1   Complications of Ophthalmic Anesthesia

Local anesthesia is the greatest single hazard in cataract surgery,^1–4 accounting for an incidence of adverse effects in as high as 3.5% of patients (orbital adverse effects in 2.6%, and systemic effects in 0.9%), according to a study by the Royal College of Ophthalmologists. A cataract surgeon in the United States has, on average, a 3% chance each year of being sued over cataract surgery,⁵ and the majority of such cases relate to anesthesia complications, such as globe perforations, inadvertent intraocular injections and retinal detachment, and intraocular hemorrhage associated with these misadventures.⁶

The purpose of anesthesia is to convert an otherwise painful, anxiety-producing, and unpleasant experience into a tolerable, comfortable, and even pleasant and restful experience. In choosing the anesthesia, the least invasive and the safest method should always be employed. The extensiveness, duration, and complexity of surgery, factors that are often intertwined, should be evaluated in choosing the route, duration, and depth of anesthesia employed. Exposure to anesthesia in excess of that which is necessary adds unnecessary risk to the procedure, with no tangible benefit to the patient or the surgical team. Regional anesthesia is usually preferable to general anesthesia, producing safer, equally effective, and cost-efficient results. However, just as it is inappropriate for a surgeon to use the same technique for every surgical intervention, it is similarly incorrect to use the same anesthesia for each case. Although surgeons may subscribe to a particular practice of anesthesia for routine cases, it is important to assess each patient’s needs and act appropriately for exceptional cases. Such exceptions may exist either because of the patient’s medical conditions or personality, or because the surgical intervention may be more complex or is anticipated to be of longer duration than is routine.

Definition of Injectable Block

For the purposes of this discussion, I am using the term injectable techniques to refer to any anesthesia method involving the use of a sharp needle and an injectate, which includes peribulbar as well as retrobulbar techniques, unless otherwise disqualified. The procedures collectively are referred to as “regional orbital anesthetic block.”⁷ It has been suggested that a peribulbar block (also referred to as a periconal block), involving injection outside of the muscle cone, entails less risk of complication than a retrobulbar technique. However true this may be, complications have been observed with both techniques.⁸

Preoperative Assessment

Good planning is always part of the strategy to limit risk in anesthesia administration. Some authors believe that if the patient has preexisting systemic medical conditions, a history should be taken and a physical examination and laboratory testing should be performed. But there is considerable regional and international variation in these requirements; in fact, in some states, there are regulations that require a medical evaluation before major surgery, even on a perfectly healthy patient. However, no consistent standards have been established, and there is little evidence that such evaluations have a significant bearing on the safety of cataract surgery in general, and even less in healthy patients. A prospective multicenter clinical trial evaluating this issue in 19,557 elective cataract operations in the United States and Canada, conducted by the Study of Medical Testing for Cataract Surgery, randomized patients into either a No Routine Screening group or a Routine Screening group; in patients in the latter group, an electrocardiogram (ECG) was performed, and electrolytes/glucose and complete blood count (CBC) were assessed. Demographic, clinical, perioperative, and medical event data were collected for seven days postsurgery, and they demonstrated that “perioperative morbidity and mortality are not reduced by routine use of commonly ordered preoperative medical tests.”⁹ A study by Rosenfeld et al¹⁰ similarly showed that the need for anesthesia intervention during cataract surgery was correlated neither with the presence of an abnormal preoperative ECG nor with the presence of diabetes, two tests almost always performed during a preoperative evaluation. Nonetheless, a history of systemic hypertension, pulmonary disease, renal disease, or cancer was associated with a statistically significant increase in the incidence of intervention, suggesting that at least a review of the patient’s medical conditions may be prudent in the immediate preoperative assessment.

Some investigators have reported that the anesthesia team did not make use of reported results of preoperative tests and examinations, and that perioperative management was not influenced because of these investigations.¹¹ Findings from the National Survey of Local Anesthesia for Ocular Surgery in 1997 reveal further that in patients who had no preoperative tests, there was a very low rate of serious adverse events that would have been influenced by such tests.¹²

Because cataract surgery is most frequently performed on geriatric patients, a high incidence of systemic illnesses may coexist, such as diabetes, hypertension, coronary artery disease, obesity, chronic obstructive pulmonary disease, and arthritis. These conditions may pose special challenges to the surgical and anesthesia teams. To limit these risks, every effort should be made to ensure that the patient is in optimal condition for surgery. Nonetheless, in most instances cataract surgery can take place even in the presence of these conditions; there are almost no contraindications to surgery in patients whose medical condition has been optimized.

