Speaker: Dr. Pranab Kumar Roy Chairperson: Dr. A. Chakraborty

Aim of Anaesthesia Akinesia Analgesia Amnesia Post operative comfort Abolition of oculo-systemic reflex Maintainance of intra-ocular pressure

Anatomy of Surgical Spaces of orbitThe subperiosteal space : A potential space between bone and periorbita. 2. The peripheral space : Peripheral boundary: periorbita Internal boundary: four recti with thin intermuscular septum Anterior boundary : septum orbitale Posterior boundary: merges with the central space1.

Anatomy of Surgical Spaces of orbit3. The central space : anterior boundary : Tenons capsule lining back of the eyeball peripheral boundary : Four recti muscles and their intermuscular septum4. Tenons space : a potential space around the eyeball between the sclera & Tenons capsule

Types of anaesthesia General anaesthesia Local anaesthesia

1) Topical anaesthesia 2) Infiltrating anaesthesia a. Local infiltration b. Nerve block Parabulbar block - Intracameral anaesthesia - Peribulbar block - Retrobulbar block - Facial block - Frontal block

General anaesthesia Indications - paediatric patients

- uncooperative patients not allowing regional anaesthesia - adults undergoing extensive orbital surgery Premedication - Diazepum/midazolam reduces IOP Induction - Thiopentone/propofol reduces the IOP Muscle relaxants - NDMR reduces the IOP Maintainance - Oxygen, Nitrous oxide & Halothane/Isoflurane Reversal - Atropine given IV or IM with anticholinesterases

Drugs in local anaesthesiaLOCAL ANAESTHESIA USE ( CONCENTRATION )

Benoxinate Proparacaine Amethocaine Lignocaine Bupivacaine Ropivacaine

Topical ( 0.4% ) Topical (0.5% ) Topical (0.5-1%) Topical ( 4% ) Infiltration (0.5% - 2% ) Infiltration (0.25%-0.75% ) Infiltration (1% )

Topical anaesthesia Indications - Reserved for superficial corneal and

conjunctival surgery - Phacoemulsification in cooperative patients in well dilated pupil - Prior to regional block - For syringing , tonometry , gonioscopy Drugs used - 4% lignocaine , .5% tetracaine ,

paracaine , benoxinate .4% , cocaine.

Deep topical forniceal nerve block A sponge or cotton soaked with preservative free lignocaine

placed in the superior & inferior fornix 5 to 10 min before surgery Pressure of 30 mmHg applied by a hoonan ball. Anaesthesia of conjunctiva, ciliary body, iris, sclera done.

Parabulbar block A conjunctival incision of 2-3 mm is made halfway between

inferior limbus and fornix to open sub -tenons space Cauterisation A curved metal cannula or a needle is introduced 1-2 ml. Of anaesthetic mixture is infused quickly

Intracameral anaesthesia Local anaesthetic delivered into ant. Chamber using a

small cannula through side port. Given additionally with topical anaesthesia in phacoimulsification for better comfort. Helpful in small pupil during cataract surgery.

Peribulbar block

Steps : -Anaesthtic mixture : 5 ml. Lignocaine 2% with 1:200000 adrenaline and 5 ml. Bupivacaine .75% mixed with 75 units of hyaluronidase. -Needle : A 25 gauge 2.5 cm. disposable needle is attached to the 10 ml. Syringe. -Topical anaesthesia instilled into the conjunctival sac. -Patient position : supine and asked to look straight ahead.

