Lecture: Anesthesia for Ophthalmic Surgery

DR SCHELL: Good morning and good afternoon and evening, I guess, depending on where you are. My name is Dawn Schell. I’ll be talking this morning about anesthesia for ophthalmic surgery. I hope to take about 40 minutes to discuss anesthesia for this type of surgery, and leave about 20 minutes for questions. I did see the list of questions that you provided ahead of time, which was extremely helpful. Hopefully I’ll answer most of those questions within the presentation, but again, we’ll have time for additional questions at the end. Like I said, my name is Dawn Schell. I’m director of anesthesia at the Cole Eye Surgery Center, which is at the Cleveland Clinic in Cleveland, Ohio. For those of you who are not as familiar with Cleveland or the geography of the United States, we are in the Midwest. We are about five hours by car South of Toronto, Canada. About five hours East of Chicago, and about eight hours West of New York City. This is a picture of our campus in Cleveland. This is the entire campus of the Cleveland Clinic, and this is actually a photo of Cole Eye, which is the building that does only eye or ophthalmologic care for patients. Our surgery center is on the first floor. It has five operating room suites, and we do many different types of ophthalmic surgery, including cataracts, glaucoma surgery, cornea surgery, oculoplastics, ocular oncology, vitreoretinal procedures, and strabismus procedures. The objectives today are to understand the anatomy and innervation of the eye, to know the various anesthetic options for ophthalmic surgery, what their indications and contraindications are, and when to use them. And then last, to be able to recognize potential complications associated with anesthesia for ophthalmic surgery. And I apologize in advance. I know there are a lot of different individuals in the audience. Many of you are ophthalmologists, and so some of this will be review. But I tried to do the presentation with a number of different specialties, subspecialties, in mind. So hopefully it won’t be too much review for all of you. First, let’s review the anatomy of the eye. As we all know, the outer layer is made up of the cornea. That is the layer covering the anterior aspect of the eye. And which contains most of the nerve fibers, innervation, and causes all that pain that we all experience if we get a corneal abrasion, or get something caught — an eyelash caught in our eye. The sclera, then, is on the posterior aspect of the eye, and is a fibrous covering that goes all the way around to the back of the eye. The eye is typically divided into two segments, the anterior segment, and the posterior segment. In the anterior segment, we have the anterior chamber, which is the contents of the eye, anterior to the iris. And the posterior chamber, which is behind the iris, and in front of the lens. The ciliary body and ciliary processes control the thickness of the lens and secrete the aqueous humor. The posterior segment, then, is comprised of the choroid or the vascular layer between the retina and the sclera, the vitreous humor, the retina in the back, and of course the macula, which is the part of the retina responsible for central vision. Innervation of the eye. Sensation is provided by the ophthalmic branch, which is division 1 of cranial nerve number V, also known as the trigeminal nerve. And this nerve passes through the muscular cone, on its way to innervating the eye and providing sensation to the eye. Motor innervation is provided by three separate nerves. The trochlear nerve, cranial nerve IV, innervates the superior oblique muscles, the abducens, cranial nerve VI, innervates the lateral rectus muscle, and the oculomotor, cranial nerve III, innervates all the other muscles. All of these pass through the muscular cone except for the trochlear nerve. So you do have sparing of some, the superior oblique muscle, which allows inward gaze, when you block the nerves that pass through the muscular cone. Vision, as we all know, is supplied by the optic nerve, or cranial nerve II. Lid movement is supplied by two separate nerves: The facial nerve, or cranial nerve VII, has a superficial branch that innervates orbicularis oculi, and that is the nerve or the muscle that allow you to close the eyelid. The oculomotor nerve innervates the levator palpebrae muscle, which opens the eyelid. So again, when you block those nerves that innervate the eye, the ones that pass through the cone allow you to not open the eye, but the facial nerve is preserved, because that comes in laterally or more superficially. And we’ll talk more about that later. Well, what are the types of anesthesia that we employ when we are doing anesthesia for ophthalmic surgery? Probably the most common one, and the most common procedure, ophthalmic procedure, that is done on patients, is cataract surgery. At least in the United States, and I would think in many parts of the world now, local or topical anesthesia is the most commonly employed type of anesthetic for cataract extraction, if it is being done with phacoemulsification. That can be accomplished with topical drops. The topical drops are placed on the surface of the eye. They anesthetize the cornea. Then once you get under the cornea, you inject some intracameral lidocaine or local anesthetic to, again, supplement that local anesthesia. And the cataract can be removed without significant pain, when you use this type of local anesthesia. Some people will also use subconjunctival local anesthesia. However, I have to say that at our institution, we use just the topical drops and intracameral injections. Regional anesthesia — you have the retrobulbar block, peribulbar block, sub-Tenon injection, and in some situations, in any type of ophthalmic procedure, you need to employ general anesthesia, and we’ll talk about the indications for that a little bit later. So first, let’s talk about topical anesthesia. The topical local anesthetics that are used to anesthetize the cornea usually at least what we use — are 4% lidocaine drops or 2% lidocaine jelly, depending on the preference of the surgeon. There are some surgeons who feel that the 2% lidocaine jelly is more effective. But probably the majority of our surgeons here use 4% lidocaine drops. You can also use tetracaine 0.5% drops. I think our surgeons, again, believe that the 4% lidocaine is more effective, and at least here in the United States, tetracaine is much more expensive than the 4% lidocaine drops, so 4% lidocaine drops is what we use. This can be suitable for cataract extractions or removal of superficial corneal lesions or superficial corneal surgeries. The one thing to keep in mind when you use topical anesthesia is that it does require an awake and cooperative patient. The eye is not immobilized, because of having blocked the ocular muscles. And so the patient is required to focus on a point either on the microscope, on the light above the microscope, or with the surgeon telling them to look up or look down. And so if you have a patient that’s not cooperative and unable to do that, sometimes it’s difficult to do the procedure, because the eye itself doesn’t hold still, if the patient is unable to focus persistently on a specific area. Topical anesthesia is usually combined with sedation here. Although it can be done without sedation. The