During the immediate preoperative consultation, the patient should provide a list of current medications so that any potential drug interactions can be anticipated, and to verify that the patient has taken the medications appropriately. It is useful to schedule surgery for diabetics during the early morning, so that their oral hypoglycemics or insulin dosage can be taken with food immediately after the surgery without interrupting their usual routine. Alternate strategies may make surgery safe during any time of the day; for example, diabetics can be scheduled during the early afternoon so that they can take their insulin and breakfast earlier in the day with enough time to fast prior to surgery. In any case, it is best to avoid conditions that place the patient at risk of hypoglycemia; elevated blood glucose levels can generally be managed postoperatively, if medically appropriate.

Considerations Regarding Anticoagulation

In general, it is advisable to continue patients on systemic anticoagulants during routine cataract surgery, particularly in cases of small-incision phacoemulsification. Discontinuation of anticoagulant therapy may bear a greater risk than that of significant intraoperative ocular bleeding, even with retrobulbar injection.¹³ In these cases, however, it is of particular importance to use small needles and correct anatomic placement, and to avoid excessive manipulation during the injectable block. Studies to date, however, have not distinguished among the risks of discontinuing anticoagulation prior to cataract surgery vis-à-vis different medical indications. It is well known that stopping medications have different implications for risk depending on the condition for which the patient is being treated. For example, patients with mechanical heart valve replacement are at substantially higher risk for embolism or stroke than are patients with atrial fibrillation as the underlying reason for treatment; accordingly, mechanical heart valve replacement patients require higher routine levels of anticoagulation. These factors should be weighed carefully, in consultation with the patient’s internist, in determining the systemic and ocular risks. In patients whose International Normalized Ratio (INR; a derivative of the prothrombin time) is above 2.0, consideration should be given to reducing anticoagulation therapy preoperatively. Depending on the complexity of the surgical intervention, discontinuation of anticoagulation therapy can be considered, although it is rarely necessary.

The Role of the Anesthesia Team in Systemic Sedation and General Anesthesia

In the United States, both Certified Registered Nurse Anesthetists (CRNAs) and anesthesiologists (MDs) have been trained to administer anesthesia, monitor and treat the patients’ systemic condition, and provide sedation appropriate to the patient’s need. Although there are regional variations in usage of anesthesia services both through the United States and internationally,¹⁴ the role of this vital team member cannot be overlooked. In an era where cost containment has reached a high degree of consciousness, it is important to evaluate the necessity of each aspect of the care we provide. Rosenfeld et al¹⁰ found that during cataract surgery, major anesthesia intervention (i.e., excluding verbal reassurance, hand holding, or physical restraint) was required in 28.6% of patients. Although intervention was required more often in patients with certain underlying diseases, almost a third of patients without predisposing factors required intervention of some type. This suggests that with current anesthesia methods it is impossible to predict preoperatively which patients will require intervention, thereby suggesting further that anesthesia monitoring is essential for avoiding perioperative complications, regardless of the patient’s preoperative condition.

Intravenous Sedation and Monitoring

Considerable debate has persisted regarding the usefulness of intravenous (IV) sedation for cataract surgery, particularly with the use of topical anesthetic agents and minimally invasive surgical technique (for further discussion, see Chapter 2). It is important to understand what constitutes appropriate use of this mode of treatment. First, anesthesiologists must possess appropriate personality traits and communication skills that enable them to gain the patient’s trust and confidence.¹⁵ Second, they should inform the patient about the experience he or she is about to have. This discussion will help minimize anxiety and lower complications during the perioperative period.¹⁶ Third, perioperative monitoring should generally consist of at least an ECG, pulse oximetry, and periodic blood pressure measurements.^13,17 The latter measurements should be kept to a minimum during critical surgical periods to avoid patient discomfort during surgery, which may cause undue anxiety or movement.

The goal of IV sedation should be to relieve anxiety while enabling the patient to remain stationary, calm, comfortable, and cooperative. The elderly generally require less pharmacological squelching of anxiety during surgery than do younger patients, both with regard to the absolute amount of the agent given and the level of consciousness attained; however, considerable variability exists in the amount of drug necessary to obtain the desired end point. It is usually desirable to produce anxiolysis without obtundation, because obtundation may result in a patient who is unpredictably still, then combative,^18–21 and may cause further depression of preexisting cardiac and respiratory instabilities.^22–26 Some newer sedatives, however, can achieve substantial levels of sedation without significant respiratory depression (see discussion in Chapter 2).

