Seventeen relevant RCTs were identified (n=2,448, range 16 to 502). Nine RCTs were published only as abstracts, which were presented at international meetings. Overall quality of included studies was reported as low to moderate. Most studies were not blinded. In one study the regime for administration of N-acetyl cysteine differed between intervention and control groups. Another study had a relatively high loss to follow-up.
Definitions of contrast-induced nephropathy in included studies were: an increase in serum creatinine level from baseline of more than 0.5mg/dL (two RCTs); a more than 25% increase in serum creatinine (13 RCTs); and a more than 25% decrease in glomerular filtration rate (one RCT). There was evidence for publication bias.
Sodium bicarbonate significantly reduced risk of contrast-induced nephropathy compared to saline (RR 0.54, 95% CI 0.36 to 0.83; 17 studies). Stratified analysis found a similar effect in the 11 RCTs where only sodium bicarbonate was used compared to saline (RR 0.38, 95% CI 0.18 to 0.79; 11 RCTs). The result for the five RCTs where the intervention included both bicarbonate and N-acetyl cysteine was not reported. Four RCTs compared bicarbonate alone versus N-acetyl cysteine and found a significant reduction in contrast-induced nephropathy (RR 0.57, 95% CI 0.35 to 0.95).
There were no significant differences in need for renal replacement therapy (11 RCTs) or mortality (four RCTs) between the sodium bicarbonate and control groups.
Further details of the medical background of patients were provided.