Anesthesia for Neurointerventional Procedures

Introduction

• Neurointerventional radiology (neuro IR) has grown significantly over the past 20 years and now represents the standard of care for the treatment of certain conditions.
• Procedures range from emergent interventions, such as mechanical thrombectomy for acute ischemic stroke, to elective procedures, like diagnostic cerebral angiograms. These procedures require tailored anesthetic approaches based on acuity and procedural requirements.
• As the popularity of this technique has grown, the sudden increase in volume has encouraged the procedures to shift from traditional operating rooms (ORs) to dedicated IR suites, creating unique challenges for anesthetic management.
• The anesthesiology professional’s role includes managing hemodynamics to optimize cerebral perfusion, ensuring absolute immobility during critical portions of the procedure, and preparing for potential complications.

Patient Selection and Types of Procedures

Preprocedure Evaluation and Planning

• Patient acuity varies dramatically from awake, neurologically intact individuals undergoing elective procedures, like diagnostic angiograms, to obtunded patients with acute neurologic deficits requiring emergent intervention, in the case of a stroke rescue or a ruptured intracranial aneurysm.
• Performing a quick, efficient assessment of the patient to determine the appropriate anesthetic is critical; minimizing ischemic time is important for functional recovery.
• Strongly consider GA in patients with decreased consciousness or posterior circulation strokes, as these patients are at increased risk of aspiration and respiratory instability.¹
• Patients with intracranial aneurysms or increased intracranial pressure (ICP) require meticulous control of blood pressure to maintain cerebral perfusion while minimizing risk of rebleeding or ischemia. Consider placement of a preinduction invasive blood pressure monitor.

Anesthetic Considerations by Procedure Type

Anesthetic requirements vary significantly based on:

• Patient age: Pediatric patients will typically require GA, while adult patients may tolerate MAC for select procedures.
• Procedure complexity and duration: Longer, more complex procedures favor GA to ensure immobility and patient comfort. Patient movement during a complex procedure can result in vessel rupture, dissection, aneurysm rupture, or stent or coil displacement. Examples of cases that benefit from GA include treatment of intracranial aneurysms, spinal or cranial arteriovenous malformations (AVMs), tumor embolization, and spinal angiography.
• Patient cooperation: Anxious patients, those with cognitive impairment, or those with an inability to remain motionless may require deeper sedation or GA.
• Hemodynamic considerations: Certain pathologies, such as ruptured, unprotected aneurysms, may require specific hemodynamic goals that may be better managed under GA. However, maintaining hemodynamic stability during induction and intubation is crucial to preventing neurological sequelae.

Types of Procedure

Intracranial

• Mechanical thrombectomy for acute ischemic stroke: Anesthetic choice (GA vs MAC) remains debated. Anesthetic management is further explored here. (Link)
• Embolization of ruptured and unruptured aneurysms (coiling or flow diversion) can be either emergent (ruptured) or elective (unruptured). These cases are often done under GA to ensure patient immobility during critical portions of the case. Blunting the sympathetic reflex associated with intubation is critical to preventing aneurysm re-rupture during induction. Consider pre-induction invasive blood pressure monitoring in ruptured aneurysms. Induced hypotension may be requested intraoperatively during aneurysm manipulation.
• AVM or dural arteriovenous fistula embolization: While GA allows for patient immobility, MAC allows for continuous neurological testing during AVM treatment. There is no evidence that either approach is associated with a lower complication rate.² The procedure may require controlled hypotension during polymer injection to minimize passage into draining veins. Postprocedurally, the hemodynamic goal shifts to controlled normotension to prevent breakthrough of normal perfusion pressure and hemorrhagic infarction.
• Carotid or intracranial arterial stenting: Carotid stenting is often performed under MAC, which allows continuous neurological assessment during manipulation of the artery. Given the small caliber of intracranial arteries and risk of vessel injury with patient movement, intracranial artery stenting is often done under GA to prioritize immobility. Thorough preoperative assessment of cardiopulmonary comorbidities is important, as these patients often have coexisting coronary atherosclerosis. Recommend invasive blood pressure monitoring as hemodynamic perturbations are common during carotid manipulation.
• Tumor embolization: This procedure is performed before tumor resection to reduce bleeding during resection. Similar to embolization of a vascular malformation, these procedures are often done under GA to ensure patient immobility during polymer injection. Consider obtaining consent for subsequent tumor resection if the procedures will be performed concurrently.
• Intra-arterial treatment of vasospasm: These cases are performed urgently in critically ill patients who are intubated and coming from the intensive care unit (ICU) with an external ventricular drain (EVD). They often require repeated procedures over several days. Targeted blood pressure management, often induced hypertension, is crucial to preventing cerebral ischemia from vasospasm. Additionally, providers need to be thoughtful about the appropriate management of the EVD during both transport and the procedure.³ During the procedure, the interventionalist will often infuse vasodilators directly into the vasospastic vessels, causing systemic hypotension. Pretreatment with vasopressors is critical to preventing cerebral ischemia.

