Variability of platelet degranulation by different contrast media.

RATIONALE AND OBJECTIVES: It has been suggested that nonionic but not ionic contrast media degranulate blood platelets when mixtures of blood and contrast media are studied by flow cytometry. This phenomenon was further assessed in the current study not only by performing whole-blood platelet flow cytometry but also by performing flowing blood platelet aggregometry. The latter is a highly sensitive measure of platelet function. METHODS: Blood samples were collected from six normal donors and mixed with equal volumes of an ionic monomer (diatrizoate), a nonionic monomer (iohexol), an ionic dimer (ioxaglate), and a nonionic dimer (iodixanol). Samples were collected in the presence of no anticoagulant for 1 min prior to the addition of sodium citrate or in the presence of heparin (14.5 U/ml) or recombinant hirudin (60 micrograms/ml). All samples were fixed in formaldehyde within 30 min. RESULTS: Platelet degranulation was observed with one nonionic agent (iohexol) and one ionic agent (diatrizoate). Degranulation was not seen with iodixanol or ioxaglate. CONCLUSION: These findings indicate that degranulation is independent of the ionic or nonionic nature per se of contrast media. A possible explanation for this conclusion is suggested.