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Doubt cast on sodium bicarb defense against contrast nephropathy
Baking soda has a lot of uses, but is there one too many? Perhaps, according to a retrospective look at >11 000 radiographic imaging cases in which sodium bicarbonate, increasingly given intravenously to prevent contrast-induced nephropathy (CIN) in patients undergoing CT or angiography, seemed actually to cause the serious complication rather than protect the kidneys [1].
The analysis casts doubt on a practice that has won the esteem of practitioners based primarily on one small randomized trial [2] with important limitations, according to the new study's authors, led by Dr Aaron M From (Mayo Clinic, Rochester, MN) and colleagues.
"The clinical use of sodium bicarbonate for renal protection should be reconsidered until further investigation can elucidate its proper use," the group writes in the January 2008 issue of the Clinical Journal of the American Society of Nephrology.
In another finding from the study, no increased CIN risk was observed among patients treated with another agent frequently given for renal protection, N-acetylcysteine, or those who received both that agent and sodium bicarbonate.
Sometimes when you study these agents in a real-world population, you find something different from [what you would] studying them in a randomized trial.
Speaking to heartwire, From said his group has documented an "exponential increase" in the use of sodium bicarbonate prophylaxis immediately after the 2004 publication of a 119-patient randomized study from Merten et al, in which CIN developed in 13.6% of patients hydrated with saline only but in only 1.7% of those who received sodium bicarbonate (p=0.02).
"Sodium bicarbonate is now the standard of care at our institution," Merten coauthor Dr W Patrick Burgess (Carolinas Medical Center, Charlotte, NC) told heartwire when the study was published. "We have not dialyzed a patient for contrast nephropathy for a year and a half. And that's unheard of."
An informal survey of heartwire stories as well as reviews and original studies on Medline appearing since the Merten publication does suggest that interventional cardiology has embraced the use of sodium bicarbonate, often combined with N-acetylcysteine, for CIN prophylaxis. Recommendations for preventing CIN published by the Society of Cardiovascular Angiography and Interventions in 2006 cautiously recommend sodium bicarbonate in high-risk cases [3].
But Merten et al, From said, "were very selective about the patients they included, and in our study we used a real-world population." It consisted of 7911 adult patients encompassing 11 516 cases of contrast administration, almost always with a low-osmolar nonionic agent, for which there were both pre- and postprocedure creatinine readings but no preprocedure elevations of >8 mg/dL and no history of dialysis. Thoracic and abdominal CT accounted for more than three-fourths of the imaging procedures, and coronary angiography and interventions most of the rest.