Anaesthesia for ophthalmic surgery
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This document discusses anesthesia considerations for ophthalmic surgery. It covers the anatomy of the eye, physiology factors like intraocular pressure, sensory and blood supply. It also outlines various anesthesia techniques including general, topical, peribulbar and retrobulbar blocks. Complications of regional blocks and management of specific surgical situations are addressed. Evidence-based recommendations are made regarding anesthesia choices for procedures like cataract surgery.
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Anaesthesia for ophthalmic surgery
- 1. Anaesthesia for Ophthalmic Surgery Anatomy, Physiology and Practice T Mphanza FRCA, FFICM 1
- 2. Special Considerations • Proximity to airway • Age • Anatomy • Physiology 2
- 3. 3
- 4. Anatomy • Orbit - irregular pyramid • Base at the front • Axis - points postero-medially • Optic foramen forms the apex 4
- 5. Anatomy • Orbit - irregular pyramid • 40 - 50 mm deep • Volume - 30 mls • globe - 7 mls 5
- 6. Anatomy • Globe • Anteriorly • Closer to the roof • Nearer to the lateral wall • Axial length - 25 mm 6
- 7. Anatomy 7
- 8. Anatomy • Extraocular muscles • 4 rectus muscles • 2 oblique muscles 8
- 9. LR6(SO4)3 9
- 10. Sensory Innervation • Trigeminal •V 1 • Supratrochlear, Supraorbital, Long ciliary, Nasociliary, Infratrochlear, Lacrimal •V 2 • Infraorbital, Zygomatic 10
- 11. Autonomic Innervation • Sympathetic • Superior cervical ganglion • Mydriasis • Parasympathetic • Fibres from III • Miosis 11
- 12. 12
- 13. Blood Vessels • Arterial • Ophthalmic artery • Venous • Ophthalmic veins • Superior • Inferior 13
- 14. Anatomy and Physiology 14
- 15. Physiology • Aqueous humour • Produced by ciliary body • Carbonic anhydrase • Drainage • Venous channels • SVC 15
- 16. Physiology • Intraocular pressure (IOP) • Range 10 - 20 mmHg • Increases with age • Direct correlation with axial length • Main determinant is aqueous humour 16
- 17. Physiology • Factors affecting IOP • Arterial BP • Auto-regulation • Venous BP • Valsalva, coughing, straining • Partial pressures - CO , O 2 2 17
- 18. Events that Decrease IOP • IV anaesthetics • Volatile anaesthetics • Mannitol • Timolol 18
- 19. Events that Increase IOP • Succinylcholine • Direct laryngoscopy • Hypoventilation 19
- 20. 20
- 21. Oculomedullary Reflexes • Oculocardiac • Trigemino-vagal: • Bradycardia, ectopics, sinus arrest • Oculorespiratory • Oculoemetic 21
- 22. Anaesthetic Ramifications of Ophthalmic Drugs 22
- 23. • Ecothiopate • Anticholinesterase miotic • Cyclopentolate • Mydriatic • Phenylephrine • Mydriatic 23
- 24. • Acetazolamide • Carbonic anhydrase inhibitor • Timolol • Beta blocker • Sulphur hexafluoride • Inert gas 24
- 26. • Akinesia • Profound analgesia • Minimal bleeding • Avoidance of oculocardiac reflex 26
- 27. • Control of IOP • Awareness of drug interactions • Emergence without coughing, straining or vomiting 27
- 28. Anaesthesia Techniques • General • Local • Topical • Regional 28
- 29. Factors that Influence Choice of Anaesthesia • Nature and duration of procedure • Coagulation status • Patient’s choice • Ability to communicate and cooperate 29
- 30. General Anaesthesia • Volatile vs TIVA • ETT vs LMA 30
- 31. General Anaesthesia • Special consideration • Head up tilt • Avoid hypercapnoea • Avoid N O in vitreoretinal surgery 2 • Smooth emergence 31
- 32. Topical Anaesthesia • Instillation of LA drops • Advantages • Minimal complications • Limitations • Lack of akinesia • Only suitable for uncomplicated cases 32
- 33. Regional Anaesthesia • Sub-Tenon • Peribulbar (Extra-conal) • Retrobulbar (Intra-conal) 33
- 34. Sub-Tenon’s Block • Tenon’s capsule • Dense fascial sheath surrounding the globe and extraocular muscles from the limbus to the optic nerve 34
- 35. Sub-Tenon’s Block • Sensory block • Short-ciliary nerves pass through Tenon’s capsule to globe • Akinesia • Direct blockade of ant. nerve fibres as they enter extra-ocular muscles 35
- 36. Retro & Peribulbar Blocks 36
- 37. Retrobulbar Block 37
- 38. Complications of Regional Blocks • Stimulation of oculocardiac reflex • Haemorrhage • Superficial • Retrobulbar • Retinal perfusion compromise • Loss of vision 38
- 39. Complications of Regional Blocks • Globe penetration • Intra-arterial injection • Trauma to optic nerve • Optic sheath injection 39
- 40. Complications of Regional Blocks • Extraocular muscle injury • Central retinal artery occlusion • Accidental brainstem anaesthesia 40
- 41. Anaesthetic Management of Specific Situations 41
- 42. • Open Eye, Full Stomach • Aspiration vs Blindness • Strabismus surgery • OCR • MH • PONV 42
- 43. • Intraocular Surgery • Glaucoma, vitrectomy, cataracts • IOP control • Complete akinesia • Continuation of miotics • Provide an antiemetic effect 43
- 44. • Retinal Detachment Surgery • SF injection for tamponade 6 • IV acetazolamide or mannitol • Akinesia is not critical 44
- 45. General Vs. Regional Anaesthesia 45
- 46. • Regional Techniques • Day stay surgery • Better akinesia • Less PONV • Less effect on IOP 46
- 47. Evidence Based Medicine • Cochrane Reviews • Peribulbar Vs. Retrobulbar • Sub-Tenon’s Vs. Topical 47
- 48. Evidence Based Medicine - CRTs • General Vs Regional for Cataract Surgery • Cognitive Function • Perioperative MI • Plasma catecholamine response 48
- 49. Summary • Anatomy and Physiology • Drug interactions • Special Requirements • Management of Specific Situations 49