Excessive IV sedation should rarely be used to compensate for an incomplete regional anesthesia block. Rather, this should be managed by supplementation of the local anesthesia. However, occasionally it is necessary to provide a deeper level of sedation or systemic analgesia (e.g., narcotics) to supplement the regional anesthesia block, particularly in situations where the additional block is ineffective or cannot be administered because of ongoing surgical maneuvers.

Systemic toxicity of anesthetic agents is usually associated with inadvertent ectopic injection or overdose of a particular agent, allergic reactions, or vasovagal responses. Ectopic injection may be propagated by the intravascular route or through inadvertent direct central nervous system injection through the subdural route via penetration of the optic nerve sheath. These problems will each be discussed later in their respective sections. However, as a general measure, limitation of these problems can be accomplished by slow, patient injection of anesthetics¹⁵ (no more than 2 cc/min) while monitoring the patient for any signs of systemic toxicity, and by gentle preinjection aspiration to ensure an extravascular location of the needle.

Although hyaluronidase is invaluable as a spreading agent, its use may result in allergic or frankly anaphylactic reactions.²⁷ As such, this proteolytic drug should be avoided in atopic individuals. A study by Prosser et al²⁸ suggests that hyaluronidase may not be necessary at least in peribulbar blocks.

Perforation and Penetration of the Globe

The administration of a regional orbital anesthetic block is a technique requiring specialized training and experience. In many institutions the block is given by the least experienced surgeon or by anesthesia personnel, often without adequate experience or training. This practice should be discouraged. A detailed study of the orbit, its nerves, its vasculature, and its soft tissue septa should be undertaken before administering injectable anesthesia. Regional orbital anesthesia requires an appreciation for the three dimensionality of the skill, and hands-on, one-to-one training is desirable.

This is the most common of the serious complications of injectable anesthesia and has been documented by numerous authors over the years.^29–32 Globe perforation and inadvertent intraocular injections also rank as two of the most common causes of litigation in cataract surgery.⁶ Ocular penetration refers to the entry of a needle into the globe after which the needle is withdrawn. Ocular perforation suggests that the needle entered the eye and then exited through another part of the globe prior to having been withdrawn. Because the clinical pictures are similar, the terms are used interchangeably in this discussion.

The actual incidence of ocular penetration is difficult to determine, owing to the tremendous diversity of reports that have appeared in the literature. Reported incidences range from as few as one penetration in 16,224 consecutive cases,^33,34 to as many as 1 in 100 cases. Teichmann and Uthoff³⁵ reported an incidence of 0 in 21,000 cases using their technique. If the incidences reported in several available references are averaged, the occurrence rate is ∼ 0.01%.

Because the risk of complication is directly related to the number of injections administered, every effort should be made to reduce the frequency with which multiple injections are given. Correct placement, use of hyaluronidase, and adequate volume of injectate will increase the likelihood of success of the “first take.” Ocular compression devices such as the “super-pinky” or the Honan’s balloon^36–38 may likewise improve the distribution of anesthetic, although they must be used judiciously to avoid vascular compromise to the globe. A good end point for determination of adequate block should be the ablation of sensation to the area to be operated upon. Testing by lightly pinching the conjunctiva with a 0.12-mm Castroviejo forceps will give adequate indication of anesthesia. While providing a convenient measure as to the effectiveness of the block, it is not necessary to achieve akinesia or amaurosis in every case; insisting on achieving these end points has the effect of needing more frequent readministration of anesthesia injections than are necessary.

Perforation/Penetration: Anatomic Considerations

The incidence of ocular penetration is significantly higher in eyes that have axial lengths greater than 26 mm on ultrasonic biometry. This increased incidence is most likely due to the increased incidence of staphylomata or previous scleral buckle in this population. In fact, Duker et al³⁹ estimate the incidence at 1 in 140 cases in such eyes. The increased susceptibility of staphylomatous eyes is most likely due to the fact that, whereas nonstaphylomatous eyes have predictable anterior-posterior shape and the location of the equator can be extrapolated, these proportions are distorted in eyes with staphylomata. In the latter, there is an elongated anterior-posterior dimension that is not entirely predictable,⁴⁰ in contrast even to nonpathologically myopic eyes⁴¹ (Fig. 1.1). Because a misjudgment of even 1 or 2 mm can lead to globe penetration, it is incumbent upon the person administering the block to review the patient’s chart and know the axial length of the eye prior to administering the injection.⁴² The presence of a previously placed scleral buckle bears the additional risk that the retrobulbar needle may snag behind the buckle, causing a globe penetration.

As with staphylomatous eyes, small, tight orbits with deep-set eyes are also particularly at risk for injury,⁴³ owing primarily to the unexpectedly posterior position of the equator with respect to the lateral orbital rim, and the dearth of space between the orbital rim and the globe (Fig. 1.2).