local anesthesia is actually sufficient to provide anesthesia without any kind of sedation. Here in the United States, most patients prefer and expect some type of sedation. And I have to say we typically use Midazolam, in conjunction with fentanyl. But you can use small doses of propofol, in order to maintain awareness but provide anxiolysis, and a little bit of sedation for patients as well. It is critical that you maintain patient cooperation. Like I said. And so you don’t want to get patients so sleepy that they can’t continue to focus on the light, or that they may have a startle response and move precipitously during the procedure. So we usually use quite small doses of midazolam, and very small doses of fentanyl. And sometimes even avoid the fentanyl, depending on what a patient’s history is, if they have a history of significant nausea with anesthesia. I have found that it requires appropriate patient expectations. So I actually spend a lot of my time when I’m talking with patients before going back to the operating room, telling them specifically that this is not general anesthesia. Many patients, again, in the United States, expect to be asleep for any kind of surgery. And so I have to reinforce to them that they will be awake. But relaxed. That they will be expected to move their eyes or look up or down in response to the surgeon’s requests. And that they should never have any pain. And they should feel relaxed, but they will be awake. Additionally, it requires a surgeon who is familiar with the technique. When topical local anesthetics were first being used, many of our older surgeons felt uncomfortable utilizing those, because they were used to having a completely immobile eye, after having had a retro or peribulbar block. Now most of the surgeons are trained to do the cataract extractions at least here in the United States under topical anesthesia. And they’re used to not having a paralyzed or immobile or akinetic eye. But again, it did require a little bit of a learning curve for some surgeons who weren’t as familiar with the technique. Some of you asked what local anesthetics. I just wanted to show, again, a picture of the types that we use. This is a picture of 0.5% tetracaine. Like I said, we don’t use that nearly as often. We much more commonly use 4% lidocaine. It comes in these vials, and it’s stated that it’s for topical use. And our pharmacy actually aliquots it into 1 cc aliquots, in a 3 mL syringe, so that we can get 40 different doses. Because this is a 40 mL or a 40 cc bottle. And this is what we use routinely. Again, like I said, some of our surgeons use lidocaine jelly, but this would be used most commonly. The intracameral and subconjunctival local anesthesia, like I said, are used to supplement topical local anesthesia by some people. And again, for anterior segment procedures. The intracameral local anesthetic that we use most commonly is preservative-free 2% lidocaine. And that is placed by the surgeon. Obviously after the procedure has been started. Some people will use subconjunctival local anesthesia for glaucoma procedures, instead of a retro or peribulbar block. It’s an episcleral injection, usually of a very small volume. 0.5 to 0.8 mLs. And it numbs the area locally. But if you massage it, it produces some chemosis, and then you can massage it and actually get some spread into the anterior segment and into the anterior chamber, if you wait long enough. Regionally, we can use retrobulbar or peribulbar blocks. These do usually require sedation for placement, because you want a patient that is not going to move, not going to be anxious. Move their eye when you come at them to do the block. Retrobulbar or peribulbar blocks are used when you need to provide complete anesthesia of the globe. So especially if you’re doing anything that involves anything more than the anterior segment, either the posterior segment or the ocular muscles. In those situations, you’ll want to use a retro or peribulbar block. It does cause temporary loss of vision, due to blockade of the optic nerve. And it is important to remember when we talked about the innervation of the eye that you may need to do additional lid block, often called the Van Lint block, to prevent squeezing or blinking or squeezing of the eyelids. Because you do not block the facial nerve, which innervates the orbicularis oculi. And sometimes patients may have complete anesthesia of the globe, but they get the speculum in, and they are uncomfortable, because the eyelid is not numb. And their tendency is to try and blink or squeeze on that speculum. And you can use a Van Lint block to prevent that squeezing. Relative contraindications of a retro or peribulbar block includes patients who are anticoagulated. Again, we have some of our retina surgeons who will do blocks on anticoagulated patients. Some of our surgeons are more reluctant to do a block on an anticoagulated patient. And a lot of it depends on their training and their personal preference. We also have some surgeons who do not want to block a patient who is blind in the contralateral eye, because you leave someone essentially functionally blind for the duration of the block. And then there are often patients who are unable to hold still during a procedure. And so while you may be able to do the block, they can’t hold still for the remainder of the procedure, even though the block — excuse me, even though the eye is anesthetized with the block. Many people would consider an open globe as a relative contraindication to a retro or peribulbar block. Again, if we have very small and superficial corneal lesions, sometimes, our cornea surgeons will still use a peribulbar or retrobulbar block in these patients. But the majority of the time, the concern is that by doing a retro or peribulbar block, you increase intraocular pressure, and run the risk of extrusion of ocular contents. And so the majority of open globe procedures we would do with general anesthesia. A retrobulbar block is typically performed by finding a point one third of the way in from the lateral canthus. And the objective is to advance the needle past the midway point or the equator of the globe. Once you’re past that, then you angle the needle upward, and you usually are using a B bevel or a more blunt needle, so that as you pierce through the cone muscles or get into the cone, you actually see a little bit of a twitch of the eye, and you feel a pop. As you advance into the intraconal space. The objective is to have the needle tip within the cone, and then you inject your local anesthetic. This is just a video of a retrobulbar block being performed. Again, some people will use the finger to displace the globe upward a little bit. You advance past the midway point. You see that they move the syringe just a bit to make sure that they are not caught within the sclera or the globe itself. Inject anywhere from 3 to 7 mLs. You’ll see the eye become much more proptotic. And sometimes our anesthetists and surgeons will actually give an additional bit of local anesthesia, superficially, on the surface of the globe. A peribulbar block is very similar to a retrobulbar block, but instead of advancing the needle into the cone, you actually keep the needle here, outside the cone, and inject your local anesthetic there. It was at one point believed that there were striations and septi