Ophthalmic Anesthesia

Topical anesthesia of nose and throat, abolish laryngeal and esophageal reflexes prior to diagnostic procedure Topical Direct application of a 0.25% or 0.5% topical solution or by oral inhalation of a nebulized 0.5% solution. Total dose should not exceed 20 mg. Mild pain, burning and/or pruritus associated with herpes labialis (cold sores or fever blisters) Topical Apply to the affected area no more than 3-4 times a day. Ophthalmic anesthesia Topical 1-2 drops of a 0.5% solution. 

Topical anesthesia will increase the bioavailability of ophthalmic agents by decreasing the blink reflex and the production and turnover of tears. 

Surgery In patients receiving cholinesterase inhibitors, administer succinylcholine with extreme caution before and during general anesthesia. Use prior to ophthalmic surgery only as a considered risk because of the possible occurrence of hyphema. Pregnancy Category C. 

Topical local anesthesia is often used for eye, ear, nose, and throat procedures. Satisfactory topical local anesthesia requires an agent capable of rapid penetration across the skin or mucosa, and with limited tendency to diffuse away from the site of application. Cocaine, because of its excellent penetration and local vasoconstrictor effects, has been used extensively for ear, nose and throat (ENT) procedures. Cocaine is somewhat irritating and is therefore less popular for ophthalmic procedures. Recent concern about its potential cardiotoxicity when combined with epinephrine has led most otolaryngology surgeons to switch to a combination containing lidocaine and epinephrine. Other drugs used for topical anesthesia include lidocaine-bupivacaine combinations, tetracaine, pramoxine, dibucaine, benzocaine, and dyclonine. 

History of ophthalmic drug use, including a determination of whether anesthesia and mydriasis have been used at previous examinations... 

Local anesthetics are drugs that produce reversible conduction blockage of nerve impulses. Autonomic system blockade followed by sensory anesthesia and skeletal muscle paralysis occur when local anesthetic concentration is increased. The effects of local anesthetics are completely reversible, with no evidence of structural damage to the nerve fibers. Another prominent clinical feature of local anesthesia is that loss of sensation occurs without loss of consciousness. This property makes local anesthetics highly useful for many office procedures and for eye surgery. This chapter considers the pharmacologic properties of anesthetics cmrently used for ophthalmic procedures. 

Adapted from Raj PP Handbook of regional anesthesia. New York Churchill Livingstone, 1985 Bartlett JD, Fiscella R, Jaanus SD, et al., eds. Ophthalmic drug facts. St. Louis Facts and Comparisons, 2005 Crandall DG. Pharmacology of ocular anesthetics. In Duane TD, Jaeger EA, eds. Biomedical foundations of ophthalmology. Philadelphia J.B. Lippincott, 1994 and Sobol WM, McCrary JA. Ocular anesthetic properties and adverse reactions, hit Ophthalmol Chn 1989 29 195-199. 

Figure 6-2 Comparison of onset, intensity, and duration of anesthesia obtained with tetracaine 0.5%, proparacaine 0.5%, and benoxinate 0.4%. (Reprinted with permission from Am J Ophthalmol 1955 40 697-704. Copyright, The Ophthalmic Publishing Company.)...

Patients with a reported history of allergic responses to ester and amide anesthetics pose a challenge, especially when regional anesthesia is necessary. Two alternatives may be considered when minor ophthalmic surgical procedures are performed. A 1% solution of diphenhydramine may be prepared by diluting the 5% solution (Benadryl Steri-Vials) with sterile saline. Additionally, injecting preserved sterile saline alone has been shown to be effective for superficial surgical procedures such as papilloma removal and shave biopsies. 

Although most commonly used topical anesthetics are similar in onset, duration, and depth of anesthesia (see Chapter 6), several important differences exist. For diagnostic and treatment procedures requiring topical anesthesia, the clinician essentially has two choices tetracaine or proparacaine. Both provide rapid onset of anesthesia within 10 to 20 seconds and last approximately 10 to 20 minutes. If prolonged anesthesia is required, it may be accomplished by repeated application.Tetracaine may cause more discomfort upon instillation than proparacaine and typically results in more corneal compromise. In general, proparacaine 0.5% has a low incidence of hypersensitivity reactions and is the anesthetic of choice for topical anesthesia in ophthalmic applications. Other anesthetics that have occasional topical application are cocaine (4% to 10%) and lidocaine (4%). 

