Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001

Onset within 1 minute

Duration of action 10 to 20 minutes

(Physician’s Desk Reference for Ophthalmology Oradell, NJ, Medical Economics, 1991)

occurs, but resuscitative measures should be, at hand to maintain the ventilation and circulation till the drug is metabolized.5

Action of the local anesthetic can be enhanced by the addition of epinephrine 1:200,000 in addition it also provides vasoconstriction and reduces bleeding. Caution should be exercised when the patient has systemic hypertension and cardiovascular disease or thyrotoxicosis.6

Addition of hyaluronidase, which depolymerizes hyaluronic acid, results in quicker diffusion of the agent. Mechanical pressure is needed to spread the agent through the tissues effectively.7

Local Anesthetic Agents

Topical (Table 5.1) Before starting surgical procedure under local anesthesia one should ensure that an intravenous line is started and emergency drugs are at hand. The patient should have a cardiac monitor and also his or her oxygen and carbon dioxide levels should be monitored. Facilities for oxygen administration and intubation should also be available and it is preferable if an anesthetist is available to manage an emergency or to give additional sedation if the patient is in need of it.

Injectable See Table 5.2.

TECHNIQUES OF LOCAL ANESTHETIC INJECTIONS

Orbicularis or facial block to paralyze the orbicularis muscle can be achieved by blocking the trunk of the facial nerve at stylomastoid foramen, (Nadbath block) or at the neck of the mandible (Obrien’s technique) in front of the tragus or by injecting at the orbital margin (van lint technique,/Atkinson block). When the peribulbar block with hyaluronidase is administered there is enough diffusion of the agent to block the orbicularis also and this negates a separate orbicularis block. When the trunk of the nerve is being blocked sometimes there could be

(Adapted from Raj PP: Handbook of Regional Anesthesia. Churchill Livingstone: New York, 1985; Physician’s Desk Reference for Ophthalmology Ordell NJ, Medical Economics, 1991; Crandall DC: Pharmacology of ocular anesthetics, In Duane TD, Jaeger EA (Eds): Biomedical Foundations of Ophthalmology, Harper and Row: Philadelphia, 1986)

needle injury to the nerve as it is in a relatively fixed position and cannot roll away from the needle and this could cause prolonged weakness of the facial muscles.8 Some times after the Nadbath technique dysphagia and respiratory distress can occur due to paresis of vagus, glossopharyngeal, and spinal accessory nerves, causing aspiration of oral secretion.9

Retrobulbar Injection

The technique places the anesthetic in the retrobulbar space, which contains the sensory; and the motor nerves that supply the eye. Except the superior oblique this block paralyzes the rest of the ocular muscles since the trochlear nerve is outside the muscle cone.

This injection is given with an 11/4 inch blunt-tipped Atkinson needle. It should ideally be given by the surgeon himself as he or she is familiar with the anatomy and not relegated to others and it should be given without putting the nerve on stretch and after making sure that the needle is not in a blood vessel by withdrawing the piston before injecting. The patient is asked to look medially and then midway between the lateral limbus and canthus at the lower orbital margin, the needle pierces the skin and is passed posteriorly parallel to the floor till it clears the equator of the globe, then the needle is angled upwards and inwards towards the apex of the orbit and pushed further to enter the muscle cone. The bevel of the needle should face the globe to reduce the chances of piercing the globe. One can often detect the passage through the muscle cone

by noticing a slight flick of the eye and one can also rule out globe perforation by making lateral motion to note whether the tip of the needle is fixed or free. Then about 1 cc or 2 cc of the anesthetic is introduced and observation is made of the upper eyelid, which tends to droop if the injection is in the right place. Slight pressure over the eye for few minutes after the injection helps to distribute the anesthetic and within minutes the akinesia and anesthesia is obtained, the pressure applied also helps in reducing the tension of the eye. Immediately after the injection one should check the opposite eye for any paresis of the ocular muscles in the other eye and also enquire whether there is any amaurosis of the opposite eye as this will give an immediate clue to diffusion of the anesthetic along the subarachnoid space around the optic nerve in a posterior direction, and if observed immediate resuscitative measures should be instituted and oxygen administration can be started. Repeated yawning after a retrobulbar injection can also be sign of relative hypoxia and should alert the surgeon to possible respiratory depression.

