Contrast media safety; What do we know and how do we know it?

Abstract

Use of an intravenous injection of a water-soluble iodine compound (sodium iodide) for visualizing the urinary tract was first described by Osborne in 1923. However, sodium iodide was accompanied by a high incidence of side effects and the image quality was not good. As newer, improved contrast agents were introduced, a number of investigators reported on the incidence of death and side effects incurred by their use. In 1975, the first large-scale, multicenter, prospective study on the incidence of fatal and nonfatal reactions was reported by Shehadi. In this series, the overall incidence of adverse reactions was 5.65%, of which 3.77% were mild, 1.77% were moderate, 0.02% were severe, and 0.0007% were fatal. Shehadi also noted that a history of allergy doubled the risk of adverse reaction and a history of a previous adverse reaction to contrast material trebled the risk; also, the risk of a reaction to an intraarterial injection was half that of the risk associated with an intravenous injection. With the introduction of low osmolar nonionic agents, other large-scale studies were performed because these agents appeared to cause significantly fewer adverse reactions. However, they were from 10 to 15 times more expensive than their predecessors. In 1987, Lasser reported on the increased safety of ionic agents when patients were pretreated with steroids. Palmer in Australia and Katayama in Japan collected 120,000 and 335,000 patients, respectively, and compared the incidence of adverse reactions of the ionic versus the nonionic agents. Wolf recently reported a study that included a direct comparison of ionic agents with pretreatment with steroids versus nonionic agents. The Katayama study is the most powerful statistically, and this, supported by both Wolf's study and Palmer's study, indicates that the single most important risk factor is the type of contrast agent used, with a nonionic agent having between 14 and 17% of the incidence of adverse reactions, and between 4 and 17% of the incidence of severe adverse reactions. These studies have resolved the issue of safety of the ionic agents versus the nonionic agents. The safety of ionic agents with steroid pretreatment remains to be established. Choice of a contrast agent now rests on considerations of cost, ethics and liability.