Parotidectomy and facial nerve monitoring

Surgical approach

Indications: benign tumours (e.g. pleomorphic adenoma), malignant tumours, chronic infection/sialadenitis, diagnostic excision
Incision: modified Blair (pre-auricular, around lobule, into upper neck) ± facelift-style incision
Raising skin flap; identify landmarks for facial nerve trunk (tragal pointer, posterior belly of digastric, tympanomastoid suture)
Dissection options
- Superficial parotidectomy: remove superficial lobe, preserve facial nerve branches
- Total parotidectomy: superficial + deep lobe; higher risk to facial nerve; may involve neck dissection
- Radical parotidectomy: sacrifice facial nerve if involved by malignancy; may require nerve grafting/reanimation
Haemostasis close to nerve; drain placement (e.g. suction drain); closure
Potential complications: facial nerve paresis, haematoma, salivary fistula/seroma, Frey’s syndrome, infection, cosmetic deformity

Anaesthetic management (overview)

Type of anaesthesia: General anaesthesia (standard). Regional techniques are adjuncts (superficial cervical plexus block/local infiltration) for analgesia.
Airway: ETT preferred (secure airway; head turned; long surgical time; facial nerve monitoring considerations). SGA generally avoided.
- Use reinforced (armoured) ETT if significant head rotation/neck flexion anticipated.
Duration: typically 1.5–4 hours (longer if total/radical parotidectomy ± neck dissection/reconstruction).
Pain: moderate (skin flap + deep dissection). Often manageable with paracetamol + NSAID (if appropriate) + small opioid doses; consider local infiltration/blocks.
Key anaesthetic constraint: avoid/limit neuromuscular blockade to permit facial nerve EMG monitoring; plan intubation strategy accordingly.
Position: supine, head turned away; ensure ETT secure, eyes protected, pressure areas padded; avoid excessive neck rotation (venous congestion).

Pre-operative assessment

History: tumour type/size, symptoms of malignancy (pain, rapid growth, facial weakness), previous surgery/radiotherapy, OSA risk, reflux/aspiration risk.
Airway assessment: limited mouth opening, dentition, neck mobility; consider difficult airway if large mass, prior radiotherapy, or planned neck dissection.
Comorbidity: cardiovascular/respiratory; anticoagulants/antiplatelets (bleeding/haematoma risk); diabetes (wound healing).
Baseline facial nerve function documented (important for consent and post-op assessment).
Discuss facial nerve monitoring plan with surgeon: whether continuous EMG, stimulation mapping, and how they want NMB managed.

Facial nerve monitoring: principles and practicalities

Purpose: identify facial nerve, reduce risk of iatrogenic injury, assist mapping of branches, and provide warning of traction/thermal injury (not a guarantee).
Typical modality: EMG recording from facial muscles + intermittent electrical stimulation of suspected nerve tissue.
- Recording: needle electrodes in orbicularis oculi and orbicularis oris (± mentalis/frontalis depending on system).
- Stimulation: handheld probe delivering brief current; EMG response indicates proximity/identity of nerve.
Anaesthetic implications: EMG requires intact neuromuscular transmission; volatile agents and propofol are acceptable; avoid deep NMB.
- If paralysis present, EMG response may be absent → false reassurance.
- If light anaesthesia, patient movement may occur because NMB is limited → need careful depth/analgesia.
Interference/artefact: electrocautery causes artefact; poor electrode contact; drying; dislodgement with head movement; hypothermia can alter signals.
Safety: needle electrodes are invasive (bleeding/infection risk); caution in anticoagulated patients; ensure sharps handling and documentation.