that could prevent the local anesthetic from actually diffusing inside the cone with a peribulbar block. That has for the most part been disproven. So although it may require additional time to fully set up, it should eventually provide similar coverage. I have to say, as a caveat, that occasionally I find that peribulbar blocks have not been quite as efficacious, when we’re doing our… I’m blanking on the name. When we’re doing the belts that actually are used for retinal detachments. Sometimes I find that patients are a little bit more uncomfortable, and it requires a little bit more sedation. By using a peribulbar block, you actually decrease the risk of injection into the muscular cone, which — some of those risks we’ll cover in a bit. But they include intravascular injection, because there are vessels in the cone as well. And you can get into the dural sheath covering the optic nerve, as well as you’re more likely to get globe perforation if you actually advance the needle inside the cone. So many people have gone to using peribulbar blocks exclusively, just to decrease the risks. When we do retrobulbar or peribulbar blocks here, we use a combination of 2% lidocaine and 0.75% bupivacaine, 1 to 1, with or without hyaluronidase. Again, it’s usually up to the surgeon or the provider. And we inject 3 to 7 mLs of solution, retro or peribulbarly. Most of our glaucoma, oculoplastics, ocular oncologists, and cornea surgeons only use 3 to 5 mLs. Our retinal surgeons use more. 6 to 7 mL per block. This is a picture of the needle we use, a 32 millimeter 25 gauge needle with a blunt tip, and this is the combination of lidocaine and bupivacaine that our pharmacy mixes up for us, when we’re utilizing these blocks. What are the indications for retro or peribulbar blocks? Well, any kind of anterior segment surgery, so glaucoma procedures, placement of radioactive plaques for tumors, cornea procedures, cataracts — all of those can be done with a retrobulbar or peribulbar block. In addition, you can do posterior segment surgery. The advantage of using a retro or peribulbar block is that it anesthetizes more than just the anterior aspect of the globe. And so you can do vitrectomies, retroorbital plaque insertions, scleral buckles, essentially anything that you need, that is behind the anterior chamber of the eye. You can actually do eviscerations and enucleations. My experience is that you probably will require a bit more sedation to keep the patient comfortable. But our ocular oncologist does most of his eviscerations and enucleations with a retrobulbar block. And we use either propofol sedation, or sometimes just Versed and fentanyl, for those patients, to keep them comfortable intraoperatively. Here at the Cleveland Clinic, we use general anesthesia for our strabismus surgery procedures, but there are studies that have demonstrated effectiveness for strabismus surgery by using a retro or peribulbar block. Like I said, here we typically use general anesthesia. We find that patients tolerate that better. But if you are skilled and able to do a good retrobulbar block, and are able to possibly supplement with a little bit of local anesthetic, and you have somebody who can give you sedation, you can do strabismus surgery with regional blocks as well. What are the complications of a retrobulbar block? Well, I said earlier that a lot of people have moved on to peribulbar blocks, to decrease complications. The biggest complications being: Starting with an oculocardiac reflex, which is a slowing of the heart rate, due to movement of the eye, or in this case, injection of the local anesthetic that puts pressure on the eye. The oculocardiac reflex is transmitted through the ophthalmic branch of cranial nerve V, which again is the trigeminal nerve, and the efferent branches of vagus nerve. The vagus nerve actually slows the heart rate. Most of the time, this is self-limited, and as soon as the block starts to set up, within 15 to 30 seconds, that slowing of the heart rate completely is eliminated. Occasionally, excuse me, occasionally you will see some patients have brief periods of profound bradycardia, or even a several second episode of asystole, which makes all of us get very nervous, but almost always this comes back on its own once you stop the injection, and the local anesthetic starts to set up. More serious complications are retrobulbar hemorrhage. If you get into the cone and you lacerate one of the ophthalmic arteries or veins, you can have significant hemorrhage behind the globe. This increases pressure and may decrease perfusion to the eye and the contents of the eye, specifically the retina. Which can cause permanent vision loss. If this happens, and the intraocular pressure increases precipitously, and you get an intraocular compartment syndrome, it may require a canthotomy. We have a kit that is in our preoperative holding area, that everybody is aware of, that is a canthotomy kit. So if that would happen, we have it available immediately. You can also get intravascular injection of local anesthetic. If the local anesthetic would be injected into one of the ophthalmic arteries, your drops could cause the patient to have a seizure. If it got into the vein, because the total volume is not great, you might have patients developing some brief symptoms of ringing in their ears, tingling in their ears. I suppose you could even have a brief period of seizures. But again, because that’s in the venous blood, it would require one full circulation time. And the likelihood that you would see seizures with the volumes used in a retrobulbar block… I think the likelihood of seizure with an intravenous injection would be quite low. There is the possibility that you can get perforation of the globe. When I showed you the video of the retrobulbar block being performed, you could see that the surgeon moved the syringe and needle just a little bit, to make sure that when he did that, the globe did not move as well. And that was his way of evaluating and making sure that the needle itself had not gotten — perforated the globe or punctured the sclera on its transit into the space in the cone. You can get optic nerve or retinal damage if you perforate the globe or the needle and inject local anesthetic into those areas. There can be toxicity and permanent damage to either the nerve or retina. And the feared complication for those of us in anesthesia is that you can inject local anesthetic actually into the sheath around the optic nerve, which then spreads into the brain. And this intrathecal spread can cause a complete spinal anesthetic. The first thing that you often see is a change hemodynamically. You may see actually a tachycardia, and bradycardia, and sometimes hypertension, and then many times profound hypotension. And because it will eventually get to the brain stem, the local anesthetic will anesthetize the respiratory centers as well, and these patients will need to be intubated, and you’ll need to provide ventilatory support for several hours, until the local anesthetic is metabolized. Most of the time, these patients recover uneventfully. However, it does require immediate recognition of the fact that you’ve had intrathecal spread, so that you can start ventilating the patient, and supporting their hemodynamics. Because it has been described that some patients have had profound