Anaesthesia for Awake Craniotomy

Quick Answer

Awake craniotomy allows direct cortical mapping of speech, motor, and sensory areas during resection of lesions near eloquent cortex. Indications: Low-grade gliomas, epileptogenic foci, deep brain stimulation electrode placement. Techniques: Asleep-awake-asleep (AAA - most common), awake-awake-awake (AAA with monitored anaesthesia care), asleep-awake (no return to GA). Key anaesthetic challenges: Airway management with head pinned (LMA preferred over ETT for asleep phases), smooth emergence, managing patient comfort/anxiety, seizure control during mapping, haemodynamic stability. Dexmedetomidine is the ideal sedative (anxiolysis without respiratory depression, easily arousable). Local anaesthesia: Scalp block (supraorbital, supratrochlear, zygomaticotemporal, auriculotemporal, lesser/greater occipital, great auricular) by surgeon or anaesthetist. Mapping: Direct cortical stimulation (identifies speech/motor areas), patient performs tasks (counting, naming, motor function). Complications: Seizures (2-20%, treat with cold saline, propofol), nausea/vomiting (ondansetron, dexamethasone), pain, airway compromise, tension pneumocephalus. [1-15]

Pathophysiology

Neurosurgical Indications

Primary Indications:

1. Eloquent Cortex Tumors:

• Location: Language areas (Broca's, Wernicke's), motor cortex, somatosensory cortex
• Tumor types: Low-grade gliomas (most common), meningiomas, metastases
• Goal: Maximal safe resection (preserve function while removing tumor)
• Outcome: Extent of resection correlates with survival in low-grade gliomas

2. Epilepsy Surgery:

• Lesionectomy: Removal of epileptogenic focus with functional mapping
• Cortical resection: Tailored resection based on electrocorticography (ECoG)
• Hemispherectomy: Rare (pediatric, severe epilepsy)

3. Deep Brain Stimulation (DBS):

• Targets: Subthalamic nucleus (Parkinson's), globus pallidus interna, thalamus
• Requirement: Patient awake for microelectrode recording and test stimulation
• Verification: Clinical response confirms correct electrode placement

4. Vascular Lesions:

• AVMs near eloquent cortex: Resection with functional preservation
• Cavernomas: Language/motor area lesions

Brain Plasticity Considerations:

• Reorganization: Brain can remap functions (especially in slow-growing tumors)
• Low-grade gliomas: Allow plasticity due to slow growth; function may have shifted
• High-grade tumors: Less plasticity (rapid growth, less adaptation)
• Pediatric: Greater plasticity than adult

Asleep-Awake-Asleep Technique

Phase 1: Asleep (Induction to Craniotomy):

• Induction: Standard GA (propofol/remifentanil or volatile)
• Airway: LMA (preferred) or ETT
• Positioning: Supine or lateral (depending on lesion), Mayfield head holder applied
• Monitoring: Standard + arterial line (BP control critical)
• Procedure: Scalp block, craniotomy, dural opening
• Duration: 1-3 hours typically

Phase 2: Awake (Mapping and Resection):

• Transition: Stop propofol/remifentanil, allow emergence
• LMA removal: When patient responsive, airway reflexes intact
• Patient state: Awake, cooperative, comfortable
• Monitoring: Continuous (ECG, SpO₂, NIBP, EtCO₂ if nasal cannula)
• Procedure: Cortical mapping, tumor resection, neurological testing
• Duration: 1-4 hours (variable)
• Adjuncts: Local scalp infiltration (bupivacaine), dexmedetomidine (0.2-0.7 μg/kg/hour), remifentanil (low-dose 0.02-0.05 μg/kg/min)

Phase 3: Asleep (Closure):

• Re-induction: Propofol/remifentanil or volatile
• Airway: LMA reinsertion or mask ventilation temporarily
• Monitoring: Continue arterial line
• Procedure: Hemostasis, dural closure, bone flap replacement, scalp closure
• Duration: 30-60 minutes
• Emergence: Controlled, smooth, avoid coughing/straining

