PowerPoint Presentation on OCULAR ANESTHESIA

Brief description of Ocular Anesthesia

1. OCULAR ANESTHESIA PRESENTOR- DR VISHNU S MODERATOR-DR SHRUTHI BHAT

2. BRIEF HISTORY Carl Koller first used cocaine as topical anesthetic for eye surgery in 1884 Herman Knapp introduced Retrobulbar anesthesia with cocaine Einborn synthesized Procaine and led to its worldwide acceptance in Retrobulbar anesthesia Late 1980 s Peribulbar anesthesia was introduced by David and Mandel

3. OBJECTIVES Akinesia of the globe and the lids Anesthesia of the globe ,lids and adnexa Adequate intra-operative and post-operative analgesia

4. OCULAR ANESTHESIA LOCAL GENERAL INFILTRATION TOPICAL INTRACAMERAL NERVE BLOCKS RETROBULBAR BLOCK PERIBULBAR BLOCK SUBTENON S BLOCK SUBCONJUNCTIVAL BLOCK

5. PRE-OPERATIVE CONSIDERATIONS A) PATIENT PROFILE Choice of anaesthesia depends on the age of the patient and assosciated comorbidities to a large extent. Children are usually uncooperative and require General anesthesia (GA) while older patients can be managed with regional blocks provided there are no comorbidities.

6. INTRAOCULAR PRESSURE AND ANAESTHESIA DRUGS – Almost all Inhalational & intravenous (except Ketamine ) decrease IOP Muscle relaxants have no effect on IOP except Succinyl choline Succinyl choline – prolonged contracture of Extra Ocular Muscles – Increase in IOP 2. Other factors : Hypercarbia Arterial blood pressure Venous pressure changes Intubation and laryngeal mask airway

7. GENERAL ANESTHESIA Patient Indications Children Highly uncooperative patients Mentally challenged patients Orthopnoea Senile tremors Parkinsonism claustrophobia

8. Surgical indications Vitreoretinal surgery by virtue of the long duration involved are often preferred under GA Oculoplastic surgery especially involving autologous graft Ocular trauma Orbital decompression and tumors

9. The Goals for General Anesthesia for Ocular Surgery Include Smooth induction with maintenance of anesthesia Low IOP with minimal to nil fluctuations Careful monitoring with prompt management of Oculo Cardiac R Airway control with adequate oxygenation Immobility of the patient Smooth and uneventful extubation Minimal postoperative nausea and vomiting Clear headed recovery to facilitate early discharge

10. DRUGS USED IN OCULAR ANESTHESIA ESTERS Procaine Proparacaine Cocaine Tetracaine Benzocaine AMIDES Lignocaine Bupivacaine Ropivacaine Mepivacaine

11. TOPICAL ANESTHESIA Commonly used is Proparacaine 0.5% Least irritating to the eye on application Recently Oxybuprocaine 0.4% is also used Sensory nerve supply ( Trigeminal Nerve ) is blocked

12. Indications Eye examination (to relieve any discomfort ) Tonometry and Gonioscopy Removal of corneal and conjunctival foreign body Laser procedures Phacoemulsification Contraindications Hypersensitivity to the drug Penetrating injury

13. LOCAL ANESTHESIA T he advantages of local anesthesia Continuation of analgesia in the postoperative period Respiratory and cardiovascular stability Excellent muscle relaxation No interference with the airway Decreased metabolic and neuroendocrine stress response to surgery More cost effective; low cost of anesthesia in terms of drugs, equipment and manpower Need for less intensive postoperative care and ideal for day care surgery Allows early discharge and ambulation.

14. The contraindications to local anesthesia include: Known allergy to local anesthetic drugs Psychotic or uncooperative patient Patient refusal Bleeding disorders Patients with chronic spontaneous cough, orthopnoea , P arkinsonian head tremor, or claustrophobia

15. MEC H ANISM OF ACTI O N OF L OCAL ANESTHETIC Binds with protein of Na+ channels (at interior side) Block voltage dependent Na+ conductance ( prevent Na+ influx) Block depolarization Initiation and propagation of action potential fails Afferent impulses can not go to higher center No pain sensation 16

16. DRUGS COMMONLY USED : Combination of equal parts of Alternative solution Additives- 5µg/ml Epinephrine /1:200000 ( prolongs anaesthesia ) 3-7 U/ml Hyaluronidase (enhances spread ) Faster acting, short duration Lignocaine 2% Slow onset, longer duration Bupivacaine 0.5% Lignocaine 2% Prilocaine 2% 17

17. HYALURONIDASE DEPOLYMERIZES HYALURONIC ACID AND CHONDROITIN SULFATE BREAKDOWN OF EXTRACELLULAR MATRIX INCREASES DIFFUSION CAPACITY AND BIOAVAIALABILITY OF THE ANESTHETIC AGENT

18. Regional Blocks for the Eye RETROBULBAR ( Intraconal ) block involves injection of local anesthetic agent into the part of the orbital cavity behind the globe. PERIBULBAR ( Extraconal ) block refers to the placement of needle tip outside the muscle cone. SUB-TENON block refers to the injection of local anesthetic agent beneath the Tenon capsule. This block is also known as parabulbar block, pinpoint anesthesia and medial episcleral block.

