Craniotomy for intracranial aneurysm

Craniotomy for intracranial aneurysm

Anesthesia type	General
Airway	ETT
Lines and access	PIV x2 Arterial line ± Central line
Monitors	Standard ASA 5-lead EKG Core temp UOP ABG ±CVP Neuromonitoring
Primary anesthetic considerations
Preoperative	Characterize neurologic deficits Controlled hypotension
Intraoperative	Smooth induction Controlled hypotension Have adenosine available Decrease CRMO2 Manage ICP
Postoperative	PONV
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Editor rating	Comprehensive
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A craniotomy for an intracranial aneurysm is a neurosurgical procedure performed to surgically treat intracranial aneurysms to prevent or manage rupture, which can be life-threatening.

Overview

Background

• Intracranial aneurysms are defects of arterial walls which can occur at any of the major bifurcations of the Circle of Willis.
• Most are treated endovascularly
• The Hess and Hunt scale predicts mortality based upon neuro exam findings:

Hunt-Hess Grading System for Aneurysmal Subarachnoid Hemorrhage
Grade	Description	Mortality
I	Asymptomatic, mild headache, slight neck stiffness	2%
II	Moderate-to-severe headache, neck stiffness, no neurologic deficit (other than cranial nerve palsy)	5%
III	Drowsiness, confusion, mild focal neurologic deficit	15-20%
IV	Stupor, moderate-to-severe hemiparesis	30-40%
V	Coma, decerebrate posturing	50-80%

Indications

• Complex aneurysms which cannot be definitively treated endovascularly

Surgical procedure

• The procedure is performed through a craniotomy
• For cerebral aneurysms, approach is typically through the sylvian fissure to expose the circle of Willis
• Aneurysms are treated using microsurgical clip ligation, which attempts to isolate defective aneurysmal wall and preserve flow through the vessel

Preoperative management

Patient evaluation

System	Considerations
Airway	If acute, consider RSI
Neurologic	Distinguish whether aneurysm has ruptured or not Identify any neurologic deficits
Cardiovascular	Evaluate baseline blood pressure If ruptured: May be treated with vasodilator to maintain controlled hypotension May present with ST and T-wave changes, wall motion abnormalities, and elevated troponin Neurogenic stunned myocardium from catecholamines May be misdiagnosed as ACS

Intraoperative management

Monitoring and access

Standard ASA

5-lead ECG

Core temp

UOP

Arterial line

2-3 large bore IVs

Central line if poor peripherals access

Neuromonitoring

Induction and airway management

• Stable induction of general anesthesia and intubation with fentanyl, propofol, rocuronium, and +/- vasoactive agents to avoid hypo- and hypertension. Typically MAP >65 and SBP <140, however surgical team preferences can vary.
• Moderate hyperventilation (PaCO2 30 mmHg)
• For EEG burst suppression administer additional propofol boluses (50 mg) till burst suppression is achieved. Administer additional propofol boluses as needed to maintain burst suppression.

Maintenance and surgical considerations

Patients typically receive Cefazolin, 10 mg of decadron and 1 gm/kg of mannitol on skin incision (verify all with surgeon). Keppra 1g may also be utilized

Anesthesia can be maintained safely with many different medications, and can be guided primarily by other coexisting conditions.

• An isoflurane/N2O technique offers hemodynamic stability and quick wake up test if needed. This benefit is offset by increased risk of PONV and possibility for N2O closed space expansion.
• TIVA is a reasonable option however it may not allow for a rapid wake up test if needed
• Inhalational and intravenous combination may optimize rapid emergence if needed.
• One example could be propofol infusion (approximately 50mcg/kg/min), remifentanil infusion, vecuronium infusion, and sevoflurane
• Hemodynamic "uppers and downers" should be available. For example: esmolol, labatelol, nitroglycerine, nicardipine infusion. Phenylephrine, norepinephrine drip. Adenosine can also be utilized for temporary cessation of cardiac output if surgical team requests.

Potential complications

Intraoperative aneurysm rupture can happen at any time until the aneurysm is clipped. Aneurysm rupture is a true emergency that requires rapid interventions.

If the aneurysm is exposed and surgical team can attempt to clip it:

• Consider inducted hypotension with esmolol or similar short acting medications to reduce bleeding
• Consider temporary cardiac arrest with adenosine
• Reduce CMRO2 with propofol bolus and infusion
• Resuscitate as indicated with IVF or blood products

If the aneurysm is not exposed and surgical team can not readably clip it:

• Ensure CPP is optimized between CPP 50 to 70 mmHg, generally this would require increasing the MAP. Despite ongoing bleeding, brain perfusion is still critical
• Ensure adequate oxygenation and ventilation
• Decrease ICP with head elevation, mannitol, or hypertonics

Emergence

Goals are similar to other neurosurgical procedures, including a smooth emergence, avoiding hypertension, coughing, and straining. Intraoperative medications should be titrated down to allow for a rapid return to consciousness to permit neurologic examination prior to leaving the operating room. Alternatively, postoperative CT is sometimes utilized if a neurological exam can not be performed.