MONTREAL – Some of the sickest patients treated at U.S. hospitals receive high levels of radiation exposure, based on a review of more than 4,000 medical ICU patients treated recently at one U.S. quaternary-care center.
During 2013, 98 patients admitted to the medical ICU at the Cleveland Clinic – 2% of the 4,155 patients who passed through the medical ICU that year – had cumulative radiation exposure of at least 50 mSv while in the ICU, thereby exceeding the U.S. standard for maximum annual workplace exposure, Dr. Sudhir Krishnan said at the annual meeting of the American College of Chest Physicians. The finding raises questions of whether all these exposures are appropriate and whether they reflect overuse of certain imaging modalities.
Dr. Krishnan and his associates ran a retrospective review of case records for the medical ICU–admitted patients at the Cleveland Clinic during 2013 (Chest. 2015 Oct 25. doi: 10.1378/chest.2278486). During their ICU stay, 3,490 patients (84%) received some amount of radiation exposure. Exposure averaged 7 mSv, with a median of 1.5 mSv. The radiation exposure came primarily from imaging and more specifically from CT examinations, which produced more than half of all radiation-exposure episodes. Other sources included x-rays, nuclear scans, and interventional procedures.
Based on typical radiation dosages received during each type of procedure, the researchers calculated an estimated total radiation dosage received by each patient during their ICU stay. Nearly two-thirds of patients had an exposure of less than 3 mSv, the average annual exposure a person receives from ambient radiation. A quarter of the patients had an exposure of 3-14 mSv, 11% had an exposure of 15-49 mSv, and 2% – 98 patients – had exposure during their ICU stay that ran to 50 mSv or greater, exceeding the U.S. workplace annual maximum . Thirteen patients had an exposure level during their ICU stay that reached 100 mSv or higher; the maximum exposure level was in a patient with cumulative exposure of 176 mSv, said Dr. Krishnan, a critical-care medicine specialist at the Cleveland Clinic.
He and his coworkers did a multivariate analysis to identify factors that linked with a higher likelihood of having high radiation exposure. Patients at greatest risk for high exposure levels were sicker patients with higher APACHE 3 scores, longer stays in the ICU, and the presence of cirrhosis, but those most at risk also tended to be younger. Rates of both ICU deaths and deaths during the entire hospitalization were significantly higher among those with radiation exposure that was 50 mSv or greater.
Dr. Krishnan cautioned that he has not run any analysis that assessed the appropriateness of the imaging that the ICU patients received, nor did he have any data documenting the clinical consequences to the patients who had higher radiation exposure. Despite that uncertainty, he suggested that efforts focus on avoiding unnecessary radiation exposure to patients.
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