EMBOLIZATION
Onyx
Introduction
Last updated: apr 5, 2023
Onyx is a liquid embolic system developed by Micro Therapeutics, Inc. It comprises ethylene-vinyl alcohol copolymer (EVOH) made from 48 mol/L ethylene and 52 mol/L vinyl alcohol, dissolved in dimethyl-sulfoxide (DMSO) and combined with 35% weight per volume micronized tantalum powder for radiopacity. Primarily used globally for treating cerebral and spinal arteriovenous malformations (AVMs), it also has applications in hypervascular tumors, peripheral AVMs, arteriovenous fistulas (AVFs), and endoleak treatment.
The procedure in steps
- Shake the Onyx for at least 20 minutes using an Onyx mixer set to level 8. Continue mixing until the Onyx can be injected.
- Place the attached syringes on a sterile table.
- Fill the dead space of the catheter. Draw up approximately 0.8 mL of DMSO. Inject enough DMSO to fill the dead space of the catheter. Refer to the catheter label for the volume of the dead space and check if the catheter is DMSO-compatible.
- For example, with the Headway Duo catheter, the dead space is 0.34 mL, so inject 0.4 mL.
- Next, remove Onyx from the mixer.
- Draw up 1 syringe (1 mL) and allow it to flow in over 3 minutes; start the timer.
- Draw up the next syringe, always using a new syringe but you can use the same needle.
- In the meantime, keep shaking the jar of Onyx to ensure it remains well mixed.
- Each jar contains 6 mL.
Tips and tricks
- Should catheter removal become difficult, the following technique may assist in catheter retrieval:
- Carefully pull the catheter to assess any resistance to removal.
- If resistance is felt, remove any “slack” in the catheter.
- Gently apply traction to the catheter (approximately 3-4 cm of stretch to the catheter).
- Hold this traction for a few seconds and release. Assess traction on vasculature to minimise risk of hemorrhage.
- This process can be repeated intermittently until catheter is retrieved.
- When using micro catheters, do not apply more than 20 cm of traction to catheter, to minimise risk of catheter separation.
- For entrapped catheters:
- Under some difficult clinical situations, it may be safer to leave a flowdirected catheter in the vascular system, rather than risk rupturing the malformation and, consequently a hemorrhage, by exercising too much traction on an entrapped catheter.
- This is accomplished by stretching the catheter and cutting the shaft near the entry point of vascular access allowing the catheter to remain in the artery.
- If catheter breaks during removal, distal migration or coiling of the catheter may occur.
- Same day surgical resection should be considered to minimise risk of thrombosis.
Complications
- Hematoma
- Arterial thrombosis
- Ischemic events due to embolic migration, vasospasm, thrombosis
- Catheter entrapment
- Catheter rupture
- Device migration and cast movement
- Hemorrhagic accidents: vascular rupture – perforation
- Hemodynamic changes induced by the embolisation may result in hemorrhagic complications
- Hemorrhagic complications related to attempts to remove entrapped catheter
- These ischemic or hemorrhagic complications may result in various functional neurological deficits and possibly death.
Post-op
- After the procedure, the patient may excrete a foul odor. Therefore, please place the patient alone in the room after the procedure due to potential discomfort from the smell.
- For closure with angio-seal: 2 hours of flat bed rest.
- For manual compression: 6 hours of bed rest (4 hours flat, 2 hours at a 45-degree angle).