Peribulbar Injection

There has been an increasing change to this technique to avoid the complication of the retrobulbar anesthesia. In this technique the agent is placed either in the anterior or posterior extraconal space and allowed to diffuse into the retrobulbar space posteriorly and also anteriorly to obtain an orbicularis block as well. To achieve this much larger volume of the anesthetic has to be placed and also it is preferable to use a diffusion agent like hyaluronidase and apply pressure for some time. It often takes more time than a retrobulbar injection to achieve the desired result and the incidence of incomplete akinesia and anesthesia is higher.10

Procedure of Posterior Peribulbar Block (DUANE)*

With an intravenous line running or heparin lock in place and after desired sedation and eyelid preparation, proceed with the following steps;

1. Make a small skin wheal in the lower eyelid 1 cm medial to the lateral canthus over the inferior orbital rim.

2. Make a small skin wheal in the upper eyelid in the skinfold directly inferior to the supraorbital foramen.

3. Through the inferior skin wheal, with a 27-gauge needle, inject 0.5 ml of lidocaine 1% in the

5. Through the lower lid skin wheal, inject 1 ml of lidocaine 1 percent bupivacaine 3/4 percent hyaluronidase solution in the orbicularis muscle and 1 ml immediately deep to it. Advance along the floor of the orbit to the equator of the eye; aspirate and inject 1 ml; aiming slightly superomedially, advance the needle to its full depth and inject 1 to 1.5 ml.

6. Pushing the globe inferiorly with a free index finger, enter through the upper lid skin wheal and inject 1 ml ½ inch deep to the orbicularis muscle and slightly nearer the canthus than is the original skin wheal; direct the needle along the orbital roof without engaging the periosteum

* (Adapted from Nugent CC: Peribulbar Anesthesia—A Safe, Simple Effective and Relatively Painless Technique)

7. Pressure on the globe/orbit and time are essential for a good block; after 8 minutes, if incomplete akinesia remains, 3 to 4 ml of additional anesthetic solution is injected by the lower approach if lateral or inferior movement is seen, by the superior approach if superior or medial movement is seen.

(Always perform lower lid injections before upper lid).

Complications

• Retrobulbar hemorrhage sometimes may result (1 to 3%)11,12 due to injury to

a blood vessel and this is recognized by immediate tightening of the lids and proptosis of the globe and some times the subconjunctival appearance of the hemorrhage. Pressure over the eyeball for a few minutes may arrest a minor

bleed and may allow the surgery to be undertaken. However, it is always prudent to postpone the surgery for a week and take up the case later. On most occasion no permanent damage is done to the eye. But there has been mention of optic atrophy after such an event and some times one may get occlusion of the central retinal artery.

•Perforation of the globe (0.075%)13 is a serious complication which can occur with both the retrobulbar as well as peribulbar blocks and this is more often seen when a sharp disposable needle is used and its frequency is increased if the injection is made by a person not very familiar with the anatomical knowledge of the orbit. It produces immediate rise of intraocular pressure (IOP) and may also cause sharp pain. Even double perforation of the globe has been noticed when such sharp needles are used and the complication has come to be recognized only after the surgery when the retinal examination has been done.

•Allergic reactions to the local anesthetic are relatively rare. Many of the socalled allergic reactions are often instances of toxicity. After routine testing for allergy to local anesthetic for fifteen years in all patients undergoing ocular surgery there was no instance where an allergic reaction was noted and hence this practice was stopped. But in a patient with known history of allergies and hypersensitivity reactions one can test for evidence for hypersensitivity taking care that emergency drugs and resuscitative measures are available.

•Convulsions, tremors and confusion and other central nervous system manifestations can occur especially when inadvertent intravascular injection occurs.

Alternative Methods (Table 5.3)

Any new LA technique should be as safe, effective and acceptable as its predecessors. Recently, subconjunctival, sub-Tenon’s (parabulbar), and purely topical anesthesia, sometimes with additional intracameral lignocaine have become popular. All these methods of anesthesia are useful and effective if the patient assessment and selection are good and if the surgery is not prolonged. These also necessitate more interaction between the surgeon and the patient and make the surgeon alert and be aware of the patient cooperation and comfort.

Patients with mental retardation, deafness, children and where communication between the operator and the subject is not possible are not suitable for such

techniques. But these techniques do abolish some of the complications associated with the retroand peribulbar techniques.

Topical anesthesia is achieved by instilling 4 percent lidocaine into the conjunctival cul-de-sac of the eye to be operated at five minute interval for about 15 minutes. A sponge soaked in the local anesthetic can be placed at the limbus so that the area can get the maximum contact with the agent.

