Although there is a growing movement toward the use of topical anesthesia for cataract surgery, the role for anesthesia providers has not diminished.1 Even under topical anesthesia, the proper preoperative evaluation of the patient, sedation before and during the procedure, and intraoperative monitoring all contribute to the prevention of systemic complications from ocular anesthesia. A full discussion of anesthesia is beyond the scope of this chapter, but a brief overview of systemic complications will be presented.

According to several studies, approximately 90% of cataract patients are over 50 years old and two-thirds are over 65. It is not uncommon to perform such operations on patients over 80 years of age. Therefore, many of the anesthetic considerations are those found in any procedure involving elderly patients.

PREOPERATIVE EVALUATION

The preoperative evaluation fulfills several functions. The most important is the medical evaluation of the patient prior to anesthesia and surgery. Another is reducing anxiety by educating the patient and administering preoperative medications. Both the medical evaluation and preoperative sedation contribute to preventing systemic complications in the patient having ocular surgery.

The requirements of the preoperative history and physical are variable. The history includes the major anatomic and physiologic systems, all medications, drug allergies, previous surgical procedures, and any complications related to prior anesthetics. The cardiovascular history, including previous myocar-

24 dial infarction, congestive heart failure, strokes, or

hypertension, is particularly important. A history of pulmonary diseases, especially asthma or severe chronic obstructive pulmonary disease (COPD), diabetes mellitus, or hepatic or renal insufficiency is also important. Each of these has implications for the administration of the anesthetic or potential complications that may occur.

The physical examination includes auscultation of the heart and lungs, an evaluation of the airway, and any abnormal system suggested by the patient’s history.

Unlike in the past, there is no prescribed list of laboratory tests that all patients undergo prior to surgery. Testing is now individualized to the patient’s underlying medical history. Diabetics should have a finger-stick blood sugar level performed immediately prior to surgery. Patients on digitalis or diuretics should have a recent potassium level, and coumadin users should have a prothrombin time/ partial thromboplastin time (PT/PTT) done prior to surgery, especially if a peri/retrobulbar block is used as the anesthetic. Other tests may be indicated depending on the patient’s history.

A recent electrocardiogram (EKG) is indispensable in the elderly population, especially in patients with a history of cardiac disease or diabetes, which may mask the existence of severe cardiac disease. Studies vary widely as to what percentage of patients have unknown cardiac disease discovered on a routine preoperative EKG, but even in this costconscious environment, the consensus is that EKGs are indicated in all patients over 50 years old.

Once the preoperative evaluation is complete, an IV is started and the patient is placed on monitors, including an EKG, blood pressure cuff, and pulse

oximeter. These monitors are sufficient in the freestanding ambulatory surgery center or hospital outpatient surgery department. If the patient requires more extensive monitoring, the surgery should be done only in a hospital setting.

The patient is given preoperative antianxiety medications, most commonly a combination of fentanyl (Sublimaze, a narcotic) and midazolam (Versed, a benzodiazepine). The usual dose is 1 cc fentanyl (50 µg) and 1 mg midazolam. This combination produces a relaxed, but not overly sedated patient within 2 to 3 minutes. If a patient remains anxious, a second dose may be given after approximately 5 minutes. Antiemetics are not usually necessary for outpatient ocular surgery. However, if a patient has a history of severe nausea and vomiting after surgery, either droperidol or ondansetron (Zofran) can be added.

Occasionally a patient will have elevated blood pressure even after the premedications are given. This can be treated with a rapid-acting antihypertensive agent. Commonly used agents include intravenous (IV) labetalol, hydralazine, esmolol, or sublingual nifedipine (Procardia). The blood pressure should be closely monitored, but surgery can proceed safely once the blood pressure is controlled.

GENERAL ANESTHESIA AND

ORBITAL BLOCK

Most cataract surgeries today are performed under a retrobulbar or peribulbar block.1 Some surgeons administer the block to an awake or only slightly sedated patient. Although the block is more uncomfortable than painful, it produces anxiety in awake patients. This anxiety and discomfort increase the patient’s heart rate and blood pressure, resulting in a potentially higher incidence of cardiac complications. Alternatively, the block can be safely performed under a brief general anesthetic to eliminate patient awareness and decrease the incidence of cardiac problems.

A short anesthetic, lasting only 2 or 3 minutes, is ideal for administration of the block. The anesthetic should maintain cardiovascular stability and spontaneous respiration. There are several agents or combinations of agents that will produce this.

The most commonly used agent is methohexital (Brevital, a barbiturate). This drug has a rapid onset, less than 30 seconds, and duration of approximately 3 to 5 minutes. The usual dose in an elderly patient is 0.5 to 1.0 mg/kg, which produces complete unconsciousness. Undesirable side effects are minimal and easily managed. The two most common are a slight burning at the IV site and inconsequential hiccuping in a small number of patients, usually less than 5%. Neither of these requires any specific attention. On

rare occasions a patient will move slightly or groan during the block. This is an involuntary reaction and patients have no memory of the block once they are awake.

Some anesthesiologists use propofol (Diprivan) for this brief anesthetic. The effective dose has greater respiratory depression than methohexital, so many practitioners who use propofol for other anesthetics still use methohexital for ocular procedures. Others use alfentanil or remifentanil, extremely potent but very short-acting narcotics, to induce sleep for the block. These are effective, but expensive alternatives to Brevital.

