Regional anaesthesia for intraocular surgery Springer

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636 CANADIAN JOURNAL OF ANAESTHESIA, Capsulopalpebral fascia dehiscence entropion While many participate in monitored care others are per. Extraocular muscle injury diplopia forming the eye blocks. Oculocardiac reflex It is the purpose of this review to draw the attention. Retrobulbar versus peribulbar block of anaesthetists to this neglected area A brief description. Safety of the anatomy of the orbit and its contents is presented. Effectiveness first to serve as a base for performing safe eye blocks. Operators preference This is followed by an analysis of the various ocular block. Variation in techniques techniques The complications associated with ocular. Suggested approach blocks are then presented for their awareness prevention. Role of anaesthetists and management The review will conclude with a dis. cussion of the choice between retrobulbar and peribulbar. Since the discovery of cocaine as a local anaesthetic in approaches and the role of anaesthetists in eye surgery. 1884 by Koller then an Austrian ophthalmology resident under local anaesthesia. eye surgery has been commonly performed under local. anaesthesia The retrobulbar anaesthesia technique was Anatomy of the orbit. first described in the same year by Knapp but it was Regional blocks for eye surgery involve the insertion of. not until 50 yr later when better local anaesthetic agents a needle very close to many important structures A. were available that it became generally accepted Today knowledge of the anatomy of the orbit and its contents. more than one million retrobulbar anaesthetic blocks a is essential for the safe conduct of eye block anaesthesia. year are performed in the United States 2 The insertion Detailed functional orbital anatomy can be found in the. of a needle within the muscle cone occasionally produces excellent treatise by Doxanas and Anderson 7 and the. serious complications This lead to the introduction of works on orbital connective tissues by Koornneef 8 m. peribulbar anaesthesia in which the needle is introduced. outside the muscle cone The orbit Figure 1, Regional anaesthesia is suitable for a wide variety of The orbit is 40 to 50 mm deep The commonly used. eye operations including cataract extraction trabeculec 38 mm 1 5 in retrobulbar needle is long enough to pene. tomy vitrectomy and strabismus repair Cataract surgery trate the optic nerve in front of the optic foramen in. constitutes by far the most common eye operation done about 10 of the population 11 The medial wall of the. under local anaesthesia Almost all cataract surgery is orbit is parallel to the sagittal plane and the lateral wall. performed under regional anaesthesia in the United States lies at 45 to the medial wall The volume of the orbit. and India General anaesthesia is still commonly used is approximately 30 ml and that of the globe is about. in other countries but the pattern is changing There 7 ml The injection of five to ten rnl of local anaesthetic. is evidence that in elderly patients having cataract surgery solution will increase the orbital pressure. the endocrine and metabolic responses seen during gen Above the pear shaped orbital cavity are the anterior. eral anaesthesia are inhibited by local anaesthesia Re cranial fossa and frontal sinus The maxillary sinus lies. gional anaesthesia should be considered as an alternative beneath the orbital floor The medial wall is separated. choice for eye surgery and not just for those unfit for from the ethmoid sinus by a very thin portion of the. general anaesthesia 4 The reductions in health care fund ethmoid bone called the lamina papyracea Perforation. ing and the recent trend towards day care surgery will of the medial wall by a block needle may result in orbital. increase the demand on regional anaesthesia for eye cellulitis or abscess The lateral wall is bordered by the. surgery temporal fossa in front and the middle cranial fossa at. Today most of the eye anaesthesia blocks world wide the back The orbital septum forms its anterior boundary. are performed by ophthalmic