Perforation/Penetration: Patient Movement

Patient cooperation is essential for any successful regional anesthesia. Nowhere is this more true than in orbital regional anesthesia. Critical structures within the orbit are in close proximity to one another, and any unanticipated movement may result in ocular perforation. As mentioned earlier, it is essential to obtain sedation appropriate to the patient’s clinical status. This usually means administration of a light, anxiolytic dose of sedative without obtundation, in conjunction with a skillfully performed, “painless” anesthetic block as described, for example, by Hustead,⁴⁴ in which a subconjunctival injection of dilute anesthetic precedes the retrobulbar anesthetic injection. It is my opinion that sedation resulting in complete obtundation of patients can be quite hazardous because there is little predictability of such patients with regard to sudden, unexpected movement. Unpredictable movement can be elicited in patients with psychiatric or behavioral disorders, mental retardation, or neurologic movement disorders. And pain itself may cause the patient to move suddenly. Unwanted environmental stimuli such as loud noise, power failure, or uncomfortable or unstable patient positioning may also lead to movement and should be avoided. Therefore, a quiet, comfortable room with proper head support and power backup should always be used during this critical step in cataract surgery.

Fig. 1.1 (a) Normal eye: expected anterior-posterior dimension. The needle clears the equator. (b) Larger myopic eye with normal proportions but slight posterior displacement of the equator. (c) The staphylomatous eye has an abnormal anterior-posterior dimension that is unpredictable, making the risk of ocular perforation greater.

Often, however, there are no known specific factors leading to perforation. In rare instances, well-trained, experienced practitioners working on quiet, cooperative patients will experience globe perforation. Therefore, the existence of a perforation is certainly not prima facie evidence of negligence or malpractice.⁴³

Fig. 1.2 (a) Normal set eye: the equator (solid line) is approximately at the level of the lateral orbital rim. (b) Deep-set eye: the equator (solid line) is retroplaced behind the lateral orbital rim (dotted line), increasing the risk of ocular perforation.

The occurrence of ocular penetration is often not apparent to the surgeon. Sometimes resistance to injection is appreciated at the time of injection, owing to the finite volume of the globe. Bullock et al⁴⁵ reported a case of inadvertent globe penetration in which such a large volume of fluid was injected into the vitreous cavity that it caused the eye to explode, extruding the ocular contents into the subconjunctival space. The investigators subsequently determined that 3,600 mm Hg pressure (from ∼ 2 cc of injectate) was required to cause explosion in eye-bank eyes. However, in cases of complete perforation in which the needle enters and then exits from the posterior pole, injection may be without resistance. Indeed, the presence of a “perfect block” with total globe akinesia and anesthesia may result, owing to the posterior orbital location of the injection.

Conversely, globe hypotony may be observed if the needle penetration or perforation occurred without injection into the globe.

Severe pain may sometimes herald an ocular perforation, but this may vary according to the type of needle used (sharp versus dull), the type and amount of sedation used, and the pain tolerances of the patient.⁴³

A popping sensation may be felt as the needle penetrates the globe. Because the practitioner sometimes feels this sensation during normal blocks when piercing a connective tissue septum, its significance may not be readily appreciated. This popping sensation can also be elicited from perforation of a blood vessel, the optic nerve sheath, or an extraocular muscle (EOM) as well.

A vitreous hemorrhage, retinal detachment, or retinal tear is seen in a majority of cases. The surgeon may be aware of a diminished red reflex in such patients. Frequently, the presence of these further complications, may not be appreciated until the postoperative office visits, even weeks later.

Perforation/Penetration: Prevention and Treatment

Treatment consists of early recognition of the problem, and, where appropriate, canceling the proposed surgery until the eye can be stabilized. In cases of intraocular injection, increased pressure elevation may cause closure of the central retinal artery. In such cases, consideration should be given to performing vitreous tap or even pars plana vitrectomy if needed, to lower the intraocular pressure. Mannitol may be used to create an osmotic deturgescence of the vitreous cavity. Vitreous hemorrhage or detachment requires treatment following the usual protocols.

This complication can be avoided by an awareness of the patient’s axial length, preexamination of the orbit/globe relationship, and proper instruction to the patient regarding avoiding unnecessary movement. A history of prior difficulties with regional block in the companion eye should also be investigated, and etiologic factors delineated before proceeding with the second eye.

