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JRCERT Update

Adverse Reactions to Contrast: A Review

ƒ seizure Epidemiology and Common Risk Factors
ƒ nephrotoxicity (can result in the subacute time Adverse responses occur in 5% to 15% of IV
frame, especially in patients who have pre-existing administration of ionic high-osmolar contrast media,
renal dysfunction) compared with 0.2% to 0.7% of IV nonionic low-
The widespread adoption of nonionic contrast media osmolar contrast media. Of these responses, reactions
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and larger molecular complexes (low-osmolar contrast requiring additional medical therapy occur in approxi-
media) has resulted in a 10-fold decrease in the rate of mately 0.04% of patients who receive IV low-osmolar
adverse contrast reactions; as a result, these represent contrast media. Allergiclike (anaphylactic) responses
the most used agents. 3 in patients undergoing IV gadolinium-based contrast
administration range between 0.013% and 0.22%
Gadolinium-based Contrast Agents depending on the agent administered. 9
Used primarily for magnetic resonance imag- The most important risk factor for an adverse
ing, gadolinium-based contrast agents consist of a reaction is a previous reaction. In this regard, all iodin-
gadolinium atom complexed to a large, specialized ated contrast is considered equivalent. Despite the
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macromolecule. The adverse reactions that can occur common assumption of cross-reactivity between
after administration of these agents are similar to those gadolinium-based and iodinated contrast media, such
occurring with iodinated contrast agents, although cross-reactivity is not documented in the literature. In
the rates of such reactions are lower with gadolinium addition, a previous allergic reaction to shellfish does
administration. 6,7 not place the patient at greater risk of a reaction to
Certain gadolinium-based contrast agents iodinated contrast. 11,12
(gadodiamide, gadopentetate dimeglumine, and gado- Patients at higher risk of developing anaphylactic
versetamide) are associated with the development of reactions to contrast media are those who 9,13-15 :
an often-fatal systemic soft tissue sclerosing condition ƒ take multiple medications
known as nephrogenic systemic fibrosis. The mechanism ƒ have environmental allergies (atopic)
6
by which these medications cause nephrogenic systemic ƒ have asthma
fibrosis is unknown, but the in vivo dissociation of ƒ have hypersensitivity-related disorders
gadolinium from its macromolecule and the subsequent ƒ have myasthenia gravis
deposition of free gadolinium in soft tissues are thought Risk factors also exist for physiologic contrast-related
to be important steps. Thus, similar to iodinated con- adverse events. For example, patients who have cardiac
trast agents, the specifications of the macromolecule are disease are at higher risk of developing cardiac-related
important in determining the risk profile of the magnet- contrast events. Cardiac toxicity is more common in
ic resonance imaging contrast. The products associated patients who undergo intracardiac contrast injection
with nephrogenic systemic fibrosis development rarely during angiography compared with those who undergo
are used in clinical practice. IV contrast administration. 3
Ultrasound contrast, initially approved for
echocardiography by the U.S. Food and Drug Reaction Management
Administration in 2014, is approved for additional Premedication regimens, usually consisting of oral
intra-abdominal applications. Adverse reactions are corticosteroids and diphenhydramine taken in the
rare but can include headache, nausea, and dysgue- days leading up to contrast administration, are used
sia. Extremely low rates of events with these agents to decrease the risk of reactions in patients who have
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and their relatively limited use place them outside the certain anaphylactic reactions. The goals for managing
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scope of this review. patients who have certain anaphylactic reactions are to:
Finally, oral and rectal contrast agents rarely result in ƒ identify a reaction quickly and confidently
acute adverse reactions. ƒ address treatable conditions

602 RADIOLOGIC TECHNOLOGY, July/August 2018, Volume 89, Number 6
Reprinted with permission from the American Society of Radiologic Technologists for educational purposes. ©2019. All rights reserved.