Electrocautery-induced Ignition of Spark Showers and Self-sustained Combustion of Onyx Ethylene-vinyl Alcohol Copolymer

Abstract

Ethylene-vinyl alcohol copolymer mixed with micronized tantalum (Ta) as radiopacifier (Onyx; Micro Therapeutics Inc., Irvine, CA) has emerged as a useful liquid embolic agent for vascular malformations. We describe intraoperative ignition of Onyx-embolized tissue and undertake an in vitro investigation to reproduce and characterize this hazard. Samples of Onyx, Ta-depleted Onyx, Ta-n-butylcyanoacrylate (Ta-NBCA), and Ta powder were exposed to monopolar and bipolar electrocautery in cut and coagulation modes at different power settings to reproduce the intraoperative findings. Recordings of sparking and combustion events were analyzed to characterize duration and relative frequency. Spark showers and self-sustained combustion were observed intraoperatively when an Onyx-embolized artery was coagulated with the monopolar electrocautery. Sparking covered a radius greater than 10 cm, and combustion lasted a median of 1.65 seconds (range, 0.3-12.3 s). Sparking and sustained combustion were reproduced in vitro by both cut and coagulation monopolar modes in Onyx casts and free Ta powder but not in samples of Ta-depleted Onyx or casts of Ta-NBCA. Ignition was similarly observed when using bipolar electrocautery but only at higher energy settings. Electrocautery use on tissue containing Onyx results in potentially dangerous uncontrolled sparking and combustion in a process that is Ta dependent. It is recommended that Ta-NBCA be used instead of Onyx in situations mandating the use of a liquid embolic and high-energy electrocautery, pending the development of a safer radiopacifier for use with ethylene-vinyl alcohol copolymer.