surgeons and the bulk of The supraorbital notch an often used landmark in the. information on regional anaesthesia for eye surgery is medial third of the superior orbital rim is totally enclosed. found in the ophthalmic literature However life to form a foramen in 25 of orbits The sharp border. threatening complications fortunately rare are best man lateral to it and the rounded margin medial to it may. aged by anaesthetists experienced in resuscitation s Fur give a clue to its location if it is not felt easily Nerves. thermore the care of patients having eye surgery with and vessels cross over the orbital rim medial to the su. local anaesthesia can be improved by having anaesthetists praorbital notch and may be injured if the block needle. involved in the perioperative management 6 Anaesthetists is inserted too close to the periosteum in this area. are also trained in nerve block techniques Thus it is. natural that in many centres anaesthetists have become Eyelids. more involved in local anaesthesia for ophthalmic surgery The eyelids are protracted by the orbicularis muscle. Wong REGIONAL A N A E S T H E S I A FOR I N T R A O C U L A R SURGERY 637. FIGURE 1 Volume angle and relations of the orbit, which is innervated by the facial nerve This muscle may FIGURE 2 Position of the block needle in relation to the muscle. not be paralysed by anaesthetic solutions deposited be cone in retrobulbar and peribulbar blocks. hind the globe enabling the patient to squeeze the eye. and cause an increase in intraocular pressure IOP The and outside it in peribulbar blocks Figure 2 In the. upper eyelid is retracted by the levator palpebrae super anterior orbit fibrous septa connect the adjacent muscles. ioris which originates from the annulus of Zinn at the to form a well defined cone These intermuscular fi. orbital apex and is innervated by the oculomotor nerve brous septa are often poorly developed in the posterior. The lower eyelid is retracted by the capsulopalpebral fas orbit Computerised tomography following retrobulbar. cia which is a direct extension of the inferior rectus mus and peribulbar anaesthesia demonstrated that the anaes. cle thetic solution spread freely between the inside and out. side of the cone irrespective of where it was deposited J2. Extraocular muscles The levator palpebrae muscle originates above the su. The globe is moved by four rectus superior medial in perior rectus at the orbital apex and proceeds anteriorly. ferior lateral and two oblique superior inferior mus as a functional unit with the superior rectus muscle The. cles The rectus muscles originate from the annulus of superior oblique muscle originates superomedial to the. Zinn a fibrous ring at the orbital apex which encircles annulus of Zinn and runs forward at the junction of. the optic foramen and the medial aspect of the superior the medial wall and roof of the orbit It becomes a tendon. orbital fissure Together the four rectus muscles form a before reaching the anterior orbital margin passes. cone with the point at the orbital apex and the base through the trochlea a cartilaginous ring which redirects. at the equator of the globe Within this cone lie the optic it so that it pulls in an anterior medial direction and. nerve artery vein and the ciliary ganglion When per inserts posteriorly on the sclera close to the optic nerve. forming local anaesthesia blocks the tip of the needle superotemporally The trochlea may be traumatized by. is inserted inside this muscle cone in retrobulbar blocks a needle inserted in the superomedial quadrant of the. 638 CANADIAN JOURNAL OF ANAESTHESIA, orbit while performing eye blocks The inferior oblique. muscle arises in a shallow depression lateral to the origin. of the nasolacrimal duct runs obliquely along the inferior. surface of the globe and inserts to the sclera inferior. to the macula Inadvertent penetration of extraocular. muscles by a block needle causing intramuscular haem. atoma or intramuscular injection of a large volume of. anaesthesia solution may cause ischaemia leading to fi. brosis and contracture of the muscle, The globe is enclosed by Tenon s capsule which is a.
