Anesthesia in Ophthalmic Surgery

Panit CherdchuOphthalmology department Phramongkutklao Hospital

OUTLINEReview of AnatomyAnesthetic AgentsType of AnesthesiaTake Home Message

ORBITAL ANATOMY1

measurement“The orbital entrance

averages approximately 35 mm in height and 45

mm in width” “depth varies from 40-45 mm from the orbital entrance to

the orbital apex”

7 BONES

Superior orbital fissureInferior orbital fissure

Optic canal

Infraorbital foramen

Frontal EthmoidalMaxillary Sphenoidal

Periorbital Sinuses

Ciliary Ganglion

• A long sensory root

• A short motor root

• A sympathetic root

EOMExtraocular muscles

MUSCLES• 4 Rectus: SR-IR-LR-MR• 2 Oblique: SO-IO• 1 Protractor: Orbicularis Oculi Muscle• 1 Retractor: Levator Palpebral Superioris Muscle-

Muller’s muscle

“The relationship between the muscle insertions and the ora serrata is clinically important. A misdirected suture passed through the insertion of the superior rectus muscle could perforate the retina”

IMPORTANT

Levator is innervated by

CN III

1. skin 2. eyelid margin 3. subcutaneous connective tissue 4. orbicularis oculi muscle5. orbital septum 6. levator palpebrae superioris muscle 7. Müller muscle 8. tarsus9. conjunctiva

3 parts of orbicularis oculi muscles

“The Tenon capsule (the fascia bulbi) is an envelope of elastic connective tissue that fuses posteriorly with the optic nerve sheath and anteriorly

with a thin layer of tissue called the intermuscular septum, which is located 3 mm posterior to the limbus”

Vascular Supply and Drainage of the Orbit

Vascular Supply and Drainage of the Orbit

Internal carotid artery and external carotid artery collateral anatomy

• 1, internal carotid; • 2, external carotid; • 3, facial; • 4, maxillary; • 5, superficial temporal; • 6, transverse facial; • 7, middle meningeal; • 8, frontal branch of superficial temporal; • 9, ophthalmic; • 10, lacrimal; • 11, recurrent meningeal; • 12, supraorbital; • 13, supratrochlear; • 14, angular; • 15, palpebral; • 16, zygomaticotemporal; • 17, zygomaticofacial; • 18, deep temporal; • 19, infraorbital; • 20, muscular.

3 main outlets of venous system

– Superior and inferior ophthalmic v. cavernous sinus&cranial system

– Anastomosis of the ophthalmic v.&angular v. facial venous system

– Inferior orbital fissure pterygoid venous plexus

NEUROANATOMY• Cranial Nerve II• Cranial Nerve III• Cranial Nerve IV• Cranial Nerve V• Cranial Nerve VI• Ciliary Ganglion

NEUROANATOMY

MOTOR NERVE

Local Anesthetic Agents2

“The local anesthetic drugs used in ophthalmology are tertiary amines linked by either ester or amide bonds to an aromatic

residue”

“Protonated form(inside myelin sheath) blocks the sodium channels on the inner wall of the cell membrane and increases the threshold for electrical excitability. As increasing numbers of sodium channels are blocked, nerve conduction is impeded and finally blocked”

• block the poorly myelinated and narrow parasym&sym fibers

• Optic nerve is usually not impeded by retrobulbar block

• Myelinated motor fibers (akinesia)

• Sensory fibers (pain+temp)

TOXIC• The toxic manifestations of local anesthetics

are generally related to dose• severe hepatic insufficiency • even at lower doses. These manifestations

include restlessness and tremor that may proceed to convulsions, and respiratory and myocardial depression

EPINEPHRINE• local anesthetics block sympathetic vascular

tone and dilate vessels,

• a 1:200,000 concentration of epinephrine is frequently added to shorter-acting drugs to retard vascular absorption

LIDOCAINE• Lidocaine is an amide local anesthetic used in

strengths of 0.5%, 1%, and 2% (with or without epinephrine) for injection

• It yields a rapid (5-minute) retrobulbar or eyelid block that lasts 1–2 hours.

MEPIVACAINE• Mepivacaine is an amide drug used in

strengths of 1%–3% (with or without a vasoconstrictor).

• rapid onset and lasts approximately 2–3 hours. The maximum safe dose is 25 mL of a 2% solution.

BUPIVACAINE• poor akinesia but has the advantage of a long

duration of action, up to 8 hours. • mixture with lidocaine or mepivacaine to

achieve a rapid, complete, and long-lasting effect.

• The maximum safe dose is 25 mL of a 0.75% solution.

HYALURONIDASE• combined with local injection of anesthetics to

increase the dispersion of the anesthetic drug

• More dispersion reduce the pressure rise in the limited orbital space, produce less distortion of the surgical site, decrease the risk of postoperative strabismus and myotoxicity, and increase akinesia of the globe and lid

HYALURONIDASE• lower volumes of anesthetic agent.

• For retrobulbar or peribulbar injection, 1 mL of hyaluronidase can be added to a syringe of the anesthetic to be administered.

