteine or hemofiltration, and applying these strategies to patients at lower risk could end up being quite expensive.

Even though larger prospective studies are required before sodium bicarbonate could become routine practice, such studies "would be simple, inexpensive and low risk," writes Dr. Chertow, a physician at the University of California, San Francisco.

Dr. Kennedy is not at the Mayo Clinic, Rochester, Minnesota.

JAMA 2004;291:2328-2334,2376-2377.

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