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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