Embolization of Middle Cerebral Artery Aneurysms

178 Embolization of Middle Cerebral Artery Aneurysms
Chirag D. Gandhi, David M. Johnson, and Aman B. Patel

♦ Preoperative

Special Equipment for Aneurysm Coil Embolization

6 French (F) guide catheter
High-pressure tubing for three-dimensional (3D) contrast injector
One additional heparinized bag of saline with arterial pressure bag and tubing
0.010 or 0.014 microcatheter
0.010 or 0.014 soft tip micro-guide wire
Variety of coils using the detachable coil system in various shapes (3D, 360, two-dimensional), stiffness (standard, soft, ultra soft), and sizes

Anesthetic Issues

General endotracheal anesthesia (GETA) is the best because it limits patient movement during the procedure and is especially important during roadmap guidance as well as microcatheter and coil placement
Keep systolic blood pressure < 140 mm Hg for patients with ruptured aneurysms that have not been secured
Anesthesiologist should know that any significant rise in blood pressure or intracranial pressure (ICP) with or without a drop in heart rate should be promptly communicated with the surgical team; could suggest aneurysm rupture that needs to be managed promptly

Anticoagulation

For unruptured aneurysms, systemic heparinization is initiated prior to placement of the guide catheter with a bolus of 4000 units of heparin

Heparinization is rebolused hourly with 1000 units. The target is a partial thromboplastin time 2 to 2.5 times the standard values. Activated clotting time values can be monitored to ensure adequate anticoagulation.
For ruptured aneurysms, heparinization is usually not started until the first coil has been placed because ruptured aneurysms have a higher risk of re-rupture during the catheterization and initial coil placement.
Protamine should be easily available in the event of intraprocedural aneurysm rupture

Monitoring

Strict monitoring of blood pressure with arterial line
Careful monitoring of ICP through the ventriculostomy, when appropriate
Some recommend constant electroencephalogram monitoring with the help of a neurophysiologist

Imaging Considerations

Diagnostic angiography for aneurysms includes standard anteroposterior and lateral views of all four vessels (both carotid and vertebral arteries)
Magnified oblique views of both intracranial carotid injections with special attention to Circle of Willis; should be performed even if the middle cerebral artery (MCA) aneurysm of interest has already been identified because 10 to 15% of patients have multiple aneurysms
To better characterize the dome and neck of the aneurysm as well the branch patterns of the adjacent parent vessels, a 3D rotational angiogram (3DRA) of the MCA bifurcation can be performed; these images allow for determination of the “working view”

♦ Intraoperative

Positioning

Patient is placed supine on the angiography table
GETA is performed
Foley catheter is placed
The head is positioned in neutral position and secured within the head holder
Both groins are shaved and prepped with iodine solution
Sterile drape is placed over the entire angiography table
5- and 10-mL syringes with 80% contrast solution or heparinized saline are prepared
Three pressure saline bags are prepared by removing all the air from tubing
Contrast injector is loaded with contrast and attached to high pressure tubing
All sheaths, catheters, and guide wires are flushed with heparinized saline

Technique

Femoral artery puncture is performed using 19-gauge single-wall puncture needle and a 6F sheath is placed using a Bentson wire by employing the Seldinger technique. The sheath is the attached to a continuous flush.

Four-vessel angiogram is performed with a 5F catheter and once aneurysm of interest is identified its anatomical configuration is elucidated. 3DRA can be used to obtain this information.
3DRA is used to measure aneurysm dome and neck size, parent vessel characteristics such as branching patterns, and to obtain the ideal “working view.”
A 6F guide catheter is placed into the common or internal carotid artery using roadmap guidance and attached to a continuous flush drip.
Full heparinization is performed at this point for unruptured MCA aneurysms.
Using roadmap guidance a microcatheter is then advanced over a micro-guide wire into the parent vessel.
A microcatheter is then advanced over a micro-guide wire into the aneurysm taking great care not to push either the catheter or the guide wire into aneurysm dome.
The largest coil that will safely fit within the aneurysm is chosen to provide scaffolding into which additional coils are placed. The initial coil deployed should make a framework through the aneurysm with neck coverage.
The coil is then advanced under roadmap guidance through the microcatheter until the detachment zone is seen within the aneurysm.
An angiogram is performed prior to coil detachment to assess both parent vessel and aneurysm filling after which the coil is detached either electrically or hydrodynamically, depending on the type of coil.
For ruptured aneurysms, systemic heparinization is commonly performed at this point.
The coil delivery wire is removed and additional coils are chosen in decreasing size and placed in the manner described.
Follow-up angiograms are performed prior to the detachment of each coil to assess for parent vessel compromise and aneurysm occlusion.
Coil embolization is continued until the aneurysm is no longer filling with contrast and the aneurysm has been maximally filled with coil mass.
In the case that complete embolization of a ruptured aneurysm cannot be performed without parent vessel compromise, partial embolization to secure the site of rupture within the dome is performed with plans for repeat delayed coil embolization or surgery.
The microcatheter is removed and a final angiogram of the internal carotid artery in the standard position is performed to exclude any thromboembolic vessel compromise.
The arteriotomy can be closed by using either a femoral artery closure device if the sheath is within the common femoral artery or by using 15 to 30 minutes of manual pressure on the site of arterial puncture.