FRCA Notes

Anaesthesia for Middle-Ear Surgery

This topic appeared as a CRQ in the September 2020 Final written exam, with an examiner-commended 65% pass rate.

It reappeared as a CRQ in 2024, with a focus on use of TIVA.

Resources

  • Both the type of middle-ear surgery and the patient cohort on which it is performed can be highly variable, ranging from simple procedures in otherwise-well individuals to more complex operations in those with congenital abnormalities or syndromes

Indications for surgery Procedures (non-exhaustive)
Cholesteatoma Mastoidectomy
Chronic (suppurative) otitis media Tympanoplasty
Hearing loss (sensorineural or conductive) Insertion of cochlear implant
Otosclerosis Ossicular chain reconstruction
Tympanosclerosis Stapedectomy/stapedotomy
Perforated tympanic membrane Myringoplasty


Perioperative management of the patient undergoing middle-ear surgery


  • A standard anaesthetic pre-assessment should take place
  • One should be mindful that patients are likely to have considerable hearing loss (hence the need for surgery)
  • It may be necessary to optimise the environment in which pre-assessment takes place so as to maximise communicability:
    • Ensure patient has hearing aids with them
    • Low ambient noise
    • Adequate lighting and facing patient so they can read your lips
    • Speaking to the better ear
    • Presence of sign-language interpreter if necessary

  • One should elucidate any major comorbidities, but in particular those which contra-indicate use of hypotensive anaesthesia
    • Sickle cell disease
    • Pregnancy
    • Hypertensive disorder
    • Vascular insufficiency

Paediatric considerations

  • Sensorineural hearing loss may be associated with congenital syndromes which are associated with a difficult airway e.g. Stickler syndrome, Klippel-Feil syndrome
  • Congenital sensorineural hearing loss can be associated with a long QT syndrome so a pre-operative ECG is required
    • This can occur in isolation or as part of Jervell & Lange-Nielsen syndrome

  • NB infancy (<1yrs) is a contraindication to hypotensive anaesthesia

Airway choice

  • Short, small procedures may be amenable to use of supraglottic devices, but in general I&V is required
  • A south-facing RAE tube is the usual go-to, as it:
    • Secures the airway during long procedures where access to the head and neck is both limited and distal to the anaesthetic machine
    • Facilitates MV and control of CO2
    • Is more secure than a SAD if intra-operative head re-positioning is required

Facial nerve monitoring

  • Facial nerve injuries during middle-ear surgery aren't common (0.1%), but can have devastating psycho-social impacts if they occur
  • It can be damaged by direct trauma or localised thermal injury
  • Intra-operative facial nerve monitoring is typically used to monitor EMG responses of orbicularis oculi and/or orbicularis oris
  • This reduces, but does not eradicate, the risk of damaging the nerve

  • As such, one should choose an anaesthetic technique which facilitates this, usually either:
    • A NMBA-free technique e.g. use of remifentanil although may require reasonable doses (3-4μg/kg) to achieve intubating conditions similar to those provided by NMBA
    • Use of small doses of NMBA to facilitate intubation followed by ensuring adequate return of NMJ function prior to surgery starting, as assessed by quantitative TOF monitoring

Choice of maintenance technique

  • Both TIVA or volatile + remifentanil techniques can be used
  • A TIVA technique is generally preferred as it:
    • Reduces PONV risk in a surgical cohort already at high risk
    • Does not interfere with elicited stapedius reflex threshold (ESRT) testing, which is sometimes used when testing cochlear implant function
    • Avoids theoretical middle-ear pressure changes associated with volatile anaesthetics, although these are less than those of nitrous oxide

Optimising surgical field

  • Even small amounts of bleeding can grossly compromise surgical access/vision, and is potentially associated with poorer outcome (e.g. cholesteatoma re-occurrence)
  • There are a variety of possible methods for reducing surgical-field bleeding, which are arranged in a somewhat sysmtes-based fashion:

Methods for reducing surgical field bleeding
Head up (∽10°)
Tape ETT i.e. avoid tight ETT ties
Low/no PEEP ventilation and short Ti
Low-normal PCO2
Hypotensive anaesthesia (MAP ∽80% baseline)
Boluses of β-blocker
Remifentanil TCI
Increase depth of anaesthesia
Magnesium
ɑ2 agonists

Other considerations

  • Nitrous oxide is avoided owing to its propensity to alter the pressure in fixed gas-filled spaces e.g. the middle-ear, which can disrupt surgical grafts
  • Its emeteogenic potential, in a surgical cohort already at high risk of PONV, adds to its unsuitability

  • Surgeries can be long with minimal blood loss, so judicious use of fluids ± urinary catheter is appropriate
  • Adequate temperature management with temperature probe, forced air warmer and fluid warmer in long cases
  • Mechanical VTE prophylaxis
  • Ensure adequate padding of pressure areas

Analgesia

  • Regular simple analgesia e.g. paracetamol and NSAID
  • Short-acting opioids e.g. fentanyl, immediate-release oral morphine, as patients are often day-cases
  • Local anaesthetic infiltration by surgeons
  • Use of alternative intra-operative analgesics e.g. magnesium, ɑ2 agonists

PONV

  • Patients are at higher risk of PONV owing to:
    • A younger patient cohort
    • Long duration of surgery
    • Direct stimulation of the vestibular system
    • Suction-irrigation, which is a caloric vestibular stimulus
  • Avoidance of PONV is essential as, in addition to its generally unpleasant effects, retching and vomiting may compromise surgical repairs/grafts

  • A multi-modal pharmacological approach, TIVA technique and rescue H1 receptor antagonists e.g. cyclizine, betahistine, is ideal