Residency · Residency · Anesthesiology

Anesthesia for Acute Ischemic Stroke and Neurovascular Procedures

Acute Ischemic Stroke: Overview

Pathophysiology

Acute ischemic stroke results from thromboembolic occlusion of a cerebral artery. The affected territory divides into two zones: the ischemic core, which represents irreversibly damaged tissue, and the penumbra, which is ischemic but salvageable tissue surrounding the core. The overarching goal of treatment is to reperfuse the penumbra before it progresses to infarction.

Time Windows

Intravenous thrombolysis with alteplase or tenecteplase can be administered within 4.5 hours of symptom onset, as established by the ECASS-III trial. Endovascular thrombectomy (EVT) extends the treatment window to up to 24 hours when perfusion imaging demonstrates a favorable mismatch between core infarct and salvageable tissue, as shown in the DAWN and DEFUSE 3 trials. The urgency of treatment cannot be overstated: approximately 1.9 million neurons are lost per minute of large vessel occlusion.

Reperfusion Strategies

IV thrombolysis is administered as alteplase 0.9 mg/kg (maximum 90 mg) or tenecteplase 0.25 mg/kg. Endovascular thrombectomy involves catheter-based mechanical clot retrieval using stent retrievers or aspiration devices. EVT is now the standard of care for large vessel occlusion involving the internal carotid artery, M1 segment, or proximal M2 segment, supported by evidence from the MR CLEAN, ESCAPE, EXTEND-IA, SWIFT PRIME, and REVASCAT trials.

GA vs. Conscious Sedation for Endovascular Thrombectomy

The Controversy

Early observational studies suggested that general anesthesia was associated with worse outcomes compared to conscious sedation. However, these findings were confounded by several factors: sicker patients were more likely to receive GA, intubation caused procedural delays, and hemodynamic instability was more common under GA.

Landmark RCTs

Three pivotal randomized controlled trials addressed this question. The SIESTA trial (2016), a single-center study of 150 patients, found no difference in early neurologic improvement or 3-month functional outcomes between GA and conscious sedation. The AnSTROKE trial (2017), involving 90 patients at a single center, similarly showed no significant difference in functional outcomes at 3 months, though the GA group experienced more hypotension. The GOLIATH trial (2017), a single-center study of 128 patients, found significantly less infarct growth on MRI with GA (the primary outcome), with functional outcomes showing no significant difference but a trend favoring GA.

Current Consensus

The evidence demonstrates that GA is not inferior to conscious sedation when performed with strict hemodynamic management. The critical requirement is avoiding hypotension, as a MAP decline of more than 10 to 20% from baseline is associated with worse outcomes. GA offers the advantages of immobility (improving image quality and reducing complications), airway protection, and controlled ventilation. Conscious sedation allows real-time neurologic assessment during the procedure. The choice should depend on institutional expertise, patient cooperation, and the ability to maintain hemodynamic targets.

<image>Summary infographic of the three major RCTs (SIESTA, AnSTROKE, GOLIATH) comparing general anesthesia versus conscious sedation for endovascular thrombectomy. Each trial is presented with sample size, primary outcome, and functional outcome at 3 months (mRS scores). A forest plot shows the pooled effect with confidence intervals, demonstrating non-inferiority of GA when hemodynamic targets are maintained. Key anesthetic management principles are listed below: MAP targets, rapid induction, and avoidance of delays.</image>

Anesthetic Management for Endovascular Thrombectomy

Time-Critical Considerations

The procedure must not be delayed for anesthetic preparation. The target door-to-groin puncture time is less than 60 minutes. If GA is chosen, rapid-sequence induction should be performed. Pre-procedure preparation time must be minimized in every way possible.

General Anesthesia Protocol

Rapid-sequence induction uses propofol plus rocuronium, or etomidate if the patient is hemodynamically unstable. Maintenance may consist of propofol/remifentanil TIVA or low-dose sevoflurane. An arterial line is essential for continuous blood pressure monitoring and is often placed after induction to avoid delay. The MAP target should be maintained within 10% of the patient's baseline or per institutional protocol. Hypotension must be treated aggressively, with a vasopressor infusion of phenylephrine or norepinephrine prepared and running.

Conscious Sedation Protocol

Conscious sedation typically uses a dexmedetomidine infusion at 0.2 to 0.7 mcg/kg/hr or remifentanil at 0.02 to 0.05 mcg/kg/min, supplemented by local anesthesia at the groin access site. Continuous neurologic assessment capability must be maintained, and airway management equipment must be immediately available for conversion to GA. The principal risk is patient movement during critical catheter manipulation.

Blood Pressure Management

Before reperfusion, the MAP target varies, but generally systolic blood pressure should be kept below 180 mmHg if tPA has been administered, and hypotension must be avoided. After reperfusion, the systolic blood pressure target drops to 140 to 160 mmHg, depending on recanalization status and hemorrhagic risk. Hypertension is treated with nicardipine or labetalol infusion, and hypotension is treated promptly with phenylephrine or norepinephrine. Hemodynamic instability is the most modifiable anesthetic factor affecting outcomes.

