Patients’ lives at risk from needless lung scans

It is commonplace for patients with Acute Lung Injury (ALI) to be injected with a dye, known as contrast material, before undergoing a CT (computerized tomography) scan of their lungs. Contrast material helps enhance the image so that doctors can evaluate the state of a patient’s lungs. New research published in Critical Care shows that using contrast material could worsen the condition of patients suffering from ALI because it causes the lungs to fill up with fluid, making it more difficult for patients to breathe.

ALI is a serious lung disorder characterized by the widespread destruction of lung tissue resulting in a lack of oxygen in the bloodstream. It is important for doctors to examine the lungs of these patients to see how badly they are injured. Computerized tomography is a commonly used procedure to examine the lungs, as it gives the doctors a detailed view in a series of cross-sections or “slices”.

To get the clearest possible image, patients with ALI are routinely injected with a dye, known as contrast material, before a CT scan. Contrast material helps doctors identify damage to the lungs, however there is now speculation that it may cause the accumulation of fluid in the lungs of patients with ALI, making their condition worse.

In order to test this hypothesis, Jean-Jacques Rouby and his colleagues investigated the effects of contrast material on the lungs of 14 patients with ALI. The patients were separated in to two groups, the first were given a CT scan both before and 30 seconds after injection with contrast material; the second group were given a CT scan before and after 15 minutes. The volume of lung tissue was measured from the CT scan of all patients.

The research team found that injecting contrast material increased lung tissue volume in both sets of patients, with a larger increase observed after 15 minutes. The increase in lung tissue volume is attributed to an accumulation of fluid in the lungs caused by the injection of contrast material. This suggests that the injection of contrast material is making it harder for patients to breathe leading the authors to conclude, “It seems prudent to avoid this procedure in critically ill patients undergoing a thoracic CT scan.”

The authors’ decision to publish this research in an online open access journal allows this important study to be read by the widest possible audience.