Cortical Mapping Physiology

Direct Cortical Stimulation (DCS):

• Technique: Bipolar electrode, 50-60 Hz, 1-6 mA, pulse duration 0.3-1 ms
• Mapping: Systematic grid over exposed cortex
• Positive areas: Speech arrest, motor response, sensory phenomena (numbness, tingling)
• Negative mapping: Identify eloquent areas by observing function disruption
• Interpretation: Areas producing dysfunction cannot be resected

Speech Mapping:

• Tasks: Counting (1-20), naming objects (pictures), reading, repetition
• Speech arrest: Stimulation prevents speech production (Broca's area)
• Comprehension loss: Cannot name objects despite attempt (Wernicke's area)
• Anomia: Cannot retrieve names (temporal language areas)

Motor Mapping:

• Tasks: Hand/foot movements, tongue protrusion, facial movements
• Response: Contralateral muscle contraction (twitch)
• After-discharges: Seizure-like activity (stop stimulation immediately)

Sensory Mapping:

• Response: Numbness, tingling in contralateral distribution
• Localization: Somatotopic organization (Penfield homunculus)

Limitations:

• Depth: DCS only stimulates superficial cortex (2-3 mm)
• Subcortical: Cannot map white matter tracts directly (subcortical stimulation possible)
• False negatives: Deep tumors may affect function not detected on surface
• Patient factors: Cooperation essential, language barriers, cognitive impairment

Seizure Physiology and Management

Types:

1. Focal Motor Seizure:

• Trigger: Cortical stimulation, manipulation near motor cortex
• Manifestation: Rhythmic clonic movements (face, hand, arm)
• Awareness: Patient usually aware initially
• Spread: May become generalized

2. Focal Impaired Awareness:

• Manifestation: Confusion, unresponsiveness, automatisms
• Risk: Airway obstruction, awareness lost

3. Generalized Tonic-Clonic:

• Trigger: Spread from focal or direct cortical irritation
• Manifestation: Tonic phase (rigidity) → clonic phase (rhythmic jerking)
• Risks: Airway obstruction, tongue injury, desaturation, patient injury

Treatment:

1. Stop stimulation: Immediate cessation
2. Cold saline: Irrigation of cortex (rapid cessation of focal seizures)
3. Propofol: 25-50 mg IV (anticonvulsant properties)
4. Midazolam: 2-4 mg IV (if propofol ineffective)
5. Airway protection: Turn head, suction, supplemental O₂
6. Protect patient: Remove dangerous objects, pad bed rails

After-discharges:

• Definition: Electrical seizure activity on ECoG without clinical manifestations
• Significance: Indicator of cortical irritability, warning of clinical seizure
• Action: Stop stimulation, irrigate with cold saline

Clinical Presentation

Preoperative Assessment

History:

• Neurological: Seizure history (type, frequency, triggers), baseline deficits (document carefully), language dominance (usually left hemisphere), cognitive function
• Psychological: Anxiety, claustrophobia, depression (predict cooperation), previous surgical experience
• Medical: Comorbidities (cardiac, respiratory - may preclude awake procedure), obstructive sleep apnea (airway risk), GERD (aspiration risk)
• Social: Language barriers, hearing impairment, vision deficits
• Medications: Antiepileptics (continue), steroids (if mass effect), antihypertensives

Physical Examination:

• Airway: Assessment (difficult airway may preclude awake procedure or require ETT instead of LMA)
• Neurological: Complete exam (document deficits - new deficits post-op may be pre-existing)
• Cognitive: Orientation, memory, attention span (predict cooperation)
• Cardiovascular: Baseline BP (hypertension risk), arrhythmia

Investigations:

• MRI: Tumor location, relation to eloquent areas, edema, midline shift
• fMRI: Language lateralization, motor/sensory cortex mapping (preoperative planning)
• DTI (Diffusion Tensor Imaging): White matter tracts (corticospinal tract, arcuate fasciculus)
• MEG (Magnetoencephalography): Additional functional mapping (rare)
• Wada test: Language/memory dominance (if fMRI inconclusive, rare now)
• ECoG grid: If epilepsy surgery (preoperative grid placement possible)
• ECG: Baseline
• Blood work: FBC, coagulation, electrolytes, creatinine, LFTs

