Anaesthesia for cataract surgery

Ophthalmology presentation on anaesthesia for cataract surgery

1. Type of anaesthesia for cataract surgery Roll no 0954

2. Local Anaesthesia Surgery can be undertaken as a day-care procedure Entails little risk and is less dependent upon patient’s general health Does not require sophisticated equipment Easy to perform, has got rapid onset of action Provides a low intraocular pressure with dilated pupil. Can be used to reduce intraocular pressure and vitreous volume when necessary Economical

3. Local anaesthetics Temporary loss of sensation, analgesia and/or function ( akinesia ) Protein bound receptors located near sodium channel Anaesthesia causes ↓ depolarisation of nerve membrane Local anaesthetic Onset of action Duration Use(concentration) Benoxinate 6-20 seconds 15 minutes Topical(0.4%) Proparacaine 15-30 seconds 15-20 minutes Topical(0.5%) Amethocaine 10-25 seconds 10-20 minutes Topical(0.5-1%) Lignocaine (3 mg/kg max) 10-35 seconds 5-10 minutes 15-20 minutes 30-60 minutes Topical(4%) Infiltration(0.5%-1%) Bupivacaine (2 mg/kg max) Moderate 75-90 minutes Infiltration(0.25-0.75%) Ropivacaine Moderate 1.5-6 hours Infiltration(1%) Adrenaline-to prolong duration, reduce bleeding Propofal and midazolam - anxiety, amnesia

4. Surface (Topical) anaesthesia Phacoemulsification in cooperative patients Prior to regional blocks for intraocular surgery Usually a drop of anaesthetic solution instilled 4 times after every 4 minutes is sufficient to produce conjunctival and corneal anaesthesia . Lignocaine 4 % Amethocaine 1% Benoxinate 0.4% Cocaine , Paracaine Oxybuprocaine or benoxinate : bactericidal properties Available mixed with flourescein for applanation pressure recordings

5. REGIONAL ANAESTHESIA

6. Peribulbar block This technique described in 1986 by Davis and Mandel Almost replaced the time-tested combination of retrobulbar and facial blocks In a 10 ml syringe- 5 ml bupivacaine 0.75% Provides early onset of action 5 ml lignocaine 2% with 1:20000 adrenaline Prolonged efficacy 75 units hyaluronidase Permits diffusion into orbit 25 gauge 2.5 cm disposable needle is attached to the syringe Topical anaesthesia is instilled into conjuctival sac Patient placed in supine position and asked to look steadily straight ahead

7. Needle is inserted transconjuctivally or transcutaneously at junction of middle 2/3 and lateral 1/3 of lower lid adjacent and parallel to orbital floor for about 2.5 cm Gentle aspiration is performed and 5 ml of mixture is injected into lateral adipose tissue of orbit Pressure is applied to the site for a couple of minutes Just medial to middle canthus same needle is inserted to 2.5 cm and 3 ml is injected Pressure is applied for couple of minutes Or, inferomedial to supraorbital notch , more complications. Honan pressure cuff applied for 15 minutes

8. Anaesthesia and analgesia begin in 5 minutes Most patients- takes 15 minutes Supplemental injections: Inferiorly- persisting inferolateral movements Superiorly-residual superior or medial movements

9. Complications Chemosis Periorbital ecchymoses Penetration of globe- more in myopes with larger eyes and staphylomas Oculocardiac reflex Retrobulbar hemorrhage Inadvertent intravascular or intrathecal injection Anaphylactic shock

10. Retrobulbar block introduced by Herman Knapp in 1884. 22 gauge 3.5 cm long needle is used to enter transcutaneously at junction of middle and lateral thirds of lower orbital margin It is first directed straight backwards for about 15 mm then angled upwards and medially towards the apex of the orbit, up to a depth of 2.5 to 3 cm. As needle pierces the intermuscular septum between lateral and inferior rectus muscles, the feel is altered. After aspiration, 2 -4 ml of anaesthetic solution is injected into the muscle cone behind the eyeball

11. (2% xylocaine with added hyaluronidase 5 IU/ml and with or without adrenaline one in one lac )

12. Retrobulbar block anaesthetizes the ciliary nerves, ciliary ganglion and third and sixth cranial nerves thus producing globe akinesia (better than peribulbar ), anaesthesia and analgesia. The superior oblique muscle is not usually paralyzed as the fourth cranial nerve is outside the muscle cone. Needs an additional facial block

13. Complications retrobulbar haemorrhage globe perforation optic nerve injury extraocular muscle palsies. amaurosis Oculocardiac reflex Anaphylactic shock

14. Parabulbar / sub- Tenon block Conjunctival incision 2-3 mm is made halfway between inferior limbus and fornix to open into sub- Tenon space A blunt cannula or needle is used to inject anesthetic into posterior sub- Tenon space, bathing the nerves and muscles within the cone Thought to completely avoid vascular and optic nerve injury Low volumes of anaesthetic required Better anesthesia to iris and anterior segment More postoperative morbidity

15. Complications Chemosis Subconjunctival hemorrhage Penetration of globe Oculocardiac reflex Anaphylactic shock

16. Facial block To block the facial nerve which supplies the orbicularis oculi muscle , so that patient cannot squeeze the eyelids . Necessary with retrobulbar block 1 . van Lint’s block: Blocks the terminal branches of the facial nerve produces localized akinesia of the orbicularis oculi without associated facial paralysis . 22 gauge 3.5 cm needle is inserted subutaneously outside the lateral canthus and advanced upwards towards the brow, and downwards towards the infraorbital foramen, injecting along both paths

17. 2. O’Brien’s block. facial nerve is blocked near the condyloid process of mandible. The condyle is located 1 cm anterior to the tragus. It is easily palpated if thepatient is asked to open and close the mouth with the operator’s index finger located across the neck of the mandible. At this point the needle is inserted until contact is made with the periosteum and then 4 to 6 ml of local anaesthetic is injected while the needle is withdrawn Pain at the injection site and unwanted facial paralysis .

18. 3. Nadbath block: the facial nerve is blocked as it leaves the skull through the stylomastoid foramen Painful 4. Atkinson’s block: In it superior branches are blocked Anaesthetic injected at the inferior margin of the zygomatic bone.

19. Complications Bruising Full hemifacial palsy- stylomastoid foramen 9, 10 nerves : Dysphagia , respiratory difficulty

20. Intracameral anaesthesia Lignocaine 1% without preservative or adrenaline Provides only anaesthesia With topical anaesthesia For phacoemulsification

21. GENERAL ANAESTHESIA Indications infants and children anxious,unco -operative and psychiatric patients those suffering from dementia or Alzheimer disease, perforating ocular injuries, major operations like exenteration the patients willing for operation under general anaesthesia .

22. In perforating injuries and other ocular emergency cases, use of suxamethonium should always be preferred over non-depolarizing relaxants use of relaxants, endotracheal intubation and controlled respiration is preferred. it must be ensured that patient does not develop carbon dioxide retention. When this occurs, choroid swells to many times its normal value and ocular contents prolapse as soon as the eye is opened.