Role of hypertonicity in the endothelial injury caused by angiographic contrast media

The effect of hyperosmolality on the permeability of vascular endothelium was investigated using light microscopy and silver staining of the thoracic aorta in the rat. The threshold osmolality causing significant endothelial injury was 1.41 to 1.59 tested with sodium chloride solutions. The osmolalities of ionic contrast media in clinical concentrations were at or over the osmotic threshold. Most angiographic contrast media injured the endothelium more than equiosmolal sodium chloride solutions. Hyperosmolality is only one factor contributing to the increased endothelial permeability.