Principles of anaesthesia for ophthalmic surgery

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Slide 1 :

Principles of anaesthesia for ophthalmic surgery Ben Shelley SHO Hairmyres

Slide 2 :

Contents Local Topical Regional General Emergency eye surgery

Slide 3 :

Local anaesthesia for eyes Many benefits ? Physiological disturbance ? PONV Economic Topical / Regional

Slide 4 :

Topical anaesthesia for eyes Non-invasive Virtually no complications Challenging operating conditions – no akinesia Increasingly popular for phacoemulsification cataract surgery

Slide 5 :

Topical anaesthesia Careful patient selection Co-operative Not distressed Straightforward surgery Must be able to lie supine and still Sedation

Slide 6 :

Topical anaesthesia IV access / supplementary O2 Which LA? Proxymetacaine / amethocaine Preservative free preferred +/- topical NSAID and mydriatic

Slide 7 :

Procedure 20-30 mins before surgery Two to three drops every 5 minutes Cornea is avascular – once absorbed LA remains for about 30 mins Supplemented by incremental injection

Slide 8 :

Regional anaesthesia

Slide 9 :

Regional anaesthesia Advantages Day cases Good akinesia and anaesthesia Minimal effect on IOP Minimal equipment required Disadvantages Not suitable for all patients Complications Skill of anaesthetist Unsuitable for certain types of surgery

Slide 10 :

Anatomy Orbit – shape of irregular pyramid Base at front Axis points posterio-medially towards skull Globe lies in anterior part of orbit - sits high and lateral

Slide 11 :

Anatomy Four rectus muscles arise from the back of orbit Insert into the globe just forward of equator Form a cone - boundary between two compartments CENTRAL (retrobulbar) PERIPHERAL (peribulbar)

Slide 12 :

Anatomy Within the cone Optic nerve Opthalmic artery & vein Ciliary ganglion Oculomotor nerves Sensory supply to orbit - from opthalmic division Trigeminal nerve - enters the orbit through superior orbital fissure

Slide 13 :

Slide 14 :

Types of regional anaesthesia Peribulbar block (Pericone) Retrobulbar block (Intracone) Sub-Tenon’s block

Slide 15 :

Peribulbar Large volume of LA out with the cone using a short needle (25mm) 2 injections Inferotemporal Medial Beware axial myopia 30 x increased risk globe puncture if > 26mm axial length

Slide 16 :

Peribulbar IV Access Topical LA to conjunctiva 10ml LA 5ml Bupivicaine 0.75% 5ml Lidocaine 2% Hyaluronidase 75 units +/- Bicarbonate +/- Warming Supine and looking straight ahead

Slide 17 :

Inferotemporal injection Lower lid retracted Junction of inner 2/3 and outer 1/3 Needle advanced in sagital plane // floor Once past equator of globe, turned medially and cephalad Advance to hub – 25mm

Slide 18 :

Nasal injection Inserted medial to the carnucle and directed straight back // medial wall & slightly cephalad Until hub of needle at same level as the iris

Slide 19 :

Peribulbar block Eye closed, taped, covered with gauze Pressure applied with Macintyre oculopressor - ? IOP by ? aq. humour prod & ? reabsorption Signs of a good block Ptosis Akinesia (or minimal movement) Inability to fully close eye once opened

Slide 20 :

Retrobulbar block Use of a long needle (35 to 50mm) to inject LA into muscular cone close to the orbital apex Largely replaced by peribulbar because of higher incidence of complications

Slide 21 :

Retrobulbar block Junction of inner 2/3 and outer 1/3 Directed backwards under the globe Once past equator ? upwards & inwards Aiming to enter space behind the globe between inferior and lateral recti

Slide 22 :

Sub Tenon’s Anaesthesia Recent alternative to retro / peribulbar Trans-conjunctival injection of LA into the potential sub-Tenon’s space Frequently used for cataract surgery

Slide 23 :