Numerous authors have described techniques that may reduce the likelihood of perforation. Current practice consists of a sharp needle technique with insertion either at the lateral canthus or slightly below the canthus, or, alternatively, at the medial canthus, preferably though the conjunctiva and not through the lid. The eye should be held open, remain in primary gaze, and be observed throughout the insertion and injection. The eye should not move during this maneuver, as this may indicate that the sclera has been engaged. The classic concept of looking “up and in” as popularized by Atkinson, should be avoided because it brings the optic nerve closer to the inferotemporal quadrant and places it on stretch, making it more susceptible to injury.

There is still some debate about the ideal needle for this task. Waller et al⁴⁶ recommend a dull needle, citing the theoretically greater force required to penetrate the sclera. This argument, however, fails when one considers that any needle sharp enough to penetrate the skin will probably have no trouble penetrating the sclera. Further, because eyes at high risk often have scleral ectasias, there would be sufficient thinning to allow even a dull needle to penetrate. I prefer a straight, sharp, 27-gauge needle no longer than 31 mm inserted as described above, with the bevel toward the globe, thus reducing the risk of damage to critical structures.

A medial orbital injection is also sometimes favored. In this technique the needle is placed at the caruncle, and injection is administered with the needle positioned with the bevel facing away from the globe so as to accommodate the sharply medioposterior sloping of the medial orbital wall.

Retrobulbar Hemorrhage

Retrobulbar hemorrhage occurs in 0.44% to 3% of retrobulbar anesthetic cases.^47,48 Because of the extensive vascular plexus within the orbit, any vessel may be nicked and caused to bleed. This may be aggravated in patients taking anticoagulants, anti-platelet aggregation medications (e.g., aspirin), steroids, nonsteroidal anti-inflammatory drugs (NSAIDs),¹³ or in the presence of poorly controlled hypertension or in cases of excessive manipulation of the needle.

Retrobulbar hemorrhages vary in severity. Although some are venous in origin and may spread slowly, arterial hemorrhages tend to be rapid and produce an aggressive orbital swelling, marked proptosis with immobility of the glove, and massive subconjunctival and eyelid blood staining. Serious vascular compromise to the globe may ensue.^49,50

Retrobulbar Hemorrhage: Treatment and Prevention

Treatment of this condition depends entirely on its severity. If a tense orbit and globe are observed, prompt treatment is essential to avoid permanent visual loss. The central retinal artery should be immediately assessed, and if it is pulsatile or closed, immediate decompression of the anterior orbit must be performed. In these cases, lateral canthotomy should be performed, and if necessary a complete disinsertion of the lateral canthal tendon and incision of the lower fornix may provide further decompression. If surgery is canceled, the patient should be observed until the vision and circulation are stabilized, and periodic frequent measurement of visual acuity should be made for several hours postoperatively.

In milder cases, immediate compression of the globe with digital pressure, intravenous mannitol, and observation may be sufficient to limit the spread of blood. It is not unreasonable to proceed with surgery if the hemorrhage is sufficiently innocuous that ballottement of the globe is soft, there is no intraocular circulatory compromise, and visualization of the anterior segment is unimpeded.

This complication may be avoided in most cases by taking several precautions. First, gentle yet decisive insertion of the needle without tilting, jiggling, or continually stabbing with the needle will minimize the risk of piercing a vessel. Second, a small-diameter, disposable needle that does not exceed the desired orbital depth of penetration is preferable. A needle length of less than 31 mm will limit access to the most posterior vessels of the orbital apex,⁵¹ which contains the largest vessels, and the small bore (27 gauge or less) will limit the amount of bleeding that may occur in the event that a vessel is pierced, because a smaller rent in the vessel will be created.

Fig. 1.3 (a) Inferotemporal block. The eye is held in primary gaze, and the injection is performed through the conjunctiva. The needle passes posteriorly at a 10-degree elevation from the coronal plane until the equator is reached. Then it is passed slightly medially and superiorly entering the cone. The globe is continually observed to detect movement, which may indicate an entering of the sclera. (b) Superotemporal pericone (peribulbar) block. The needle is directed through the lid 3 mm lateral to the lateral limbus and aimed toward the roof of the orbit. Slow injection and careful observation of the globe are performed. (c) Medial block. A 30-gauge, 20- to 25-mm, sharp disposable needle is placed just medial to the caruncle with the bevel pointed away from the globe. When the needle hub reaches the plane of the iris, the anesthetic is injected near the medial orbital wall. (Modified from Hamilton RC. Complications of ophthalmic regional anesthesia. Ophthalmol Clin North Am 1998;11:99–114.)

