What is the recommended anesthesia approach for neurosurgery?

Neurosurgery Anesthesia Considerations

For neurosurgical procedures, use total intravenous anesthesia (TIVA) with propofol and short-acting opioids (remifentanil or fentanyl) as the preferred approach, as this technique reduces intracranial pressure (ICP) and improves cerebral perfusion pressure compared to volatile anesthetics. 1, 2

Anesthetic Technique Selection

Primary Recommendation: TIVA

• Propofol-based TIVA is superior to volatile anesthetics for intracranial procedures because it decreases ICP, increases cerebral perfusion pressure, and reduces cerebral metabolic rate for oxygen (CMRO2) 2, 3
• Volatile anesthetics (sevoflurane, desflurane) increase cerebral blood flow and ICP in a dose-dependent manner, making surgical access more difficult in patients with elevated ICP 2, 4
• Nitrous oxide should be avoided entirely as it stimulates cerebral metabolism and increases cerebral blood flow 3, 1

Induction Protocol

• High-dose opioid induction is essential: fentanyl 3-5 μg/kg, alfentanil 10-20 μg/kg, or remifentanil target-controlled infusion (TCI) with target concentration ≥3 ng/ml 1
• Neuromuscular blockade with rocuronium 1 mg/kg or succinylcholine 1.5 mg/kg 1
• In patients with elevated ICP, use slow bolus technique: administer propofol approximately 20 mg every 10 seconds rather than rapid bolus to avoid precipitous drops in mean arterial pressure and cerebral perfusion pressure 5
• Have vasoconstrictors (ephedrine or metaraminol) immediately available to treat hypotension 1

Maintenance Strategy

• Continue propofol infusion with remifentanil or fentanyl 6, 2
• Avoid volatile anesthetics entirely if ICP is elevated or cerebral compliance is compromised 2
• If volatile agents must be used, isoflurane at 0.5-1% is least detrimental, as it maintains autoregulation up to 1.5 MAC and causes minimal myocardial depression 4

Critical Monitoring Requirements

Mandatory Monitors

• Standard ASA monitors: ECG, SpO2, capnography, temperature 1
• Direct arterial blood pressure monitoring with transducer at the level of the tragus (not the phlebostatic axis) to accurately reflect cerebral perfusion pressure 1, 7
• Processed EEG monitoring (BIS) is mandatory when using TIVA with neuromuscular blockade to prevent awareness and guide anesthetic depth 1
• Quantitative neuromuscular monitoring whenever neuromuscular blocking drugs are used 1

Target Parameters

• For elderly patients (>60 years), target BIS approximately 50 to reduce postoperative delirium risk 1
• Avoid BIS <30 as excessively deep anesthesia increases delirium and mortality 1
• Maintain PaCO2 at 4.5-5.0 kPa (approximately 34-38 mmHg) with mild hypocapnia 1
• Avoid profound hypocapnia unless specifically needed for acute brain swelling control 1

Hemodynamic Management

Blood Pressure Control

• Frequent intraoperative BP monitoring and tight control are essential in patients with unsecured aneurysms to prevent both ischemia and rerupture 7
• Maintain normotension and euvolemia as baseline goals 1
• In patients with increased ICP, avoid significant decreases in mean arterial pressure as this reduces cerebral perfusion pressure 5
• Correct fluid deficits before propofol induction, or use vasopressors and leg elevation if additional fluids are contraindicated 5

ICP Management

• Mannitol or hypertonic saline are effective for reducing ICP and cerebral edema intraoperatively 7
• Mannitol causes diuresis and potential hypotension; hypertonic saline increases BP with minimal diuresis 7
• No evidence supports one hyperosmotic agent over the other 7
• Maintain isotonicity; avoid hypoosmotic fluids entirely 7
• Hyperventilation and hypocarbia should accompany propofol administration when increased ICP is suspected 5

Metabolic Goals

Glucose Management

• Prevention of both hyperglycemia and hypoglycemia during surgery is reasonable to improve outcomes 7
• Target blood glucose <10 mmol/L using intravenous insulin when needed 1

Additional Metabolic Considerations

• Maintain normothermia using active warming devices 1
• Monitor serum triglycerides during prolonged propofol infusions, especially in patients at risk for hyperlipidemia 5
• Propofol emulsion contains 0.1 g fat per mL (1.1 kcal); reduce concurrent lipid administration accordingly 5

Emergence and Recovery

Emergence Strategy

• Titrate anesthetic depth to facilitate rapid neurological examination immediately post-procedure 7
• Propofol's rapid clearance allows prompt awakening for early neurological assessment 2
• Minimize postprocedural pain, nausea, and vomiting as these increase ICP and aspiration risk 7
• Implement multimodal antiemetic prophylaxis (incidence of postoperative nausea/vomiting after craniotomy is 22-70%) 7

Special Considerations

Aneurysmal Subarachnoid Hemorrhage (aSAH)

• Intraoperative neuromonitoring may be reasonable to guide anesthetic and operative management 7
• Adenosine may be considered for uncontrolled intraoperative aneurysmal rupture to induce temporary cardiac standstill and facilitate clip placement 7
• Induced mild hypothermia during aneurysm surgery is NOT beneficial in good-grade aSAH patients 7

Endovascular Procedures

• Either general anesthesia or conscious sedation can be used; no evidence supports superiority of either approach 7
• General anesthesia provides better immobility and ventilatory control 7
• Conscious sedation allows real-time neurological testing but requires patient cooperation 7
• If using sedation, propofol and midazolam are equally effective 7

Common Pitfalls to Avoid

• Never use rapid bolus propofol administration in elderly, debilitated, or ASA III-IV patients during sedation, as this causes profound cardiorespiratory depression 5
• Do not abruptly discontinue propofol infusion during weaning from mechanical ventilation, as rapid awakening causes anxiety, agitation, and resistance to ventilation 5
• Avoid excessive depth of anesthesia (BIS <30) particularly in elderly patients 1
• Do not use nitrous oxide in neurosurgical cases 1, 3
• Ensure adequate reversal of neuromuscular blockade before extubation using quantitative monitoring 1