Hello. I'm Elizabeth Du. I practice Comprehensive Ophthalmology, at the University of Michigan Kellogg Eye Center. Today, we are going to discuss anesthesia for cataract surgery. As a resident or trainee, it is easy to focus on the nuts and bolts of surgery. However, the anesthesia is equally important. The goal of anesthesia is to eliminate patient pain, reduce anxiety, and ensure that the eye is not a moving target. The more comfortable the patient is, the greater ease and more success you will have at performing the steps of cataract surgery. So let's begin. The goal of this lecture is to describe the indications and techniques of different methods of anesthesia for cataract surgery. By the end of this lecture you should be able to list the pros and cons of different kinds of anesthesia and appropriate usage, describe proper technique for various forms of cataract surgery anesthesia. And identify potential complications of anesthesia. I will provide a brief overview of all the different types of anesthesia that are available. Then we will go through them individually and discuss the indications, advantages and disadvantages, potential complications and proper technique. When should you determine what type of anesthesia you plan to use? In the office, not in a preoperative area. Should you discuss the type of anesthesia you plan to use with the patient? Yes, and why? You want the patient to have appropriate expectations and not to have any surprises on the day of surgery. You also want to be able to discuss potential risks depending on what type of anesthesia you are planning to use. There are 7 different types of anesthesia that are used in cataract surgery. General, Retrobulbar block, Subtenon block, Peribulbar, Intracameral, Topical and Facial. In order to know the difference between the local anesthetics, it is important to understand some anatomy of the eye and orbit. First, you need to know whats the difference between the intraconal space, and the extraconal space. The interconal space is formed by the four extraocular muscles and the fascia that connects them. it starts posteriorly at the annulus of Zinn and extends anteriorly all the way to the back of the globe. It is bounded by the four extraocular muscles and the fascia that connects them. The extraconal space is the space inside the orbit, but outside the muscle cone. As you can see, blood vessels and nerves course through the muscle cone. In particular, cranial nerves II, III, and VI course through the muscle cone. These pictures illustrate, based on the need or the cannula, where the anesthetics are placed. Needle A, demonstrates that the anesthetic is placed in the intraconal space, and this is a retrobulbar block. Needle B demonstrates that the anesthetic is placed in the extraconal space, and this is a peribulbar block and canula C shows that, the anesthetic is placed in the anterior intraconal space, and this would be a sub tenon's block It's placed underneath conjunctiva and tenon's capsule. Topical anesthesia involves using drops and fluids. The eye drops are placed on the surface of the eye, and they anesthetize the cornea, the conjunctiva and the anterior sclera. Intracameral anesthesia is placed in the anterior chamber, in this space here, and provides additional anesthesia to the iris and ciliary body. Facial nerve block anesthetizes cranial nerve VII. Cranial nerve VII controls the orbicularis oculi muscle, which is involved in eyelid closure. Ultimately, what are you achieving with all of these different types of anesthesia? Akinesia is blocking the movement of the eye. Retrobulbar block does its routinely, since it's placed in the intraconal space and anesthetizes cranial nerve III and VI. Peribulbar and subtenon's block may or may not achieve akinesia since they rely of the diffusion of the anesthetic into the intraconal space. Analgesia is blocking pain sensation, and all the different types of anesthetics should do this at different levels with the exception of the facial nerve block. First we will discuss general anesthesia, this is used very rarely in cataract surgery. Indications include, children, patients with dementia, patients who are mentally incapable or who have high anxiety, such as claustrophobia, patients who are unable to lie supine due to breathing difficulty or arthritic pain, and those with a severe head tremor. The advantages of using general anesthesia, are that it provides 100% patient comfort and immobility. The disadvantages are greater costs and time inefficiencies. Potential serious complications such as death and malignant hyperthermia. And a prolonged recovery time during which coughing and vomiting may be a problem, risking wound dehiscence. A suture would be helpful here, or a drowsiness and confusion. Next, we will talk about retrobulbar block. As I mentioned previously, this is placed in the intraconal space. The indications for using retrobulbar block include, if you are a beginning surgeon, patients who are anxious or have psychological and mental disorders. Or if you anticipate extensive intraocular manipulation, relative contraindications include patients with long axial length, a staphyloma which is a thinning or protrusion of the sclera, and patients on blood thinners. Although studies do not show that blood thinners increase the risk of bleeding, when a bleed occurs it is usually more severe. Ratrobulbar block complications are rare but can be quite serious, they are divided into ocular and systemic. The ocular complications include retrobulbar hemorrhage. As