ANDRÉ BOEZAART, ROLAND BERRY AND MERCIA NELL
MediClinic Hospital, Paarl, Western Cape, South Africa, and Department of Anesthesiology, University of Stellenbosch, Western Cape, South Africa
J. Clin. Anesth., 12: 58–60, 2000
Patients’ perceptions of topical anesthesia (TA) were compared with combined peribulbar and retrobulbar block (PRBB) for cataract surgery in a prospective, randomized, controlled, crossover observational study of 98 ASA physical status I and II patients in a private clinic. The patients presented for bilateral cataract surgery one week apart and were prospectively randomized to receive either TA surgery to one eye followed by PRBB for surgery on the other eye one week later, or to receive PRBB first, followed by TA for the second operation the following week. Surgery, PRBB, and TA were standard for all cases. Interviews were conducted the day after surgery by an unbiased observer who was unaware of the technique used. Estimates of surgical pain were made on a visual analog scale of 0 to 10, and the surgeon determined the difficulty of surgery on the basis of patient compliance and cooperation on a scale of 0 to 5. Means and variance of results were compared using analysis of variance. The mean age of patients was 71.45 ± 9.76 yrs. (mean ± standard deviation). Seventy patients (71.43%) preferred PRBB, whereas 10 patients (10.20%) preferred TA techniques. Eighteen patients (18.37%) reported no difference between the two techniques. Ninety-six patients (97.96%) were unaware of the PRBB being injected. The duration of surgery was similar for TA (11.92 ± 3.43 min) and PRBB (10.78 ± 3.00 min). Surgery was more difficult during TA and pain was worse. Surgical and anesthetic complications were unremarkable for both techniques. Patients who experienced both TA and PRBB preferred the latter.
The anesthetic options for cataract surgery include general anesthesia, retrobulbar blockade, peribulbar blockade, parabulbar methods of sub-Tenon’s anesthesia, and topical anesthesia. In the United States today general anesthesia is administered only rarely in conjunction with cataract surgery. Typically, either regional block or topical analgesic is used. Nonetheless, it is imperative to appreciate that the complications of ophthalmic anesthesia can be potentially vision-threatening or life-threatening.
Retrobulbar blockade entails injection of local anesthesia behind the eye into the muscle cone. Often a facial nerve block is performed in conjunction with retrobulbar block to prevent squeezing of the eyelid that could result in extrusion of intraocular contents if the ocular incision is large. It is important not to be lulled into a false sense of security with retrobulbar anesthesia, however, because this technique does not necessarily involve less physiologic trespass than does general anesthesia. The most common serious complication of retrobulbar block is retrobulbar hemorrhage (incidence: 1 to 3%). Other major complications include, but are not limited to, direct intravascular injection that can produce virtually instantaneous seizures if located intra-arterially, stimulation of the oculocardiac reflex; puncture of the eye ball producing retinal detachment and vitreous hemorrhage; unintentional intraocular injection; central retinal artery occlusion; and penetration of the optic nerve. Optic atrophy may occur as a result of direct injury to the nerve, injection into the nerve sheath with ensuing compressive ischemia, and intraneural sheath hemorrhage. An initially insidious but potentially fatal complication may also develop when accidental access to cerebrospinal fluid during performance of a retrobulbar block occurs owing to perforation of the meningeal sheath that surrounds the optic nerve. This can result in the gradual onset of unconsciousness, cessation of breathing, and cardiovascular collapse. Clearly, there is a continuum of sequelae, depending on the amount of drug that gains entrance to the central nervous system and the specific area of the brain to which the drug spreads. In a series of 6000 retrobulbar blocks, Nicoll 1 reported 16 cases of apparent central spread of local anesthesia; respiratory arrest developed in 8 of the 16 patients.
Because of the potentially serious complications of retrobulbar block, alternative methods of local anesthesia have been developed. Since the late 1980s, peribulbar block has become popular because, with this approach when properly performed, the muscle cone is not entered and, therefore, injury to the optic nerve should theoretically be prevented and the likelihood of central spread of local anesthetic should be greatly minimized. Ocular perforation, however, has been reported, as have peribulbar hemorrhage and ecchymoses. Additionally, some surgeons object to increased forward pressure on the eyeball consequent to the larger volume of local anesthetic deposited in the orbit compared with retrobulbar block. Moreover, it should be noted that both retrobulbar and peribulbar block can be painful for the patient when administered, and sedation is typically given. Administration of this short-acting sedation can, in and of itself, occasionally produce allergic reactions, cardiac depression, respiratory depression, loss of airway patency, and inadequate oxygenation of the patient.
A parabulbar method of sub-Tenon’s infusion of anesthetic via a flexible, curved cannula also has been developed. Because it does not involve the use of a sharp needle, this approach eliminates the risk of globe penetration, retrobulbar hemorrhage, and optic nerve trauma.
During the past seven or eight years ophthalmologists increasingly have been returning to a technique that was popularized during the early 1900s—the use of topical anesthetic agents, particularly when the surgical incision is being made through clear cornea. Many advances in cataract surgery that have enabled faster operations with greater control and less trauma have allowed ophthalmologists to re-examine the use of topical anesthesia for this procedure. Phacoemulsification, with its small incision, is the procedure of choice for using topical anesthesia; however, planned extracapsular procedures can also be performed under topical anesthesia, thereby circumventing potential complications of retrobulbar or peribulbar block that can result in blindness or death. Potential disadvantages of topical anesthesia are typically less serious and include eye movement during surgery, patient anxiety, and, rarely, allergic reactions. Patient selection is important and should be restricted to individuals who are alert, able to follow instructions and can control their eye movements. Patients who are demented, photophobic, or cannot communicate are inappropriate candidates, as are those individuals with an inflamed eye. Similarly, patients with small pupils who may require significant iris manipulation or those who need large scleral incisions generally are excluded as candidates for topical anesthesia.
Clearly, the risk of major complications associated with topical analgesia are significantly less than with other types of ocular anesthesia. This study by Boezaart and colleagues, however, serves to remind us that in medicine (as in life) nothing is ever perfect and sometimes it is necessary to sacrifice a bit of comfort for a considerable amount of safety.
Kathryn E. McGoldrick M.D.