R E F E R E N C E S

1. Dejong RH: Neural blockade by local anesthetics. JAMA 238: 1383, 1977.

2. Zahl K, Jordan A, McGroarty J et al: Peribulbar anesthesia—effect of bicarbonate on mixtures of lidocaine, bupivacaine, and hyaluronidase with or without epinephrine. Ophthalmology 98: 239, 1991.

3. Eccarius SG, Gordon ME, Parelman JJ: Bicarbonate-buffered lidocaine-epinephrine-hyaluronidse for eyelid anesthesia. Ophthalmology 97: 1499, 1990.

4. Goodman LS, Gilman A: The Pharmacological Basis of Therapeutics (4th ed), 1970.

5. Mauger TF, Craig EL: Havener’s Ocular Pharmacology (6th ed), Mosby Year Book: St. Louis, 1994. 6. Mauger TF, Craig EL: Havener’s Ocular Pharmacology (6th ed), Mosby Year Book: St. Louis, 1994. 7. Mauger TF, Craig EL: Havener’s Ocular Pharmacology (6th ed), Mosby Year Book: St. Louis, 1994. 8. Atkinson WS: Facial nerve block. Am J Ophthalmology 57: 144, 1964.

9. Koenig SB, Snyder RW, Jonathan K: Respiratory distress after a Nadbath block. Ophthalmology 95: 1285, 1988.

10.Mauger TF, Craig EL: Havener’s Ocular Pharmacology (6th ed), Mosby Year Book: St. Louis, 1994.

11.Linn Jr JG, Smith RB: Intraoperative complications and their management. Int Ophthalmol Clin 13: 149,

1973.

12. Cionni RJ, Osher RH: Retrobulbar hemorrhage. Ophthalmology 98: 1153, 1991.

13.Zaturansky B, Hyams S: Perforation of the globe during the injection of local anesthesia. Ophthalmic Surg 18:585, 1987.

injection sites, or injection styles are immune to the risk for damage to the globe or other orbital structures.3-5

Another issue regarding the blind passage of sharp needles into the orbit concerns those patients on anticoagulant medications or those with naturally occurring coagulopathies. It should be obvious that these patients are at greater risk for periocular hemorrhage with needle injection, but often the medical necessity for anticoagulation dictates that patients remain on treatment during the perioperative period. Often,

the systemic risk to cessation of anticoagulant treatment is greater than the risk of intraoperative bleeding. Indeed, the published guidelines for cataract surgery

in the United Kingdom suggest that cataract surgery should proceed up to an INR (International Normalized Ratio) of 4.0 for patients taking Coumadin. It is evident that non-injection forms of local anesthesia are safer for anticoagulated patients.

Additional consequences of periocular anesthetic include an inability of the patient to move the eye during and after surgery. While it was once considered essential that the eye be fully still for safe surgery, it is now recognized that purposeful eye movements, on command, can benefit the progress of surgery. As an example, in cases with narrow palpebral fissures, the eye can be moved to facilitate incisions, etc. A further consequence of regional anesthetic infiltration is amaurosis. As a result, the patient cannot see to fixate a target. However, with topical/intracameral anesthesia, the patient can be asked to follow a light source or other visual target to help fixate the globe in a satisfactory position for surgery.

Movement away from periocular injection toward topical methods of ocular anesthesia is natural, given the overall changes in small-incision cataract surgery that have progressed to outpatient surgery with methods that allow for immediate ambulation, rapid return to a full lifestyle, and stable optical results of surgery within days.6 The immediate use of the eye after cataract surgery is possible only with topical or intracameral methods and is in keeping with the concepts of modern surgery.

Topical anesthesia resurfaced in this decade as a useful tool after Fichman’s suggestion regarding the use of tetracaine 0.5 percent applied to the eye as the only anesthetic for cataract surgery.7 Other agents, such as bupivacaine and lidocaine have been popularized because of a reduced tendency to cause corneal epitheliopathy and to have a longer period of action as compared with tetracaine. However, patients are not universally comfortable with topical anesthesia as the only agent. Many surgeons employ small amounts of intravenous, oral, or sublingual sedation as an adjunct. However, in 1995 Gills suggested the routine use of intracameral nonpreserved lidocaine in addition to topical anesthesia with or without systemic sedation,8 although the concept had been mentioned earlier by Fichman who considered intraocular tetracaine for use in difficult case situations. Safety and efficacy of intracameral lidocaine has been further established by Koch9 and Masket with Gokmen in separate studies.10 In the latter investigation, approximately 40 percent of greater than 300 patients receiving only topical anesthesia required intraoperative conversion to a deeper level of local anesthesia, whereas fewer than 1 percent of 300 cases receiving intracameral lidocaine had need for an additional local anesthetic

