Anesthesia for Ophthalmic Procedures PDF

Anesthesia for Ophthalmic Procedures Prof. Albert J. Albors DNP, CRNA, APRN University of Puerto Rico Medical Sciences Campus Nurse Anesthesiology Program 1 Ophthalmic anesthesia continues to be an exciting and challenging segment of anesthesia practice. Ophthalmologists recognize the value anest...

Anesthesia for Ophthalmic Procedures Prof. Albert J. Albors DNP, CRNA, APRN University of Puerto Rico Medical Sciences Campus Nurse Anesthesiology Program 1 Ophthalmic anesthesia continues to be an exciting and challenging segment of anesthesia practice. Ophthalmologists recognize the value anesthesia practitioners provide to their patients and practice. Introduction Anesthesia practitioners have also taken a leading role in advancing safer orbital regional needle block techniques. Today, more than 1 million ocular blocks are performed annually for surgical procedures. As a result of anesthesia practitioners’ active involvement in ophthalmic anesthesia, safer ocular blocks are being administered, and more efficient patient care is being provided. Anatomy Review- Extraocular muscles Anatomy Review- Extraocular muscles Ocular Perfusion • The ophthalmic artery is the main blood supply to the eye. • It branches off the internal carotid artery near the circle of Willis. • The ophthalmic artery divides into the central retinal artery and posterior ciliary arteries. • The superior and inferior ophthalmic veins transport venous blood to the cavernous sinus. Intraocular Pressure • Intraocular perfusion pressure = MAP - 10P • The globe is a relatively noncompliant compartment. Therefore, IOP is determined by the choroidal blood volume, aqueous fluid volume, and extraocular muscle tone. • Normal IOP = 10 - 22 mmHg • Aqueous humor is produced by the ciliary process (in the posterior chamber) • Aqueous humor is reabsorbed by the canal of Schlemm (in the anterior chamber) Cranial Nerves • The optic nerve is not a true cranial nerve but an outgrowth of the brain. As a result, the optic nerve is also covered by the meninges, the fibrous wrappings of the arachnoid, dura, and pia mater, which envelop the central nervous system (CNS). Therefore, any anesthetic agent injected into the optic nerve sheath can find its way back to the midbrain through the cerebrospinal fluid, resulting in CNS depression and respiratory arrest. • The ophthalmic nerve has three main branches: lacrimal, frontal, and nasociliary. • Ocular anesthesia is more concerned with the upper branch of the facial nerve than with the lower. The upper branch further divides into the temporal and zygomatic branches, which innervate the orbicular muscle of the eye, the superficial facial muscles, and the scalp muscles. • The vagus nerve (cranial nerve X) provides motor function to the intrinsic muscles of the larynx and the heart; it provides major parasympathetic visceral innervation elsewhere. It is also the efferent pathway for the oculocardiac reflex. Oculocardiac Reflex • The stimulus for this reflex is generated by pressure on the globe, the orbital structures (e.g., the optic nerve), or the conjunctiva, or by traction on the extraocular muscles (particularly the medial rectus muscle). • The afferent pathway for the stimulus is via the long and short ciliary nerves to the ciliary ganglion and then through the gasserian ganglion along the ophthalmic division of the trigeminal nerve, terminating in the main trigeminal sensory nucleus in the floor of the fourth ventricle. • The efferent pathway consists of the vagus nerve to the cardioinhibitory center. • The oculocardiac reflex most often results in acute sinus bradycardia. However, it may also cause a wide variety of other cardiac dysrhythmias, such as nodal rhythms, atrioventricular block, ventricular ectopy, idioventricular rhythm, and asystole. Oculocardiac Reflex • If cardiac dysrhythmias are observed, the surgeon must be instructed to immediately cease all pressure or traction on the orbit. Simultaneously, the patient should be assessed for adequate oxygenation and ventilation and for adequate anesthetic depth because one or more of these may be an underlying cause for the dysrhythmia. • Atropine, 2 to 3 mg, may be required for complete vagal blockade. Caution should be exercised with the administration of atropine because atropine itself may induce cardiac dysrhythmias. Glycopyrrolate may be given for less severe bradycardic episodes. The surgeon may proceed only after the dysrhythmia is resolved. • https://youtu.be/HtyMI7pqTvE?si=b9vy6GnormoSar24 Topical/Intraocular Anesthesia • Cataract and vitreoretinal surgeries are the most frequently performed intraocular surgical procedures. Topical anesthesia for cataract surgery (2% lidocaine) has proven to be effective in providing adequate analgesia for most patients during the surgical procedures. • Topical anesthesia is applied as drops or gels and may be supplemented by intracameral injection by the surgeon for better intraoperative pain control. • Today’s smaller-incision surgical techniques with foldable intraocular lenses provide a safer surgical experience for the