Additional use of extrinsic warmer for intravenous CT contrast media and its impact on incidence of contrast extravasations and allergic like reactions: a prospective observational case control study.

Aims: To prospectively determine whether extrinsic warming of the low-osmolality CT contrast media (Iohexol 350, Iodixanol 320, Iopromide 300, and Iopamidol 300) to 37°C prior to intravenous administration affects extravasation and allergic-like reaction rates.
Materials and Methods: This large scale prospective case control study of adverse events included all the patients between the age group of 15-80 years undergoing routine contrast-enhanced computed tomographic (CECT) examinations from April 2018 to March 2020 at our institute. Ex vivo experiments were also performed to demonstrate change in contrast viscosity and fluid dynamics in relation to temperature.
Results: A total of 24,379 CECTs were conducted during the study period. Extrinsic warming showed a significant decrease in extravasation rates for Iohexol 350 at flow rates <3.5 mL/sec (P=0.037). No significant difference was observed with Iopromide 300 (P=0.432). Overall, a significant decrease in allergic reactions and overall contrast-related reactions (excluding physiologic reactions) was noted (P<0.001), with Iohexol 350. However, no significant difference was found with Iopromide 300. The most common physiological reaction was a sense of warmth, more prevalent in the warmed group, aligning with ex-vivo experiments demonstrating decreased viscosity with contrast warming.
Conclusions: Extrinsic warming of contrast helps reduce the incidence of allergic-like reactions and extravasations for Iohexol 350, but no significant difference was noted with Iopromide 300 even at low injection rates (<3.5 mL/sec).
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