FRCA Notes

Strabismus (Squint) Surgery

This topic was the subject of an SAQ in 2019 (52% pass rate), although part of the question focused instead on elements of day case surgery.

The examiners lamented poor knowledge of suitable analgesia, as well as relevant perioperative factors.

Resources

  • Squint affects 3-5% of the paediatric population
  • Although many settle with conservative measures, surgery may be required to tighten, lengthen, shorten or transpose the extra-ocular muscles

Patient Factors

  • Paediatric patients of varying age: altered anatomy, physiology and psychology
  • Requires paediatric-trained staff and logistical set-up
  • May be anxious as can require multiple procedures
  • Consent is required from parents

  • May be associated with:
    • Down's syndrome
    • Edward's syndrome
    • Treacher-Collins syndrome
    • Crouzon syndrome
    • Apert syndrome
    • Cri-du-chat syndrome
    • Goldenhar syndrome
    • Primary or secondary myopathies including ocular myopathies

Anaesthetic Factors

  • Must fulfil satisfactory anaesthetic criteria for day-case surgery
  • Often Eye Theatres are more remote and therefore considerations of remote anaesthesia apply
  • Limited airway access intra-operatively

Surgical Factors

  • High risk of oculo-cardiac reflex
  • High risk of PONV
  • Significant post-operative pain

Perioperative management of the child undergoing strabismus surgery

  • Most patients will be ASA 1 or 2 and require little more than a standard paediatric pre-assessment

Monitoring and access

  • AAGBI
  • IV cannula

Anaesthetic technique

  • Induction modality of choice
  • Due to increased incidence of squint in children with underlying (primary or secondary) myopathy and associations with MH, consider avoiding suxamethonium and volatiles
  • Flexible LMA usually suitable; south-facing RAE if need intubating
  • TIVA may be preferable due to high incidence of PONV
  • Limited airway access-intra-operatively so ensure airway well-secured

Oculo-cardiac reflex

  • See dedicated page on prevention and management of the oculo-cardiac reflex
  • Consider giving 5μg/kg glycopyrrolate after induction to reduce risk of induced bradycardia and the increased PONV that is associated with it; can give a second dose prior to surgery starting if feel further increases in heart rate are required

Analgesia

  • Mutli-modal approach with:
    • IV intra-operative paracetamol
    • IV intra-operative NSAID (or PR diclofenac for <8yrs)
    • Local anaesthetic
      • Sub-Tenon's block at either start or end of case (if given at start may reduce incidence of oculo-cardiac reflex)
      • Topical LA e.g. amethocaine, tetracaine 0.5%, oxybuprocaine 0.4%
    • Fentanyl e.g. 1μg/kg IV at induction followed by a second dose prior to incision of second muscle

PONV prophylaxis

  • Avoid prolonged fasting times; 'sip until send'
  • Avoid nitrous oxide and consider using TIVA
  • Avoid (excessive) opioids
  • Multi-modal anti-emesis:
    • Dexamethasone 0.15mg/kg IV
    • Ondanstron 0.15mg/kg IV
  • Adequate fluid hydration

Analgesia

  • Regular paracetamol and NSAID to continue post-operatively

  • Prescribe proxymetacaine eye drops for PRN/stat use post-operatively to treat eye pain