FRCA Notes

Orthognathic Surgery

Resources

  • Orthognathic surgery used to treat skeletal disproportion of the lower face
  • It involves manipulation of the maxilla ± mandible, which are fixed in their new position

  • Indications for orthognathic surgery include:
    • Functional and/or cosmetic correction of dental malocclusion
    • Functional correction arising from congenital head & neck conditions e.g. cleft palate, Crouzen's, Treacher-Collins, Apert's syndromes
  • Sagittal split of the mandible

  • Le Fort I maxillary osteotomy
    • This involves an intra-oral incision followed by a transverse maxillary osteotomy
    • There is then a 'down-fracture' mobilisation of the maxilla

  • Bimaxillary osteotomy, which involves osteotomy of both mandibular and maxillary components

  • Le Fort II and Le Fort III osteotomies, which are mostly performed in craniofacial units to manage patients with congenital facial abnormalities


Pre-operative Intra-operative Post-operative
Patients may have comorbidities associated with difficult laryngoscopy Shared airway surgery Inter-maxillary fixation
Previous airway surgery or treatment e.g. radiotherapy Nasal tube often required Throat pack use
Previous difficult airway Dislodgement of tube during head movement Post-operative haematoma/bleeding
Damage to nasal tube by over-enthusiastic surgeons


  • Patients may have often undergone considerable orthodontic work-up, including creation of bespoke surgical components to demarcate new spatial relationships

Anaesthetic concerns

  • Although most patients are young and fit, some will present with OSA and/or congenital syndromes

  • The presence of a shared airway requires close communication between anaesthetic and surgical teams, as well as an understanding of the planned intra- and post-operative surgical interventions
  • Techniques to reduce intra-operative bleeding may be required
  • Higher risk of PONV; plan effective anti-emesis
  • Require higher vigilance for post-operative complications

  • Given the above, appropriate airway assessment and planning, including that for a difficulty airway and for post-operative management

Induction

  • Typically requires a nasal ETT
  • This ensures surgical access, surgical assessment of bony alignment and full occlusion post-operatively
  • Other options include retrograde intubation, submental airways, retromolar reinforced COETT or tracheostomies

  • Elective patients may have chronic, fixed defects, which are unlikely to improve following induction of GA (unlike facial trauma patients), necessitating ATI
  • Whether for ATI or old-fashioned nasal intubation, the nasal mucosa should be prepared to avoid haemorrhage e.g. with co-phenylcaine

  • Whichever airway is used, it should be taped/positioned out of the surgical field

Airway loss

  • There is limited/difficult airway access intra-operatively
  • This can be problematic, as the maxillary osteotomy occurs close to the nasal ETT
  • This can cause tube dislodgement, kinking, obstruction or frank damage, with a consequent inability to ventilate

Maintenance

  • Although both volatile agents and propofol/remifentanil TIVA are valid, many will choose the latter as it:
    • Reduces PONV, of which there is a higher incidence with bimaxillary osteotomies
    • Facilitates hypotensive anaesthesia
    • Can provide smooth extubation without coughing or straining

Management of bleeding

  • The bony mid-face is vascular and has the propensity to bleed profusely from both soft tissue and bone
  • Surgical haemostasis is often difficult due to limited access and/or rapid obscuration of the field with blood
  • Bleeding occurs from branches of the maxillary artery (e.g. palatine, alveolar) and the pterygoid venous plexus
  • Methods to reduce bleeding include:

    • Pharmacological Physiological
    Induced hypotension e.g. remi, deep volatile Head-up position to aid venous drainage
    Adrenaline-containing solutions e.g. LA Low-normal EtCO2
    TXA Avoid tight ETT ties
    Pre-operative eGFR ≤60ml/min (CKD stage 3a) Avoid hypothermia

Analgesia

  • Paracetamol
  • Remifentanil, if used, provides analgesia as well as blunting of airway reflexes, permissive hypotension and is rapidly titratable
  • Surgical nerve blocks e.g. mandibular, maxillary
  • Steroids are almost always given to help reduce swelling, with the added benefit of reducing PONV
  • Long-acting opioids at the end of the case; may need to be judicious in the patient with a history of OSA

Bradycardia

  • There is a theoretical risk of bradycardia during maxillary down-fracture, owing to pressure effects on cranial nerves II - VII and activation of the trigeminocardiac reflex
  • Cessation of the down-fracture can reverse the bradycardia, which should otherwise be managed as normal

Extubation

  • Ensure normotension to provide 'haemostatic challenge' and assess for further bleeding
  • Suction under direct vision
  • Ensure throat pack removed!

  • One can extubate the patient awake, though will need to take care to avoid jaw thrusts or excessive facemask pressure given the nature of the surgery
  • Instead, one can keep the remifentanil TCI going and do one of:
    • Withdrawal of the nasal tube such that it becomes an NPA
    • ETT - to - SAD swap
    • Extubation following insertion of an airway exchange catheter

PONV

  • High incidence of PONV (40%) due to patient cohort and ingested blood
  • A multi-modal approach is required

Airway obstruction

  • Can be from haematoma, bleeding e.g. nasal or oedema
  • Vigiliance for airway obstruction and extended monitoring time in recovery (or other suitable area) should take place
  • Hilotherapy can also be used i.e. cold/ice therapy to reduce swelling

Inter-maxillary fixation

  • Although jaws are no longer 'wired' shut, use of elastic bands to maintain alignment may occur post-operatively
  • One should suction under direct vision before bands are applied
  • Ideally the bands should only be applied once patient is fully awake to ensure lower risk of aspiration/vomiting