Peribulbar block-Point of insertion : transconjunctivally or transcutaneously at the junction of middle 2/3rd and lateral 1/3rd of lower lid adjacent and parallel to orbital floor for about 2.5 cm. -Aspiration - 5 ml. of mixture is injected - Second injection : infero medial to supraorbital notch a second injection of 3 ml. is injected. - Pressure: for 10 minutes against the closed eyelid - Anaesthesia begin in 5 minutes but in most patient takes about 15 minutes

Peribulbar block- Supplemental injection : inferiorly for persisting inferolateral movements and superiorly for persisting superior or medial movements Advantage : - least chance of retrobulbar haemorrhage , globe perforation or optic nv. damage. - no need of additional facial block Disadvantage : - chemosis of lid and conjunctiva are common - hyaluronidase is essential

Retrobulbar block Steps :

- Position of eye : -A 3.5 cm. long 22 gauge needle is introduced transcutaniously at the junction of middle third and lateral third of the lower orbital margin - Direction of needle : directly backward for about 15 mm. Then upward and medially towards the apex. Anaesthetic solution : Effects : - analgesia of deeper structure. - akinesia of all extra - ocular muscle - hypotony, proptosis

Facial block 1)

Indication : If a retrobulbar block is planned. Types : van Lint technique : a 22 gauge 3.5 cm. needle is inserted subcutaneously 1 cm. outside the lateral canthus and advanced upwards towards the brow and downwards towards the infraorbital foramen injecting along both paths in a v shaped manner. Modified van Lint technique : anaesthetic mixture is injencted more temporal to lateral canthus further away from supra and infra orbital rim.

Facial block 2) OBrien technique : A needle is placed posterior to

condyloid process of mandible and anaesthetic mixture is injected around it to block the facial nerve and its branches. 3) Nadbaths block : a 25 gauge needle is inserted behind the posterior border of ramus of mandible in front of mastoid process. Aspiration and 3-5 ml. of anaesthetic mixture is injected. 4) Atkinson block : needle is inserted along the inferior edge of zygomatic bone and upwards across the zygomatic arch towards the top of ear.

Frontal blockIndication : Wound closure, pain relief, surgical

debridement. Steps :

- A 4 cm. needle is entered the orbit transcutaneously just below the mid point of supraorbital margin. - Direction : towards the roof of orbit and follow its contour for 4 cm. distance. - Aspiration - Injection of 2 ml. of anaesthetic mixture.

Local infiltration Indication :

- subconjunctival infiltration : For most strabismus surgery particularly for rectus muscle surgery. - subcutaneous infiltration : for upper and lower eyelid surgery. Drugs used : Lignocaine, Bupivacaine, Ropivacaine.

Complications of Ocular Anaesthesia Drug relatedAll types of block retrobulbar, peribulbar, subtenon, subconjunctival & topical

Procedure- relatedMost adverse effects observed with needle-delivered anaesthesia viz. retro- & peribulbar & subconj. Inj.

Procedure related complications of needledelivered anaesthesia

Globe perforation Retrobulbar haemorrhage Extraocular muscle trauma, ptosis & diplopia Optic nerve trauma, subdural injection & its sequelae Increased IOP & occlusion of retinal circulation Retinal Detachment Others: pain & ecchymosis, amaurosis, post-op. facial pasly.

Oculosystemic reflexes Particularly seen in the setting of strabismus surgery more

often in young patients. Oculogastric reflex: Post-op. nausea and vomiting linked to this reflex. Preventive measures include use of intraoperative antiemetics like metoclopramide esp. if narcotics are used & minimal muscle manipulation. Oculocardiac reflex: - Triggered by pressure on the globe, tight-fitting speculum, traction on extraocular muscles, esp. medial rectus as well as on other ocular tissues.

- Associated with bradycardia, hypotension, asystole, ventricular dysrhythmias. - Reported incidence ranges from 10 82%. Strabismus pts not pretreated with atropine have 90% incidence. - Reflex has its afferent limb in trigeminal system & efferent limb in vagal system. Afferent limb can be blocked by a retrobulbar anaesthetic. -Tetracaine drops may be applied to surgical field to decrease afferent limb. Deep anaesthesia may help pts. who are prone to oculocardiac reflex. Also, adequate oxygenation should be maintained.