dense fibrous layer of connective tissue The rectus mus. cles penetrate Tenon s capsule posterior to the equator. of the globe while the oblique muscles penetrate anterior. to the equator of the globe In the recently described. sub Tenon block anaesthetic solutions are deposited in. the retrobulbar space with an irrigating cannula through. an incision made in the Tenon s capsule,Nerves and vessels. Nerves and vessels coming through the optic foramen. and medial portion of the superior orbital fissure go. through the annulus of Zinn to supply the structures. within the muscle cone The optic nerve ophthalmic ar. tery and ocular sympathetics pass through the optic canal. and foramen The dura is adherent to the optic canal. and the optic nerve itself Inadvertent needle penetration. of the optic nerve sheath may result in depositing the. local anaesthetic directly in the subarachnoid space. The abducens nerve divisions of the oculomotor and. trigeminal nerves sensory root of the ciliary ganglion. and superior ophthalmic vein come into the orbit through. the medial portion of the superior orbital fissure The FIGURE 3 Somatosensory innervation of the eye and surrounding. tissues from the ophthalmic division of the trigeminal nerve. inferior orbital fissure transmits the maxillary division of. the trigeminal nerve and permits venous drainage from. the inferior ophthalmic vein to the pterygoid plexus the anterior half of the posterior third of the muscle on. These vessels and nerves are at risk of being traumatized its orbital surface This may explain why this muscle often. by injections in the retrobulbar space 13 continues to function after a low volume retrobulbar. Three cranial nerves serve the motor functions of the block. extraocular muscles the oculomotor nerve supplies the. medial superior and inferior rectus the inferior oblique Somatosensory innervation. and the levator palpebrae superioris muscles the trochlea All somatosensory inputs from the eye are transmitted. nerve supplies the superior oblique muscle the abducens mainly through the ophthalmic nerve and to a much. nerve supplies the lateral rectus muscle The motor nerves less extent the maxillary nerve to the sensory root of. to the superior medial and inferior recti enter the muscles the trigeminal nerve. from within the muscle cone at approximately the junc The ophthalmic nerve divides into three branches the. tion of the middle and posterior thirds and to the lateral frontal lacrimal and nasociliary nerves These branches. rectus at just posterior to the middle Deposition of an enter the orbit through the superior orbital fissure and. aesthetic solution inside the muscle cone or in the pos provide the innervation of the eye and surrounding tissues. terior orbit would thus produce akinesia of the rectus Figure 3. muscles more readily The inferior oblique is supplied The frontal nerve enters the orbit supero lateral to the. at about the middle of its posterior border The trochlear annulus of Zinn and runs forward above the recti and. nerve enters the orbit outside the annulus of Zinn and levator palpebrae superioris muscles just below the pe. supplies the superior oblique in several branches that enter riosteum It divides into a medial supratrochlear nerve. Wong R E G I O N A L ANAESTHESIA FOR 1NTRAOCULAR SURGERY 639. and a large lateral supraorbital nerve midway through side the cone The sensory supply to the conjunctiva in. the orbit The supratrochlear nerve passes above the pul cludes the supraorbital lacrimal infratrochlear and in. ley of the superior oblique muscle and supplies the me fraorbital nerves most of which run outside the muscle. dial part of the upper eyelid The supraorbital nerve exits cone and may not be totally blocked Despite an oth. the orbit via the supraorbital notch and supplies the mid erwise satisfactory block the patient may feel pinching. dle two thirds of the upper eyelid and superior conjunc at the beginning or antibiotic injection at the end of. tiva surgery However this can be managed easily with topical. The lacrimal nerve follows the upper border of the anaesthetic placed directly on the conjunctiva The sen. lateral rectus muscle close to the junction of the roof sory supply to the eyelids and conjunctiva arise from the. and lateral wall of the orbit It supplies sensory inner lacrimal supraorbital supratrochlear infratrochlear and. vation to the lacrimal gland and the lateral part of the infraorbital nerves The plexus formed by these nerves. upper eyelid and conjunctiva lies deep to the palpebral fibres of the orbicularis oculi. The nasociliary nerve conveys the principal somatos muscle Anaesthetics must be deposited deep into the or. ensory inputs from the eye It passes through the annulus bicularis muscle in order to anaesthetize the eyelids. of Zinn and between the two divisions of the oculomotor. nerve and crosses the orbit oliquely below the superior Ocular blocks. rectus muscle deeper than the other branches of the oph. thalmic nerve As it crosses above the optic nerve it sends Retrobulbar block. a sensory root to the ciliary ganglion from which the Retrobulbar anaesthesia was first described by Knapp. short ciliary nerves continues to the eyeball The ciliary of New York in 1884 for enucleation of an eyeball 1 The. 635 Review Article David H W Wong MB aS FRCPC Regional anaesthesia for intraocular surgery The role of anaesthetists in providing local anaesthesia for in

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