Craniotomy for extracranial-intracranial revascularization

Craniotomy for extracranial-intracranial revascularization

Anesthesia type	General
Airway	ETT
Lines and access	PIV x2 Arterial line
Monitors	Standard ASA 5-lead EKG Core temp UOP ABG EEG
Primary anesthetic considerations
Preoperative	Characterize neurologic deficits Consider anxiolytic
Intraoperative	Smooth induction Maintain CPP Maximize flow to ischemic areas Decrease CMRO2 Smooth extubation
Postoperative	Careful control of BP PONV prophylaxis
Article quality
Editor rating	Comprehensive
User likes	2

Craniotomy for extracranial-intracranial revascularization (also referred to as EC-IC bypass) is an intracranial procedure which augments cerebral blood flow by relocating an extracranial vessel intracranially.

Overview

Indications

An EC-IC bypass is performed when there is severe stenosis or occlusion of an intracranial artery. Some common scenarios include:

• Moya-moya disease
• Intracranial aneurysms which cannot be directly treated and require complete occlusion of the proximal artery

Surgical procedure

The procedure is performed through a craniotomy. The extracranial source is most commonly the superficial temporal artery, but other branches of the external carotid artery are possible. The temporalis muscle or omentum can also be used when using an external carotid branch is not preferred.

The extracranial source is then routed through the craniotomy, and revascularization is achieved in one of two approaches:

• "Direct", where the extracranial vessel is directly anastomosed to an intracranial vessel (typically to a branch of the middle cerebral artery)
• "Indirect", where the donor source is laid on the surface of the brain but not directly anastomosed, with the expectation that over time vascular growth will occur to provide additional flow to the brain.

Preoperative management

Patient evaluation

System	Considerations
Neurologic	Patients typically present with variable focal neurologic symptoms, which should be well characterized and documented
Cardiovascular	Hypertension is a common adaptive response to maintain CPP Normotension may be undesirable in the setting of severe cerebrovascular disease Patients are often treated with midodrine preoperatively to induce hypertension and improve CPP
Hematologic	Patients often on aspirin through day of surgery Anticoagulants impacting PT/PTT typically discontinued 1 week prior to surgery

Labs and studies

• EKG
• Echo (if concern for cardiovascular disease)
• Coronary angiography (depending on cardiac risk factors)
• Complete blood count
• Chemistry panel
• Coagulation panel
• Cerebral angiography performed to identify cause of neurologic symptoms

Operating room setup

• Infusion pumps
• If inducing hypothermia
  • Surface cooling device (i.e. cold-water circulating blanket)
  • Warming device
    • Patient will need aggressive rewarming post-anastomosis
    • Consider bladder irrigation, warm-water circulating blanket, forced warm air blanket
  • Consider central heat exchanger, especially if patient has high surface-to-volume ratio

Patient preparation and premedication

• Consider aprepitant if patient has history of severe PONV
• Avoid scopolamine for PONV, as it may confound post-op neurologic exams
• Anxiolysis typically reasonable

Regional and neuraxial techniques

• Avoid scalp blocks, as they may interfere with donor vessel blood flow

Intraoperative management

Monitoring and access

• Standard ASA monitors
• 5-Lead EKG
• Core temperature
• Urine output
• Arterial blood pressure
• EEG (particularly if inducing burst suppression)
• Central line typically not required

Induction and airway management

• Maintain controlled hypertension throughout induction (MAPs 90-110) to maintain cerebral perfusion pressure
  • One effective approach is to use high-dose narcotic (fentanyl 7-10 mcg/kg) and low-dose propofol (0.5 mg/kg)
    • Limits postinduction hypotension
    • Prevents hemodynamic response to laryngoscopy
  • Ephedrine may preserve cerebral blood flow better than phenylephrine
• Muscle relaxant may require reversal if neuromonitoring is used

Positioning

• Supine
• Table turned 180
• Mayfield skull fixation
  • Prior to pinning, a remifentanil bolus (2-4mcg/kg) is useful to minimize hemodynamic lability
• Shoulder roll

Maintenance and surgical considerations

• Anesthesia is typically maintained with a combination of a general anesthetic and remifentanil
• Controlled hypertension (MAPs 90-110) to preserve cerebral perfusion pressure
  • Ephedrine boluses may be preferable to improve cerebral blood flow and avoid reflexive bradycardia
  • Phenylephrine infusion typically used to maintain CPP during procedure
• Normocarbia
  • Cerebral vasoconstriction from hypocarbia may lead to cerebral ischemia in these patients
• Normovolemia
• Dexamethasone useful to reduce intracranial swelling and decrease PONV
• Some centers use mild hypothermia (33-34°C) to decrease cerebral metabolic rate and increase tolerance to ischemia
• Preincision antibiotics
• If performing a direct anastomosis
  • Some centers use mild hypothermia (33-34 °C) for cerebral protection
  • Establish burst suppression (propofol 1mg/kg) immediately prior to cross clamping of cerebral artery
    • Theoretical benefit of decreasing cerebral metabolic rate and increasing tolerance for ischemia, though evidence is limited
    • A bolus dose of ephedrine and/or phenylephrine typically needed to counterbalance hypotensive effect of propofol

Emergence

• Controlled hypertension typically maintained in postoperative period even if direct anastomosis performed
  • Titrate vasoactive infusions down as anesthetic weaned
  • If excessive hypertension develop, beta-blockers (esmolol, labetalol) and/or vasodilators (clevidipine, SNP) may be needed to maintain control during emergence
• Long-acting opioids typically not needed and may interfere with postoperative neurologic examination
• Consider IV acetaminophen
• Consider emergence and extubation on low-dose remifentanil (0.05 mcg/kg/min) to minimize bucking and hemodynamic lability

Postoperative management

Disposition

• ICU (typically monitored overnight in ICU)
• Supplemental O2
• Head of bed at 20-30°
• Tight BP monitoring and management post-op (typically maintain at baseline levels)
• Regular neuro checks post-op

Pain management

• Multimodal pain management
• Consider acetaminophen
• Avoid scalp blocks, as they can interfere with donor vessel blood flow

Potential complications

• Seizures
• Stroke
• Hemorrhage at anastomosis
• Brain swelling can be caused by hyperemia in revascularized areas

Procedure variants

	"Direct" revascularization	"Indirect" revascularization
Unique considerations	Involves temporary clipping of intracranial vessel to perform anastomosis Cerebral protection strategies may include burst suppression and mild hypothermia
Surgical time	↑	↓
Potential complications	Cerebral infarction