Anatomy Tenon’s capsule – dense fascial sheath surrounding the globe and extraocular muscles from the limbus to the optic nerve Sensory blockade Short-ciliary nerves pass through Tenon’s capsule to globe Akinesia Direct blockade of ant. nerve fibres as they enter extra-ocular muscles (volume dependant)

Slide 24 :

Procedure Topical local Speculum to keep eyelids appart Scissors and forceps Small opening made in conjunctivae - inferomedial quadrant - eye in full abduction and elevation Space bluntly dissected (to bare sclera) Curved blunt – Sub Tenon’s cannula inserted 5mls LA injected (initial resistance)

Slide 25 :

Sub Tenon’s anaestheisa

Slide 26 :

Sub-Tenon’s Anaesthesia Advantages Blunt cannula - avoids sharp needle complications Safe and simple to teach Provides reliable anaesthesia and akinesia Disadvantages Subconjunctival haemorrhage Conjunctival chemosis Care when previous eye surgery Inferior rectus injury

Slide 27 :

Care of the patient Comfort Assistant providing reassurance O2 saturation, ECG, BP monitoring Right angled screen providing O2

Slide 28 :

Complications of regional eye anaesthesia Intravascular injection Anaphylaxis Haemorrhage Subconjunctival oedema Penetration / perforation of the globe Central spread (sub-arachnoid) Optic nerve atrophy

Slide 29 :

The Rules 2001 Guidelines (RCA & Coll. of Opthalmologists) Trained staff Surgeons – topical / sub-conjunctival / sub-Tenon – without anaesthetist Anaesthetist & iv access when retrobulbar / peribulbar Anaesthetist in charge when sedation used

Slide 30 :

General anaesthesia for ophthalmic surgery Indications: Patient refusal Children / learning difficulties / movement disorders Major / lengthy procedures Inability to lie still / flat

Slide 31 :

General anaesthesia for opthalmic surgery Considerations for anaesthetist: Patients at extremes of age Co-morbidity common in elderly - esp. diabetes and hypertension Opthalmic drugs - eg. Timolol – B-Blocker Phospholine iodide - anticholinesterase

Slide 32 :

Intra ocular pressure Normally 10-20 mmHg Must be controlled when operating within the globe ?IOP ? impaired op. conditions expulsion of intra-ocular contents Mild ?IOP ? improved op. conditions

Slide 33 :

Factors affecting IOP Increasing External pressure ? Venous pressure ? Arterial pressure Hypoxia Hypercarbia Suxamethonium Ketamine Decreasing ? Venous pressure ? Arterial pressure Hypocarbia IV induction agents NDMRD ?Aqeous volume (acetazolamide) ?Vitreous volume (mannitol)

Slide 34 :

Anaesthetic technique Careful with face mask No ketamine ETT vs LMA Obviates laryngoscopy Minimal stimulation Superior emergence Delayed and careful laryngoscopy IPPV to moderate hypocarbia

Slide 35 :

Anaesthetic technique 2 Head up tilt Peripheral nerve stimulator Avoid nitrous in vitreoretinal surgery Bubbles of sulphurhexafluoride SF3 Emergence without coughing Deep extubation Lignocaine on cords Bolus lignocaine/ propofol beforehand

Slide 36 :

Penetrating eye injury To sux….. Or not to sux? Sux ? ? IOP - extra-ocular muscle contraction - ? intra-ocular blood volume

Slide 37 :

Penetrating Eye Injury To sux……. Emergency case – presumed full stomach or not to sux? IOP reduced to atmospheric Any rise on induction could ? expulsion of intraocular contents

Slide 38 :

Penetrating eye injury (Risk of) Aspiration vs. E

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Increasingly popular for phacoemulsification cataract surgery. Topical anaesthesia. Careful patient more Increasingly popular for phacoemulsification cataract surgery. Topical anaesthesia. Careful patient selection. Co-operative; Not distressed ... less
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