Ophthalmic procedures such as cataract extraction with phacoemulsification can be performed with either topical or regional anesthesia (1). Regional anesthesia is still widely used in cases of difficult surgery and extended time surgery (1).
Retrobulbar anesthesia is the standard technique for regional anesthesia in ophthalmic surgery, but complications of this technique, although relatively uncommon, can be catastrophic. However, the complications associated with retrobulbar anesthesia have been subsequently described with peribulbar anesthesia with less, but still unacceptable, frequency (2–7).
An overview of the ASA Closed Claims Project database reported that the most common disabling injuries associated with regional anesthesia are related to nerve blocks of the eye (8). These potential risks led to the proposal of a single, rather than multiple, injection technique of peribulbar and episcleral anesthesia in order to decrease the risks of complications (9–12).
The purpose of this study was to evaluate the efficacy and safety of a percutaneous peribulbar single injection technique of regional anesthesia with a small volume of anesthetic for various ophthalmic procedures.
The study was conducted after approval of our institution’s local ethics committee and patients’ verbal, informed consent. Eight-hundred-fifty-seven consecutive patients scheduled for elective ophthalmic procedures at Department of Oto-Neuro-Ophthalmological Surgery, Section of Ophthalmology, University of Florence from September 2001 to March 2003 were included. Exclusion criteria were contraindications to ocular regional anesthesia and patient refusal. The patients were not fasted. A few uncooperative patients (approximately 8%) were premedicated with midazolam IV (0.02 mg/kg) 5 min before the block. All patients had a peripheral IV line inserted and the usual standard monitoring was used.
The injections were given with a 25-gauge, 16-mm bevel disposable needle. The anesthetic was 2% lidocaine; volume ranged from 5 to 6.5 mL on the basis of dimension of the eye socket. The patients were asked to move their eye so as to expose the area to be injected (to 10 o’clock for right eye and to 2 o’clock for left eye).
The injection site was percutaneous and limited superiorly from inferior lacrimal canaliculus, median from lateral margin of nose, laterally from imaginary perpendicular line that join inferior lacrimal papilla to inferior margin of orbit and inferiorly from inferior margin of orbit (Fig. 1).
The needle was advanced percutaneously in an antero-posterior direction for half of its length (never more than 10 mm) (Fig. 2a) and later obliquely in the direction of the optical foramen until the needle was on the same plane of the bony margin of orbit (Fig. 2b). After aspiration, the anesthetic was injected in approximately 30 s.
An initial transient fullness in the supero-internal region of superior lid was predictive of successful blockade. After the needle was removed, moderate digital massage of the eyeball and compression of the site of injection were performed. Patients were observed carefully during the injection and immediate complications were noted.
Akinesia of the globe and eyelids was assessed at 2 min (T1) and 5 min (T2). A 12-point scale (13) was used (each of the 4 rectus muscles and each lid was scored from 0 to 2; 0 = no block, 1 = partial akinesia, 2 = total akinesia).
Five-hundred-forty-two female (mean age 72 ± 11 yr) and 315 male (mean age 70 ± 12 yr) patients (ASA physical status I–III) were studied. The procedures were 517 phacoemulsifications and posterior chamber artificial lens implantations, 137 open globe procedures for lens extraction (intracapsular or manual extracapsular extraction), 109 trabeculectomies, and 94 other procedures including vitrectomy and retinal surgery.
At T1 85.6% of patients had a motor block of at least 50% (score 6 of 12) and at T2 78.6% of patients had a motor block >80% (score 8 of 12). After 7 min 100% of patients had adequate anesthesia to proceed with and complete the surgery. Only 107 patients required midazolam 0.015 mg/kg intraoperatively.
Complications included one case of inferior lid hematoma for perforation of a superficial vein tributary of the angular vein and four cases of chemosis that did not hinder surgery. There were no cases of perforation of the globe, retinal or optic nerve damage or orbital hematoma or postoperative diplopia.
In this large series of patients peribulbar anesthesia by a medial percutaneous single injection was a valid alternative technique for ocular regional anesthesia because of the infrequent complications we observed. This site of injection is relatively avascular, which may decrease the risk of hematoma. Indeed, we noted no orbital hematoma in this series. Because the insertion of the needle is limited to the anterior orbit, ophthalmic artery, optic nerve or retinal injury is unlikely. It should be stressed that akinesia and analgesia of the globe and eyelid were obtained with our technique using a very small volume of anesthetic (no more than 6.5 mL).
To determine the exact pattern of distribution of anesthetic fluid in this type of regional anesthesia in 27 patients we performed B-scan ultrasonography before (Fig. 3, left) and at few minutes (Figs. 3, right, and 4) after the administration of anesthetic (14). After the injection, the fluid tracked behind the globe in the sub-Tenon capsule space (Fig. 4, left). Posterior, the fluid around the optic nerve developed a characteristic T sign (Fig. 4, right). The fascial sheath of the eyeball (Tenon’s capsule) is a fibrous layer that surrounds the eyeball from the optic nerve to the corneal ring. It is a thick membrane at the equator of the globe, where it is pierced by the rectus muscle tendons and is continued by the muscle sheaths. The episcleral space is a virtual gliding space between the sclera and the fascial sheath of the eyeball. The sensitivity of the eyeball is provided by the ciliary nerves, which cross the episcleral space after they emerge from the globe. We confirmed that a small volume of local anesthetic (5–6.5 mL) injected in this space is guided to surround the eyeball and produce analgesia. The fascial sheath of the eyeball extends to the rectus muscle sheaths. This explains why the anesthetic is preferentially guided to those muscle sheaths to produce good akinesia. Furthermore the fascial sheath of the eyeball guides the injected solution to the lids, especially to the orbicularis muscle. This explains how we can prevent blinking during surgery without performing any facial nerve block.
Our medial single injection technique is a simple and satisfactory alternative approach for ocular regional anesthesia. The advantages include decreased pain with percutaneous and short needle insertion, decreased volume of anesthetic, single rather than multiple punctures, puncture in a relatively avascular area, and a needle path that is less subject to misdirection.
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© 2005 International Anesthesia Research Society
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