cardiovascular collapse and significant hypotension that requires epinephrine for a period of time, to maintain an adequate blood pressure, until that returns. And again, like I said, you will need to provide ventilatory support until that local anesthetic is metabolized as well. Let me just say that… Again, the peribulbar block, the only complication that you can see routinely with it is the oculocardiac reflex. But by going peribulbarly and staying outside the cone, you essentially eliminate these more serious complications. Again, which is why many practitioners have gone to using peribulbar as opposed to retrobulbar. The Van Lint block I talked about. Which blocks the superficial nerves of the facial nerve and prevents squeezing of the eyelid. In this situation, you want to introduce your needle 1 to 2 centimeters lateral to the rim of the orbit. And you inject several ccs of local anesthetic infraorbitally and supraorbitally in a D-shaped distribution. So our surgeons will inject under the skin, following this trajectory and this trajectory, and this blocks the distal branches of the facial nerve and the innervation to the orbicularis oculi, and prevents closure of the eyelid. Tenon’s capsule and sub-Tenon injection has gained in popularity recently. And many of our ophthalmologists who have trained more recently are in fact using Tenon’s injections preferentially, over either a retro or peribulbar block. Now, Tenon’s capsule is a thin layer of connective tissue which surrounds the globe. It’s usually in continuity with the cornea. Anteriorly. And continues around to the back of the globe, superior to the sclera. You can advance a needle. If you look here, you can advance a needle into the sub-Tenon’s space, and eventually move that needle with a curvature on it, all the way to the posterior aspect of the eyeball and inject local anesthetic, and it will block the innervation to the eyeball and provide coverage comparable to what you see with a retro or peribulbar block. The technique itself is to create a small tent of the conjunctiva and raise the Tenon’s capsule with a pair of blunt, non-toothed forceps, inferonasally. And I have a video that I’ll show in just a second. You insert a curved cannula. You pass it posteriorly, following the curvature of the globe, until its tip is perceived to pass the equator. By doing so, you minimize the risk of creating chemosis anteriorly, where you’re going to be working in the eye. You then inject 3 to 5 mLs of local anesthetic. And like I said, this has actually increased in popularity, and is much less risky in patients who are anticoagulated. So many of our retina surgeons who have patients that are on blood thinners will use sub-Tenon injection. Some of our more recently trained glaucoma surgeons are doing sub-Tenon injections on the field, after they’ve prepped the eye. And using that almost exclusively for their glaucoma procedures. This is a video of a sub-Tenon injection. You’ll see they’ll lift the cornea there. And in this situation, they didn’t open that. But they just used a blunt tipped, curved catheter. They advance that catheter all the way past the equator to the back of the globe, and then will inject 3 to 5 mLs of local anesthetic, that spreads out circumferentially around the globe, and provides a block similar to that provided by a retro or peribulbar block. Well, what about patients who do receive blocks? We often administer sedation during the procedures, even though the eye is immobile, and anesthetic. Again, part of that is: Americans’ tendency to expect that they will be asleep or very sedated for their surgeries. I would say that the majority of our short procedures, our patients get only mild sedation with Midazolam and fentanyl. For example, the anterior segment surgeries like cataracts or glaucoma procedures. In our patients who have more pronounced anxiety, we will often use an infusion of propofol or even propofol and ketamine mixed together. By adding ketamine, we can decrease the amount of propofol that we need to provide the same amount of anxiolysis, and we see much less respiratory depression. And since obviously getting under the drapes and doing a little bit of chin support or respiratory support for someone — moves the patient’s head and can interfere with the ophthalmologist’s surgery — we try and limit this sedation, so that we don’t have to do that. And I think when we add ketamine to our propofol infusion, we find we can run much lower doses. Typically 15 to 25 mcg per minute of a propofol-ketamine combination. Dexmedetomidine has been used for some, but the big concern is slow elimination and wake-up, and if you have a busy surgery center, it can take a while for it to wear off and it keeps patients in recovery for too long. What about anesthesia for oculoplastic surgery? Typically, we do deep sedation, using methohexital, which is a short acting barbiturate, or propofol, and we allow the surgeon to inject the local anesthetic. Our oculoplastic surgeons typically use 1 to 2% lidocaine with 1:100,000 epinephrine. We will continue to provide mild sedation with midazolam, sometimes a little bit of fentanyl, or a propofol infusion. The issue for us is, however, that we don’t want to use supplemental oxygen when the surgeon is actually operating, because our surgeons use electrocautery on the field. And in order to eliminate the fire risk after the first injection of the local anesthetic, we try and turn off the oxygen and have them breathing only room air. So most of the time, our patients are fairly awake after that brief sleep with methohexital for the injection of the local anesthetic. Once the eyelids are completely numb, they usually tolerate the procedure very well. The methohexital with the midazolam provides a bit of ongoing sedation for the 40 or 45 minutes that is required for most of the oculoplastics procedures that we perform. We do use general anesthesia for tear duct surgery, with a supraglottic airway, typically. Our tubes and dacryocystorhinostomies are usually done under general anesthesia. I worked at a center where the oculoplastic surgeon preferred to do them under local anesthesia, but we provided pretty significant sedation. Because when they got down to the periosteum to open the area for the DCR, it’s much harder to get the periosteum and bone completely anesthetized. So in those situations, we would use a little bit more propofol sedation to provide analgesia during the procedure. And last, we have the option of general anesthesia in our patients. Typically, general anesthesia requires analgesia or pain control, immobility, and amnesia. We always talk about general anesthesia as being a triad or combination of these three things. What are the indications for general anesthesia? Well, all of us will have the uncooperative patient, or developmentally delayed or developmentally challenged patient. And obviously children need to be anesthetized under general anesthesia. Because they aren’t able to hold still for the procedures. Some of our retina procedures get quite long. If our surgeons know that it’s going to be a fairly complex procedure, and going to take 2.5, 3, 4, sometimes even 5 hours, in those cases, we will oftentimes preferentially use general anesthesia as well. Because a patient gets tired of holding still for long periods of time, and oftentimes