SVM Communications: Contrast media shortage and Society updates

Contrast media shortage

Why is there a contrast shortage?

In May 2022, GE Healthcare announced a supply chain disruption affecting the global supply of iohexol and iodixanol (Omnipaque and Visipaque; GE Healthcare, Chicago, IL, USA) due to local COVID-19 lockdowns that affected their primary manufacturing facility in Shanghai, China.

Owing to this temporary lockdown, GE announced that it anticipated an 80% reduction globally in contrast media supply for several months through mid-summer.^1,2

What is the impact of this contrast shortage on clinical practice?

Owing to the global shortage from this predominant vendor, many institutions faced unprecedented challenges, including identifying their contrast stockpile, seeking pathways to secure contrast from alternative brands, and determining how to prioritize distribution and utilization of the contrast available. This last aspect is of the utmost importance to avoid interruptions in life- and limb-saving procedures, such as coronary and vascular interventions. ³ During this period of time, several institutions reported having critically low stock of iodinated contrast and to only have enough stock to perform a limited number of emergent cases. ⁴

How has your institution navigated this contrast media shortage?

At our institutions, multiple steps were taken to navigate this contrast shortage and prevent interruptions in cardiac catheterization and endovascular procedures. First, most elective contrast-enhanced computed tomographic (CT) scans were deferred until later in the summer when contrast shortage is expected to have resolved. Diversion to other alternative studies that do not use intravenous iodinated contrast were recommended, such as arterial duplex, magnetic resonance angiogram with gadolinium, and unenhanced CT scans whenever feasible. ⁵

Second, guidelines were also created for the catheterization laboratories and angiography suites across the hospitals within our healthcare system that included close monitoring of the amount of contrast used during cases, redistribution of contrast to smaller vials to reduce waste, switching from automatic injectors to manifold use to minimize daily waste, and the use of carbon dioxide (CO₂) angiography and intravascular ultrasound (IVUS) for endovascular procedures in the appropriate patient. ⁶ These guidelines were effective in reducing the amount of contrast used per procedure by nearly half without the need to delay patient care. ⁶

How should a patient with suspected pulmonary embolism (PE) be evaluated with the ongoing contrast shortage?

Providers at the University of Virginia regularly utilize the ‘PE Toolkit’ developed by the Society for Vascular Medicine (SVM) as a practice resource (www.mypulmonaryembolism.com). The toolkit provides a clinical decision tool in the form of a flow chart (Figure 1), which combines clinical prediction scores and laboratory tests such as D-dimer that safely exclude PE as a diagnosis in one-third of patients with suspected PE without requiring a contrast study such as a CT pulmonary angiogram (CTPA). ⁷ This clinical decision model is also supported by the American College of Physicians. ⁸ Assessment starts with using validated clinical prediction tools such as the original Wells criteria, the simplified Wells criteria, the revised Geneva score, and the simplified Geneva score. All of them are similarly accurate and only one of these needs to be used consistently. For patients identified as low risk based on the Wells criteria or Geneva score, the Pulmonary Embolism Rule-out Criteria (PERC) is obtained. Components of PERC include age ⩾ 50, heart rate ⩾ 100, oxygen saturation on room air < 95%, unilateral leg swelling, hemoptysis, recent surgery or trauma, prior PE or deep venous thrombosis, and hormone use. If the patient does not meet any of the PERC, then PE can be safely ruled out. A large meta-analysis showed that PERC could safely exclude PE and reduce the need for D-dimer testing by 22%. ⁹ Patients who are identified as low risk per the initial clinical prediction tool, either Wells criteria or Geneva scores, but have at least one criteria of PERC, and those who are identified as moderate risk for PE per the initial clinical decision tool, should undergo D-dimer testing. According to the SVM PE toolkit, a D-dimer cut-off level of 499 is negative for patients younger than 50 years of age. For those older than 50 years of age, it recommends an age-adjusted D-dimer cut-off (age × 10 ng/mL), which can also safely exclude PE (sensitivity of > 97%) and increase the sensitivity. ¹⁰ Those with an elevated D-dimer should undergo CTPA to identify PE. Patients with a high risk for PE based on clinical prediction tools such as the Geneva score or Wells criteria should undergo CTPA. D-dimer or PERC criteria testing is not indicated in this situation. The toolkit recommends V/Q scans when CTPA are contraindicated or not available (such as in the setting of contrast shortage). Implementing such prediction models in the emergency department and the inpatient setting can significantly reduce the need for contrast-based imaging while safely excluding PE. The PE toolkit also provides an excellent guide to identify patients that can be treated safely as an outpatient or discharged early from hospital or emergency department. It also provides an easy-to-read review of anticoagulants, particularly direct oral anticoagulants, including prescription details, prescription assistance programs, and cost reduction strategies.

Figure 1.

Assessment of a patient with suspected pulmonary embolism.

How do you perform endovascular interventions with a reduced contrast dose?

In our experience for peripheral angiograms, we are able to obtain good quality diagnostic images by selectively cannulating the vessel of interest and diluting the contrast with saline for a 1:4 ratio. For this we typically load saline first followed by contrast in the syringe, this way it would be a ‘contrast bolus’ followed by a ‘saline chase’. Using this contrast dilution, we can perform a standard unilateral lower-extremity angiogram with no more than 10 mL of iodinated contrast. We can perform complete lower-extremity peripheral interventions with an average of 20–40 mL of contrast. In addition, the use of a roadmap to avoid taking multiple angiograms, CO₂ angiography, and augmentative intravascular ultrasound (IVUS) can help further reduce contrast use and still maintain good quality diagnostic studies and perform adequately successful interventions.

CO₂ angiography has traditionally had a role in endovascular therapies, particularly for patients with chronic kidney disease where contrast use needs to be limited. ¹¹ We found this to be a good resource during the contrast media shortage, particularly for the more proximal iliofemoral vessels. However, image quality remains imperfect in below-the-knee vessels, where smaller diseased vessels can be difficult to visualize, and collateral vessels can be more prominent. Thus, its application in chronic limb-threatening ischemia may be limited, though can be used in conjunction with IVUS for improved imaging capacity.

Overall, it is feasible to conserve iodinated contrast media and still perform timely and adequate cardiovascular interventions by implementing multiple strategies at the institution and procedural level. The lessons learned from this shortage will translate into a more effective use of contrast even beyond this period of shortage.