ENT Surgery/Maxillofacial Surgery

General Principles

Link: 28.full.pdf

The Shared Airway

• Good relationship with surgeon paramount. Usually they will specify type of ETT and position.
• ETTs can become displaced, compressed and kinked easily. Vigilance is necessary. Reinforced ETTs are commonly used.
• Nasal ETTs are commonly required for procedures involving the jaw and oral cavity.
• Flexible reinforced LMAs are being increasingly used for short procedures that are not expected to bleed. This must be a measured informed decision taking into account increased risk of displacement and surgical access restriction.
• Throat packs may be inserted by the surgeon or anaesthetist. Local policy must be followed with regard to safety and avoidance of retention.
  • Verbal declaration of insertion and removal
  • Visual cue on the patient themselves (e.g. sticker or part of pack)
  • Written on board in theatre
  • Part of swab count
  • Recorded in anaesthetic chart
• Eyes should be kept closed with appropriate tape and padded as necessary, ensuring pressure from equipment is prevented.

Patient Population

• Range from the young and fit to elderly and with many comorbidities.
• Head and neck cancer patients are often smokers with co-existant cardiorespiratory disease and all the associated complications.
• Previous neck irradiation is common and may cause problems during airway management due to immobility of neck, poor mouth opening and lack of saliva.

Common operations

• ENT: Tonsillectomy; septoplasty; rhinoplasty; FESS (Functional endoscopic sinus surgery); myringoplasty; stapedectomy/tympanoplasty; BAHA (bone anchored hearing aid); cochlear implant; parotidectomy; thyroidectomy; tracheostomy; laryngectomy; radical neck dissection; stapling pharyngeal pouch; panendoscopy.
• Maxillofacial/Dental Surgery: Surgical extraction of impacted/buried teeth; maxillary/mandibular osteotomy; fixation of zygomatic fracures; ORIF fractured mandible; major head and neck reconstructions and free flap surgery (see separate section)

Complications

• Bleeding
  • May occur intra-operatively or post-operatively. Can occur into the airway which could become threatened. Primary haemorrhage usually requires rapid re-intubation and surgical exploration.
  • Operations such as radical neck dissection and laryngectomy have potential for major haemorrhage due to proximity of major vessels and IV access should be planned accordingly.
• Laryngospasm
  • The nature of the operation and the patient population lends itself to high rate of laryngospasm.
  • Awake extubation or deep extubation (especially in children) to avoid this.
  • Awake extubation in ALL patients with a difficult airway.
  • Deep extubation in adults should only be done by an experienced anaesthetist in this area. It is best suited to SV.
    • At the end of surgery, increase volatile agent concentration, discontinue NO. After careful suction, insert guedel airway, turn patient left lateral/head down, check respiration is regular then extubate. Keep patient in this position until airway reflexes return.

Key Drugs

• Remifentanil
  • Intense opioid action of remifentanil and its rapid recovery profile makes it ideal for many ENT/MaxFax procedures.
  • Facilitates controlled arterial hypotension to reduce bleeding in middle ear surgery/major head and neck resections.
  • In procedures where facial nerve monitoring occurs (e.g. parotidectomy), remifentanil facilitates IPPV without relaxant.
  • Attenuates hypertensive response during prolonged laryngoscopy/pharyngoscopy.
• Dexamethasone
  • Superior antiemetic properties. Attenuates post operative airway swelling. Morphine-sparing.

End of procedure laryngoscopy

• Removal of coroner’s clot (blood accumulation in nasopharynx which can be aspirated following extubation with fatal results)
• Suction under direct vision, especially around vocal cords: vigilance with this can avoid post operative complications e.g. laryngospasm

Total Intravenous Anaesthesia (TIVA)

Link: 24.full.pdf

Principles

• Particularly useful in head and neck/ENT as procedures can be emetogenic (e.g. inner ear) and airway surgery/jet ventilation may necessitate IV anaesthesia.

Advantages

• Smooth emergence and recovery; less nausea; easily titrated; no pollution

Disadvantages

• Risk of awareness (especially when used with NMB); expense; extra equipment required (especially if BIS used); risk of disconnection; syringe changing

Risk of Awareness: EEG based DOA (depth of anaesthesia) monitoring is now recommended when neuromuscular blockade is used in combination with TIVA. (See new draft AAGBI guidelines link)

Link: Standards%20of%20monitoring%2020150812.pdf

Guaranteeing Drug Delivery: Safety notice issued by the Safe Anaesthesia Liaison Group October 2009.

