Volume 25 ’ Number 12 ’ December ’ 2014 2005

may fail to recognize it in a patient with sudden-onsetthrombocytopenia. Given the widespread use of intrave-nous and intraarterial contrast medium, this complicationhas important implications for interventional radiologistsand cardiologists, by whom potent antiplatelet andantithrombotic therapies are commonly used.

REFERENCES

1. Naranjo CA, Busto U, Sellers EM, et al. A method for estimating theprobability of adverse drug reactions. Clin Pharmacol Ther 1981; 30:239–245.

2. Aspelin P, Stacul F, Thomsen HS, Morcos SK, van der Molen AJ. Effectsof iodinated contrast media on blood and endothelium. Eur Radiol 2006;16:1041–1049.

3. Bata P, Tarnoki AD, Tarnoki DL, Horvath E, Berczi V, Szalay F. Acutesevere thrombocytopenia following non-ionic low-osmolarity intravenouscontrast medium injection. Korean J Radiol 2012; 13:505–509.

Re: “Selective Arterial Embolization withEthylene–Vinyl Alcohol Copolymer forControl of Massive LowerGastrointestinal Bleeding:Feasibility and InitialExperience”

From: Romaric Loffroy, MD, PhDDepartment of Vascular, Oncologic andInterventional RadiologyLaboratoire d’Electronique, d’Informatique et de l’ImageUnité Mixte de Recherche, Centre National de laRecherche Scientifique 6306University of Dijon School of MedicineBocage Teaching Hospital14 Rue Paul GaffarelBP 7790821079 Dijon, France

Editor:

I read with great interest the article by Urbano et al (1)reporting the effectiveness of selective arterial embolizationwith the use of Onyx (Covidien, Mansfield, Massachusetts)in patients with acute arterial bleeding from the lowergastrointestinal tract. We have several comments. First ofall, I would like to congratulate the authors for their study,which represents the main series to date reporting results onarterial embolization with Onyx as an embolic agent in thelower gastrointestinal tract. Until now, the only availabledata on the use of this embolic material for peripheralapplications came from case reports. However, the authorsdid not bring to attention several other disadvantageouscharacteristics of the use of Onyx.The main disadvantage of Onyx is its relatively high

cost compared with other embolic agents. Its prohibitive

http://dx.doi.org/10.1016/j.jvir.2014.08.010

The author has not identified a conflict of interest

cost has led to its restricted use in neuroradiology inmost institutions around the world (2). Anotherdisadvantage is that, if the operator does not haveenough experience with the use of Onyx, the time,radiation dose, and complexity of the procedure maybe excessively increased. Some authors have reportedsevere vasospasm in cases of rapid injection (3). This isespecially important during the early stages of theembolization procedure when the dimethyl sulfoxide(DMSO) is being replaced by Onyx in the catheter“dead space.” Therefore, the first 1 mL of embolicagent must be injected very slowly. I have neverexperienced severe vasospasm related to DMSOinjection. Even if the authors reported a total injectiontime of DMSO and Onyx of less than 5 minutes onaverage for their procedure, in my experience, theduration of injection is often much longer and variesdepending on the amount of Onyx used.DMSO is volatile and is excreted via respiration and

sweat. This has a typical smell not unlike that of diabeticketoacidosis, and may last a few days. The patient andward staff should be warned to expect this. In addition,chemical irritation caused by DMSO is usually verypainful, at least in my experience. It is recommended touse general anesthesia to ensure patient comfort duringembolization. I am very surprised that Onyx injectionwas well tolerated, without noticeable pain, in patientswho were not under general anesthesia (1). Could theauthors provide their detailed protocol used for adjuvantanalgesia medications in their study? Do the authorsalways use Onyx without general anesthesia for othervisceral arterial applications?In conclusion, in my experience, selective arterial

embolization with Onyx is a very interesting and prom-ising treatment option for lower gastrointestinal bleed-ing. Onyx seems to provide controlled embolization as aresult of its slow polymerization, which enables deeppenetration with less risk of catheter gluing because of itsnonadhesive nature. Currently available data in theliterature are very limited, and further studies are neededto better characterize its safety profile in the visceralvasculature. In addition, the important cost aspect needsto be borne in mind when there are other cheaperalternatives that would be as effective and faster whenused on an emergency basis.

REFERENCES

1. Urbano J, Cabrera JM, Franco A, Alonso-Burgos A. Selective arterialembolization with ethylene–vinyl alcohol copolymer for control of massivelower gastrointestinal bleeding: feasibility and initial experience. J VascInterv Radiol 2014; 25:839–846.

2. Panagiotopoulos V, Gizewski E, Asgari S, Regel J, Forsting M, WankeI. Embolization of intracranial arteriovenous malformations with ethylene-vinyl alcohol copolymer (Onyx). AJNR Am J Neuroradiol 2009; 30:99–106.

3. Lenhart M, Paetzel C, Sackmann M, et al. Superselective arterialembolisation with a liquid polyvinyl alcohol copolymer in patients withacute gastrointestinal haemorrhage. Eur Radiol 2010; 20:1994–1999.