FRCA Notes

Anaesthesia for Ophthalmic Surgery

The most relevant curriculum item is: 'discusses the choice of local or general anaesthetic techniques in relation to the patient and surgery including their advantages, disadvantages and indications'.

Resources

  • Eye surgery can be performed under topical or regional anaesthetic techniques, with or without varying degrees of sedation
  • Of course the trusty old general anaesthetic remains a viable option too...

Surgical factors

  • Type of surgery
    • Corneal or conjunctival procedures are generally possible with topical anaesthesia
    • E.g. IOP measurement, removal of foreign bodies, irrigation of lacrimal ducts, small incision cataract surgery

    • Intra-ocular procedures may require regional blockade to block sensory ± motor innervation of the globe
    • E.g. cataract surgery, vitreoretinal surgery

  • Previous issues such as scleral buckling or SOL removal
  • The duration of surgery; typically those >90mins in length are not amenable to topical techniques

  • Axial length
    • A distance of >26mm from cornea to retina can be associated with a thinning of the globe wall, leading to outpouchings (staphylomata)
    • The presence of these increases the risk of globe perforation from peri- or retro-bulbar blocks
    • The risk of staphyloma increases with increasing axial length:
      • 27 - 29mm: 15% risk
      • >31mm: 60% risk

Patient factors

  • These are mostly covered in the page on pre-assessment
  • Factors such as true local anaesthetic allergy and active eye infection will contraindicate regional techniques

  • Topical anaesthesia is simple, quick and carries the lowest risk of complications
  • However, it is only suitable for compliant patients undergoing uncomplicated surgery, and does not provide akinesis

  • Local anaesthetic drops are applied to the conjunctiva, for example:
    • 0.5% proxymetacaine
    • 0.4% oxybuprocaine
    • 0.5 - 1% tetracaine
    • 3.5% lidocaine
    • Although cocaine was the original topical anaesthetic for eye surgery, it is no longer suitable

  • An amount of the local anaesthetic will enter the aqueous humour, in theory providing a degree of anaesthesia of the iris, conjunctiva and cornea

Intracameral anaesthesia

  • The surgeon injects preservative-free lidocaine into the aqueous chamber
  • It is safe and effective in reducing intraoperative pain

  • Sedation is used as an adjunct to either topical or regional techniques to provide anxiolysis
  • The aim is conscious sedation, which is used to facilitate LA injection and then surgery

  • The general principles of sedation apply, though beyond that the choice of sedation method is at the discretion of the anaesthetist
  • Examples include:
    • No sedation
    • Oral temazepam
    • Oral clonidine
    • Oral or intravenous midazolam
    • Short-acting opioids such as remifentanil, alfentanil or just plain ol' fentanyl
    • Dexmedetomidine, which has the added bonus of reduced IOP (BJA [2007], BJA [2007])
    • Propfol, via intermittent bolus or as a TCI

  • Although ketamine is a good sedative in other settings, its tendency to increase IOP, increase secretions, cause tachycardia and the risk of emergence phenomenon make it a less suitable option for ophthalmic surgery

  • Considerations when using general anaesthesia include:
    • A higher-than-average risk patient population
    • Difficult airway access intra-operatively
    • Airway tolerance is vital; coughing or bucking may have catastrophic effects
    • Principles of day-case anaesthesia
    • Minimising the intrusion of the airway device into the operative field
    • Surgical need to check IOP peri-operatively, which may influence choice of drugs

  • In general, the aims are to minimise cardiovascular instability and avoid raised IOP, while providing optimised operating conditions for our surgical colleagues

Airway

  • Supraglottic devices are preferable to endotracheal tubes, as they negate the need for laryngoscopy and its effects on IOP
  • If intubation is indicated, aim to prevent coughing on emergence via one's method of choice e.g. deep extubation or airway exchange

Ventilation

  • For minor or extra-ocular procedures, self-ventilation is appropriate (although hypercarbia will raise IOP and potentiate the oculo-cardiac reflex)
  • For major intraocular surgery, mandatory ventilation may be preferable as it allows control over CO2 levels and therefore IOP

Maintenance

  • No robust evidence of volatile or TIVA superiority
  • Volatile anaesthesia ensures a neutral gaze
  • Some suggestion TIVA is associated with an increased incidence of the oculo-cardiac reflex
  • Nitrous oxide should be avoided in vitreoretinal surgery where gas-tamponade is planned
  • Whichever technique is chosen, avoiding patient movement is essential - the advent of sugammadex has helped facilitate this