Other Considerations

Glucose should be managed to a target below 180 mg/dL while avoiding hypoglycemia. Normothermia must be maintained, as hyperthermia worsens ischemic injury. Ventilation should target normocarbia with a PaCO2 of 35 to 40 mmHg, since hyperventilation reduces penumbral perfusion. Anticoagulation with heparin during EVT follows interventionalist preference, typically targeting an ACT above 250.

Anesthesia for Cerebral Aneurysm Surgery

Preoperative Considerations

Preoperative assessment includes grading by the Hunt and Hess scale and Fisher grade for subarachnoid hemorrhage (SAH) patients. Key concerns include the risk of rebleeding before definitive treatment, vasospasm risk during days 3 through 14 post-SAH, and hydrocephalus that may require an external ventricular drain.

Anesthetic Goals

The anesthetic goals include avoiding hypertension (which increases rebleeding risk before clipping), avoiding hypotension (to maintain perfusion to ischemic brain), achieving a smooth induction without hemodynamic swings, providing brain relaxation for surgical exposure, and enabling rapid emergence for neurologic assessment.

Intraoperative Management

Monitoring includes an arterial line and large-bore IV access given the risk of hemorrhage. TIVA with propofol and remifentanil is preferred. A lumbar drain provides CSF drainage and brain relaxation. During temporary clip application, burst suppression with propofol or thiopental may be used for neuroprotection during the period of highest ischemic risk. In rare cases, adenosine-induced brief cardiac arrest is used for controlled hypotension during difficult clip placement.

Vasospasm Management (Post-SAH)

The traditional triple-H therapy (hypertension, hypervolemia, hemodilution) has largely been replaced by euvolemia with induced hypertension using phenylephrine or norepinephrine infusion. Nimodipine, administered at 60 mg orally every 4 hours for 21 days, is the only calcium channel blocker with proven benefit in SAH. For refractory vasospasm, endovascular rescue with intra-arterial vasodilators (verapamil or nicardipine) or balloon angioplasty may be employed.

<image>Perioperative management timeline for a patient with subarachnoid hemorrhage undergoing aneurysm clipping. The timeline spans from ED presentation through ICU stay, with key interventions marked: initial blood pressure control and airway management, angiographic diagnosis, surgical clipping under TIVA with brain relaxation techniques, and postoperative vasospasm surveillance period (days 3-14). Nimodipine dosing, hemodynamic targets, and vasospasm treatment options are annotated at their respective time points.</image>

Anesthesia for Arteriovenous Malformation (AVM) Surgery

Key Concerns

AVMs are high-flow vascular lesions carrying the risk of massive hemorrhage. The surrounding brain may have impaired autoregulation, producing a "steal" phenomenon. After resection, normal perfusion pressure breakthrough (NPPB) can occur -- a sudden hyperperfusion of surrounding brain tissue that can cause edema or hemorrhage. A staged approach with embolization followed by surgical resection is common.

Anesthetic Management

Preparation includes large-bore IV access, an arterial line, and consideration of a central line. Blood products must be immediately available. Controlled hypotension to a MAP of 60 to 70 mmHg may be requested during resection. After resection, blood pressure is controlled to prevent NPPB, targeting a systolic blood pressure below 120 to 130 mmHg. Postoperative ICU monitoring with neurologic checks is essential, with readiness for emergent return to the operating room.

Clinical Pearls

For EVT, the most important anesthetic consideration is avoiding hypotension; MAP decline > 10-20% from baseline is associated with worse neurologic outcomes regardless of anesthetic technique. GA is not inferior to conscious sedation for EVT when hemodynamic targets are rigorously maintained; do not reflexively choose CS just because older observational data suggested it was better. Time is the most critical factor in acute stroke management; never delay groin puncture for anesthetic setup. During aneurysm clipping, temporary clip application is the period of highest ischemic risk; consider burst suppression with propofol for neuroprotection. After SAH, vasospasm peaks at days 4-14; maintain euvolemia and use induced hypertension (not hypervolemia) as first-line treatment. Normocarbia is critical during stroke cases; hyperventilation reduces penumbral blood flow and may worsen outcomes.

References

• Schonenberger S, Uhlmann L, Hacke W, et al. Effect of conscious sedation vs general anesthesia on early neurological improvement among patients with ischemic stroke undergoing endovascular thrombectomy: the SIESTA randomized clinical trial. JAMA. 2016;316(19):1986-1996.
• Lowhagen Henden P, Rentzos A, Geijer B, et al. General anesthesia versus conscious sedation for endovascular treatment of acute ischemic stroke: the AnSTROKE trial. Stroke. 2017;48(6):1601-1607.
• Simonsen CZ, Yoo AJ, Sorensen LH, et al. Effect of general anesthesia and conscious sedation during endovascular therapy on infarct growth and clinical outcomes in acute ischemic stroke: the GOLIATH randomized clinical trial. JAMA Neurology. 2018;75(4):470-477.
• Powers WJ, Rabinstein AA, Ackerson T, et al. Guidelines for the early management of patients with acute ischemic stroke. Stroke. 2019;50(12):e344-e418.
• Connolly ES, Rabinstein AA, Carhuapoma JR, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage. Stroke. 2012;43(6):1711-1737.

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