you can see if any of the blood vessels in the intraconal space are sheered it can cause a hemorrhage. Globe perforation, especially in those with long axial length or staphyloma, optic nerve injury, which is rare, and strabismus, and ptosis. Systemic side effects include the oculocardiac reflex. When the globe is compressed, or the extraocular muscles are manipulated, it can cause significant reduction in heart rate, or bradycardia. If the anesthetic is injected intra-arteial it can lead to a seizure or within the optic nerve sheath and it connects down to the brainstem causing severe respiratory depression. To prepare the retrobulbar block we generally use a 50 50 mixture of Lidocaine two to four percent which is quick acting. And Marcaine, 0.5 to 0.75%, which is longer lasting. And you can draw off about five cc's of this. Occasionally, adjunct medications are used, such as Hyaluroidase, which promotes the spread, and quickens the onset or Epinephrine, which is intended to prolong the effect. A special needle is used, it's a little bit longer. 1.5 inch, it's 23 or 25 gauge. And it has a blunt tip. And you want a blunt tip in order to avoid globe perforation. And this needle's also called Atkinson or retrobulbar needle. To prepare for the block you want to identify the injection site. One way to identify it, is to divide the orbit into thirds and it's the junction of the middle third, and the lateral third. Another way to think about it is if you draw a vertical line down from the lateral limbus. And the point above the orbital rim is where you want to inject. Then you'd want to put on some gloves, after you locate your injection site, you can clean the area on the skin with an alcohol swab. You want the patient to be quite sedated. And often propofol or versed are used to render the patient nearly unconscious, since this anesthetic can be quite painful. Then you want to have the patient look in the straight ahead position. Avoid the Atkinson position which is having the patient look up and in. This can expose the optic nerve to injury. Generally people go through the eyelid, however, you can also pull the eyelid down and go through the conjunctiva. So, here are the steps of the block. You want to enter inferior to the globe, perpendicular to the patient's face. As you go through the skin, you'll feel a first pop and this is as you're going through the orbital septum. Then continue to advance the needle tangential to the globe, and parallel to the orbital floor. It's about a 10 degrees incline. Once you're past the equator, redirect the needle slightly upward and medial. As you go through the intraconal space, often you will feel a second pop. Once you're in the intraconal space, slightly withdraw the plunger to make sure you're not intraarterial. Some also suggest wiggling the needle to make sure you're not within the globe. Then slowly inject 3-5 cc's of the anesthetic into the intraconal space. After that withdraw your needle, and then provide about three minutes of gentle compression over the eye. This is supposed to promote the spread of the anesthetic, and also quicken the onset. After that you can check the eye movements. If there are no movements of the eye, then you've performed a successful retrobulbar block. If there are still some movements of the eye, then the block may be incomplete, and you can consider supplementing with additional anesthesia such as drops or intracameral anesthesia. Here's a video demonstrating proper technique for retrobulbar block, on a right eye, and then also following that on a left eye. Next we will talk about peribulbar block. This is placed in the extraconal space. Indications for peribulbar block include beginning surgeon, and similar patient criteria as to when you'd want to use a retrobulbar block. It's more appropriate if the patient has a long eye, staphyloma, scleral buckle, or orbital implant. The advantages to using peribulbar anesthesia are reduced risks, such as globe perforation and optic nerve injury since you are not entering the intraconal space, and you still achieve akinesia and anesthesia. However, the effect maybe sub-optimal compared to a retrobulbar block, which is one of the disadvantages. The onset is also delayed, and you have to inject a higher volume of anesthetic, which can lead to post-year pressure, making the case more difficult to perform. The entrance site is the same as what you would do for your retrobulbar block, and you can use the same anesthetic mixture. The needle can be shorter, 1.25 inches or anywhere from 16 to 25 millimeters. The steps of peribulbar block include inserting the needle, and then advancing tangential to the globe and parallel to the orbital floor. You want to insert the needle about 3-4 millimeters past the equator, withdraw the plunger, and then inject 4-8 cc's of the anesthetic, then compress the eye. You can also add supplemental peribulbar anesthesia in the superior extraconal space. This is usually through the upper eyelid, and the point that you want to inject is the point midway between the medial canthus and the supraorbital notch. The star here demonstrates the injection sight. And you want to advance needle tangential to the globe, withdraw the plunger and inject your anesthetic, this is rarely done. When performing retrobulbar or peribulbar block what is the correct answer? A, ask the patient to look up and in, B, retrobulbar block has a slower onset, C, always withdraw the plunger slightly prior to injection or D, compression of globe after injection is not