Prevention of Contrast-Induced Nephropathy with Sodium Bicarbonate: Randomized Trial of Hydration Fluids

Background Contrast-induced nephropathy remains a common complication of radiographic procedures. Consistent evidence of benefit in the face of preexisting renal insufficiency has been shown only by pretreatment hydration with saline, nonionic contrast, lowor iso-osmolar contrast, and smaller volumes of contrast. Prophylactic use of the free radical scavenger, N-acetylcysteine has shown benefit in some studies and in a recent meta-analysis, supporting the hypothesis that contrast-induced renal failure is a result of free radical generation. We hypothesized that low renal tubular pH contributes to free radical formation and renal failure from contrast. Thus, NaHCO3 should be superior to NaCl in preventative hydration. All prophylactic protocols to prevent contrast-induced nephropathy include the infusion of sodium chloride (NaCl) either alone or with other agents. However, in prophylactic hydration to combat contrast-induced nephropathy, it is possible that the most efficacious anion for sodium is not chloride (Cl), but bicarbonate (HCO3). As a consequence of the kidney’s role in excreting inorganic acids, urine is usually acidic, creating a setting that may facilitate free-radical mediated injury. Free radical formation in human tissue is subject to the biochemical milieu: promoted by an acidic environment, and reduced by an environment with the pH of normal extracellular fluid. Since a postulated mechanism of contrast-induced nephropathy is oxidant damage by free radicals, attempts to alkalinize renal tubular fluid may reduce renal injury.