19. prerequisites

20. RETROBULBAR BLOCK Technique : The patient is instructed to look straight ahead in the primary gaze position. Needle approach is through the infratemporal region A 24 G , <3.1 cm needle is inserted close to the lateral canthus tangential/away from the globe, below it and along the floor of the orbit On crossing the equator as gauged by axial length of the globe, the needle is directed upwards and inwards to enter the conal space just behind the globe.

21. After careful aspiration, 2 to 4 ml of local anesthetic agent is injected . The globe is continuously observed for any rise in IOP and proptosis during the needle placement and injection of the drug A reliable sign of successful block is onset of ptosis with injection of the local anesthetic.

22. RETROBULBAR BLOCK

23. PERIBULBAR BLOCK Advantages- There is no penetration of the muscle cone ( formed by the EOM) Hence there is less risk of injury to the optic nerve and vessels and is safer compared to Retrobulbar block. Less pain on injection Disadvantages- Slow onset of action More likelihood of ecchymosis Need for supplementary injections

24. Technique The patient is instructed to look straight ahead in the primary gaze position Topical Local anesthetic drops are instilled to minimize pain Eye is painted with 10% Povidone -Iodine solution A 25 G, 2.5 cm needle is inserted away from and then below the globe First injection is given inferiorly at the junction of medial 2/3 rd and lateral 1/3 rd of the lower orbital rim. second injection is given superonasally beneath the supraorbital notch.

25. Once in the extraconal space, the needle direction is not changed (not directed upward and inward) but directed along the orbital floor 5 ml of the local anesthetic is injected A rise in the orbital pressure with injection of the local anesthetic is watched for Pressure applied for 10-15min

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27. PERIBULBAR ANESTHESIA

28. SUB TENONS BLOCK Technique Conjunctival incision 2-3 mm , is made between the inferior limbus and fornix to open into the sub- Tenon space Blunt plastic cannula passed to posterior pole of eye , deep to Tenon’s fascia 3-5ml injected into posterior Sub - T enon space Bathing the nerves and muscles within the cone. 31

29. SUB TENON S BLOCK

30. FACIAL NERVE BLOCKS O’BRIEN technique : This is an intraparotid injection and blocks the facial nerve as it passes over the condyle of the mandible . Technique: Needle is inserted just anterior to the tragus of the ear, just above the condyloid process of the mandible . Disadvantage: Frequent blockade of only the upper portion of the peripheral facial nerve.

31. NADBATH / REHMAN Technique Injection just inferior to the earlobe . Technique : Injection is given at the dorsal rim of the mandible near the tragus of the ear . Five millimeter of the anesthetic solution injected at a maximal depth of 1.7 cm Advantage: Better orbicularis akinesia due to blockade of the upper and lower portions of the peripheral facial nerve.

32. Van LINT technique Infiltration anesthesia at the temporal orbital margin, aiming at the short zygomatic branches of the facial nerve . Disadvantage: Lower lid swelling, hematoma, poor orbicularis akinesia .

33. INTRACAMERAL ANESTHESIA Instilled by injecting non-preserved 1% Lignocaine in the Anterior chamber through paracentesis or side port incision. Causes anesthesia of iris and ciliary body and hence reduces pain and IOP fluctuations Drug must be washed after 15-30 seconds by irrigation through viscoelastics as it may reach retina and cause gradual decrease in vision.

34. COMPLICATIONS 1. Systemic toxicity CNS Peri oral tingling Numbness Confusion Tinnitus Seizures CVS Bradycardia Hypotension Arrhythmias CVS collapse

35. 2. Retrobulbar Hemorrhage Most dreaded complication 1 in 700 Signs : 1. Increasing proptosis 2.Periorbital ecchymosis 3. Tight eyelids 4. Peri / sub conjunctival hemorrhage 5. Rise in IOP Treatment : Surgery postponed Gentle pressure for 20-30min Orbital decompression- Lateral canthotomy and Cantholysis

36. Prevention of Retrobulbar Hemorrhage : Fine gauge needles (25-30G) Lateral inferotemporal approach Avoiding deep needle placement Pressure for 1min post injection 3. Globe penetration & perforation Severe pain sudden diminision of vision Hypotony

37. 4 . Optic Nerve damage Direct trauma or injection into optic nerve sheath Rise in pressure due to Retrobulbar hemorrhage also damages Optic Nerve 5. Amaurosis Temporary loss of vision follows spread of local anesth etic into optic nerve with retrobulbar block Reassurance ExtraOcular Muscle palsy Medial Rectus & Inferior Oblique- most commonly involved Self limiting

38. 7. Others Failure of block Corneal abrasion Chemosis Conjunctival hemorrhage

39. OCULO CARDIAC REFLEX Traction of Extraocular muscles, pain or pressure on eyeball evokes - Trigeminal -Vagal reflex Manifests as cardiac dysrhythmias (Bradycardia, ventricular ectopics , Ventricular fibrillation, cardiac arrest) Most common in strabismus and pediatric patients 44

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41. Preventing Oculo Cardiac Reflex Intramuscular Atropine or Glycopyrrolate prior to the surgery Gentle manipulation of extraocular muscles Control of ventilation to maintain normocapnia

42. REFERENCES PARSON ’ S DISEASES OF THE EYE-21 st EDITION DR ZIA CHOUDHURY, POST GRADUATE OPHTHALMOLOGY ,VOLUME 1 EYEWIKI- AMERICAN ACADEMY OF OPHTHALMOLOGY INDIAN JOURNAL OF OPHTHALMOLOGY ,71(7):p 2649-2655, JULY 2023

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