needs to move around, just to keep their muscles or their back or their legs from aching. Then there are patients that have a contraindication to having a peribulbar or a retrobulbar block. Like we talked about, sometimes patients with monocular vision, the surgeons don’t want that good eye blocked. Because you don’t want to make the patient blind for those several hours. And in patients who have anticoagulation, there are some who prefer not to subject the patient to the risk of having a retroorbital bleed. As discussed earlier, open globe procedures frequently require general anesthesia. And many times, the oculoplastics and strabismus procedures are more easily done with general anesthesia as well. Well, what about intraocular pressure? Historically, there was a concern that some of our anesthetic agents or anesthetic drugs could increase intraocular pressure. Namely, succinylcholine and ketamine. And in fact, there were studies done that showed that succinylcholine would increase intraocular pressure briefly. For about 10 to 20 millimeters of mercury. It usually did not last more than a few minutes. But there was concern that especially, for example, in an open globe injury patient, that that would be enough to extrude eye contents. More recently, the belief is that it’s unlikely that these drugs will increase intraocular pressure any more than coughing, straining, or moving to the OR table from a stretcher. So I think most people believe that if you weigh the risks and benefits that if somebody really does need a quick securing of their airway, due to an aspiration risk, that succinylcholine is acceptable in these patients. And that the intraocular pressure increase is unlikely to cause significant damage. I don’t know what the availability of sugammadex is in the locations that you practice. Now that we have sugammadex, we can easily reverse non-depolarizing muscle paralysis. So that may eliminate the need to use succinylcholine in these patients. But if you have it available and need to use it, with open globes, the intraocular pressure increase is unlikely to cause extrusion of eye contents for this brief moment that it causes increase in pressure. It’s important to note that there’s an absolute contraindication of use of nitrous oxide in patients who have gas or air injected inside the eye. What happens is that nitrous oxide will diffuse into that gas or into the air that’s inside the eye, and rapidly increase the volume of that. And increase intraocular pressure. And in situations has been found to increase pressure so rapidly that it has been found to cause permanent vision loss. Our technique for general anesthesia in the majority of our patients is that we give glycopyrrolate, 0.2 milligrams, as an antisialagogue. I personally believe that if you decrease secretions in the mouth you decrease risk of coughing or laryngospasm during the time that you remove the airway. So I’ll give all patients glycopyrrolate as an antisialagogue. It also has the ability to prevent the oculocardiac reflex in the majority of patients as well. We induce anesthesia with IV lidocaine and propofol, and secure the airway with patients who do not have a contraindication to supraglottic airways with a laryngeal mask airway, an LMA. Our clinic uses the curved airway called the AuraOnce. It’s curved and sits out of the way of the surgeon and doesn’t interfere with the microscope that sits right above the eye. We use spontaneous ventilation without muscle relaxants for these cases. With Sevoflurane. The exception being the penetrating keratoplasties, when surgeons are concerned about any kind of movement or coughing when the eye is open. In those situations, we will give muscle relaxant and paralyze as well. But in most cases we use spontaneous ventilation with sevoflurane. Because it’s problematic for patients to have significant nausea, retching, and vomiting after procedures, I prophylax everyone with dexamethasone and ondansetron to try to minimize the likelihood of post-op nausea and vomiting. I also do the absolute majority of my cases without any type of opioids under general anesthesia. I believe that it decreases the risk of postoperative nausea and vomiting, and since the majority of our patients will always get a retro or peribulbar or sub-Tenon injection in addition to the general anesthetic, for postoperative pain, there really is not a need for opioids or analgesia from the general anesthetic itself. We can always give opioids in the recovery if they need it. But to just give it without knowing whether or not they’re having pain, I think, increases the risk for post-op nausea and vomiting. Complications and side effects of general anesthesia. Again, the post-op nausea and vomiting is probably the most problematic. And the most annoying for patients. Then there are issues of the airway. Even with a laryngeal mask or supraglottic airway, patients will complain of some sore throat. And we always as anesthesiologists are incredibly aware of and fearful of any patient in whom you have difficulty securing the airway. With a supraglottic airway, the majority of patients oftentimes can be supported, but there is that dreaded cannot ventilate, cannot intubate scenario in patients with difficult airways. So there’s always that concern, when you’re using general anesthesia. A supraglottic airway also provides some protection, but not complete protection against aspiration. So any time you use supraglottic airways, that is a potential risk. And in patients with severe systemic disease, you have the potential for hemodynamic compromise. And in some situations, you may want to avoid general anesthesia, because of that. There’s probably also a slightly increased time to discharge, to wake up from general anesthesia, as compared to sedation with a block. But again, in certain situations, general anesthesia is really the only option that you have to provide anesthesia for these patients. Postoperative pain management of the ophthalmic patients. The regional blocks, like I said, peribulbar, retrobulbar, sub-Tenon, are actually the best. Obviously that minimizes sedation. It minimizes nausea and vomiting. In someone with sleep apnea, you don’t have to worry about giving them any kind of opiates because of that. So those are ideal. We also, for our cataract patients, will use topical 4% lidocaine drops in our recovery, if they’re having a lot of irritation or itching. Or pain in that eye. And that’s very effective. Our patients also will get 650 milligrams to 1,000 milligrams of acetaminophen. More commonly called paracetamol for those practicing elsewhere, and that does help with pain and headache associated with ophthalmic surgery. Nonsteroidal antiinflammatory medications are incredibly helpful. We use celecoxib, which is a Cox II inhibitor and does not worsen bleeding here. We use that a lot in our retina patients. Although the concern with any of the nonsteroidal antiinflammatories is that if there’s any kind of renal insufficiency, you want to be sure to not give too much, in terms of non-steroidals, for fear of worsening the renal insufficiency. And last, if all of these other options fail, you do have the option of opioids. We will use oxycodone or tramadol occasionally. But we try and do the majority of our cases without opioids. In part due to their side effects. In part due to the fact that they don’t make people feel well. And here in the United States, we also have a significant opioid addiction problem amongst many patients. And we try and limit exposure if we can. We don’t want to send people home with pain. But if we can, we try to use non-opioid therapies first. I would be happy to take any questions that you might have, regarding this presentation. And I’ll also hopefully have left about 15 minutes for questions now.

