Introduction There is currently minimal information in the literature defining the interactions of ethanol with various non-ionic contrast agents. There are two main questions to explore: 1) at what concentration ratio will precipitation occur? And 2) does the dilutional effect of contrast reduce the embolic effect of ethanol? The aim of this project is solely to answer the first question.

At our institution, iopamidol (Isovue) and iohexol (Omnipaque) are the main non-ionic contrast agents of choice. We plan to conduct a simple experiment where we will add sequential amount of absolute ethanol to these non-ionic agents until we reach the crystallization threshold concentration. This will provide useful information for the interventionalist such that concern for intracatheter or proximal vessel precipitation can be avoided when using ethanol as a sclerosant for vascular malformations.

Absolute ethanol embolization has been used for the treatment of brain and other AVMs such as those involving the mandible. Ethanol directly damages the endothelial layer and fractures the vascular wall to the level of the internal elastic lamina, which provides a more curative and permanent effect. As a fluid agent, ethanol penetrates to the capillary level. Inflow occlusion with balloon catheters may be required to induce decreased flow and vascular stasis such that full contact of ethanol with endothelium is obtainable. Given its penetrance to the capillary level, all collateral circulation is shut down and necrosis can occur. The amount of ethanol is dependent on the flow and volume characteristics with no set pre-determined amount. The amount of contrast needed to displace blood and not reflux provides a good estimate of the amount of ethanol required for embolization.

Methods We continuously added small amounts of pure ethanol (98% ethanol) at a rate of .15 mL ethanol/min using a syringe pump to a vial containing 3 mL of Isovue 300 contrast agent. A spinning magnetic stirrer was used in the vial of Isovue to aid in mixing. We monitored for particle precipitation utilizing the Tyndall effect by shining light through the vial.

Results/Discussion There was no evidence for particle precipitation with concentrations reaching as high as 75% ethanol (9 mL of ethanol/3 mL of Isovue 300). This concentration is even higher than an optimal concentration of 50% ethanol/50% Isovue, which would provide adequate visualization of the sclerosing agent, while also maintaining its destructive properties.

Conclusion We conclude that adding ethanol to Isovue provides a safe visible liquid embolic agent able to reach the capillary level without causing microcatheter occlusion or proximal artery occlusion from precipitation.

Disclosures S. Rudkin: None.