With open-angle glaucoma, elevated intraocular pressure (IOP) exists in conjunction with an anatomically patent anterior chamber angle. It is thought that sclerosis of trabecular tissue produces impaired aqueous filtration and drainage. Treatment consists of medication to produce miosis and trabecular stretching. Commonly used eye drops include epinephrine, echothiophate iodide, timolol, dipivefrin, and betaxolol. Carbonic anhydrase inhibitors such as acetazolamide can also be administered by various routes to reduce IOP by interfering with the production of aqueous humor. All these drugs are systemically absorbed and can, therefore, have anticipated side effects.

It is important to appreciate that maintenance of IOP is determined primarily by the rate of aqueous formation and the rate of aqueous outflow. The most important influence on formation of aqueous humor is the difference in osmotic pressure between aqueous humor and plasma. This concept is illustrated by the equation:

IOP = K [(OP_aq − OP_pl) + CP]

where K = coefficient of outflow, OP_aq = osmotic pressure of aqueous humor, OP_pl = osmotic pressure of plasma, and CP = capillary pressure. The fact that a small change in solute concentration of plasma can dramatically affect the formation of aqueous humor, and hence, IOP is the rationale for administering hypertonic solutions, such as mannitol, to reduce IOP. Fluctuations in aqueous outflow can also markedly change IOP. The primary factor controlling aqueous humor outflow is the diameter of Fontana’s spaces, as illustrated by the equation:

where A = volume of aqueous outflow per unit of time, r = radius of Fontana’s spaces, P_IOP = IOP, P_v = venous pressure, η = viscosity, and L = length of Fontana’s spaces. When the pupil dilates, Fontana’s spaces narrow, resistance to outflow is increased, and IOP rises. Because mydriasis is undesirable in both closed- and open-angle glaucoma, miotics such as pilocarpine are applied conjunctivally in patients with glaucoma to effect papillary constriction.

The aforementioned equation describing the volume of aqueous outflow per unit of time clearly underscores that outflow is exquisitely sensitive to fluctuations in venous pressure. Because an elevation in venous pressure results in an increased volume of ocular blood as well as decreased aqueous outflow, it is obvious that a considerable increase in IOP occurs with any maneuver that increases venous pressure. Hence, in addition to preoperative instillation of miotics, other anesthetic objectives for the patient with glaucoma include perioperative avoidance of venous congestion and of overhydration. Furthermore, hypotensive episodes are to be avoided because these patients are purportedly vulnerable to retinal vascular thrombosis.

Although glaucoma usually occurs as an isolated disease, it may also be associated with such conditions as Sturge-Weber syndrome, aniridia, mesodermal dysgenesis syndrome, retinopathy of prematurity, Refsum syndrome, mucopolysaccharidosis, Hurler syndrome, Stickler syndrome, Marfan syndrome, and von Recklinghausen disease (neurofibromatosis). Additionally, ocular trauma, steroid therapy, sarcoidosis, some forms of arthritis associated with uveitis, and pseudoexfoliation syndrome can also be associated with secondary glaucoma.

Primary closed-angle glaucoma is characterized by a shallow anterior chamber and a narrow iridocorneal angle that impedes the egress of aqueous humor from the eye because the trabecular meshwork is covered by the iris. Relative pupillary block is common in many angle-closure episodes in which iris-lens apposition or synechiae impede the flow of aqueous from the posterior chamber. In the United States, the prevalence of angle-closure glaucoma (ACG) is one-tenth as common as open-angle glaucoma. In acute ACG, if the pressure is not reduced promptly, permanent visual loss can ensue as a result of optic nerve damage. It is thought that irreversible optic nerve injury can occur within 24 to 48 hours.

Echothiophate is a long-acting anticholinesterase miotic that lowers IOP by decreasing resistance to the outflow of aqueous humor. Useful in the treatment of glaucoma, echothiophate is absorbed into the systemic circulation after instillation in the conjunctival sac. Any of the long-acting anticholinesterases may prolong the action of succinylcholine because after a month or more of therapy, plasma pseudocholinesterase activity may be less than 5% of normal. It is said, moreover, that normal enzyme activity does not return until 4 to 6 weeks after discontinuation of the drug. Hence, the anesthesiologist should anticipate prolonged
apnea if these patients are given a customary dose of succinylcholine. In addition, a delay in metabolism of ester local anesthetics should be expected.

Although topical epinephrine has proved useful in some patients with open-angle glaucoma, the 2% solution has been associated with such systemic effects as nervousness, hypertension, angina pectoris, tachycardia, and other dysrhythmias.