Neuromuscular blockade strategy (core FRCA topic)

Goal: facilitate intubation and surgical conditions while allowing reliable facial EMG monitoring during dissection.
Common approaches
- Single intubating dose of non-depolarising NMBA (e.g. rocuronium 0.3–0.6 mg/kg) then allow to wear off; avoid top-ups.
- Suxamethonium for intubation then no further NMBA (beware myalgia, bradycardia, hyperkalaemia, MH risk).
- High-dose rocuronium for RSI with planned reversal using sugammadex before monitoring begins (requires coordination and cost consideration).
Monitoring: use quantitative neuromuscular monitoring (e.g. TOF at ulnar nerve) to document recovery before nerve monitoring is required.
- Aim for minimal/no block when surgeon starts facial nerve stimulation (often TOF ratio ~0.9 at adductor pollicis; note facial muscles recover earlier than adductor pollicis).
If movement problematic: deepen anaesthesia (propofol/volatile), optimise analgesia (opioid, local infiltration), consider short-acting NMBA only if surgeon accepts temporary loss of monitoring.

Intra-operative anaesthetic technique

Induction: standard IV induction; plan for limited NMBA; ensure good IV access; consider arterial line if major resection/neck dissection, significant comorbidity, or expected blood loss.
Maintenance: volatile (sevoflurane/desflurane) or TIVA (propofol/remifentanil) both compatible with EMG monitoring.
- TIVA can reduce PONV and may provide stable conditions when avoiding NMBA (remifentanil useful).
Analgesia: paracetamol + NSAID (if not contraindicated) + opioid titration; consider local infiltration by surgeon; consider superficial cervical plexus block as adjunct (operator-dependent).
PONV prophylaxis: moderate–high risk (head and neck surgery, opioids). Use multimodal prophylaxis (e.g. dexamethasone + ondansetron ± droperidol).
Antibiotics: per local policy (often given due to clean-contaminated potential and drains).
Temperature: active warming; hypothermia increases bleeding and delays drug metabolism.
Local vasoconstrictor infiltration: surgeon may use adrenaline-containing local anaesthetic; anticipate transient tachycardia/hypertension; communicate before injection.

Airway and extubation considerations

Extubation strategy: aim for smooth extubation to reduce venous pressure and bleeding/haematoma (lidocaine, opioid titration, consider deep extubation only if appropriate and safe).
Haematoma risk: neck swelling can threaten airway; ensure surgeon satisfied with haemostasis; consider short period of observation in theatre before leaving if concern.
Drain: ensure secured and not kinked; document output expectations and post-op plan.
Post-op destination: day-case possible for limited superficial parotidectomy in selected patients; otherwise ward/HDU if extensive surgery, OSA, major comorbidity, or airway concern.

Post-operative care and complications

Pain control: regular paracetamol ± NSAID; opioids as needed; avoid oversedation in OSA.
Facial nerve dysfunction: assess and document early; eye protection if incomplete eyelid closure (lubrication, tape, ophthalmology advice).
Bleeding/haematoma: increasing pain, swelling, dysphagia, voice change, stridor; urgent surgical review; prepare for airway management.
PONV: treat promptly to avoid retching/bleeding; consider rescue antiemetic from different class.
Other: seroma/salivary fistula, infection, Frey’s syndrome (late), numbness (great auricular nerve).

You are anaesthetising a patient for superficial parotidectomy with facial nerve monitoring. Outline your anaesthetic plan.

Structure: pre-op assessment → airway/positioning → monitoring/NMB plan → maintenance/analgesia → extubation/post-op.

GA with ETT; secure tube well due to head turn; protect eyes and pressure points; consider reinforced ETT.
Plan minimal NMBA: either sux for intubation then none, or single dose rocuronium and allow to wear off; quantify TOF recovery before monitoring required.
Maintenance with volatile or TIVA; ensure adequate depth/analgesia to prevent movement when not paralysed (e.g. remifentanil infusion).
Analgesia: paracetamol ± NSAID; opioid titration; surgeon local infiltration/± superficial cervical plexus block.
PONV prophylaxis; smooth extubation; vigilance for post-op haematoma and facial weakness; eye care if needed.

Explain how facial nerve monitoring works and how anaesthesia can affect it.

Core points: EMG recording + stimulation; requires intact neuromuscular transmission; artefact sources.

EMG electrodes in facial muscles record activity; surgeon stimulates suspected nerve tissue and observes EMG response.
Neuromuscular blockers reduce/abolish EMG response → false negative; therefore avoid top-ups and confirm recovery with quantitative TOF.
Volatile agents/propofol do not abolish EMG but deep anaesthesia reduces movement; opioids help provide immobility when NMBA is limited.
Electrocautery and poor electrode contact cause artefact; ensure correct placement and secure leads before draping.

