Microvascular embolization following polidocanol microfoam sclerosant administration

BACKGROUND. Intravenous microfoam sclerotherapy solutions can potentially cause cerebrovascular arterial embolization. OBJECTIVE. To determine the relationship between polidocanol microfoam formulation and arteriolar embolization bubble lodging and clearance in vivo. METHODS. Three polidocanol microfoams (one made by the double-syringe method using air and two Varisolve (Provensis, Inc., West Conshohocken, PA, USA) formulations using different physiologic gas mixtures composed primarily of oxygen and carbon dioxide and dispensed from a proprietary canister mechanism) were mixed with venous blood and injected into the rat cremaster arterial microcirculation. Bubble dimensions and dynamics were recorded using intravital microscopy. RESULTS. Bubble entry frequency, size, and dynamics depended on microfoam formulation. Air-based bubbles (2.72 +/- 1.38 nL; n = 21) lodged, obliterating blood flow. Varisolve bubbles (0.20 +/- 0.02 nl; n = 2 and 0.53 +/- 0.27 nl; n = 27 for the two gas compositions) entered but either did not lodge or cleared within seconds. Bubble size and number were different among these microfoams. CONCLUSIONS. Both Varisolve formulations produced smaller embolism bubbles than occurred with air-based microfoam. Rapid clearance of Varisolve bubbles suggests that they are so small that they do not have adequate surface area available for significant binding interactions with arteriolar endothelium. Larger air-based bubbles obstruct arteriolar vessels and block blood flow.