method. In the same study safety was measured by comparing the degree of corneal edema on the first postoperative day between the two groups, a reduced likelihood for corneal edema was associated with the use of intracameral nonpreserved lidocaine hydrochloride 1

percent, but this finding may be related to the use of chop style phacoemulsification for the latter group. Nevertheless, based upon the early postoperative appearance of the cornea, non-preserved lidocaine is seemingly non-toxic although Koch reports reduced contrast sensitivity and visual acuity in the first few hours after surgery.

Other methods to provide ocular anesthesia for cataract surgery without the risks of blind pass, sharp needle orbital injection have evolved during the same era as the movement to topical anesthesia. Posterior sub-Tenon’s infiltration employs a blunt cannula (Fig. 6.1) to place local anesthesia directly in the retrobulbar space. A conjunctival button hole incision, performed under topical anesthesia, is necessary for the cannula to gain direct access to the sub-Tenon’s space. This method was suggested as an alternative to sharp needle orbital injection,11 and has been further popularized by Greenbaum as a primary method for cataract anesthesia; he coined the term “parabulbar” anesthesia to describe the concept.12 Additionally, the method may be used for surgeons in transition to topical/intracameral anesthesia and is very useful to convert from topical methods in cases where complications occur, surgery is prolonged, or if the patient is otherwise in need of a deeper level of anesthesia. As long as the cataract incision is self-sealing, the parabulbar infiltration may be given at any time during the surgery. Varying with the nature of the agent used for infiltration, parabulbar anesthesia may provide complete ocular akinesia and amaurosis. Other alternatives include anterior subconjunctival injection given diffusely or only focally in the region of the incision, so-called “pin-point” anesthesia.13

It is evident that traditional ocular anesthesia for cataract surgery, utilizing sharp needles passed blindly through the skin of the lids or the conjunctiva engenders risks (Table 6.1) that are avoidable with topical or intracameral or other recently developed means for local anesthesia. However, in addition to the greater safety associated with newer anesthetic systems, topical and topical or intracameral methods avoid the need for patching and allow patient the use of the eye immediately following surgery in the overwhelming majority of cases. Advantages, therefore, include safety, improved cosmesis, ability to use the eye immediately following surgery, and the ability to move and fixate the eye during surgery in response to the surgeon as an aid to the procedure (Table 6.2).

Varying with the experience of the surgeon, certain conditions may contraindicate the use of topical/intracameral anesthesia (Table 6.3). Given the ability to move

Table 6.2: Advantages of topical/intracameral anesthesia

______

•Avoids pain, blemish and risk of injection anesthesia

•Allows immediate useful vision after surgery

•Eliminates need for patch after surgery

•Reduces anxiety and/or heavy sedation associated with injection anesthesia

•Compatible for patients on anticoagulants

•Patients can aid surgeon by moving eye for favorable exposure

______

Table 6.3: Contraindications to topical/intracameral anethesia

____

A. Relative

1. Language barrier

2. Anticipated difficult surgery

3. Poorly cooperative patient B. Absolute

1. Total deafness

2. Coarse nystagmus

____

the eye, the patient can aid in the surgery or create significant obstacles; cataract surgery under topical or intracameral anesthesia is, by necessity, interactive. Poor patient cooperation is a relative contraindication, as is the inability of the surgeon and patient to adequately communicate in the same language. Often, an interpreter or bilingual family member can be present in the operating theater in order to facilitate surgery without need for injection anesthesia. However, absolute congenital deafness with speaking difficulty is an absolute contraindication, since the patient may become disoriented under the surgical drapes and cannot be expected to communicate by the usual means of lipreading or sign language; patients of this nature often require general anesthesia. Ocular conditions may also act as relative or absolute contraindications; cataracts too dense to allow fixation on the microscope light, potentially complicated surgery (preoperative zonulysis, etc.), and nystagmus are common examples. Nevertheless, the huge majority of patients may safely experience small-incision cataract surgery under topical/intracameral anesthetic with very limited sedation.

Methods

The author prefers the use of lidocaine HCl 4.0 percent non-preserved for topical anesthetic. It is long acting and non-mucogenic (Previous experience with 0.75 percent