How would you manage neuromuscular blockade for intubation while ensuring reliable facial nerve monitoring during surgery?

Discuss options and how you would coordinate timing with the surgeon.

Option 1: suxamethonium for intubation then no further NMBA; maintain immobility with adequate hypnotic + opioid (e.g. remifentanil).
Option 2: low/moderate-dose rocuronium for intubation, no top-ups; allow spontaneous recovery; verify with quantitative TOF before monitoring begins.
Option 3: RSI with rocuronium and reverse with sugammadex before nerve dissection; confirm recovery and communicate with surgeon.
If movement occurs: deepen anaesthesia/analgesia first; only consider NMBA bolus if surgeon agrees to temporary loss of monitoring.

The surgeon complains that facial nerve stimulation is not producing EMG responses. What are your differential diagnoses and immediate actions?

Think: patient factors, anaesthetic drugs, equipment, and surgical factors.

Residual NMBA: check quantitative TOF; review timing/dose of NMBA; consider reversal (e.g. sugammadex for rocuronium).
Electrode issues: displaced/poor contact/dried gel; check connections, impedance, and that electrodes are in correct muscles.
Equipment/settings: monitor muted/off, incorrect channel, stimulation current too low, leads swapped; liaise with neurophysiology/rep if present.
Physiology: hypothermia; severe electrolyte disturbance (less common); ensure normothermia and correct major abnormalities.
Surgical: stimulating non-neural tissue; nerve already compromised (pre-existing palsy, tumour infiltration).

What are the key positioning and airway risks during parotidectomy and how do you mitigate them?

Head turned, long case, shared head/neck field.

ETT displacement/kinking with head rotation: secure tube, consider reinforced ETT, re-check after positioning and draping.
Pressure/nerve injuries: pad eyes, ears, occiput; avoid excessive neck rotation; protect brachial plexus and ulnar nerve.
Venous congestion from extreme head turn → bleeding: position neutrally as feasible; communicate with surgeon.
Eye protection: tape and lubrication; risk increased if facial nerve weakness post-op.

Describe the causes, recognition and management of post-parotidectomy neck haematoma with airway compromise.

This is a time-critical airway emergency.

Recognition: neck swelling/tight dressing, increasing pain/pressure, dysphagia, voice change, stridor, hypoxia, agitation; drain may block or suddenly stop draining.
Immediate actions: call for help (ENT/surgeon, anaesthetic backup), high-flow O2, sit up, prepare difficult airway equipment; consider awake approach if stable.
Definitive: urgent wound decompression by surgeon (or in extremis, release sutures/clips) to relieve airway compression; return to theatre for haemostasis.
Airway plan: anticipate difficult laryngoscopy; consider videolaryngoscopy, fibreoptic intubation, or front-of-neck access if cannot intubate/oxygenate.

How would you provide analgesia for parotidectomy while minimising opioid-related side effects?

Use multimodal analgesia and local techniques; balance against bleeding risk and PONV.

Regular paracetamol; NSAID if not contraindicated (renal disease, bleeding risk, asthma sensitivity).
Local anaesthetic infiltration by surgeon; consider superficial cervical plexus block as adjunct (with ultrasound if trained).
Opioid-sparing intra-op technique: remifentanil infusion with careful transition to longer-acting analgesia before end; small dose morphine/oxycodone as needed.
Aggressive PONV prophylaxis and rescue plan to reduce retching/bleeding risk.

A patient has pre-existing facial weakness and is listed for parotidectomy. What are the implications for anaesthesia and monitoring?

Baseline dysfunction affects interpretation of monitoring and post-op assessment.

Document baseline facial nerve function clearly; ensure consent includes risk of worsening palsy and eye complications.
EMG monitoring may show reduced/absent responses even without iatrogenic injury; discuss expectations with surgeon.
Post-op eye protection may be required; plan lubrication/taping and clear handover.