Although the vast majority of eye operations and anesthetics are relatively straightforward, the anesthesiologist must exercise careful judgment as to which patients are appropriate candidates for procedures in the office setting.

Sedation and anxiolysis of varying depth in conjunction with a regional anesthetic, such as a retrobulbar block or facial nerve block usually administered by the ophthalmologist, is the typical anesthetic technique utilized. As with any office-based procedure, the use of general anesthesia may be needed and is based on any number of patients or surgical considerations.

Intraocular surgery with regional anesthesia/monitored anesthesia care (MAC) requires significant patient cooperation; movement during the procedure or performance of the block may result in severe complications such as blindness, perforation of the globe, and retrobulbar hemorrhage.

Therefore, patients with conditions such as chronic cough, orthopnea, excessive anxiety, language barrier, or agitation may be better managed with general anesthesia in a hospital or ambulatory surgical center (see Box 12.1).

As previously noted, office ophthalmic cases are currently being performed most frequently using a local/regional anesthetic with or without MAC. Typically, patients are treated with a mild sedative, anxiolytic, or short-acting
narcotic medication. This can be administered throughout the procedure, or just before performance of the regional technique, which is often the part with the most patient stimulation.

Propofol, remifentanil, and midazolam are intravenous medications that are frequently used individually or in combination during ophthalmic surgery. A one-time propofol bolus before the regional technique has been shown to be safe and effective in reducing patient recall (1), and propofol may continued to be administered throughout the procedure through infusion or bolus dosing without substantial lingering sedation. Remifentanil is popular with outpatient ophthalmologic procedures because it is an ultra short-acting potent analgesic whose effects cease rapidly upon discontinuation. Propofol and remifentanil have been used together with excellent results (2). Midazolam is notable for its anxiolytic and amnestic properties, along with a relatively short half-life. Dexmedetomidine, an α₂ receptor agonist, has been used more recently in the outpatient setting; its benefits stem from its cardiorespiratory sparing effects and its ability to decrease the requirements of other sedatives. An important point to remember is that patient sedation should be titrated to a level at which the patient is alert enough to cooperate with the requests of the ophthalmologist.

Standard monitoring (see Chapter 5) provides adequate surveillance during ophthalmic surgeries. The head of the table is usually rotated 90 or 180 degrees away from the anesthesiologist. Supplemental oxygen should be administered throughout the procedure, preferably with end-tidal CO₂ monitoring. A nasal cannula is sufficient in most cases and will not intrude onto the surgical field. The intravenous line should be placed so that it is easily accessible throughout the case, and efforts should be made to keep a direct line of vision in order to observe the patient’s face. Drapes should be organized in a manner that maximizes patient comfort.

The three major regional techniques performed in ophthalmology procedures are retrobulbar, peribulbar, and sub-Tenon’s nerve blocks (see Table 12.1). All are widely used and accepted in clinical practice, and the first two may be performed by both anesthesiologists and ophthalmologists. The terms retrobulbar and peribulbar are used to differentiate whether the injection of local anesthetic is made inside or outside of the cone formed by the extraocular muscles. Tenon’s capsule is a semiopaque fibrous tissue layer in which local anesthetic solution can be injected. It is found underneath the conjunctiva and inserts circumferentially 1 mm posterior to the limbus. A small surgical dissection is required to access this space. Regional techniques can provide the necessary anesthesia, akinesia, and hypotonia required for eye surgery when performed properly. These conditions are especially important with more intricate ocular surgeries. Many factors play a role in determining
the safety and efficacy of regional anesthesia in ophthalmologic surgery. These include the experience of the physician, knowledge of orbital anatomy and physiology, composition of the anesthetic solution, patient positioning, and the type of equipment used.

Researchers at the Johns Hopkins University performed a literature review and data analysis to compare the effectiveness of regional techniques for cataract surgery (3). Two of the conclusions from the study were that peribulbar and retrobulbar blocks provide equivalent akinesia and intraoperative pain control. However, there still exists much variation in the choice of regional technique in most clinical situations and opinions about efficacy.