The role of osmolality in the incidence of contrast-induced nephropathy: a systematic review of angiographic contrast media in high risk patients.

BACKGROUND: The role of osmolality of contrast media (CM) in the pathogenesis of contrast-induced nephropathy (CIN) has been suggested by studies comparing high osmolality CM (>1500 mOsm/kg) with low-osmolality CM (550-850 mOsm/kg), and by the results of a recent comparison of a CM isotonic to plasma (iodixanol, 290 mOsm/kg) with a low-osmolality CM (iohexol, 844 mOsm/kg) in high-risk patients undergoing cardiac or peripheral angiography.
METHODS: Using prospectively defined search criteria, we performed a systematic overview of prospective, randomized, controlled studies of CIN in renally impaired patients receiving intra-arterial doses of iodixanol or low-osmolality, nonionic CM, and conducted a systematic review of the data from those studies to determine whether the osmolality of CM was predictive of CIN incidence.
RESULTS: Seventeen primary studies met the selection criteria, for a total of 1365 patients. Overall, the incidence of CIN was 16.8%. A multivariate logistic regression model showed that the risk of CIN is similar with the iso-osmolality iodixanol and the low-osmolality iopamidol (796 mOsm/kg). The risk of CIN was significantly lower with iodixanol and iopamidol compared to iohexol. The incidence of CIN with iohexol was also significantly higher than with iopamidol, despite their similar osmolalities.
CONCLUSION: These data suggest that factors other than osmolality play a significant role in the pathogenesis of CIN, at least for agents with osmolalities of 800 mOsm/kg or less.