patient and a more rapid recovery. • Intraocular anesthesia can further enhance the analgesia for the surgical procedure; 1% lidocaine (preservative free) has been studied and recognized as safe for intraocular administration. Ocular Regional Anesthesia • The ocular regional needle block remains the most common and effective way to consistently produce a profound analgesia and akinesia of the eye and eyelids. • The term ocular local anesthesia has been used to refer to retrobulbar or peribulbar blocks. • Retrobulbar and peribulbar injections are categorized under regional anesthesia methods. These blocks are designed to anesthetize multiple cranial nerves (III, IV, V, VI, and VII). • Local anesthesia is preferred to general anesthesia for eye surgery because it involves less physiologic trespass. • The most important considerations for ocular blocks are the position of the eye and the depth and angle of the needle. Retrobulbar block • The patient is instructed to look up and nasally. • A 23-gauge retrobulbar (dull) needle is inserted through the skin in the infratemporal area, just above the inferior orbital rim and advanced toward the orbital apex 35 mm (1.38 in) deep into the muscle cone (retrobulbar space). • After negative aspiration, 2 to 4 mL of anesthetic solution is injected into the muscle cone. • After the injection is completed, the eyelids are closed, and digital pressure is applied over the globe to the orbit. • A few minutes later, the eyelids are opened, and the globe is inspected for akinesia. Retrobulbar block demonstration Please click on the following link for a video demonstration of the retrobulbar block for eye surgery. https://www.youtube.com/watch?v=5KedJhF8cYA Ocular Block Evaluation • After an ophthalmic block is performed, partial movement of one or more of the ocular muscles may occur. • Residual movement should be assessed to determine which muscles are involved and whether additional anesthesia is required. • Analgesia of the globe generally precedes akinesia of the eye muscles. Therefore, analgesia of the globe may be assumed but not guaranteed in the presence of an akinetic muscle. • The effectiveness of a modified intraconal retrobulbar block may be evaluated 2 minutes after it is administered, and an extraconal peribulbar block 10 minutes after it is administered by observing for eye movement in all four quadrants. Anesthesia Management • Ophthalmic procedures are most performed on young children and elderly persons. Each age group has a unique set of physical problems. • For the young child, the questions regarding the patient’s history should include any congenital, metabolic, and musculoskeletal abnormalities, such as malignant hyperthermia, that may affect anesthesia care. • In the elderly patient, multisystem medical problems may be present, and drug interactions from multiple medication regimens may exist. Therefore, a thorough patient history is paramount. Regional anesthesia • Most adults tolerate ophthalmic procedures well when regional anesthesia is used. Given the potential risks associated with general anesthesia regional anesthesia should be considered the anesthetic of choice in adults, especially the elderly, for ophthalmic procedures. • Communication is the cornerstone of interacting with the patient who is awake. • Positioning of the patient is very important. For example, pillows under knees are recommended to decrease back strain. Patients with arthritis must be carefully padded. • Claustrophobia can be a problem for the awake patient. Consider using tape on the nonsurgical eye. Adjust the drape, so the patient can see the room. Consider if patient can continue with regional or needs GETA. • Coughing increases IOP up to 40 mmHg. If patient presents history of postnasal drips a nasal vasoconstrictor can be given preoperatively. • Instruct patient to give notice before coughing. Intravenous lidocaine can help. General Anesthesia • For general anesthesia, preoperative patient preparation should include the appropriate fasting guidelines for the patient’s age and physical condition. • The patient should be reminded that the surgical eye will be patched upon awakening. • Sedation should be administered as needed to help the patient relax. Benzodiazepines such as midazolam are effective in low doses. • For reduction in the incidence of postoperative nausea, the use of a standard multimodal approach should be considered. • Induction of general anesthesia with propofol or etomidate is recommended because they both decrease IOP. For infants and children, inhalation induction also decreases IOP. Due to the emetic effects, narcotics should be used in low doses. General Anesthesia • Succinylcholine causes a transient increase in IOP; however, it can be used safely for ocular procedures. • Nondepolarizing muscle relaxants are satisfactory for induction and have the advantage of decreasing IOP. Laryngoscopy, especially with light anesthesia, increases IOP, but intravenous lidocaine (1.5–2mg/kg), given 1 to 1.5 minutes before laryngoscopy, helps attenuate this response. • Inhalation anesthetics, which also decrease