Patients who have had acute allergic-like reactions to
nonionic iodinated contrast material rarely develop any
serious long-term problems and can be treated safely with
commonly used medications according to a recent study conducted
by researchers at the University of Michigan Hospitals
in Ann Arbor.
"While adverse reactions to iodinated contrast media
are rare, they are encountered regularly by all physicians
who administer contrast material to patients and some of
these reactions will require treatment," said Richard
Cohan, MD, lead author of the study. "We reviewed
our experience to determine how often we encountered these
reactions in our practice and how often the reactions required
treatment. We also wanted to know what happened to those
patients who required treatment, particularly when they
had reactions that were moderate or severe," said
Dr. Cohan.
The study consisted of 84,928 IV injections of nonionic
iodinated contrast media in adults. In this group, there
were 545 (0.6%) patients who had allergic-like reactions,
with 221 receiving treatment. The most commonly administered
medications were diphenhydramine to 145 (27%) reacting
patients, corticosteroids to 17 patients, albuterol to
16 patients, ephinephine to 15 patients, and nitroglycerin
to eight patients. According to the study, 99% of the allergic-like
reactions resolved completely within 24 hours. This included
all 418 patients who had mild reactions, all 116 patients
who had moderate reactions, and nine of the 11 patients
who had severe reactions.
"Commonly used medications can be administered safely;
however, treatment errors are not uncommon and in a few
instances can lead to patient morbidity," said Dr.
Cohan. "In our study, we found a number of instances
in which non-recommended treatment was provided. These
cases included the administration of oxygen by nasal cannula
(rather than mask) and at lower than recommended doses,
over-utilization of diphenhydramine (including to a few
patients who were hypotensive), and the administration
of higher than recommended doses of epinephrine, as well
as occasional confusion about which concentrations of epinephrine
should be injected in which manner (subcutaneously or intravenously).
In our study, the most striking example of patient morbidity
from non-recommended treatment occurred in the two patients
who received doses of 1 mg of epinephrine in the absence
of cardiopulmonary arrest, who both had cardiac complications.
Fortunately, these complications were mild and transient
and caused no serious morbidity," he said.
"We hope that after reading our study, radiologists,
nurses, and technologists will agree that they must review
the algorithms for treating contrast reactions on a regular
basis (particularly issues related to diphenhydramine,
oxygen, and epinephrine administration)," said Dr.
Cohan. "In fact, we would suggest that such a review
should probably occur at least twice a year. However, it
is also consoling to know that even when patients have
moderate or severe contrast reactions, the vast majority
recover promptly and without any long term complications," he
said.
This study appears in the August issue of the American
Journal of Roentgenology.
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