Which block is better between sub-Tenon or reticular for manual small incision cataract surgery? We rarely do sub-Tenon injections for cataract surgery. Again, we’ll use topical drops and then the intracameral. I think most of our surgeons feel that topical and intracameral is the preferable technique. The only times that we will do a sub-Tenon or even a peribulbar block for cataract procedures is when the patient has trouble holding the eye still, and they can’t focus or stare at a point, and the eyeball is moving continually. When do you choose for a patient between topical and block anesthesia? Are there criteria? Again, I think the majority of our cataracts and anterior segment are done with topical. If it’s anything more invasive than that, with glaucoma, we’ll often do a block or sub-Tenon. Anesthesia. And then if the surgeon feels that the patient will have difficulty focusing and holding the eye still, we’ll default to a block instead. Measures for oculocardiac reflex in the case of extraocular muscle surgery. Again, I would not hesitate to give glycopyrrolate. In much of our literature, they say you shouldn’t give that to prevent it. But I find that glycopyrrolate is really very well tolerated. People do complain of dry mouth for about 4 hours, but I have found that the incidence of significant oculocardiac reflex when I have used glycopyrrolate is really very small. Most oculocardiac reflexes will stop on their own, once you stop the inciting — either pulling on the muscle, the traction on the muscle, or whatever the insult is that you’re causing. But since I’ve been using glycopyrrolate in many of our cases, I just don’t even see the oculocardiac reflex much at all. Which block is better for corneal suturing and anterior segment foreign body? Since I’m not an ophthalmologist, I would have to say I would have to default to our ophthalmologists on that. But in watching them, I would say that if they feel that it’s fairly superficial in the cornea, a lot of times topical anesthesia is more than adequate. If they have any concern, however, our cornea surgeons will use retrobulbar or sub-Tenon injections. And it has more to do with surgeon preference than anything else. I don’t think that a block is necessarily better, but a lot of times, it just has to do with what the surgeon is familiar with using. What are the other facial block advantages or disadvantages? I know there are some people who use certain facial blocks for oculoplastics procedures. I have to say that our… Here at the clinic, we use really just subcutaneous injection. And we don’t use any other facial blocks. I think the challenge with some of these blocks is that it requires much more skill and experience. And sometimes because of differences in patients’ anatomy, you can end up missing some of them, and getting suboptimal blocks. So what our oculoplastic surgeons do is just a subcutaneous local infiltration to numb up the eyelid areas. They don’t use a particular block, per se. Thank you so much for the kind words. Advise measures to control vitreous pressure in case of cataract surgery with lens implantation and posterior… I asked one of my retina fellows about this yesterday, because again, my area of expertise is anesthesia. And he said… There were some things that I would say I would have to defer to an ophthalmologist in terms of surgical techniques. But he said in some of these cases, you can use… Diamox or acetazolamide as a diuretic to decrease that pressure. What instruments are included in the canthotomy kit? Um… That’s a good question, because I honestly can say I haven’t seen it opened. I would think there is a scissor, to be able to cut down and allow the eye to become proptotic. But I could get that information and actually send a photo, if somebody would like to see our canthotomy kit. What is the early sign of brain stem anesthesia? Since I’ve been here, in the past five years, we’ve only had one brain stem anesthesia. The biggest thing that they noticed initially is that the patient did not come back breathing. We typically, like I said, use methohexital to get somebody very relaxed or sedated for the placement of the block. Occasionally you’ll see a 30 second period of apnea, but they’ll come back breathing on their own. When they went to do a jaw thrust or stimulation, the patient didn’t take a deep breath. There was no response to painful surgical stimuli. And then they started seeing drops in blood pressure. It was commonly taught that when you would have brain stem anesthesia, you would see profound hypotension and bradycardia. Several years ago, or maybe even up to 10 years ago, someone actually went through the case reports, and what they found was that you can in fact see tachycardia and hypertension as well as bradycardia and hypotension. In fact, it’s not uncommon, as the local anesthetic moves from high up in the brain down to the brain stem, to first see hypertension, which then can turn into profound hypotension. Or tachycardia which then becomes bradycardia. The key is to have a high index of suspicion, and as soon as you think that you see that the patient is not breathing, and not responding normally, that you do positive pressure ventilation. And if they still don’t come back, then you secure the airway with an endotracheal intubation, and continue checking the vital signs frequently. As you may need intravenous epinephrine. I think initially, you shouldn’t go with resuscitation doses. Usually a milligram of epinephrine would be too much for these patients. But I would start with 10 to 50 micrograms of epinephrine. And if that didn’t very quickly control the symptoms, you could go up to 100, 200, 500 mcg, et cetera. I’ve seen, however, in our trainees too many times that when they have hypotension in the operating room, they go to ACLS protocol and a milligram of epinephrine for whoever is experiencing hypotension under anesthesia. It may be too much and cause significant hypertension. How to assess long-term complications/consequences of hazards of general anesthesia in a young child? I’m not a pediatric anesthesiologist. I know that that has become a very hot topic. I think that our pediatric anesthesiologists would tell you that we don’t know for sure that it’s so much anesthesia, or whether having some of the underlying problems and requiring frequent surgeries is contributing to some of the developmental challenges these kids have been found to have. But that in everything, you ought to balance the risks and benefits. In other words, if that child, by not being able to see, and having strabismus, is unable to learn, then it’s probably far better to go ahead and provide general anesthesia, so that this child can see better, in that the developmental consequences of not being able to read, see, et cetera, far outweigh the potential hazards of general anesthesia in a young child. Obviously you wouldn’t want