- Early recognition by audible pulse tone from pulse oximeter. - Prompt release of tension on extraocular muscles. Muscle hooks to be relaxed instead of trying to remove them. -If bradycardia is associated with hypotension or an irregular rhythm, surgery to be stopped & heart rate allowed to normalize. -Atropine 0.01 mg/kg iv may be given. Ventricular arrhythmia may require iv lidocaine 1 to 2 mg/kg.

Toxicity of common anaesthetic agentsToxicity of Local Anaesthetics Sensitivity reactions: characterized by wheals, intense itching, asthmatic breathing & hypotension. Systemic disturbances: numbness of tongue & mouth, tinnitus, visual disturbances, slurring of speech, muscular twitching, irrational conversation, unconciousness, convulsions, coma & apnoea. Acidosis (both resp. & metabolic) increases severity of reaction while alkalosis reduces it. Toxic reactions more common when injections have been made rapidly or large quantities of drugs released into circulation.

Prevention of L.A. emergency Availability of adequate equipments for treatment of

emergencies: oxygen, masks, rebreathing bags, laryngoscopes, selection of endotracheal tubes. Before admin. L.A. ideally an iv cannula or atleast a needle should be in place in a peripheral vein. Avail. of emergency drugs: thiopentone, diazepam, adrenaline 1:1000, chlorpheniramine, aminophylline (250 mg ampoules) & hydrocortisone (100 mg amp.)

Management of L.A. emergency Promptly stopping the injection Oxygen admin. by face mask, manual inflation of lungs if

apnoea has occurred. If convulsion last > 30 secs, anticonvulsive drugs like thiopentone 2.5% 150-200 mg or diazepam 5-10 mg given i.v. Diazepam is better in hypotension. Treat bronchospasm by slow iv inj of aminophylline 250-500 mg Treat intense itching/urticaria by chlorpheniramine 10-20 mg iv Treat hypotension by rapid infusion of normal saline 1 litre, or plasma expanders like Haemaccel 500 ml. Repeat accor. to response and G.C. of patient.

Toxicity of surface anaesthetic agents Cocaine 4%

* cloudiness of cornea * mydriatic effect may lead to acute attack of angle closure glaucoma in predisposed pt. Amethocaine (tetracaine) * tranisent burning sensation, blepharospasm, hyperaemia Lignocaine: sensitivity (but no cross sensitivity with ester L.A.) Preservatives might cause epithelial toxicity.

Toxicity of drugs used in dissociative anaesthesia Ketamine: Dissociative anaesthesia

- overdose: resp depression. Tx: supportive ventilation to maintain adequate blood oxygen saturation & carbondioxide elimination. - contra-indicated in pts. with h/o cerebrovascular disturbance, hypertension & severe cardiac decompensation. - Ketamine tends to elevate IOP. This may be secondary to increase in extraocular muscle tone & may be as high as 10 mmHg.

Ocular anaesthesia in special circumstances Diabetics: Type I more affected than type II.

- schedule surgery early in the day - give 1/3 to 1/2 of standard morning dose of int. or long acting insulin. Blood glucose checked before inj. & at hourly intervals throughout perioperative period. Hyperglycemia to be treated with small amt of short acting insulin, hypoglycemia with iv infusion of 5% dextrose. - pts. on oral hypoglycaemics: discont. medication on day of surgery. Regulate blood sugar with insulin. Pts. on corticosteroids: Additional 100 mg of hydrocortisone intraoperatively.

Ocular anaesthesia in special circumstances Marfans syndrome: often have CVS abnormality,

incompetant/prolapsed valves, arrhythmias, aortic aneurysms and pulmonary abnormalities. LA may be safer. Myotonic dystrophy: bradycardia, prolonged PR interval unresponsive to atropine, respiratory complications, increased risk of aspiration. Again LA is preferable. H/o malignant hyperthermia: In adults LA. In children precautionary steps like iv dantrolene, cont body temp monitoring, use of agents considered safe for this population like narcotics, benzodiazepines, barbiturates and non-depolarizing muscle relaxants. Careful monitoring to continue atleast 8 hours post op.