Psychological Preparation:

• Patient education: Detailed explanation of procedure (expectations reduce anxiety)
• Simulation: Practice lying still, performing tasks (counting, object naming)
• Visualization: Video of awake craniotomy process
• Family involvement: Support person for preoperative period
• Anaesthesia consultation: Meet anaesthetist, discuss sedation plan

Patient Selection Criteria

Ideal Candidates:

• Cooperative: Able to follow commands, stay still
• Psychologically stable: Can handle stress of awake neurosurgery
• No language barriers: Fluent in language of testing
• No severe comorbidity: Cardiac/respiratory disease controlled
• Appropriate age: Adult (children rarely cooperative enough)
• Understanding: Comprehends procedure and can provide consent

Contraindications:

• Absolute: Patient refusal, inability to cooperate (cognitive impairment, severe anxiety), language barrier without interpreter, young children
• Relative: Severe OSA (airway risk), morbid obesity (difficult airway, hypoventilation), significant cardiopulmonary disease (tolerate GA better), GERD with aspiration risk, difficult airway anatomy (may convert to ETT technique)

Alternative Approaches:

• Motor mapping under GA: Phase reversal technique, cortical stimulation with EMG
• High-field intraoperative MRI: Localization without awake mapping (less precise)
• Functional neuronavigation: fMRI/DTI overlay on surgical navigation
• Cortical stimulation with short-acting anaesthetic: Dexmedetomidine-based technique without full awakening

Management

Asleep-Awake-Asleep Technique

Preoperative:

• Premedication: Avoid heavy sedation (masks neurological assessment)
  • Consider: Paracetamol 1 g (analgesia), ondansetron 4 mg (prophylaxis), dexamethasone 8 mg (edema, nausea)
  • Avoid: Benzodiazepines (impair cooperation), opioids (respiratory depression)
• Antiepileptics: Continue (maintain therapeutic levels)
• Scalp block: Can be performed by surgeon after draping or by anaesthetist pre-induction
  • Nerves: Supraorbital, supratrochlear, zygomaticotemporal, auriculotemporal, lesser/greater occipital, great auricular
  • Local anaesthetic: Bupivacaine 0.25-0.5% with adrenaline (vasoconstriction, prolonged duration)

Phase 1: Asleep (Induction to Craniotomy)

Induction:

• Pre-oxygenation: 100% O₂, 3-5 minutes
• Agents: Propofol 2-3 mg/kg + remifentanil 0.5-1 μg/kg (or fentanyl 2-3 μg/kg)
• Muscle relaxation: Rocuronium 0.6 mg/kg (or suxamethonium if RSI)
• Airway: LMA insertion (Classic, ProSeal, or Supreme)
  • Advantages: Easy emergence/removal, less coughing than ETT, airway protection adequate
  • Contraindications: Severe OSA, morbid obesity, GERD (consider ETT)
• Positioning: Mayfield head holder pins (local anaesthetic infiltration at pin sites)
• Monitoring: Arterial line (essential), standard monitors

Maintenance:

• TIVA: Propofol infusion 100-200 μg/kg/min + remifentanil 0.05-0.2 μg/kg/min
  • Easy titration for emergence
  • Anticonvulsant properties (propofol)
  • Rapid clearance
• Ventilation: Controlled, normocapnia (PaCO₂ 35-40 mmHg)
  • Avoid hypocapnia (cerebral ischemia)
  • Avoid hypercapnia (cerebral vasodilation, increased ICP)
• Hemodynamics: Target MAP 70-80 mmHg (cerebral perfusion)
  • Labetalol or hydralazine for hypertension
  • Phenylephrine for hypotension
• Temperature: Maintain normothermia (forced air warming)
• Mannitol: 0.5 g/kg before dural opening (brain relaxation)

