Purpose: To determine why nonionic, low-osmolality contrast media (LOCM) at high concentrations (> 30%) induce almost immediate platelet activation and to explore preventive measures.
Materials and methods: Nonionic LOCM, when added to blood, activates platelets, raises the osmolality, and lowers the ionic strength. To clarify the mechanisms involved, platelet activation was studied in sodium chloride-sucrose solutions of varying osmolalities and varying ionic strengths. Several salts and Iloprost were evaluated as potential inhibitors of platelet activation.
Results: Platelets are activated by both osmolality and ionic strength changes. The salts most inhibitory to platelet activation were magnesium sulfate and sodium citrate. Iloprost lowered platelet activation to control levels at 4.3 ng/mL of nonionic LOCM and completely eliminated it at 8.6 ng/mL.
Conclusion: Three-quarters of nonionic LOCM-induced platelet activation appeared to be due to increased osmolality-the remainder to the decrease in ionic strength. Magnesium sulfate and Iloprost are potent inhibitors of this type of platelet activation.