Intravenous contrast media for CT exams isn't as dangerous as previously thought, according to a recent study published in Annals of Emergency Medicine.

"These data add to the mounting retrospective evidence that contrast administration can be done safely, and that any harm caused to patients by withholding contrast for indicated time-sensitive diagnostic studies is likely not justifiable," Dr. Jeremiah Hinson, lead author of the study and instructor of emergency medicine at Johns Hopkins University School of Medicine, told HCB News.

Some studies have shown that the use of IV contrast media can cause serious kidney problems in up to 14 percent of patients. However, Hinson argues that most of these studies lacked adequate controls or were performed before modern contrast reagents were developed.
"Nearly all studies were performed without controls, and a causative relationship was assumed from a temporal relationship," said Hinson. "Data from our group, and several others, suggest this assumption may be inaccurate."

Hinson and his team examined five years of records for patients who received a CT exam with or without contrast in the emergency department. About 57 percent of the exams used contrast.

They found that the likelihood of developing acute kidney injury was 6.8 percent for patients who underwent contrast-enhanced CT, but 8.9 percent for those who received CT alone and 8.1 percent for those who didn't receive an exam.

Not everyone is convinced of the study's findings, however. "This is a classic case of selection bias. Physicians are more likely to give contrast if they feel the patient is at low risk of AKI, so we see a lower risk in that group," explained Dr. F. Perry Wilson, an assistant professor of medicine at the Yale School of Medicine, in a report for MedPage Today.

"The authors tried to adjust for this using something called propensity score matching which is a statistical technique that attempts to minimize this type of bias," wrote Wilson, adding that it isn't a perfect system and there may be other factors pushing clinicians to avoid contrast in certain patients that weren't measured.

A well-controlled, randomized study is needed to confirm the recently published findings, but the researchers assert that an important discovery has been made: taking nephroprotective measures such as IV fluid administration in this patient population can reduce the incidence of AKI.

"AKI is actually a very serious problem in our patient population, occurring in a high percentage of admitted patients for a variety of reasons," said Hinson. "Our data show that, as emergency physicians, we have the potential to prevent many of these cases through nephroprotective practice patterns, and we hope to work toward that goal in the coming years."

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