Type of Anesthesia3

FACIAL NERVE BLOCK

LOCAL ANESTHESIA

Topical Anesthetic BlockSubconjunctival Block

Intracameral Block

GENERAL ANESTHESIA

REGIONAL ANESTHESIA

Peribulbar BlockParabulbar BlockRetrobulbar Block

LOCAL ANESTHESIA

• Topical Anesthesia Block– Block superficial cornea and conjunctiva– Block long and short ciliary nerve, nasociliary

nerve, lacrimal nerve– Disrupt intercellular tight junction

LOCAL ANESTHESIA

• Subconjunctival block – Anterior segment is blocked but no akinesia– At posterior to phaco incision/ perilimbal

conjunctiva

LOCAL ANESTHESIA

• Intracameral block– Anesthetic agent: 0.2-0.5 ml of unpreserved 1%

lidocaine hydrochloride– If absence of posterior capsulemight cause

transient retinal toxicity “Transient Amaurosis”

Regional anesthesia• Parabulbar block (sub-tenon block)– Inferonasal, inferotemporal– Inject anesthetic agent into sub-tenon space– Patient look upward+outward– Drug : 2% lidocaine, +hyaluronidase

Method– Grab conjunctiva+Tenon’s capsule with blunt non-

toothed forceps– Small cut with westcott scissors– Blunt curved posterior sub-tenon’s cannula with

local anesthetic– Move along the curvature of the sclera– Inject anesthetic agent into sub-tenon space

move along the curvature

BLUNT curved

• Expected outcome– Akinesia– Mydriasis– Analgesia – Hypotonia of lidsptosis

Button hole formed ~10 mm from the corneal limbus

Freeing the Quadrant

Lacrimal cannular

Insertion of cannula and injection of anesthetic.

• Still!!– Superonasal block is indicated as supplementary

block– Locate the needle at upper eyelid vertically above

the medial limbus– Intermittent of ocular compression (10-

20minutes)

Pros consReduce retrobulbar hemorrhage accident

Might not achieve at akinesis effect

Reduce risk of injury at globe or optic nerve

Larger volume is needed

Reduce risk of intradural injection

More incidence of periorbital ecchymosis+chemosis

Regional anesthesia• Peribulbar block (Extraconal block)– Inject into extraconal spacedrug spread to whole

area including intraconal area– The larger space to apply, the more volume of

drug is needed.

Method– Patients lies in supine + neutral position – ¾ inch, 24-26G needle– Anesthetic agent: 5ml of 0.75%bupivacaine// 5 ml

of 2%lidocaine with 1:200,000 adrenaline//150 units of hyaluronidase

Method– Point at lateral1/3 and the medial 2/3 of the

inferior orbital edge– Directed to the apex of the orbit– at equator of globe

• Retrobulbar block (intraconal block)– 25G, 1 ½ inches needle– Neutral position– Point at lateral 1/3 and medial 2/3 of inferior orbital edge– Posteriorly parallel to the orbital floor, incline of 15

degree– Pass equatorshift to medially and superiorly angle of 45

degree– Depth 25-35 mm– Compress for 15 sec on5 sec off for 1-2 minutes

Regional anesthesia

• Akinesia and Anesthesia are quickly ensure the complete block

Retrobulbar Block - Step 1

• Enter just inferior to the globe and perpendicular to the plane of the face.

Retrobulbar Block - Step 2

• Once you feel the first pop through the orbital septum, angle 45 degrees medially and 45 degrees superiorly towards the apex of the orbit until the second pop through the muscle cone is felt.

Retrobulbar Block - Injection

Pull back on the syringe to ensure the needle is not in a vessel, then inject 3-5 cc of anesthetic, palpating the globe to assess for posterior pressure

Pros ConsLow volume of drug Risk of retrobulbar

hemorrhageHigh potency of blocking Oculocardiac reflexRapid onset CRAO

Puncture into globe,optic nerveRisk of brain stem anesthesiaEpinephrine toxicity

Retrobulbar hemorrhage

• increasing proptosis with tight eyelids, subconjunctival and periorbital haemorrhage, and a dramatic increase in intraorbital pressure

Lateral Canthotomy

Oculocardiac reflex

• rapid distension of the tissues by volume or haemorrhage provoke it occasionally

• Bradycardia, Junctional Rhythm, Asystole

Central Retinal Artery Occlusion

• Sudden, complete, and painless loss of vision • Must!! immediately reduce the IOP

Puncture into globe

• myopic eyes which are longer but also thinner• globes longer than 26 mm are at risk• A diagnosis of perforation may be made by

pain at the time the block is performed, sudden loss of vision, hypotonia, a poor red reflex or vitreous haemorrhage

Puncture into optic nerve

Brainstem Anesthesia• Onset can be 2-40 minutes after injection• symptoms are drowsiness, vomiting,

contralateral blindness caused by reflux of the drug to the optic chiasm, convulsions, respiratory depression or arrest, neurological deficit, cardiac arrest

Brainstem Anesthesia

Facial Nerve Block

Van Lint Method

• 1 cm below and behind the lateral canthus

O’Brien’s Method

• The condyloid process of the mandible

Atkinson Method

• At Inferior edge of the zygomatic bone

Nadbath Ellis Method

Where facial nerve first emerges from stylomastoid foramen

THE END