to do cosmetic things in a young child, below the age of 3, if you could avoid them. Most people would say after the age of 3, the likelihood of harm is much less. What is the minimum INR to go for a retro or peribulbar anesthesia? I have to confess, we never check an INR. And when our surgeons are not concerned about it, they will do it without us checking. So I don’t think there is a minimum. That does open up the risk for — if somebody’s INR was really high, because they had taken way too much, or somehow that their dosages had been interfered with by other medications, et cetera. If you would have an INR of 6 or 7, I think there would be much higher risk. But we don’t ever check an INR. I would say about 30% of our surgeons will go ahead and do a retro or peribulbar injection when patients are on coumadin. The rest will have those patients hold the coumadin for several days to minimize the risk of bleeding. Is it considered mandatory to give a retrobulbar while a cannula is inserted? I’m thinking you’re meaning if you’re doing a vitrectomy? And I would think that it would be challenging to do vitrectomies with just topical or anterior chamber anesthesia. Even when our patients get lasers to the retina, they do feel that. And it causes… Not a sharp, but a headachy pain. And so if you haven’t anesthetized the posterior segment of the eye, I think patients would be uncomfortable. Is aspirin a contraindication for… No. In fact, in patients that we have, that have cardiac stents in place, we almost always tell them not to discontinue aspirin. Because the risk of discontinuing aspirin in somebody with a cardiac or coronary stent increases their risk of having a thrombosis of that stent. So we will continue aspirin on almost all of our patients who are taking it, and do not have them stop the aspirin. What are the causes for failure of anesthesia and akinesia despite injecting adequate amounts of anesthetic in case of peribulbar? And somebody had asked about pre-op ultrasound. I think the problem is — when you do a peribulbar or retrobulbar block, these are done blindly. Some have looked at the use of ultrasound in these blocks, but the bony windows really prohibit you from seeing it well. So we are not using ultrasound to visualize for our peribulbar and retrobulbar blocks. I think most of the time, the problem is that the needle — you don’t know where it is. And so in certain cases, it may, in an area that is much farther away from the cone than what you anticipate, and the diffusion of local anesthetic, has trouble getting there. I also think that in some people who have had many retro or peribulbar blocks, you actually develop some scarring or adhesions in the retrobulbar space. In the same way that we see patients who have had multiple epidurals sometimes have patchy blocks when we use epidural anesthesia again. I think the injection of local anesthetic can be irritating enough that you can cause some scarring, and that may also prevent you from getting a really good block. What is your opinion of no anesthesia cataract surgery? I’ve never tried it. I would… Think that it would be really hard. Because the cornea is so sensitive. And I know the incisions are kind of lateral to the main portion of the cornea. But I think that it would be very hard. And because local anesthetic topically is so easy and so non-invasive and so… Safe, I’m not sure that there would ever be an indication for no anesthesia cataract surgery. What do you think about sub-Tenon anesthesia for akinesia effect? We dilute lidocaine bupivacaine… Yes, that’s exactly why. The lidocaine will wear off in 4 hours. The bupivacaine will give you 8 to 24 hours, in some cases longer. Most of our surgeons feel that sub-Tenon anesthesia will produce akinesia, but it does take anywhere from 7 to 10 minutes for that to set up. When to do a canthotomy after retrobulbar hemorrhage has happened? Again, that would be something that I would defer ultimately to our ophthalmologists. But I think if you check the pressure and in somebody who has a normal intraocular pressure, who has gotten above a pressure of 40, you would probably want to consider doing that sooner as opposed to later. Obviously a canthotomy is not a benign procedure. But compared to losing vision because of it… I would think you would want to do it sooner. Our retina surgeons can actually see the perfusion of the retina. And so they make their decision based on perfusion. But for others, I think you would want to check the intraocular pressure. The gauge needle that you use for peribulbar and retrobulbar is a 25-gauge short bevel needle. So that you can feel the pops. Ask your opinion on ultrasound guided peribulbar. Like I said, I think that we have not used it, because it’s been hard to get good visualization, because of the bony windows. As you know, ultrasound does not go through bone very well. And so to be able to visualize behind the eye and to see the tip of your needle with that takes some significant skill. There are people researching and trying to get more information and more data, but currently, it’s not used routinely. The risk of globe perforation during retrobulbar anesthesia, and any signs and symptoms to look for. Again, I don’t know that I’ve ever seen it. Like I was saying, if you move the needle and the syringe when you’re doing a retro or peribulbar block and you see the globe move, that’s a sign that you probably may have pierced the globe itself. Unfortunately, there aren’t a lot of other signs. And sometimes… Well, the one other one that I know of in case reports that we had is severe pain when you inject local anesthesia. But I think far too many times this has been determined retrospectively, when you have somebody who ends up with vision loss or trouble. Any recommendation for COVID-19 patient? Which one is preferable? We have been, even during COVID-19, we have been doing local… And have not induced general anesthesia. My preference was that it didn’t make sense for me in my mind to take something where people were ventilating spontaneously, and we could even keep a mask on them, under anesthesia, and subject them to an endotracheal intubation. Because I felt that that actually, with all of the coughing that happened, and the aerosolization that happens with intubation, would cause more dispersion of the virus. So we continued to do cases under MAC. We did have them wear those masks until we had them fully draped, and we didn’t have any problem. Tranexamic acid with general anesthesia. We give it routinely with our orthopedic patients. I don’t think I’ve ever given it in an ophthalmology patient. Good afternoon. Diabetic patients. Diabetic patients are just very challenging, because they have a lot of comorbidities. I think the key is that if you have a diabetic patient, you want to make sure you check their glucose, you want to avoid hypoglycemia, you want to make sure they don’t have any renal insufficiency before you give antiinflammatory medications in them. And always be conscious of the fact that many of these diabetic patients may have cardiovascular disease as well. And then you give your anesthesia accordingly. Most of our diabetic patients — we do under retro, peribulbar, or regional blocks, but we do not… We also will do general anesthesia in these patients as well. Since age use ocular blocks in child. I