recommended? The correct answer is C, always withdraw the plunger slightly prior to injection to make sure that you're not injecting intra-arterially. Next we will discuss subtenon anesthesia. This is placed in the anterior intraconal space underneath conch and tenon capsule. This is often used in the middle of a case. If the case is going longer than you anticipated. If there's a complication, or if the patient is having a lot of pain moving their eye about this may be useful to add. Also patients who have high myopia Subtenon's block is also a good type of anaesthetic to use. Absolute contraindications include patients with active eye infection or prior scleral buckle. The main advantage of the subtenon's block, is reduced risk of complications compared to retrobulbar block. It's an effective form of anesthesia but less so with akinesia, and potential complications include local chemosis and subconjunctival hemorrhage. This series of pictures demonstrates how to do a subtenon's block. You'll want to use blunt Westcott scissors and 0.12 castor Viejo forceps. Create a button hole through conjuctiva and down the their sclera. Use the blunt Westcott scissors, to dissect posteriorly past the equator. Then, take your cannula which is curved, you can either use a olive tipped or lacrimal cannula, and place it in this space posteriorly. Then inject your anesthetic. Despite all of these different types of anesthetics, a problem you may encounter is forceful eyelid closure. If this happens you may want to use a facial nerve block. The most common techniques that are used are the van Lint, which anesthetizes the terminal branches of cranial nerve VII and O'Brien, which anesthetizes cranial nerve VII more towards the trunk. One of the complications includes a subcutaneous hemorrhage. And this picture demonstrates where the anesthetic is placed. The [INAUDIBLE] anesthetizes the terminal branches of cranial nerve VII, and O'Brien anesthetizes closer to the trunk. The most common form of anesthetic that is used now, is topical anesthesia. Patients who are good topical candidates include, those who are relaxed and who don't have high anxiety. Patients who can tolerate bright lights, those who can hear and communicate well, and also follow directions. Especially as a beginning surgeon, you may want to avoid using topical anesthesia in cases that you anticipate to be difficult. For example, patients with a white mature cataract. Those with iphis could have the potential for iris prolapse. Those with pseudo exfoliation, or post There are several different types of, topical anesthetics, that you can use. There's 2% lidocaine gel. 0.5% proparacaine. Tetracaine or tetravisc. 4% lidocaine drops, and bupivacaine. Again, these anesthetize the cornea, conjunctiva, and anterior sclera. Often these drops or gels are used in conjunction with intracameral anesthetic, which is placed in the anterior chamber. 1% non-preserved lidocaine is used and provides additional anesthesia to the iris ancillary body. The advantages of using topical anesthesia are many. Mainly, you provide more patient safety in that you avoid complications from the needle, as we had discussed previously. Also less patient sedation is required. There are advantages for yourself as a surgeon as well, it saves you time and increases the wow factor, since the patient doesn't have to be patched after surgery. The disadvantages of using topical anesthesia are that, you rely on patient cooperation, they have to keep their eyes still. The duration is limited, and it requires less ocular manipulation on your part. Some commonly encountered problems when using topical anesthesia are, patients may have an intolerance to the bright lights, they may still move their eye about, and, they may complain of pain. Some helpful hints as you use topical anesthesia, it is good to avoid shocking the patients. So, when you turn your microscope light on, or before you put lidocaine into the eye, you may want to warn the patient. In addition, talking to your patients can also be a very effective form of pain control, providing them reassurance can calm their nerves. It is important to remember that appropriate patients may have similar levels of comfort between topical, and retrobulbar anesthesia. When surgery is performed by an experienced surgeon. Here's a final question, you are preparing to do a cataract surgery on a 74 year old male patient, with a 3+nuclear sclerotic cataract. The patient takes Xanax as needed for anxiety issues, and he is quite photophobic. He is a high myope with axial length of 28mm's. What is the best type of anesthesia to give? A retrobubar block, B peribulbar, C intracameral, or D facial? The correct answer is B peribulbar. You'd want to avoid retrobulbars since he has a long axial length, and you would risk globe perforation. Intracameral may not be enough anesthetics, since he's anxious and photo-phobic. And facial would not provide and type of pain control. In summary, anesthesia should be individualized, our preoperative discussion with the patient is important. And remember you have options, use the anesthesia that will make the case easiest for you to perform, and is also safe for the patient. Factors to consider include patient characteristics and comorbities, surgeon skill and difficulty of the case. Don't forget as you perform cataract surgery, that verbal anesthesia is also quite effective. Thank you for listening in. Hopefully you found this lecture, useful. And if you have any questions we'd love to hear from you.
