Radiation Exposure in the Medical ICU: Predictors and Characteristics

Background: Patients admitted to the medical ICU (MICU) are often subjected to multiple radiologic studies. We hypothesized that some endure radiation dose exposure (cumulative effective dose [CED]) in excess of annual US federal occupational health standard limits (CED ≥ 50 mSv) and 5-year cumulative limit (CED ≥ 100 mSv). We also evaluated the correlation of CED with Acute Physiology and Chronic Health Evaluation (APACHE) III score and other clinical variables. Methods: Retrospective observational study conducted in an academic medical center involving all adult admissions (N = 4,155) to the MICU between January 2013 and December 2013. Radiation doses from ionizing radiologic studies were calculated from reference values to determine the CED. Results: Three percent of admissions (n = 131) accrued CED ≥ 50 mSv (1% [n = 47] accrued CED ≥ 100 mSv). The median CED was 0.72 mSv (interquartile range, 0.02-5.23 mSv), with a range of 0.00 to 323 mSv. Higher APACHE III scores (P =.003), longer length of MICU stay (P <.0001), sepsis (P =.03), and gastrointestinal disorders and bleeding (P <.0001) predicted higher CED in a multivariable linear regression model. Patients with gastrointestinal bleeding and disorders had an odds ratio of 21.05 (95% CI, 13.54-32.72; P <.0001) and 6.94 (95% CI, 3.88-12.38; P <.0001), respectively, of accruing CED ≥ 50 mSv in a multivariable logistic regression model. CT scan and interventional radiology accounted for 49% and 38% of the total CED, respectively. Conclusions: Patients in the MICU are exposed to radiation doses that can be substantial, exceeding federal annual occupational limits, and in a select subset, are > 100 mSv. Efforts to justify, restrict, and optimize the use of radiologic resources when feasible are warranted.