Transition Preparation (30-60 minutes before wake-up):

• Reduce TIVA: Gradually decrease propofol to 50-100 μg/kg/min, remifentanil to 0.02-0.05 μg/kg/min
• Load dexmedetomidine: 1 μg/kg over 10 minutes (if not already started), then 0.2-0.7 μg/kg/hour
• Anti-emetics: Ondansetron 4-8 mg, dexamethasone 8 mg
• Analgesia: Ensure scalp block effective (reduces opioid need)
• Position: Head elevated 15-30° (reduces venous engorgement, ICP)

Phase 2: Awake (Mapping and Resection)

Emergence Protocol:

1. Stop propofol: 10-15 minutes before wake-up
2. Remifentanil: Continue low-dose (0.02-0.05 μg/kg/min) or stop
3. Dexmedetomidine: Continue 0.2-0.7 μg/kg/hour (anxiolysis without respiratory depression)
4. LMA removal: When patient responsive, opens eyes, follows commands
   • Suction oropharynx
   • Deflate cuff, remove LMA
   • Place nasal cannula (O₂ 2-4 L/min, EtCO₂ monitoring if available)
5. Position: Ensure comfortable, head immobilized (Mayfield), drapes allow visualization
6. Communication: Establish communication protocol (hand signals, speech)

Awake Phase Management:

• Sedation: Dexmedetomidine is ideal (easily arousable, no respiratory depression)
  • Dose: 0.2-0.7 μg/kg/hour (titrate to Ramsay 2-3)
  • Alternative: Remifentanil 0.02-0.05 μg/kg/min (more respiratory depression risk)
• Analgesia: Scalp block primary, supplemental fentanyl 25-50 μg PRN (avoid oversedation)
• Nausea: Ondansetron 4 mg IV PRN, dexamethasone 8 mg (already given)
• Seizure prophylaxis: Cold saline available, propofol 25-50 mg IV PRN
• Anxiolysis: Reassurance, nurse/anaesthetist at head, music (patient preference)
• Monitoring: Continuous ECG, SpO₂, NIBP q15min, temperature

Mapping Phase:

• Surgeon communicates: Explains each step to patient
• Neuropsychologist: Administers language tests
• Tasks: Continuous counting (1-20), naming objects shown on cards, motor tasks
• Seizure management: Ready to treat (see above)
• Communication: Patient signals if uncomfortable, nauseous, tired

Resection Phase:

• Patient comfort: Ensure not overly tired (breaks allowed)
• Continuous testing: Regular language/motor assessments
• New deficit: Stop resection immediately if function lost
• Duration: As long as patient tolerates (typically 1-4 hours)

Phase 3: Asleep (Closure)

Re-sedation:

1. Increase propofol: 1-2 mg/kg bolus, then 100-200 μg/kg/min
2. Remifentanil: 0.1-0.2 μg/kg/min
3. Airway: LMA reinsertion (or mask ventilation temporarily if brief closure)
4. Position: Ensure comfortable, pressure points padded

Closure:

• Duration: 30-60 minutes typically
• Hemostasis: Critical (awake patient cannot be emergently intubated as easily)
• Bone flap: Replace or store (infection risk if tumor)

Emergence:

• Goal: Awake, comfortable, neurological exam possible
• Analgesia: Paracetamol, NSAIDs (if appropriate), morphine PRN
• Antiemetics: Continue prophylaxis
• Extubation: If LMA used, remove when awake; if ETT, standard extubation criteria

Alternative Techniques

Asleep-Awake (No Return to GA):

• Indication: Short procedures (biopsy, DBS), patient tolerant
• Technique: Asleep phase for exposure, awake for procedure, remain awake for closure
• Advantage: Avoids second emergence
• Disadvantage: Patient must tolerate closure (noise, pressure sensations)

Monitored Anaesthesia Care (MAC):

• Technique: No GA at any point
• Sedation: Dexmedetomidine ± remifentanil throughout
• Airway: Spontaneous ventilation, nasal cannula
• Patient: Awake or lightly sedated for entire procedure
• Advantage: Smooth throughout, no airway manipulation
• Disadvantage: Patient experiences opening, may move, less ideal for lengthy procedures

