Friday, October 30, 2020

crossreactivity of contrasts

 Q: 58 years old male is admitted to ICU due to Atrial Fibrillation associated Rapid Ventricular Rate (AF-RVR). Patient developed acute abdominal pain after a few hours of admission and requires CT scan with contrast. Patient has a previous history of allergies with shellfish and gadolinium contrast. Your next step of management? (select one)

A) Proceed with CT scan with IV contrast

B) 'Prep' patient with steroid & diphenhydramine  

Answer: A 

'CT scan with IV contrast' is an everyday affair in ICU. There are two objectives to this question. The first is to clarify the misconception that prophylactic 'preps' are needed in IV contrast for CT scan, in cases with hypersensitivity to other compounds including gadolinium contrast as well as shellfish, and topical povidone-iodine solutions. In actuality, in a strict sense, there is no such thing as "iodine allergy", a frequently used misterm. Iodine is a fundamental element in the human body.

The second objective of this case scenario is to emphasize learning the art of risk vs. benefit. In many situations like severe acute abdominal pain as in our patient with AF-RVR, it may be required to 'bite the bullet' and proceed to CT scan. Delay in many clinical situations may be detrimental to the patient.




1. Macy EM. Current Epidemiology and Management of Radiocontrast-Associated Acute- and Delayed-Onset Hypersensitivity: A Review of the Literature. Perm J. 2018;22:17-072. doi:10.7812/TPP/17-072 

2. Schabelman E, Witting M. The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed. J Emerg Med 2010; 39:701. 

3. Bottinor W, Polkampally P, Jovin I. Adverse reactions to iodinated contrast media. Int J Angiol. 2013;22(3):149-154. doi:10.1055/s-0033-1348885

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