Retrobulbar and Peribulbar Blocks

Clinical Applications

Retrobulbar (see Chapter 65 ) and peribulbar blocks provide anesthesia for corneal, anterior chamber, and lens procedures when combined with a block of the orbicularis oculi muscle. These blocks are often performed by the surgeon rather than the anesthesiologist, and they have gained increasing popularity for cataract surgery in the elderly outpatient population. Retrobulbar and peribulbar blocks provide equivalent akinesia and anesthesia. ^[58] The safety of these regional anesthetic techniques was documented by Backer and coworkers,^[59] who demonstrated a zero incidence of reinfarction or death in 288 patients with a history of myocardial infarction undergoing local anesthesia or retrobulbar block, or both, for ophthalmologic procedures.

Technique

The retrobulbar block is performed with the patient supine and looking straight ahead. A 23-gauge, 3-cm, blunted needle is inserted at the inferolateral border of the bony orbit and is directed toward the apex of the orbit. A pop is often felt as the needle tip enters the orbital muscle cone, and 2 to 4 mL of solution is injected. With the peribulbar approach, the needle is inserted at the inferior orbital rim in the inferolateral quadrant and advanced along the floor of the globe to a depth of approximately 2.5 cm, and 5 mL of local anesthetic is injected. Many patients require a second injection to develop complete akinesia and anesthesia. For the medial injection, the needle is inserted through the conjunctiva on the nasal side and is directed straight back 2.5 cm, parallel to the orbital wall. An additional 5 mL of local anesthetic is injected. With both techniques, blockade of the facial nerve fibers that innervate the orbicularis oculi muscle is also performed to complete the anesthesia.

Side Effects and Complications

Retrobulbar and peribulbar blocks are associated with several possible complications, including globe perforation, hematoma formation, local anesthetic toxicity, development of the oculocardiac reflex, and possible spinal anesthesia via the optic nerve sheath.^[60] The risk of globe perforation is theoretically less with the peribulbar approach. Because both of these blocks may be uncomfortable for the patient, a small dose of a short-acting sedative, such as propofol, just before the injection prevents pain and patient movement.