Patients who note a seafood or iodine allergy can safely receive intravenous (IV) contrast
Patients who note a seafood or iodine allergy can safely receive intravenous (IV) contrast: Excerpt from Avoiding Common Pediatric Errors
Author:
Craig DeWolfe, MD
What to Do - Gather Appropriate Data
A previous reaction to seafood, povidone iodine, or other iodine-containing
substance does not have any predictive value beyond a reaction to contrast material. The practitioner may also counsel the patients who have
had a reaction to contrast material that they can continue to ingest iodine-
containing foods or drugs. The false link between iodine-containing foods
and contrast material can be traced to two studies in the early 1970s that
reported a 6% rate of reaction in patients with a reported seafood allergy.
Subsequent reports have not confirmed these findings. Instead, oversight
committees, such as the one sponsored by the American College of Radiology, have regularly counseled that a seafood allergy should be considered
in the same category as any other allergy when considering the individual
risk of contrast material to the patient. Unfortunately, reports firmly establish that physicians resist performing needed studies in patients with a
seafood allergy. In 2004, Confino-Cohen and Goldberg reported that 77%
of physicians would have unnecessarily withheld radiocontrast material in
patients with a history of a seafood allergy or rash after local application
of iodine-containing antiseptics. Moreover, 69% of them would have taken
various irrelevant precautions when using iodine-containing antiseptics in
patients who have had a history of reaction to an iodinated contrast media
(ICM).
ICM is regularly used for opacification in computed tomography, excretory urographic, and angiographic studies. ICM is classified into two
groups: ionic high-osmolality contrast media and nonionic low-osmolality
contrast material. The former is associated with a 5% to 12% incidence of
adverse reactions, whereas the latter is associatedwith a 1% to 3%incidence,
but because they both contain iodine, the discrepancy is related to another
property of the media.
ICM reactions are related to either an anaphylactoid or a chemotoxic
effect of the media. Anaphylactoid reactions occur spontaneously and independently of the dose or concentration of the material. Symptoms include
urticaria, swelling of the mucus membranes, bronchospasm, hypotension,
convulsions, and cardiac arrest. Reactions are generally thought to be caused
by a combination of histamine release and activation of vasoactive cascade
system.
Chemotoxic reactions are related to the concentration and dose of the
ICM. Common symptoms include a hot, flushed, or tingly sensation; metallic taste; and nausea. Rarer but more serious reactions include acute renal failure, convulsions, cardiac arrhythmias, or cardiac failure. The reactions are caused by physiochemical effects of the injected agent on a specific
organ.
Thereareseveralriskfactorsthatincreasethelikelihoodforareactionto
ICM. Sicker patients are more likely to have an adverse reaction associated
with a chemotoxic effect, whereas patients with allergic tendencies are at
increased risk for an anaphylactoid reaction. Studies suggest that patients
with a history of an allergy to any substance are twice as likely to have an
allergy to ICM, whereas patients with a history of asthma may have five
times the risk. Patients with a past reaction to ICM may be at three to eight
times the risk of the general population. A detailed screening of the patient
for hemodynamic, neurologic, and general nutritive status in addition to
history of allergies, asthma, and the use of beta-blockers should occur prior
to ordering or administering the ICM. Higher-risk patients should receive
low-osmolar, non-ICM. Corticosteroids and antihistamines should also be
considered, although the need for the latter has been called into question
by a recent meta-analysis. In addition, the practitioner should be prepared
for the development of a reaction, usually within the first 20 minutes of the
infusion. Fortunately, because of the greater awareness and preparation for
reactions, the mortality rate associated with ICM has dropped to 0.9 per
100,000 administrations.
A reaction to seafood or iodine should not be treated differently than
another allergic reaction when considering the risk of ICM. Iodine is an
essential element for life, thus it is unlikely that a patient has a reaction
to elemental iodine alone. Rather, in some rare cases, an iodine/protein
complex triggers the reaction, but the reaction is not predictive beyond the
fact that the patient is prone to allergic reactions. If a patient has a severe
reaction that appears to be anaphylactoid to an iodine-containing product,
then pretreatment with corticosteroids and antihistamines for subsequent
exposure to ICM would be indicated. Less-significant reactions would likely
not benefit from treatment.
In summary, patients who note a seafood or povidone iodine allergy can
safely receive ICM. Similarly, those patients who have reacted to ICM can
continue to ingest iodine-containing products.
Suggested Readings
American College of Radiology. Committee on Drugs and Contrast Media. Manual on
contrast media version 5.0; 2004. Available at: http://www.acr.org/SecondaryMainMenu
Categories/quality safety/contrast manual/FullVersionofManualonContrastMedia
Doc12.aspx. Accessed February 1, 2007.
Bush WH, Swanson DP. Acute reactions to intravascular contrast media: types, risk factors,
recognition, and specific treatment. AJR Am J Roentgenol. 1991;157:1153–1161.
Confino-Cohen R, Goldberg A. Safe administration of contrast media: what do physicians
know? Ann Allergy Asthma Immunol. 2004;93:166–170.
Book Source Details
- Book Title: Avoiding Common Pediatric Errors
- Author(s): Anthony D Slonim MD, DrPH; Lisa Marcucci MD
- Year of Publication: 2008
- Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Avoiding Common Pediatric Errors
Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7489-6
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