The anterior orbit is relative avascular in three sites: the inferotemporal quadrant (junction of the lateral one third and medial two thirds), the superotemporal quadrant in the sagittal plane of the lateral limbus, and directly nasally in the compartment nasal to the medial rectus. This avascular property makes these sites ideal for orbital injection.⁵² The superotemporal quadrant is particularly suitable for periconal injection. The superonasal area is to be avoided because the end vessels of the ophthalmic artery and the trochlea of the superior oblique are located there (Fig. 1.3).

Subconjunctival Hemorrhage

Within the spectrum of orbital bleed, a less severe problem is that of subconjunctival bleed. These may occur with some frequency and, unfortunately, may be part of the criteria by which the patient evaluates the immediate postoperative success. Aside from their cosmetic appearance they are rarely of significance medically. If a patch is applied, the patient may be unaware of the problem, but should be reassured as to the benign nature of the condition.

Extraocular Muscle Paresis

Transient and reversible akinesia is the hallmark of most injectable anesthesia. Many operators use this as the end point to determine the appropriateness of the block. The introduction of ropivacaine 1% as an agent for injection has been shown to have less motor neuron effect, with similar anesthetic effect,⁵³ with the result that there is a decrease in intra- and postoperative akinesia. In cases where peribulbar anesthesia is given, neither amaurosis nor akinesia will occur, obviating to some extent the need to patch the eye at the conclusion of the procedure.

In some cases the injection of local anesthetic has been shown to cause persistent or even permanent EOM paresis. It is important to realize that some postoperative diplopia may be due either to preexisting strabismus masked by the cataract, commonly from prolonged occlusion, or to preexisting ocular palsy.⁵⁴ Further, some postoperative diplopia is based on optical problems, for example anisometropia⁵⁵ or the decompensation of a previously compensated tropia, especially if there is decline in vision immediately following surgery. However, in many cases, the diplopia is likely due to injury related directly to the anesthetic injection.

Hamed⁵⁴ postulates that there is a direct mechanical injury due to injection directly into the belly of the EOM, or by laceration of the anterior ciliary arteries causing an intra-sheath hematoma, resulting in a compartment syndrome. Hypoperfusion, ischemia, inflammation, and permanent muscle fiber damage may then ensue. The inferior rectus muscle is most likely to be damaged.^56,57

The role of direct chemical myotoxicity from the anesthetic agents has been studied but remains unclear. Animal studies using bupivacaine, lidocaine, and mepivacaine^58,59 found that when injected around but not into the EOMs, there was negligible effect, which was fully reversible in time. These findings are in contrast to the high degree of myotoxicity demonstrated in other skeletal muscles. However, when these drugs were injected directly into the EOMs, histological changes deemed to be severe enough to cause strabismus were observed.

In the 1990s, when Wydase (hyaluronidase, Wyeth) was unavailable, an increase in persistent postoperative diplopia was noted in patients undergoing cataract surgery with retrobulbar and peribulbar anesthesia.⁵⁵ One theory that may have explained this finding is that the absence of the hyaluronidase may have caused a pooling of anesthetic near the muscle for a prolonged period of time and that this may have in turn caused more toxicity than usual. With the current availability of hyaluronidase, these complications are rare.

Brainstem Anesthesia and Injection into the Optic Nerve

The optic nerve sheath is continuous with the dura of the brain. As such, injection beneath the sheath can result in injectate tracking back into the subarachnoid or subdural space. Symptoms of such “brainstem” anesthesia are protean and include respiratory arrest; cardiopulmonary arrest^60,61; hypertension; tachycardia; dysarthria⁶²; confusion; marked shivering; convulsions; loss of consciousness; hemi-, para-, or quadriplegia; and contralateral blockade of the optic nerve and the third, sixth, and twelfth cranial nerves.^63,64 Hamilton⁶⁵ has explained the occurrence of hypertension and tachycardia on the basis of a parasympathetic blockade after the anesthetic enters the cerebrospinal fluid. An alternate explanation suggests vagal blockade at the brainstem.⁶⁶

Although the consequences of undetected brainstem anesthesia can be quite dire, immediate diagnosis and appropriate treatment and supportive measures usually result in an otherwise uneventful outcome. The onset is usually within 2 to 10 minutes of injection and resolves over several hours. It is therefore advisable that patients should not be draped for at least 15 minutes following retrobulbar injection so that in the event this complication occurs, it can be immediate recognized, and unobstructed access to the patient can be obtained.⁶¹

Treatment consists of ventilatory support with oxygen, intravenous fluid therapy, and use of systemic pharmacological agents such as vasopressors, vasodilators, or adrenergic blocking agents, and close monitoring of the vital signs.