Endotracheal Tube Technique:

• Indication: Difficult airway, severe OSA, GERD risk, prolonged procedure
• Modification: Asleep phases with ETT, awake phase requires extubation then re-intubation
• Challenge: Re-intubation with head pinned and draped (difficult)
• Alternative: Laryngeal mask for awake phase (safer if reinsertion needed)

Complication Management

Seizures (Most Common Complication):

• Incidence: 2-20% depending on lesion location (motor cortex highest risk)
• Treatment:
  1. Stop stimulation immediately
  2. Irrigate cortex with cold saline (4°C) - highly effective for focal seizures
  3. Propofol 25-50 mg IV (additional anticonvulsant)
  4. Midazolam 2-4 mg IV if propofol fails
  5. Protect airway (turn head, suction)
  6. Supplemental O₂
• Generalized seizure:
  • Cold saline + propofol + midazolam
  • May need to convert to GA and intubate if prolonged
  • Check glucose (treat hypoglycemia)

Airway Compromise:

• Causes: Tongue edema (LMA compression), blood/secretions, seizure, oversedation
• Prevention: Head elevated, dexmedetomidine (less respiratory depression), excellent scalp block (reduces opioid need)
• Management:
  • Turn head to side, suction
  • Jaw thrust
  • Nasal/oral airway
  • Re-insert LMA (emergency airway with head pinned)
  • Rarely: Wake patient completely, convert to full airway control

Nausea and Vomiting:

• Incidence: 15-30%
• Risk factors: Posterior fossa surgery, opioid use, anxiety
• Prevention: Dexamethasone 8 mg, ondansetron 4-8 mg, propofol (antiemetic properties)
• Treatment: Additional ondansetron, droperidol 0.625-1.25 mg, metoclopramide 10 mg
• Consequence: Vomiting with open skull (risk of contamination, herniation)

Hypertension:

• Cause: Pain, anxiety, stimulation, dexmedetomidine (mild pressor effect at high doses)
• Risk: Intracranial hemorrhage, edema
• Management: Labetalol 5-20 mg IV, hydralazine 5-20 mg IV, GTN infusion
• Target: SBP <140-160 mmHg (balance with cerebral perfusion)

Pain:

• Sources: Scalp incision, dural traction, bone manipulation (vibration), prolonged positioning
• Management:
  • Excellent scalp block (prevents most pain)
  • Dexmedetomidine (reduces opioid requirements 30-50%)
  • Supplemental fentanyl 25-50 μg PRN
  • Local infiltration by surgeon if needed
• Contraindication: No nitrous oxide (pneumocephalus risk)

Tension Pneumocephalus:

• Cause: Nitrous oxide (if used), CSF drainage, air entry through dural opening
• Risk: Brain compression, delayed awakening, neurological deterioration
• Prevention: Avoid N₂O entirely
• Treatment: 100% O₂, head CT, urgent decompression if symptomatic

Venous Air Embolism:

• Cause: Open venous sinuses, head elevated (negative pressure)
• Detection: EtCO₂ decrease (if monitoring), precordial Doppler (if available)
• Treatment: Flood field, Trendelenburg position, aspiration via central line

Agitation/Delirium:

• Cause: Pain, anxiety, full bladder, uncomfortable position, seizure post-ictal state
• Prevention: Excellent analgesia, reassurance, comfortable position, empty bladder pre-op
• Management: Treat cause, increase dexmedetomidine, avoid benzodiazepines (delirium), calm voice, music

Conversion to General Anaesthesia:

• Indications: Seizure (prolonged, generalized), airway compromise unresolvable, severe agitation, massive hemorrhage
• Technique: Propofol bolus, remifentanil, re-insert LMA (or intubate if necessary)
• Challenge: Difficult with Mayfield pins and drapes; plan for this possibility

Indigenous Health Considerations

Aboriginal and Torres Strait Islander Patients

Access and Cultural Factors:

