Peripheral Nerve Blocks: A Color Atlas, 3rd Edition

18.Retrobulbar Block

Richard S. Ruiz

Patient Position: Supine, with the head flat.

Indications: Anesthesia for the majority of surgical procedures in and around the eye (e.g., cataract extraction, glaucoma filtering procedures, iris surgery, trans-par-plana vitrectomy, or orbital exploration [combined with second injection in the superior nasal quadrant]).

Needle Size: A 30-gauge short needle and a 27-gauge, 31-mm needle.

Local Anesthetic Solution: Half 0.5% or 0.75% bupivacaine, half 2% lidocaine, plus 100 to 150 IU/10 mL hyaluronidase.

Volume: 2 mL plus 5 to 7 mL.

Approach and Technique: The proper technique begins with the patient's arrival for surgery. Apprehension in anticipation of eye surgery is common and should be expected. The concept of a needle being stuck behind the eye is frightening; therefore, sedation should be given upon arrival and not delayed until just before administration of the retrobulbar injection. Patients need to have their fears allayed during the preparation and waiting period and not so much at the actual time of the injection, which if done properly causes little pain.

The technique of the block is of paramount importance, and strict attention to detail minimizes the risk for complications. Instruct the patient to keep both eyes open and to look straight ahead. Visualize the globe and orbit as divided into four quadrants (Fig. 18-1). Using a 30-gauge short needle and a 10-cc syringe containing the anesthetic agent, raise a skin wheal 8 to 10 mm posterior to the lid margin so as to be inferior to the tarsal plate and in the center of the inferior temporal quadrant (Fig. 18-2A). Without being withdrawn, the needle is turned and directed through the skin, posteriorly toward the back of the orbit without angulation. It is inserted to the hilt, and with the laxity of the lid and further posterior pressure, the hilt indents the lid, thereby advancing the needle tip past the equator of the globe and into the retrobulbar space. During insertion of the needle, approximately 2 mL of anesthetic agent is injected, and the needle is then withdrawn. Moderate digital pressure is applied to the globe and orbit through the closed lid for approximately 3 to 5 minutes. A 27-gauge, 31-mm disposable needle is placed on the same syringe, and the lower lid is immobilized by the needle tip so that it is at the level of the equator of the globe prior to penetrating the skin (Fig. 18-2B). The needle is guided along the previously anesthetized tract, angulated only slightly toward the apex of the orbit, and advanced carefully to the hilt and into retrobulbar space. After negative aspiration for blood, 5 to 7 mL of the local anesthetic mixture is injected. In the case of trans-par-plana vitrectomy or orbital exploration, a complete akinesia of the extraocular muscles and total anesthesia is indicated. This may require a supplemental injection in the superior nasal quadrant. For that purpose, the same 27-gauge, 31-mm needle is introduced at the level of the skin of the upper lid just below the superior orbital rim at the 1:30 position (Fig. 18-3). The needle is directed posteriorly along the roof of the orbit to a depth of 2.5 cm, where an additional 2 to 3 mL of anesthetic solution is injected. It is important not to slant the needle toward the apex of the orbit since the optic nerve is nasally located in the orbit and may be damaged.

Figure 18-1. Visually partition the globe and orbit into four quadrants.

Figure 18-2. A: Using a 30-gauge needle and a 10-cc syringe containing the anesthetic agent, raise a skin wheal 8 to 10 mm posterior to the lid margin so as to be inferior to the tarsal plate and in the center of the inferior temporal quadrant. B: A 27-gauge, 31-mm disposable needle is placed on the same syringe, and the lower lid is immobilized by the needle tip so that it is at the level of the equator of the globe prior to penetrating the skin.

Figure 18-3. Supplemental injection at the superior nasal quadrant.