The patients are fully awake within several minutes. Akinesia of the eye provides an assessment of the block. Even if some motion remains, the eye is usually insensate. If not, a few drops of topical anesthetic will eliminate any remaining sensation. Only rarely must a block be repeated or supplemented with a subconjunctival injection of local anesthesia.

INTRAOPERATIVE MONITORING

AND TREATMENT

Proper monitoring during surgery prevents or reduces the severity of systemic complications. Patients are given supplemental oxygen by nasal cannula. Although most patients are comfortable during surgery, a few apprehensive patients require additional medications for relaxation. A small dose of Brevital (one-third to one-half the initial dose) or a repetition of the preoperative medications is usually sufficient.

With the above regimen, most patients are awake during surgery. They are able to eat and drink right afterward and are ready for discharge within 30 minutes. Rarely do patients require any further treatment in the postoperative period.

Topical and general anesthetics have specific considerations. If the surgeon prefers to operate under topical anesthesia, the patient must be sedated enough to feel relaxed, yet awake enough to cooperate with the surgeon. Under rare circumstances a general anesthetic may be necessary. Coughing and “bucking” on the endotracheal tube, either during or after the procedure, can cause injury to the eye. Using a laryngeal mask airway (see Chapter 2) instead of an endotracheal tube usually prevents this problem.

COMPLICATIONS

Anesthetic complications during surgery range from minor to life-threatening.2 Fortunately, serious complications are rare. In one unpublished series of over 8000 ocular surgical patients treated by a single

anesthesiologist, the serious complication rate is less than 0.2%. Minor complications occur more frequently, but are of little consequence. Table 3–1 lists systemic complications of ocular anesthesia seen in that series and other potentially serious complications that were not observed.

The systemic complications of ocular anesthesia generally fall into several broad categories: airway obstruction and respiratory complications, cardiac complications, injuries associated with the block, and reactions to general anesthetics. Most airway difficulties are easily relieved with minimal airway support such as a jaw lift maneuver. Brevital causes relaxation of the airway musculature allowing the patient’s tongue to obstruct the airway. Gentle airway support lifts the tongue away from the hypopharynx, relieving the obstruction. Rarely does this require more than lifting the patient’s mandible or chin. In the above series of 8000 patients, none needed any other airway intervention such as placing an oral airway or intubation with an endotracheal tube. One patient with a history of asthma developed acute bronchospasm in the postoperative period that required treatment.

TABLE 3–1 SYSTEMIC COMPLICATIONS OF

OCULAR ANESTHESIA IN APPROXIMATELY 8000

PATIENTS

The source data are from the author’s unpublished series.

Potential cardiac anomalies include hyperor hypotension, minor or severe arrhythmias, angina, myocardial infarction, or cardiac arrest.3 These should be treated according to standard protocols. Severe cardiac complications are rare. In the above series there were no cardiac arrests in the operative or immediate postoperative period. One patient developed severe bradycardia during surgery but responded to atropine, and the surgery continued without complication. Although the patient had initially denied any history of cardiac problems, he admitted that he had had several such episodes in the past. A pacemaker was placed 6 hours later and the patient was discharged from the hospital within 18 hours.

Traumatic injuries can occur during the retro/ peribulbar needle placement. Injuries to the intraorbital structures have been discussed previously, but systemic complications can also occur from the needle placement. If the needle tip penetrates the neural sheath surrounding the optic nerve, local anesthetic can travel within the nerve sheath into the midbrain.4 This produces a complete respiratory arrest. Both tachycardia and bradycardia have been reported. The process is self-limiting, but requires immediate cardiopulmonary support. Intubation and ventilation are required until the respiratory effects have resolved, usually within 1 to 4 hours. Cardiac support consists of treating the underlying rate and pressure abnormalities. Usually all treatment can be discontinued within several hours.

Malignant hyperthermia is a rare, potentially fatal reaction to general anesthesia. This is a hereditary disorder of calcium uptake and release at the cellular level. Certain anesthetics, such as the inhaled volatile agents or succinylcholine, trigger this disorder. It is manifested by marked tachycardia, tachypnia, increased carbon dioxide production, and a rapid rise in body temperature. Treatment must be initiated promptly. Dantrolene is administered and mechanical ventilation provided as necessary. If this occurs in a freestanding ambulatory surgical center, the patient should be transferred by ambulance to the nearest hospital equipped to handle this emergency.

CONCLUSION

Anesthetic complications during ocular surgery are not common. However, vigilance is necessary to recognize and treat complications when they do occur. Anesthesia personnel should monitor each patient during the critical portions of the procedure, such as during the block and the surgery. During other times, such as the preand postoperative periods, they should be immediately available for consultation and treatment should the need arise.

REFERENCES

1.Leaming DV. Practice styles and preferences of ASCRS members: 1997 survey. J Cataract Refract Surg 1998;24: 552–561.

2.Hamilton RC, Gimbel HV, Strunin L. Regional anaesthesia for 12,000 cataract extraction and intraocular

lens implantation procedures. Can J Anaesth 1988;35: 615–623.

3.Rosenblatt RM, May DR, Barsourmian K. Cardiopulmonary arrest after retrobulbar block. Am J Ophthalmol 1980;90:425–427.

4.Rosen WJ. Brainstem anesthesia presenting as dysarthria. J Cataract Refract Surg 1999;25:1170–1171.