• Geographic barriers: Remote communities require transfer to metropolitan neurosurgical centres (Sydney, Melbourne, Brisbane, Perth)
• Cultural considerations: Awake craniotomy requires exceptional cooperation and communication; cultural factors may affect willingness/ability to participate
• Family involvement: Extended family may need to be present for consent and support

Health Disparities:

• Higher comorbidity: Diabetes, renal disease, hypertension may complicate anaesthetic management
• Communication: Ensure clear explanation in accessible language; interpreter services if needed
• Cultural safety: Aboriginal Liaison Officers essential for support

Practical Considerations:

• Language: Ensure patient fluent in English or interpreter available for complex commands during mapping
• Cultural protocols: Respect for Sorry Business, family decision-making processes
• Follow-up: Remote communities challenge postoperative surveillance (tumor recurrence, epilepsy management)
• Rehabilitation: Speech therapy, occupational therapy access limited in remote areas

Māori Health Considerations

Whānau and Cultural Context:

• Decision-making: Whānau involvement essential for informed consent for high-risk procedure
• Communication: Clear explanation of awake craniotomy process (unusual concept)
• Cultural support: Māori Health Workers involvement

Access Issues:

• Geographic: Neurosurgical services concentrated in Auckland, Wellington, Christchurch
• Rural Māori: May need inter-island transfer
• Equity: Ensure timely access to functional neurosurgery

Postoperative Considerations:

• Rehabilitation services: Coordination with primary care for ongoing therapy needs
• Surveillance: MRI follow-up for tumor recurrence may be challenging
• Cultural safety: Kaupapa Māori approaches to health and recovery

ANZCA Final Exam Focus

SAQ Patterns

Common Questions:

• "Describe the asleep-awake-asleep technique for awake craniotomy."
• "What are the anaesthetic challenges during the awake phase of craniotomy?"
• "How would you manage a seizure during cortical mapping?"
• "Compare the advantages and disadvantages of LMA vs ETT for awake craniotomy."
• "What is the role of dexmedetomidine in awake craniotomy?"

Marking Scheme Priorities:

• AAA technique phases and transitions
• Airway management (LMA preferred, dexmedetomidine advantages)
• Seizure management (cold saline, propofol)
• Scalp block techniques
• Complication prevention and management
• Patient selection criteria

Viva Scenarios

Scenario 1: Transition to Awake Phase

• Patient not waking appropriately after stopping propofol
• Check: Oversedation (decrease remifentanil), metabolic (glucose), neurological (stroke)
• Management: Reduce all sedatives, ensure patient comfort, consider delaying mapping

Scenario 2: Seizure During Mapping

• Focal motor seizure starts during speech mapping
• Immediate: Stop stimulation, cold saline irrigation, propofol 25-50 mg
• Airway protection, patient safety

Scenario 3: Airway Compromise in Awake Phase

• Patient becomes drowsy, SpO₂ falling, tongue obstruction
• Management: Reduce dexmedetomidine, head positioning, suction, re-insert LMA if needed

Scenario 4: Patient Refusal/Agitation

• Patient becomes uncooperative, refuses to continue
• Management: Calm reassurance, increase dexmedetomidine, identify cause (pain, nausea, anxiety), consider converting to GA if unable to continue

Key Points for Examination Success

1. Technique: Asleep-awake-asleep most common; allows maximal resection with functional preservation
2. Airway: LMA preferred (easier emergence/removal, less coughing); ETT for difficult airway/GERD/OSA
3. Sedation: Dexmedetomidine ideal (easily arousable, no respiratory depression, anxiolysis)
4. Scalp block: Essential for awake phase comfort; covers all scalp innervation
5. Seizure management: Stop stimulation, cold saline irrigation (highly effective), propofol 25-50 mg IV
6. Mapping: Direct cortical stimulation identifies eloquent areas; patient performs continuous tasks
7. Complications: Seizures (2-20%), nausea/vomiting (15-30%), airway compromise, hypertension
8. N₂O: Contraindicated (tension pneumocephalus risk)
9. Patient selection: Cooperative, psychologically stable, no severe comorbidity
10. Conversion to GA: Be prepared for emergency conversion (seizure, hemorrhage, airway compromise)