would think… If you’re doing general anesthesia, that would be at the… Preference and the comfort of the person doing the blocks. Once the child was anesthetized, I know that, for example, our strabismus patients or surgeons inject local anesthetic around and into the muscles, or around the muscles, to try and provide postoperative pain relief. And as long as you felt comfortable doing the blocks, I would think once a child is anesthetized, that would be up to the comfort of the person doing it. What do you do for DCR? Like I said, here we do general anesthesia. And I think if you’re gonna be doing a DCR, the best is actually not gonna be a peribulbar block. Because so much of it is outside the globe. And so if you’re gonna do a DCR, you’re gonna use local lidocaine injection and deep sedation or general anesthesia. In your opinion, some literature states that a sub-Tenon or peribulbar block reduces the risk of an oculocardiac reflex, especially… Definitely. I think once you have a sub-Tenon or peribulbar block in place, it’s almost unheard of to see a significant oculocardiac reflex. Because that prevents any of the afferent stimulation from getting to the vagus nerve to effect an afferent response. Elaborate on blocks used for lacrimal surgeries. I’m not sure. We do lacrimal gland biopsies. Depending on how deep within the lacrimal gland it is, we’ll either do local infiltration, where we get people really sleepy with methohexital, while the oculoplastic surgeon injects around the lacrimal gland and where they’re going to be going in. If it’s anything deeper or more retroorbital, at the back of the lacrimal gland, then we do general anesthesia. Can I use epibulbar anesthesia in all cases? As it seems easy and safe? I’m not sure what you mean by epibulbar, other than the episcleral injection. I would think so. Again… Most of our surgeons that are doing cataracts will put on 4% topical drops. If they do any further injection, they either do episcleral or sub-Tenon injection on the field. If the patient is still uncomfortable. Although for most cataract surgeries, I think the majority would just do the intracameral 2% local lidocaine, and feel that that’s more than adequate. Muscle fibrosis and local anesthesia. There’s always been the concern for muscle toxicity. Especially with bupivacaine. I think with lidocaine, there’s less of that concern. And you can always try and infiltrate around the muscles, and many times you’ll block the nerves that innervate the muscles, if you’re concerned about fibrosis, by doing direct muscle injections. Which of the anesthetic procedures are performed by the ophthalmologist? The majority of our blocks are actually done by our ophthalmologists. The reason being is that many of our fellows and residents in ophthalmology are trained, and because we have so many rooms that we’re required to supervise that from a time standpoint, it’s hard for our anesthesiologists to be doing the blocks. That is not necessarily typical. There are many places where the anesthesiologists do all of the blocks. But on any given day, I will be responsible for 30 to 40 cases, and for me to try and do the blocks, plus do the preoperative evaluation and the sedation is… Too much. Again, I don’t think it matters. You just want somebody who is trained and experienced. If I make general anesthesia for a child, well, any time you have general anesthesia, you always run the risk of losing an airway and causing death. Either due to malignant hyperthermia, depending on what kinds of agents you use, but it is very rare. So I would say that you have to weigh the risks and benefits. There’s always that risk. But it is fairly low. In most studies, they would say less than 1 in several hundred thousand, due to anesthesia itself. There are things that anesthesiologists look at, that can determine the risks associated with anesthesia ahead of time as well. Prerequisites for topical anesthesia for cataract extraction? As long as a patient can get into our center and lie flat, most of these patients can be done. I recently was co-author of a paper coming out that talks about dealing with perioperative or preoperative problems in cataract patients. But the majority of patients, even really sick patients, can have topical anesthesia from cataract surgery. And because it is such a quality of life issue, I think if those patients can lie flat, we try to get them into the center and get them done. Any special considerations for orbital decompression? I’m an anesthesiologist. I think I’m gonna have to defer to an oculoplastic surgeon on that. From my standpoint, it would just be when you need to do it — any other issues in terms of trauma, do they have any brain trauma, do you need to get a CT scan to rule out subdural hematoma, and then full stomach issues. How long you want to wait before you take them to the operating room, because of the risk of aspiration. What questions to ask the patient before peribulbar anesthesia? I think you want to know whether they’re on anticoagulation. And whether they have any bleeding tendencies. And then obviously we bring somebody in. They need to have an empty stomach. So we make sure they haven’t eaten anything for 8 hours. You want to know about allergies, because you want to make sure you’re not administering a medication that the patient is allergic to. And you want to know if they’ve had any previous problems to anesthesia. I think those would be the main things. Incidence of strabismus after an ocular block. I actually am not aware of there being a significant incidence of strabismus after any kind of peribulbar or retro block. I don’t remember ever having heard about it. I could again follow up and ask some of our surgeons. But that’s not something that we talk with patients about as being a complication. Under which conditions do you prefer deep sedation? We do some… Like I said… Propofol ketamine. And I guess you could call that deep sedation for the duration of the procedure. That’s probably the only time when we do it. But we find that really deep sedation oftentimes, especially in anybody with sleep apnea, they end up snoring, which causes movement of the patient. So if somebody really needs to be very deeply sedated, it’s much easier, I believe, to put a supraglottic laryngeal mask airway in and have them breathe enough sevoflurane to keep them still and from moving on the bed. What maneuvers do you recommend to avoid injury in high myopes? A lot of our people will do peribulbar and not retrobulbar. We also oftentimes have the length of the eye. So they’re always watching that. But many times what they do is just avoid retrobulbar blocks and do a peribulbar or even a sub-Tenon block. Do you suggest to add a facial block with… The majority of the time, we do not do the Van Lint or facial nerve block. Most patients, there is a spring-loaded speculum in there, which keeps the eyelids open. And I would say probably less than 10% of the time do we need to do the Van Lint or facial nerve block. All right. Thank you. It was a privilege and a pleasure. Like I said, if you have any additional questions, don’t hesitate to email me. And topical anesthesia for trabeculotomy? Yes. Some of our glaucoma surgeons are using just topical anesthesia for their trabeculotomies. Trabeculectomies not so much. But it depends on the surgeon and the patient.