In the US alone, over 80 million CT scans are carried out every year. Many thousands of those have been delayed due to an unusual reason: a shortage. Not of equipment, but rather of contrast fluid: a substance injected to enhance CT images. As the flurry of shortages continue to create a domino effect, spilling into many unexpected areas, a group of researchers suggests a set of strategies to reduce this shortage and ration the fluid so that there's enough for everyone to go around.
The pandemic and Russia's invasion of Ukraine have triggered a cascading chain of shortages in many different areas. The contrast fluid shortage is linked to a manufacturing facility in Shanghai that was closed for two months in the city's "zero-Covid" lockdown. Several key factories in China were shut down, but this particular facility was the main U.S. supplier of contrast fluid.
Even as the company has recently resumed work, there's a great deal of backlog and delay and getting back on track will take months, if not longer. With this in mind the researchers propose three strategies:
- deploying weight-based dosing;
- reducing the contrast dose while reducing tube voltage;
- replacing contrast-enhanced CT with non-enhanced CT when it will affect accuracy only minimally.
The third strategy alone could reduce dye use by 78%, but it could only be deployed in cases where the maximum accuracy isn't needed.
“Contrast is essential in any situation where we need to assess the blood vessels – for example, for some trauma patients or those with a suspected acute gastrointestinal bleed – and it is also needed for evaluation of certain cancers, such as in the liver or pancreas,” said senior study author Rebecca Smith-Bindman, MD, UCSF professor in the Department of Epidemiology and Biostatistics.
“However, most CT scans are done for less specific indications such as abdominal pain in a patient with suspected appendicitis,” Smith-Bindman added. “These can and should be done without contrast during the shortage, because the loss of information in these patients will be acceptable for most patients.”
The first strategy can reduce contrast fluid usage by 10%, while the second one can produce a 25% reduction. Combining all the three approaches, and considering when the third one could be realistically applied without any important downsides, the approach could lead to a 83% reduction in the amount of fluid used.
Some facilities may only be able to use one or two of these, but it's important to be aware of these options.
“Given the acute shortage, it’s important that clinicians who order imaging exams coordinate with radiology to cancel scans that aren’t absolutely necessary, postpone exams that can be safely delayed, replace CT with MRI and ultrasound where possible, and order an unenhanced scan where possible. Further, clinicians should communicate with their patients about why this is necessary. It is crucial that contrast be conserved for clinical situations where its use is essential for accurate diagnosis,” said Smith-Bindman.
Even when the shortage subsides, medical facilities can continue using some o these practices, either to reduce costs, or for other reasons. For instance, reducing the tube voltage also results in lower radiation doses to patients -- in most cases, this won't make a difference, but when a patient has to undergo multiple measurements that will expose them to radiation, it can be significant. In addition, the practices can also be deployed in hospitals that aren't well-funded and are struggling to obtain all the fluid they require.
“By carrying some of these practices forward, we can mitigate future supply-chain risk and reduce overall waste,” concludes Smith-Bindman.
The paper was published in JAMA.