Assessment Content

SAQ 1: Asleep-Awake-Asleep Technique (20 marks)

Question: A 45-year-old right-handed man with a low-grade glioma in the left frontal lobe (near Broca's area) is scheduled for awake craniotomy with cortical mapping and maximal safe resection.

a) Describe the "asleep-awake-asleep" (AAA) technique for this procedure, including each phase and the anaesthetic management. (10 marks) b) What specific measures would you take to ensure patient comfort and cooperation during the awake phase? (6 marks) c) How would you manage a focal motor seizure that occurs during cortical mapping? (4 marks)

Model Answer:

a) AAA technique (10 marks):

Phase 1: Asleep (Induction to Craniotomy):

• Induction with propofol 2-3 mg/kg + remifentanil 0.5-1 μg/kg (1 mark)
• LMA insertion (preferred over ETT for easier emergence) (1 mark)
• Maintenance: TIVA with propofol 100-200 μg/kg/min + remifentanil 0.05-0.2 μg/kg/min (1 mark)
• Positioning: Supine, Mayfield head holder, scalp block performed (1 mark)
• Duration: 1-3 hours for craniotomy and dural opening

Phase 2: Awake (Mapping and Resection):

• Transition: Stop propofol 10-15 min before, continue dexmedetomidine 0.2-0.7 μg/kg/hour (1 mark)
• LMA removal when responsive, nasal cannula for O₂ delivery (1 mark)
• Patient awake, cooperative, performing language tasks (counting, naming) (0.5 marks)
• Duration: 1-4 hours for mapping and tumor resection

Phase 3: Asleep (Closure):

• Re-sedation: Propofol bolus 1-2 mg/kg + infusion, remifentanil (0.5 marks)
• LMA reinsertion for airway control (0.5 marks)
• Hemostasis, dural closure, bone flap replacement
• Controlled emergence for postoperative neurological assessment (0.5 marks)

b) Patient comfort and cooperation (6 marks):

• Scalp block: Complete blockade of all scalp nerves (supraorbital, supratrochlear, zygomaticotemporal, auriculotemporal, occipital, great auricular) with bupivacaine (1.5 marks)
• Dexmedetomidine: 0.2-0.7 μg/kg/hour (anxiolysis without respiratory depression, easily arousable) (1.5 marks)
• Positioning: Head elevated 15-30°, comfortable padding, ensure bladder empty pre-op (1 mark)
• Communication: Continuous reassurance, explain each step, neuropsychologist support (1 mark)
• Anti-emetics: Dexamethasone 8 mg, ondansetron 4-8 mg (0.5 marks)
• Music: Patient preference via headphones (0.5 marks)

c) Seizure management (4 marks):

• Stop stimulation immediately (1 mark)
• Irrigate cortex with cold saline (4°C) - highly effective for focal seizures (1.5 marks)
• Propofol 25-50 mg IV (additional anticonvulsant effect) (1 mark)
• Protect airway (turn head, suction, supplemental O₂) (0.5 marks)

SAQ 2: Airway Management and Complications (20 marks)

Question: A 52-year-old woman with a left temporal low-grade glioma undergoes awake craniotomy. During the awake phase, she becomes increasingly drowsy, her oxygen saturation drops to 88%, and you notice snoring respiration with tongue obstruction.

a) What is the differential diagnosis for this presentation? (4 marks) b) Outline your immediate management priorities. (8 marks) c) What strategies could have been employed to prevent this complication? (4 marks) d) If this patient requires re-establishment of general anaesthesia, how would you manage the airway given the Mayfield head pins and surgical drapes? (4 marks)

Model Answer:

a) Differential diagnosis (4 marks):