Spinal Procedures

• Spinal angiography: While this procedure can be performed under MAC, as with a diagnostic cerebral angiogram, given its length and the small caliber of the vessels, we often elect for GA for patient comfort and immobility.
• Vertebral augmentation (vertebroplasty, kyphoplasty): Depending on the interventionalist’s requirement and patient preference, GA or MAC can be selected for these procedures. Some providers may elect for GA, given that the patient is prone with limited airway access.

Location and Workflow Considerations

Location: Non-OR vs OR Anesthesia

• Non-OR anesthesia challenges: Neuro IR suites are remote locations with unique challenges, including unfamiliar equipment, limited space, variable availability of assistance, and distance from emergency resources. Unlike ORs with standardized layouts, each IR suite may be configured differently, requiring familiarization with equipment locations, oxygen supply, suction access, and code cart placement before emergencies occur.
• Support staff availability: Compared to ORs, IR suites often have fewer nurses and IR technicians who are familiar with anesthesia needs. Clearly establish who can assist you in an emergency. Know how to activate additional help, whether that’s a rapid response team, additional anesthesia personnel, or backup OR staff.
• Communication systems: Established hospital communication systems should be used, including landline phones, overhead paging systems, hospital-issued pagers, and intercom systems that are reliably functional throughout the IR suite. Personal electronic devices (cell phones) should not be used. Cell service towers vary, and IR suites often have dead zones or poor reception, causing critical delays in getting help during emergencies.
• Radiation exposure: Regardless of OR or non-OR location, all providers will need appropriate shielding and monitoring during these procedures. The availability of protective lead aprons and screens should be determined prior to the procedure.

Workflow Integration with IR Team

• Prenotification coordination: Anesthesia should be alerted simultaneously with the interventionalist when a stroke patient is en route. Know your institution’s activation process and expected response time.
• Parallel processing and rapid focused evaluation: Once a stroke patient arrives, the teams can simultaneously assess the patient. While the interventionalist is prepping the patient, the anesthesia team can efficiently evaluate the patient and obtain a baseline neurological exam (Glasgow Coma Scale or National Institutes of Health Stroke Scale), while monitoring and vascular and arterial access are established. Every 20 minutes of delay costs patients approximately 3 months of disability-free life, so the assessment must be thorough yet expedited.⁴ This parallel workflow, rather than sequential steps, significantly reduces door-to-groin puncture time.
• Clear communication about care goals and hemodynamic baseline: Blood pressure trends, heart rate, volume status, and need for vasopressor support should be checked. Stroke protocols differ from other procedures; permissive hypertension (systolic blood pressure (SBP) 140-180 mmHg) is often requested prior to recanalization to maintain collateral perfusion. After recanalization, tighter control (SBP less than 140-160 mmHg) is required to prevent reperfusion hemorrhage.⁵

Emergencies in Neuro-IR

Conversion to GA

Indications for conversion from MAC to GA include:

• Patient movement or agitation: Movement of a patient during an endovascular procedure threatens the catheter’s position and puts the vessel at risk for rupture or dissection. During treatment of an aneurysm or AVM, patient movement may cause the coils or stent to migrate as they are being deployed.
• Respiratory compromise: Airway obstruction, aspiration, or respiratory depression may occur secondary to sedating medications or to the patient’s neurological condition. Respiratory compromise can lead to hypercapnia, which can be especially dangerous in patients with underlying neurologic conditions with reduced intracranial compliance.
• Hemodynamic instability: Patients with severe hypertension or hypotension will require aggressive management, best facilitated under GA. Additionally, in a patient with an acute ischemic stroke, maintaining hemodynamic stability during induction is critical to preventing a poor outcome.
• Allergic reaction: Anaphylaxis to antibiotics, paralytics, or contrast dye may require airway and hemodynamic management.
• Intraprocedural complication: In the setting of vessel perforation, aneurysm rupture, or acute neurologic deterioration, conversion to GA provides airway protection and allows for subsequent procedures.

Intraprocedural Aneurysm Rupture

Aneurysm rupture during treatment is a catastrophic complication that needs to be managed urgently. Immediate consideration includes:

• Quick recognition in the setting of sudden loss of consciousness (if awake), extravasation of contrast, acute hypertension followed by bradycardia and hypotension, or sudden increase in ICP.
• Immediate actions by the provider include:
  • Hemodynamic management: Permissive hypotension (mean arterial pressures 60-70 mmHg) should be considered to reduce bleeding while maintaining cerebral perfusion.
  • Airway management: Immediate intubation and conversion to GA if not already done.
  • Reversal of anticoagulation: Protamine should be considered if the patient is on heparin or platelets for patients on antiplatelet therapy.
  • Neuroprotective measures: Normocapnia, normoglycemia, and normothermia should be maintained.
  • Prepare for transfer: Transfer should be either to the ICU, if stabilized, or to the OR for emergency craniotomy. If transferring to the ICU, consider obtaining a head CT en route to assess the extent of hemorrhage.