Link: CSQ-PS-2-Safety-notification-TIVA.pdf

Laryngotracheal Surgery (e.g. removal of small vocal cord tumours, subglottic stenosis treatment)

Link: 28.full.pdf

Jet Ventilation Techniques

Link: [271%20High%20frequency%20Jet%20Ventilation6.pdf]6

• High Frequency Jet Ventilation: using specialised ventilator.
  • Supraglottic
    • Allows completely tubeless field for surgeon.
    • Surgeon must maintain airway. Quality of ventilation can be impaired by malalignment of the jet.
    • Not possible to monitor PAWP or ETCO2. Alternative techniques include trans-cutaneous CO2 monitoring or intermittent blood gas sampling.
  • Subglottic
    • Small diameter specialised ETT used e.g. Hunsaker Mon-Jet Catheter (35.5cm long, ID 2.7mm, ed 4.3mm); LaserJet Catheter (2 lengths 40cm and 70cm; ED 3.4mm
    • PAWP and ETCO2 monitoring is possible
  • Ventilators can deliver heated, humidified jets at a high frequency (usually 150 per minute)
  • Time cycled, pressure limited ventilation
  • Tidal volume is not set - it is a function of driving pressure, cannula resistance, inspiratory time, entrainment volume and impedance of the respiratory sytem.
  • Complications
    • Barotrauma: gas trapping (if there is an inadequate expiratory pathway); pneumothorax; pneumopericardium; pneumomediastinum
    • Dry Gas: mucosal trauma; tracheal necrosis; atelectasis
    • Impaired Ventilation: hypoxia; hypercapnia; airway soiling by debris/secretions
  • The important and inter-related variables are: rate/frequency f; driving pressure DP; inspiratory time I-time (%ventilatory cycle); inspired oxygen fraction FI02.
  • A typical parameter set for HFJV via a subglottic catheter is DP 2 atm; f 150 per min; FI02 1.0 (can be decreased to 0.25 if using LASER); I-time 50%
• Low Frequency Jet Ventilation: hand held apparatus e.g. Sander’s injector/Manujet. Used for short procedures.
  • Hand held jet apparatus used supraglottically and attached to a rigid bronchoscope
  • Attached to high-pressure wall piped O2 at 4 bar. Passed through pressure reducing valves and can be further adjusted via a regulator near the handset to a pressure that produces desired chest wall movement
  • Frequency of 8-10 per minute allows adequate time for exhalation via passive recoil and prevents air trapping.
  • Effective FI02 in trachea is 0.8-0.9 because of entrainment of ambient air
• TIVA must be used
• Muscle relaxant usually used, but some centres use alternative methods such as strong short acting opioid (e.g. remifentanil); local anaesthetic to cords to facilitate passage of small diameter tube

LASER (Light Amplified by Stimulated Emission of Radiation)

Link: 255%20Basic%20Principles%20of%20Laser%20Technology.pdf

• Anaesthesia Technique
  • TIVA if high frequency ventilator, manual jet ventilation or THRIVE used.
  • If specific LASER ETT used normal ventilation with volatile agents should be possible but be wary of surgical compression/high airway pressures.
  • Inspired O2 should be decreased to 25% or less when LASER is in use.
  • Air/O2 mixtures only. No nitrous oxide.
  • Equipment: LASER endotracheal tubes
    • Silicone rubber tubes with metal links incorporated into the tube wall with either a sponge cuff or a double cuff. If the cuff bursts the sponge will maintain a sealed airway. If one cuff bursts in the double cuff option, the second cuff can be used.
    • Foil wrapped tubes with outer Teflon coat with cuff filled with methylene blue crystals so that if the laser bursts the cuff it is detected quickly by the surgeon.
    • Cuffs should be inflated with saline and not air.
  • Safety
    • Patient: Eye protection with moist pads
    • Patient: Other nearby tissues should be protected with wet swabs. Beware of drying out of swabs and pledgets inserted into airway by surgical team.
    • Staff: Protective LASER goggles
    • LPS (laser protection supervisor) should be named for every clinical area in which a laser is used.
    • Non reflective black-matt surgical instruments to minimise reflection
  • Airway Fires
    • SWITCH OFF LASER
    • FLOOD OPERATION SITE WITH SALINE
    • DISCONNECT ANAESTHETIC CIRCUIT AND REMOVE ETT IF FEASIBLE
    • VENTILATE PATIENT with AIR using bag/valve/mask
    • After fire has been extinguished, the surgeon should inspect the airway with a rigid bronchoscope. Consider keeping patient intubated and transfer to ICU in case of developing airway oedema.