Injection directly into the optic nerve causing severe visual loss or blindness has also been reported.⁶⁷

Prevention of this problem may be accomplished in much the same way as prevention of other needle-related complications: proper placement of the needle, both with respect to orbital position and depth, avoidance of the “up-and-in” positioning of the eye, and awareness of the axial length.

Limitation of Ocular Blood Flow

Limitation of blood flow from retrobulbar hemorrhage has been discussed above. In addition, studies by Findl et al⁶⁸ have shown that peribulbar and retrobulbar anesthetics have a negative effect on the choroidal and retinal blood flow. This phenomenon may not be clinically significant in every patient. However, for those with compromised circulation such as diabetics, hypertensives, and those in whom normal autoregulation of ocular blood flow is impaired, such as those with diabetic retinopathy or glaucoma, this phenomenon may take on increased significance, because even a small reduction in ocular perfusion in these patients may result in ischemia. These factors should be considered when evaluating a patient with underlying ocular or systemic disease for injectable anesthesia.

Ocular compression devices, which are used to enhance the spread of anesthetic and reduce intraocular pressure prior to surgery, have been implicated in the production of ischemia as well. Because blood flow to the retina is influenced by a balance between intraocular and extraocular arterial blood pressure, the application of external pressure from devices such as the Honan’s balloon or “super-pinky” may cause an initial increase in intraocular pressure,^69–72 thus reducing blood flow in patients with arterial disease, diabetes, or glaucoma.^73–75

The use of epinephrine in the injectate may similarly be implicated in production of ischemia,⁷⁶ and is probably both unnecessary and best avoided.

Oculocardiac Reflex

The oculocardiac reflex is commonly seen in conjunction with ocular surgery. Most commonly, it is seen under general anesthesia when the EOMs are stretched, but it also can be seen in conjunction with retrobulbar block. According to Hamilton,⁵² the latter finding is attributable to the use of dull large-bore needles.

Because the afferent limb of this reflex is trigeminal, arising from within the orbit, and because the efferent limb is vagal, ablation of this reflex may be accomplished by administering retrobulbar lidocaine⁷⁷ (with a sharp small-bore needle) or by the aggressive administration of atropine⁷⁸ (2–3 mg in adults).

Facial Nerve Block

Although rarely used anymore as a separate injection during routine cataract surgery, seventh nerve blockade using the van Lint, O’Brien, or Nadbath techniques is sometimes required. Complications from this technique are reported most commonly with the Nadbath technique, in which injection in or near the stylomastoid foramen is accomplished. The complications include swallowing difficulty (spread to the glossopharyngeal nerve) and respiratory difficulty (vagus and spinal accessory blockade). Cases of permanent facial palsy are most commonly reported with the Nadbath approach as well.

Separate injection of the seventh nerve is best avoided, if possible. If an orbital injection is administered using hyaluronidase, a sufficiently high volume of anesthetic should be given and an ocular decompression device should be used to aid in the spread of the anesthetic; eyelid akinesia is accomplished by spreading anesthesia to the lids through the orbital septum, thus obviating the need for the painful percutaneous nerve block technique.⁵² In cases where a separate injection is required as a supplement, avoiding hyaluronidase and limiting the injection to a superficial depth (no more than 12 mm) are recommended.^79,80

Corneal Exposure

As the cornea may remain anesthetic for a period of time following surgery, it is prudent to take appropriate measures to protect it against inadvertent injury, particularly when lid akinesia exists concomitantly. An occlusive eye patch is most commonly employed for this purpose. However, with shorter duration anesthetics, appropriate patient counseling (frequent lubrication and blinking, avoidance of touching or rubbing the eye) may be sufficient until sensation returns. Advantages of using an occlusive dressing must be weighed against the potential hazards, such as contributing to the development of postoperative ptosis,⁸¹ increased moisture and temperature enhancing the growth of pathogenic organisms,⁸² and the patient’s loss of peripheral vision and stereopsis, which may lead to accidental injury from a fall or bump.

Atonic Pupil

Postoperative atonic pupil is a rare but reported complication of cataract surgery. Suggestions that this may be related to damage to the ciliary ganglion or adjacent parasympathetic branches⁸³ have been countered by the observation that pilocarpine instilled in these eyes did not induce pupillary constriction, suggesting a direct iris sphincter malfunction as the etiology.⁸⁴ Although some patients are asymptomatic following this occurrence, patients who experience symptoms, such as photophobia, decreased vision, and glare, may require repair or implantation of an iris prosthetic device (see Chapter 32 for further discussion).

Summary

Complications related to regional orbital anesthesia occur infrequently, but their consequences can be substantial. Awareness of the potential for these problems, with meticulous attention to detail and the institution of prompt corrective measures, optimizes the outcomes in these cases. A summary of these conditions, their clinical presentations, and treatment is given in Table 1.1.

