Radiation Exposure in the Medical ICU: Predictors and Characteristics

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.

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.

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.

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.