New York, NY- Using sodium bicarbonate does not prevent contrast-medium-induced nephropathy in patients with moderate to severe renal dysfunction, a new randomized study has found [1]. Dr Somjot S Brar (Columbia University Medical Center, New York) and colleagues report their findings in the September 3, 2008 issue of the Journal of the American Medical Association.

Dr Somjot S Brar

The practice of using sodium bicarbonate to prevent contrast-medium-induced nephropathy has grown exponentially since the 2004 publication of a small randomized trial that showed that it was of benefit. But critics have said that there were important limitations to that study and others that followed, and earlier this year a new analysis found evidence that use of sodium bicarbonate may harm rather than protect the kidneys.

"Understanding that this doesn't work is the bottom line," Brar told heartwire, adding that he believes that "a good proportion of the people who have been doing this will no longer do it" as a result of this new study. "This is something that is not readily available in the hospital, it has to be mixed, it needs IV access, and it's incompatible with certain drugs, including a number of cardiac medications. It's not necessarily complicated, but it comes with inconveniences that would be worth doing if there were potential for benefit. However, in the absence of benefit, there's really not a good rationale to jump through those hoops," he told heartwire.

It's not necessarily complicated, but . . . in the absence of benefit, there's really not a good rationale to jump through those hoops.

Brar et al explain that contrast-medium-induced nephropathy is a recognized complication of exposure to iodine contrast media and a common cause of renal failure. The incidence ranges from 2% in low-risk populations to 50% in high-risk populations, such as those with chronic kidney disease, diabetes, heart failure, and the elderly.

In their new study, they randomized 353 patients with stable renal disease (glomerular filtration rate [GFR] of <60 mL/min per 1.73 m² and one or more of the following: diabetes mellitus, history of congestive heart failure, hypertension, or age older than 75) who were undergoing coronary angiography to hydration with either sodium chloride or sodium bicarbonate administered at the same rate—3 mL/kg for one hour before angiography, reduced to 1.5 mL/kg during the procedure and for four hours afterward.

There were no differences between the two groups in the primary end point—a 25% or greater decrease in the estimated GFR on days 1 through 4 after contrast exposure—with 13.3% of those receiving sodium bicarbonate meeting this end point vs 14.6% of those who received sodium chloride (p=0.82).

There were no differences at 30 days in rates of death, dialysis, MI, or cerebrovascular events between the two groups or at 30 days to six months (p>0.10 for all).

"The results of this study do not suggest that hydration with sodium bicarbonate is superior to hydration with sodium chloride in patients with moderate to severe chronic kidney disease who are undergoing coronary angiography," Brar et al conclude.

Brar said the strengths of this study were that the patients were undergoing one uniform procedure and the hydration protocol was consistent between the two groups. "These things have been issues with prior studies," he noted, "That is, patients have been undergoing a multitude of procedures and differing hydration protocols.

"We believe that it is really being adequately hydrated that is most important, whether it's bicarb or saline," he stresses. "The longer one can hydrate the patient, the better."

But he concedes that there are still many unanswered questions when it comes to hydration. "Interestingly, we still don't know for how long and at exactly what rate to hydrate, and there are other fundamental issues we still don't have great answers to."