Sodium bicarbonate hydration significantly reduces the risk of contrast-induced nephropathy (CIN), although the benefits might have been overstated in prior studies, authors of a meta-analysis concluded.

1. Sodium Bicarbonate Halves Nephropathy Risk
Sodium bicarbonate hydration significantly reduces the risk of contrast-induced
nephropathy (CIN), although the benefits might have been overstated in prior studies,
authors of a meta-analysis concluded.
Compared with saline hydration,sodium bicarbonate halved the risk of
nephropathy, Pascal Meier, M.D., of the University of Michigan, and colleagues
reported online in BMC Medicine.
The studies included in the analysis uniformly demonstrated superiority of
sodium bicarbonate versus saline hydration, the authors said.
"The lack of any study to date showing superiority of saline-based hydration
suggests that baking soda hydration should be considered the optimal hydration in
high-risk patients undergoing exposure to iodinated contrast," the authors concluded.
CIN accounts for about 10% of hospital-acquired renal failure, and intrarenal
accumulation of reactive oxygen species has been postulated as a possible cause of
CIN.
The theory has provided a rationale for sodium bicarbonate hydration, which
may lead to tubular fluid alkalinization that diminishes production of free oxygen
radicals, the authors said.
Previous studies, including meta-analyses, yielded conflicting results regarding
the safety and efficacy of sodium bicarbonate hydration versus saline. In an effort to
resolve the statistical impasse, the authors performed an updated meta-analysis that
included published and unpublished data.
Their literature search turned up multiple sources of data reported or presented
from 1990 through Dec. 15, 2008. The authors ultimately used data from 17 clinical
trials involving a total of 2,633 patients.
The analysis disclosed 109 cases of CIN in 1,327 patients who received sodium
bicarbonate hydration, compared with 175 cases in 1,306 patients treated with saline.
The difference translated into an odds ratio for CIN of 0.52 in favor of sodium
bicarbonate (95% CI 0.34-0.81, P<0.004).

2. The authors calculated that 16 patients would have to receive sodium bicarbonate
hydration to prevent one case of CIN.
Need for dialysis and mortality (secondary endpoints) did not differ between
sodium bicarbonate and saline. Stratified analyses showed a more dramatic effect of
sodium bicarbonate hydration in two trials that exclusively involved patients
undergoing emergency procedures (OR 0.10, 95% CI 0.02-0.42, P=0.002).
The benefits of sodium bicarbonate diminished somewhat in patients undergoing
elective procedures but remained statistically significant (OR 0.63, 95% CI 0.43-0.92,
P=0.017).
Similarly, analysis by type of contrast agent showed a greater benefit with
sodium bicarbonate in patients who received low-osmolar contrast media (OR 0.29,
95% CI 0.15-0.57) versus iso-molar iodixanol (OR 0.73, 95% CI 0.32-1.64, NS).
Exploratory analyses showed a greater benefit of sodium bicarbonate hydration
in the eight published studies (OR 0.4, 95% CI 0.21-0.76, P=0.005) than in the nine
unpublished studies (OR 0.64, 95% CI 0.34-1.21, NS).
Moreover, two published studies that were stopped early showed a greater
benefit with sodium bicarbonate 99% than did the six studies that completed
enrollment and follow-up. Exclusion of those two trials resulted in a lower estimated
benefit (OR 0.60, 95% CI 0.40-0.91, P=0.016).