Topical and Intracameral Anesthesia

The continuing evolution of minimally invasive techniques for cataract surgery has been paralleled by a concomitant development of less invasive anesthesia techniques that have been used increasingly in recent decades.⁸⁵ The parallel improvement in both surgical and anesthetic technique is noteworthy for the relative paucity of complications.⁸⁶ Nonetheless, if these innovative procedures are to yield reproducible results with few complications, we must continue to evaluate the way in which we approach the patient and the surgical procedure.

What has usually been called “topical anesthesia” should more suitably be called “noninjection anesthesia” or “minimally invasive anesthesia,” because it encompasses techniques such as parabulbar, sub-Tenon’s, and pinpoint anesthesia, as well as intracameral techniques. Furthermore, the term topical anesthesia suggests the emphasis on the application of drugs to the ocular surface, or within the anterior chamber. In fact, the technique comprises a unique skill set that requires different interaction with the patient and balancing the topical anesthesia with systemic sedation or even general anesthesia. The adjunctive use of IV sedation varies greatly, particularly among geographic regions.² Perhaps, then, we ought to collectively call this array of ophthalmic anesthetic techniques “topically assisted anesthesia.”

An understanding of this global approach is essential to the successful outcome of what we will call, for expedience’s sake, “topical anesthesia” from this point on. In contradistinction to common usage, the word anesthesia in the context of intraocular surgery does not simply connote analgesia alone. It encompasses amaurosis, akinesia, sedation, and amnesia.⁸⁷ The absence of amaurosis and akinesia in patients receiving topical anesthetic with IV sedation, and the absence of all four characteristics in patients receiving topical anesthetic alone, are the hallmarks of this multifaceted technique. Retention of vision during and immediately after surgical intervention is not merely window dressing. A parallel exists between the rapid return of visual function and the likelihood of return to activities enjoyed prior to the development of visual impairment.⁸⁸ Immediate vision, as an index of a successful outcome, is reassuring to surgeon and patient alike.

The introduction of femtosecond laser technology has created a two-step process for cataract surgery: The femtosecond laser procedure is generally performed without sedation, and requires absolute cooperation of the patient in lying still and fixating. Topical anesthetic drops alone are usually sufficient, although very anxious patients can be given mild sedation usually in the form of oral benzodiazepines (e.g., alprazolam, lorazepam, diazepam), although in some centers IV sedation is also available. Once the patient arrives in the surgical suite, IV sedation is generally administered for the cataract surgery itself.

Assessment of immediate postoperative vision can be useful in diagnosing increased intraocular pressure, retinal vascular compromise, and intraocular lens (IOL) power errors. Furthermore, several surgical techniques (for example, intraoperative wavefront aberrometry) are largely dependent on the patient’s maintaining fixation, which can only be achieved with topical anesthetic techniques.

Preoperative Assessment and General Considerations

A patient undergoing topical anesthesia will have a different experience before, during, and after surgery than a patient having injection-based anesthesia. Therefore, in preparation for surgery, it is essential for a successful outcome that the patient receive careful and consistent counseling.

Patient Selection

The patient must be evaluated as to suitability for this type of anesthetic. Some authors have suggested that there is a correlation between the patient’s preoperative responses to topical anesthetic drops or to preoperative testing using tonometry and ultra sound (such as the “drop then decide” method of Dinsmore⁸⁹ and the patient’s suitability for topical anesthesia.⁹⁰ However, in my experience, usually patients who are candidates for injectable anesthesia are also candidates for topical anesthetics.³¹ Nonetheless, patients who are demented, extremely anxious, or psychotic, or have certain movement disorders, as well as children, may not be candidates for any type of local anesthesia, and a general anesthetic with topical supplement should be considered for them (exceptions to this paradigm will be discussed later). Patients with hearing impairment or language barriers pose special challenges with topical anesthesia.⁹¹ Preoperative counseling is essential, and a family member or friend can help in translation of information when language barriers exist. A predetermined series of signals should be developed between patient and operating room personnel to allow communications during surgery. These issues are discussed further below.

Finally, patients with movement disorders should not automatically be excluded from topical, or, for that matter, injection anesthetic procedures, because these movements are frequently ablated with sedation. Ophthalmic movement disorders (e.g., nystagmus) are frequently ablated with appropriate levels of IV sedation. Therefore, only if a tremor persists after induction of IV sedation should a general anesthetic be considered.

Table 1.1 Complications of Injectable Regional Ophthalmic Anesthesia: Clinical Presentation, Prevention, and Treatment

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