Adverse Systemic Reactions to Contrast Media

Abstract

Toxic effects resulting from contrast medium (CM) injections can be considered in two major categories: (a) local and (b) systemic. Local toxicity results from injections of high concentrations and/or quantities of CM into a vessel supplying an organ or tissue. Ultimately, the degree of toxicity must be a function of the concentration and the application time of the injected material. Hence, such factors as organic luminal obstructions, functional obstructions, viscosity changes, and other hemodynamic alterations that prolong the application time increase the chemo toxicity of the injected CM. The precise etiology of chemotoxicity is still poorly understood, but it is thought to involve such factors as molecular interference with functional proteins such as enzymes and regulators and/or hyperosmolarity of the CM solution. Underlying the potential of CM to act as general enzyme inhibitors is their ability to bind to proteins. Such binding appears to reflect principally the degree of hydrophobicity of the CM molecules [1–5]. The correlation between the lethal doses of CM in experimental animals and the binding of CM to serum albumins and various enzymes has been established [6]. In a series of studies, all the CM investigated, if present in sufficiently high concentrations, inhibited the enzymes tested [1–3]. The concentrations and total dosages of CM used in intravascular studies are so high that it is not surprising to find downstream from an intravascular injection a concentration of CM sufficient for a 50% inhibition of a given enzyme system in vitro.