• Dexmedetomidine overdose (respiratory depression rare but possible with high doses) (1 mark)
• Remifentanil accumulation (respiratory depression, sedation) (1 mark)
• Tongue edema from LMA compression during asleep phase (1 mark)
• Seizure post-ictal state (1 mark)
• Full bladder causing discomfort and agitation/drowsiness
• Pain causing hypoventilation (less likely with good scalp block)

b) Immediate management (8 marks):

• Reduce/cessation of sedation: Stop dexmedetomidine and remifentanil immediately (1 mark)
• Airway maneuvers: Head positioning (elevated, chin lift/jaw thrust), turn head to side (1.5 marks)
• Suction: Clear oropharynx of secretions/blood (1 mark)
• Supplemental O₂: Increase to 100% via non-rebreather or assisted ventilation (1 mark)
• Nasal/oral airway: Insert if obstruction persists (1 mark)
• Continuous monitoring: SpO₂, EtCO₂ (if available), ECG, frequent BP (1 mark)
• Communication: Call for surgeon assistance, have emergency airway equipment ready (0.5 marks)
• Consider LMA reinsertion: If above measures fail and patient stable enough for brief manipulation (1 mark)

c) Prevention strategies (4 marks):

• Optimal scalp block: Reduces opioid requirements significantly (1 mark)
• Dexmedetomidine titration: Start low dose (0.2 μg/kg/hour), titrate carefully (0.5 marks)
• Head elevation: 15-30° throughout awake phase (reduces venous engorgement, improves respiratory mechanics) (0.5 marks)
• Minimize remifentanil: Use lowest effective dose or discontinue before wake-up (0.5 marks)
• Preoperative empty bladder: Catheterize if procedure >4 hours anticipated (0.5 marks)
• Patient selection: Avoid awake craniotomy in severe OSA, morbid obesity (0.5 marks)
• Anti-emetics: Prevent vomiting which worsens airway compromise (0.5 marks)

d) Emergency airway management with pins/drapes (4 marks):

• Communication with surgeon: Inform of need for airway intervention; may need to pause surgery (1 mark)
• LMA preferred: Easier to insert with limited access than ETT; can insert blindly or with laryngoscopy if partial access (1 mark)
• Alternative: Nasopharyngeal airway + bag-mask ventilation temporarily if LMA not feasible (0.5 marks)
• Drugs: Propofol 1-2 mg/kg + remifentanil to facilitate LMA insertion (0.5 marks)
• Backup plan: Surgeon may need to release Mayfield pins temporarily if desperate (rarely needed) (0.5 marks)
• Post-intubation: Secure airway carefully; consider leaving LMA in place until closure complete (0.5 marks)

Viva Scenario: Failed Wake-up

Examiner: "You are performing an awake craniotomy. After stopping propofol for the transition to awake phase, the patient is not waking appropriately at 20 minutes. What is your approach?"

Candidate: "I would first assess why the patient isn't waking. I'd check my drug infusions to ensure propofol is completely stopped and remifentanil is at a low dose. I'd check the patient's glucose to exclude hypoglycemia. I'd assess for any neurological issues - the surgery is for a brain tumor, so I need to consider whether there's been a surgical complication like bleeding or stroke causing the delayed awakening."

Examiner: "The glucose is normal, drug infusions are off, but the patient remains unresponsive. What next?"

Candidate: "This is concerning for a neurological event. I would inform the surgeon immediately and request they assess for surgical complications - intracranial hemorrhage, major vessel injury, or significant edema. I would obtain an urgent CT scan if the patient remains unresponsive. Meanwhile, I would ensure the airway is secure - if the LMA is still in place, I'd maintain ventilation, ensure oxygenation, and provide supportive care while we investigate the cause."

Examiner: "How would this affect the surgical plan?"

Candidate: "If the patient cannot be awakened for cortical mapping, the primary advantage of the awake technique is lost. The surgeon would need to decide whether to proceed with resection without functional mapping - accepting higher risk of neurological injury - or to abort the procedure and reschedule. If imaging shows hemorrhage or stroke, emergency neurosurgical intervention would be required. The decision would depend on the clinical status, imaging findings, and patient/family wishes."

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