Tips

1.   In addition to sedation to alleviate fear and apprehension, calm discussion and authoritative reassurance on the part of the person administrating the anesthesia is most helpful. Touching the patient (e.g., holding the hand or shoulder) during this preinjection talk adds to the bonding and trust, which is an important aspect of reassurance. The syringe and needle should be concealed from view and not brandished in front of the patient's face. Words like “stick,” “hurt,” “pain,” and “sting” should be avoided. Nonspecific terminology should be used, such as, “I'm going to give you a little medicine now,” or, “You may feel this for a few seconds,” or “You may feel some burning here.” A steady stream of conversation in a low, calm voice is most effective in allaying fear. Use phrases and ask questions such as, “How are you doing?”; “Do you need anything?”; “You're doing fine”; “Can I do anything for you?”; “How did you sleep last night?”; “Do you have any questions?”; and “We're going to take good care of you.”

2.   The skin wheal burns for approximately 5 seconds and requires vocal reassurance, such as “it only burns for a few seconds.”

3.   The skin wheal must be in the proper position so that the 30-gauge needle, which is advanced posteriorly, passes below the tarsal plate.

4.   For short procedures of less than 30 minutes, lidocaine is satisfactory. For longer procedures, a mixture of 50% lidocaine and 50% bupivacaine will prolong anesthesia.

5.   The addition of epinephrine also prolongs the duration of the block.

6.   The addition of hyaluronidase shortens the onset of the block and enhances the spread of the agent through the tissue.

7.   Neither hyaluronidase nor epinephrine is necessary in most cases.

8.   The use of sedation at the time of injection is rarely necessary, especially if sedation has been used earlier and the technique described is followed.

9.   Fentanyl and other opioids may be used if the patient experiences pain during the procedure, but it is rarely necessary and should not be used systematically.

10.       The most serious complications are penetration of the globe during injection, intra-optic nerve sheath injection with direct effect on the central nervous system, and retrobulbar hemorrhage.

11.       Perforation of the globe is always possible, particularly with large myopic eyes; therefore, the operator should be alerted to this possibility and follow the technique as described. If resistance to the passage of the needle is felt, the globe should be carefully observed for movement and for motions of the needle. Motion indicates the needle tip is impaling the sclera, and the needle should be retracted slightly and redirected until no motion is seen before thrusting the needle to the hilt and injecting. Tucking the lid with the needle tip also is a safeguard against penetrating the globe.

12.       Intra-optic nerve sheath injection can be minimized by using a shorter needle (31 mm rather than 38 mm). However, intra-optic nerve sheath injection may still occur without the operator's knowledge. Therefore, it is important to monitor the patient's vital signs prior to and after the performance of the block. Because patients can develop respiratory or cardiac arrest up to 1 hour after the injection, the placement of an intravenous line and immediate access to cardiopulmonary resuscitation (CPR) equipment is critical.

13.       Retrobulbar hemorrhage is not uncommon following retrobulbar injection. The hemorrhage is usually mild and rarely causes a problem. Occasionally, a retrobulbar hemorrhage may be severe causing proptosis, increased intraocular pressure, and a frozen orbit. In these cases, it is best to cancel surgery and carefully monitor the intraocular pressure. If sufficient pressure is exerted by the retrobulbar hemorrhage to potentially exceed the arterial systolic pressure and close the central retinal artery, a lateral canthotomy is indicated to relieve the pressure of the lids on the globe. This is rarely necessary, but everyone should be alerted to and prepared for the possibility.

Suggested Readings

Greenbaum S, ed. Ocular anesthesia. Philadelphia: WB Saunders, 1997.

Guise PA. Sub-tenon anesthesia: a prospective study of 6,000 blocks. Anesthesiology 2003; 98:964–968.

Saunders DC, Sturgess DA, Pemberton CJ, et al. Peribulbar and retrobulbar anesthesia with prilocaine: a comparison of two methods of local ocular anesthesia. Ophthal Surg 1993;24:842–845.

Troll GF. Regional ophthalmic anesthesia: safe techniques and avoidance of complications [Review]. J Clin Anesth 1995;7:163–172.

Wong DH, Koehrer E, Sutton HF, et al. A modified retrobulbar block for eye surgery. Can J Anaesth 1993;40:547–553.