Sodium Bicarbonate-Based Hydration May Help Prevent Contrast-Induced Nephropathy

Laurie Barclay, MD

May 21, 2009

May 21, 2009 — Sodium bicarbonate–based hydration is better than normal saline in preventing contrast-induced nephropathy (CIN), according to the results of an updated meta-analysis reported online in the May 13 issue of BMC Medicine.

"Contrast agents are administered in millions of procedures annually worldwide," senior author Hitinder Gurm, from the University of Michigan in Ann Arbor, said in a news release. "In the USA and Europe,...CIN is the third leading cause of acute renal failure in hospitalized patients, accounting for about 10% of hospital-acquired renal failure. Although CIN is generally limited to a transient decline of renal function, it cannot be regarded as a benign complication — as many as 30% of cases result in lasting kidney damage."

The reviewers note that previous meta-analyses and several recent studies have yielded conflicting findings concerning the protective effect of sodium bicarbonate, and they therefore conducted this meta-analysis to compare the efficacy of normal saline vs sodium bicarbonate in preventing CIN.

Inclusion criteria for the meta-analysis were randomized controlled trials comparing prevention of CIN vs hydration regimens based on normal saline vs sodium bicarbonate. A search of MEDLINE, EMBASE, Cochrane databases, International Pharmaceutical Abstracts database, ISI Web of Science (until 15 December 2008), and pertinent conference proceedings revealed 17 trials enrolling a total of 2633 subjects. These were pooled, and summary odds ratios were calculated with random-effects models.

The rate of CIN was significantly decreased when preprocedural hydration was performed with sodium bicarbonate vs normal saline (odds ratio [OR], 0.52; 95% confidence interval [CI], 0.34 - 0.80; P = .003). To prevent 1 case of CIN, the number needed to treat with sodium bicarbonate was 16 (95% CI, 10 - 34). Rates of postprocedure hemodialysis (P = .20) and death (P = .53) were not significantly different between groups. The reviewers therefore concluded that sodium bicarbonate–based hydration was superior to normal saline to prevent CIN.

"Six studies monitored the degree of alkalinization and all but one found a significant increase," Dr. Gurm said. "Interestingly this one study did not find a benefit of sodium bicarbonate. Therefore, it could be hypothesized that the bicarbonate should be dosed to achieve urinary alkalinization."

Limitations of this meta-analysis include publication bias, slight overestimate of the benefit of sodium bicarbonate, and insufficient power to detect a significant difference in the incidence of mortality and the need for hemodialysis. Contrast media may impair tubular creatinine excretion, resulting in possible underestimation of renal function when creatinine level is used as a marker. There was also heterogeneity in study populations and settings.

"Our meta-analysis suggested a significant benefit of using NaHCO3 [sodium bicarbonate]-based hydration for prophylaxis of CIN although the magnitude of the benefit may have been overestimated by earlier studies," the reviewers write. "However, the lack of any study to date showing superiority of saline-based hydration suggests that NaHCO3-based hydration should be considered the optimal hydration in high-risk patients undergoing exposure to iodinated contrast.”

The review authors have disclosed no relevant financial relationships.

BMC Med. 2009;7:23.

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