Ionic contrast media are characterized by what osmolarity and usage in cath labs?

• A. High osmolarity; not used in cath lab
• B. Low osmolarity; preferred in cath lab
• C. Moderate osmolarity; standard in cath lab
• D. Zero osmolarity; experimental

Answer: (A)

Ionic contrast media are hyperosmolar compared with blood. Their osmolality is much higher than plasma, which historically led to more adverse reactions—more discomfort, vasospasm, and a higher risk of contrast-induced nephropathy. Because of this safety concern, cath labs have moved toward nonionic low-osmolar agents (and sometimes iso-osmolar options), which reduce these risks. So describing ionic contrast media as having high osmolarity and not being used in cath labs captures the practical point: their high osmolality made them less favorable for interventional procedures, whereas modern practice favors lower-osmolar or iso-osmolar formulations.