One or two drops of 0.5% proparacaine are sufficient for most ophthalmic diagnostic procedures requiring topical anesthesia. Most often, procedures are performed bilaterally, and it is most efficient if the anesthetic is instilled in both eyes before beginning the procedure. Because the duration of action is 10 to 20 minutes, it is not necessary to reapply anesthetic before beginning the procedure on the second eye. If a procedure is to be performed on one eye only, it is still recommended that anesthetic be instilled in both eyes to inhibit the blink reflex in the fellow eye. Examples of diagnostic procedures that require topical anesthesia on all or some occasions are listed in Box 19-1. 

Microbiologic culture studies are useful fc>r bacterial identification, especially when an ocular infection foils to respond to treatment. Cultures are often obtained from the eyelids, the conjimctiva, expressed material from the lacrimal sac, and the cornea. Because preserved ophthalmic anesthetics have a bacteriostatic effect, cultures should be obtained if possible before anesthetic instillation. In the case of corneal sampling, it is necessary to provide topical anesthesia for patient comfort. The anesthetic of choice is 0.5% proparacaine because it causes the least bacterial growth inhibition. To enhance the bacterial yield, sterile preservative-free anesthetic may be used. Samples obtained may be inoculated directly onto soUd media plates (e.g., blood agar). Amies without charcoal transport medium (e g., BBL CultureSwab Plus) appears to be an acceptable alternative to direct plating and has the added benefit of convenience. 

Figure 19-6 Distribution of area for regional anesthesia blocks. (Adapted from Wilson RR Anesthesia. In Spaeth GL, ed. Ophthalmic surgery principles and practice. Philadelphia Saunders, 1990 81.)...

Wessels IF, Wessels DA, Zimmerman GJ. The photic sneeze reflex and ocular anesthesia. Ophthalmic Surg Lasers 1999 30(3) 208-11. 

Olitsky SE, Juneja RG. Orbital hemorrhage after the administration of sub-tenon s infusion anesthesia. Ophthalmic Surg Lasers 1997 28(2) 145-6. 

Topical Not for ophthalmic use for skin disorders apply directly to affected area or put on gauze or bandage, which is then applied to the skin for mucous membrane use apply to desired area using manufacturer s insert administer the lowest dose possible that still provides anesthesia. 

Proparacaine, a local anesthetic (ophthalmic solution 0.5%), is used in anesthesia for tonometry, anesthesia for the removal of foreign bodies or sutures from the eye, and anesthesia for cataract extraction and glaucoma surgery. 

Manually restrain mouse and apply one drop of topical ophthalmic anesthetic, such as proparacaine or tetracaine, on the eye. An alternative to topical anesthesia is general anesthesia (e.g., ketamine/xylazine). 

To prove the relevance of the acute, transient comeal hypoesthesia or even anesthesia found in rabbits after topical administration of Azelastine ophthalmic solutions, testing was additionally performed in Beagle dogs. In contrast to rabbits no indication of any acute or general reduction of the comeal sensitivity was noted in the Beagle dogs. 

According to the results of the experimental studies and to the findings of Harris et al. the acute, transient reduction of the comeal sensitivity only in rabbits was considered not to be prohibitive for the further development of Azelastine ophthalmic solutions. Clinical phase I studies were performed, where special consideration was given to the measurement of the comeal sensitivity. As in rabbits also in man the positive reference test dmg proxymetacaine hydrochloride was able to induce a distinct and measurable local anesthesia with a fast onset of action and a duration of approximately 15-30 minutes. Azelastine ophthalmic solutions at concentrations of 0.05% and/or 0.1%, however, did not produce any changes of the comeal sensitivity after both single or repeated applications. Concerning these results it must especially be noted, that in human volunteers the more sensitive pa-... 

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