Common Neurointerventional Procedures

Introduction

• INR is a rapidly expanding subspecialty that integrates advanced imaging modalities, most commonly fluoroscopy and computed tomography (CT), to guide minimally invasive endovascular procedures involving the central nervous system.
• In the emergent setting, INR plays a critical role in mechanical thrombectomy for acute ischemic stroke, intracranial hemorrhage, and cerebral vasospasm.
• As the scope of INR has broadened, anesthesiologists are increasingly involved in elective and semi-elective procedures, including diagnostic cerebral angiography, aneurysm coiling or stent placement, and embolization of tumors or AVMs.
• An understanding of common INR procedures is key to the successful anesthetic management of these patients.

Intracranial Procedures

Digital Subtraction Angiography (DSA)

• Cerebral DSA is a diagnostic procedure used to detect intracranial pathologies, such as intracranial aneurysms and AVMs.¹
• In DSA, serial images are acquired before and after contrast injection, allowing only the pixels that change (i.e., opacify) to be identified (Figure 1)
• DSA is more sensitive for the detection of small aneurysms than CT angiography.²

AVMs

• Cranial AVMs may be treated using liquid embolic agents or other occlusive materials. These materials expand to fill the AVM and prevent blood flow between the arterial and venous systems.
• These liquid agents carry a risk of embolization and occlusion of the distal cerebral vasculature.³
• These procedures also carry a significant risk of intraoperative hemorrhage due to the delicate nature of the cerebral vasculature.
• Abrupt alterations in cerebral perfusion are common; even with stable global cerebral perfusion pressure, closure of the AVM may unmask regional hypoperfusion in chronically hyperperfused territories.
• Intracranial AVMs typically require general anesthesia and arterial line monitoring.

Intracranial Aneurysms

• Intracranial aneurysms (images above) are commonly treated using platinum coil embolization to promote localized thrombosis. These coils are placed within the aneurysmal space to promote thrombosis while not occluding blood flow through the vessel. To facilitate this, most coils can be intraoperatively replaced or redeployed to optimize the final location.
• In cases of ruptured aneurysms or subarachnoid hemorrhage, cerebral vasospasm may develop intraoperatively or postprocedurally, requiring vigilant hemodynamic management.
• Clipping of aneurysms is also an option, but coiling has been shown to have superior outcomes in patients with small aneurysms.⁴
• These cases typically require general anesthesia and arterial line monitoring.

Tumor Embolization

• Tumor embolization is procedurally very similar to the treatment of an intracranial aneurysm or AVM, and may employ coils or glue.⁵
• Tumor embolization is typically used to reduce the blood flow to, and therefore the size of, a tumor such as a meningioma or an angiofibroma. This can facilitate future excision of the primary tumor.

Emergency Procedures

Treatment of Vasospasm

• Patients experiencing vasospasm of the cranial arteries, often due to a subarachnoid hemorrhage, may be treated with catheter-directed calcium channel blockers at the site of vasospasm.⁶
• Alternatively, vasospasm may be treated with percutaneous angioplasty, particularly when the spasm is isolated or readily identifiable.

Mechanical Thrombectomy

• Mechanical thrombectomy is primarily indicated for large-vessel occlusion ischemic stroke and enables direct removal of intravascular thrombus, with the goal of reperfusing the ischemic penumbra.⁷
• Permissive hypertension is frequently employed prior to recanalization to optimize collateral cerebral blood flow.
• Monitored anesthesia care and general anesthesia are both reasonable when caring for these patients, provided the patient can tolerate the procedure under sedation.⁸

Extracranial Procedures

Carotid Artery Revascularization

• Carotid artery stenosis may be treated with angioplasty and stenting in the INR suite (Figure 3).
• Balloon inflation near the carotid sinus can provoke parasympathetically mediated bradycardia and hypotension.
• Additionally, manipulation of atherosclerotic plaque carries a risk of cerebral embolization, particularly in the periprocedural period.
• These cases typically require general anesthesia and arterial line monitoring.

Spinal Angiography

• Spinal angiography is the gold standard for the detection of spinal vascular malformations (e.g., spinal arteriovenous malformation). A catheter is introduced, typically via the groin, to inject contrast into the spinal arteries under fluoroscopy.
• Spinal angiography is often performed on children, for which general anesthesia is indicated. In adults, sedation with local anesthetic infiltration at the vascular access site is possible, but general anesthesia is favored for more complex angiograms.