What are the anaesthetic considerations for a cortical mastoidectomy?

Anaesthetic Considerations for Cortical Mastoidectomy

For cortical mastoidectomy, use total intravenous anaesthesia (TIVA) with propofol-remifentanil rather than volatile agents, implement multimodal analgesia with scheduled paracetamol and NSAIDs plus intraoperative dexamethasone 10 mg IV, consider tranexamic acid 10 mg/kg to reduce bleeding, and plan for postoperative nausea and vomiting (PONV) prophylaxis given the high-risk nature of middle ear surgery.

Anaesthetic Technique Selection

Induction and Maintenance

• TIVA with propofol-remifentanil is superior to balanced anaesthesia with sevoflurane for mastoidectomy, significantly reducing PONV incidence and severity 1
• Standard induction with propofol, fentanyl, and rocuronium is appropriate 2
• Muscle relaxation facilitates surgical access and should be monitored intraoperatively 3

Patient Positioning Considerations

• Most commonly supine with head rotation (42%), though park bench (26%) and lateral (16%) positions are also used 2
• Critical pitfall: Ensure endotracheal tube is secured on the contralateral side to avoid surgical field interference 2
• Avoid excessive head rotation or neck flexion that could compromise venous drainage and increase bleeding
• Pad pressure points appropriately, particularly the shoulder on the operative side

Multimodal Analgesia Protocol

Basic Analgesics (Essential Foundation)

Administer scheduled (not PRN) combination therapy 4:

• Paracetamol: 1g IV intraoperatively, then 1g PO/IV every 6 hours for 24-48 hours
• NSAIDs or COX-2 inhibitors: Full dose intraoperatively and continued postoperatively (e.g., ibuprofen 400mg TDS or celecoxib 200mg BD)
• Dexamethasone 10 mg IV: Single intraoperative dose for analgesic and antiemetic effects 5

The evidence shows dexamethasone specifically reduces postoperative dizziness and nausea after mastoidectomy at 24 hours, though it does not significantly reduce pain 5. Despite this, it remains recommended as part of multimodal analgesia for its antiemetic properties, which are particularly important in middle ear surgery.

Regional Anaesthesia Options

• Local anaesthetic infiltration by the surgeon at incision sites provides modest short-duration analgesia 4
• Mastoidectomy can be performed under local anaesthesia alone in medically unfit patients, though this requires experienced coordination 6, 7
• For general anaesthesia cases, surgical site infiltration with long-acting local anaesthetic (bupivacaine 0.25%) is reasonable

Bleeding Management

Administer tranexamic acid 10 mg/kg IV at induction 8. This significantly reduces intraoperative bleeding and improves surgical field visualization during microscopic ear surgery, which is critical for safe dissection around vital structures.

PONV Prophylaxis

Middle ear surgery carries high PONV risk due to:

• Vestibular stimulation during surgery
• Postoperative dizziness from inner ear manipulation
• Female predominance (3:1 ratio in mastoidectomy patients) 2

Multimodal PONV prevention strategy:

1. TIVA with propofol (inherently antiemetic) 1
2. Dexamethasone 10 mg IV (already included in analgesia protocol) 5
3. Add ondansetron 4-8 mg IV near end of surgery
4. Avoid nitrous oxide if used

Intraoperative Monitoring

• Standard ASA monitoring
• Facial nerve monitoring is routine for mastoidectomy and requires avoidance of long-acting muscle relaxants near the end of surgery 2
• Maintain normothermia to optimize surgical conditions and reduce bleeding
• Controlled hypotension (MAP 60-70 mmHg) may be requested by surgeon to reduce bleeding, but balance against cerebral perfusion needs

Special Considerations

Airway Management

• Secure endotracheal tube on non-operative side of mouth 2
• Use throat pack to prevent blood entering pharynx (remember to remove before extubation)
• Smooth emergence is important to prevent coughing and bleeding

Duration and Positioning

• Surgical duration typically 2-12 hours depending on complexity 2
• Prolonged head rotation increases risk of contralateral sialadenitis (rare but serious complication presenting as rapid facial/neck swelling within 4 hours of extubation) 2

Contraindications to Consider

• If patient has systemic mastocytosis, follow specific perioperative protocols including H1/H2 blockers, avoid atracurium/mivacurium, use propofol for induction 9
• Assess for latex allergy preoperatively given proximity to surgical field 10

Postoperative Management

• Extubate fully awake with intact airway reflexes
• Monitor for 4 hours for rare sialadenitis (contralateral facial/neck swelling) 2
• Continue scheduled paracetamol and NSAIDs for 24-48 hours 4
• Opioids available for breakthrough pain but minimize use given PONV risk
• Antiemetics readily available
• Monitor for dizziness and provide vestibular suppressants if needed