IOP, are commonly used for the maintenance of general anesthesia. • The anesthetist must be aware of the adverse ECG changes that may result from the oculocardiac reflex, which may be elicited when traction is exerted on the extraocular muscles and orbital structures. • Patients undergoing eye muscle surgery have an increased incidence of malignant hyperthermia and postoperative nausea. • In retinal procedures in which sulfur hexafluoride perfluoropropane is used as an intraocular gas, the use of nitrous oxide should be discontinued 15 minutes before injection. Open-Eye Injury • Traumatic eye injuries can be categorized as either open-or closedglobe injuries. Open-eye injury in a patient with a full stomach is at best a difficult situation for the anesthesia provider. These injuries are commonly considered emergencies requiring general anesthesia. • Normal IOP is 10 to 22 mm Hg, with slight diurnal and positional changes of 1 to 6 mm Hg. It is physiologically determined by aqueous humor dynamics, changes in choroidal blood volume, central venous pressure, and extraocular muscle tone. • The most important determinant of IOP is the balance between production and elimination of aqueous humor, maintaining an average volume of 0.25 mL. • Administration of succinylcholine increases IOP within 1 minute and peaks at an increase of 9 mm Hg within 6 minutes after succinylcholine administration. Ophthalmic Anesthesia Complications • • • • • • • Retrobulbar Hemorrhage Intravascular Injection Globe Puncture Optic Nerve Sheath Trauma Ocular Ischemia Extraocular Muscle Palsy and Ptosis Facial Nerve Blocks Glaucoma Glaucoma is caused by a chronically elevated IOP that leads to retinal artery compression.IOP is reduced by drugs that reduce aqueous humor production or facilitate aqueous humor drainage Drugs that Decrease Aqueous Humor Production • Acetazolamide inhibits carbonic anhydrase and decreases aqueous humor production. • Timolol is a non-selective beta antagonist that decreases aqueous humor production. Drugs that Facilitate Aqueous Humor Drainage • Echothiophate is an irreversible cholinesterase inhibitor that promotes aqueous humor drainage via the canal of Schlemm. • It can prolong the duration of succinylcholine and ester-type local anesthetics. Strabismus Surgery Strabismus surgery corrects the misalignment of the extraocular muscles and re-establishes the visual axis. There are 2 key considerations in this population: Increased risk of PONV Increased risk of activating the oculocardiac reflex (afferent CN 5 + efferent CN 10) Ocular Gas Bubble Placement Sulfur hexafluoride (SF6) is a gas that is placed over the retina during retinal reattachment, vitrectomy, and macular hole repair. Nitrous oxide can expand the SF6 bubble, compromise retinal perfusion, and cause permanent blindness. Discontinue N2O 15 minutes before the SF6 bubble is placed. Avoid N20 for 7-10 days after the SF6 bubble is placed. Alternatives to SF6 and time to avoid NO: Silicone oil = 0 days Air bubble = 5 days Perfluoropropane (C3F8) = 30 days Other Complications • Corneal abrasion is the most common injury occurring after general anesthesia. It is believed to result from the drying of the exposed cornea or from direct trauma, such as an anesthesia-mask injury. Ensuring that the eyelids are closed and secured with tape should provide satisfactory protection of the cornea. • Chemical injury can result from spillage of cleaning materials or preparatory solutions into the eye. In these cases, the eye should be flushed immediately with saline. • Central retinal artery occlusion may result from prolonged pressure on the eye. This type of injury may result with the patient in the prone position. Attention to padding and periodic checks of the eyes is necessary, especially for long procedures. Review Conclusion Anesthesia management for ophthalmic procedures has changed rapidly in the last few years. As an anesthesia practitioner, you will be challenged with the increasingly complex comorbidities and multiple pharmacologic agents used in the care of the elderly patient. The pediatric patient also presents anesthetic challenges, many associated with the preterm infant and chronic upper respiratory infection. Newer surgical techniques for cataract surgery have increased the popularity of topical anesthesia for such procedures; however, the advances in retinal surgical techniques, corneal transplants, and adult eye muscle and glaucoma procedures are fueling an increased demand by surgeons for anesthesia practitioners to perform ophthalmic eye blocks versus general anesthesia. Orbital regional blocks have the further advantage of minimizing postoperative pain, requiring minimal to no opioid administration, with significant reductions in postoperative nausea and vomiting. General anesthesia will continue to be the technique of choice for the pediatric patient, patients with ocular trauma, and patients who are not candidates for topical or orbital regional blocks. References Nagelhout JJ, Elisha S, Heiner JS, eds. (2020). Nurse anesthesia (7th ed.). Philadelphia: Elsevier. Apex Anesthesia Review (2023) 33