Timolol, a nonselective β-adrenergic blocking drug, has historically been a popular antiglaucoma drug. Because significant conjunctival absorption may occur, timolol should be administered with caution to patients with known obstructive airway disease, severe congestive heart failure, or greater than first-degree heart block. Life-threatening asthmatic crises have been reported after the administration of timolol drops to some patients with chronic, stable asthma. Not unexpectedly, the development of severe sinus bradycardia in a patient with cardiac conduction defects (left anterior hemiblock, first-degree atrioventricular block, and incomplete right bundle branch block) has been reported after timolol. Moreover, timolol has been implicated in the exacerbation of myasthenia gravis and in the production of postoperative apnea in neonates and young infants. Patients may report feelings of fatigue and/or depression in association with the use of timolol drops.

In contrast to timolol, a newer antiglaucoma drug, betaxolol, a β₁-blocker, is said to be more oculospecific and have minimal systemic effects. However, patients receiving an oral β-blocker and betaxolol should be observed for potential additive effects on known systemic effects of β-blockade. Caution should be exercised in patients receiving catecholaminedepleting drugs. Although betaxolol has produced only minimal effects in patients with obstructive airway disease, caution should be exercised in the treatment of patients with excessive restriction of pulmonary function. Moreover, betaxolol is contraindicated in patients with sinus bradycardia, greater than first-degree heart block, cardiogenic shock, and overt myocardial failure.

For all the aforementioned reasons, it is important to continue glaucoma medications in the perioperative period. Moreover, the anesthesiologist must be aware of which medications the patient is taking and the effects of these drugs on anesthetic management.

Morbid obesity is defined by a body mass index greater than 40 kg per m². This patient has a body mass index of approximately 30 and would, therefore, be considered obese. See Chapter 63, section A.2.

A plethora of conditions may be associated with obesity and morbid obesity including diabetes, hyperlipidemia, cholelithiasis, gastroesophageal reflux disease, cirrhosis, degenerative joint and disc disease, venous stasis and thrombotic/embolic disease, sleep disorders including obstructive sleep apnea, several types of cancer, and emotional disorders. Diseases of the cardiopulmonary system are common and concerning. They include, but are not limited to, systemic hypertension, pulmonary hypertension and cor pulmonale, restrictive lung disease, and right and left ventricular hypertrophy.

Outpatient surgery typically offers greater convenience to the patient (less time away from home, family, and work), a more pleasant environment with less stress and emotional disturbance, and a reduced risk of infection, particularly for the immunocompromised or the pediatric patient. Additionally, outpatient surgery is more economical and enables more efficient use of operating rooms with greater flexibility in scheduling surgery. Finally, one is not dependent on the availability of hospital beds.

The objectives of the preoperative evaluation are as follows:

Organization of preoperative screening varies among ambulatory surgical facilities throughout the country. The screening process may be organized with an office or facility visit before the day of surgery, by a telephone interview or review of health questionnaire without a visit, or by preoperative screening and visit on the morning of surgery. Each of these systems has its advantages and disadvantages. Nevertheless, the system for preoperative evaluation of ambulatory surgical patients should ensure that screening is performed far enough in advance so that preexisting disease can be evaluated, treatment optimized, and laboratory data recorded before the patient presents for anesthesia. Written instructions should be supplied to the patient in advance describing the preoperative workup, admission, and recovery periods.

No. The practice of preoperative “shotgun” laboratory screening for outpatient surgery has received much criticism. In addition to unnecessarily adding several billion dollars annually to the cost of health care, laboratory screening tests in asymptomatic patients have been shown to be of dubious value. History and physical examination are a better means of screening for disease and should serve to reduce expensive, potentially harmful, and inappropriate tests.

Most outpatient surgical facilities consider the operative procedure and the patient’s age, medical condition, medication history, and state and local regulations in determining which preoperative tests are “required.” For the healthy ambulatory patient between the ages of 1 and 40 years having a minor surgical procedure, no laboratory testing may be required.
Pregnancy testing is a highly controversial issue. Many believe that pregnancy testing should be offered to all consenting females of childbearing potential. This approach, however, does not substitute for an appropriate pregnancy history and physical examination. Hemoglobin or hematocrit determination is appropriate for surgical procedures associated with substantial blood loss (unlikely in the ambulatory venue) and for patients at risk for anemia or polycythemia, such as children younger than 1 year or with suspected sickle cell disease, patients with a history of anemia, blood dyscrasia or malignancy, patients with congenital heart disease or chronic disease, women with heavy menstrual flow, and patients older than 60 years old. Additional testing depends on an individual’s preexisting condition. For example, serum electrolyte testing would be indicated for a patient with a history of hypertension, diabetes mellitus, renal disease, or for those patients taking diuretics, digoxin, steroids, or angiotensin-converting enzyme inhibitors. Likewise, measurement of the partial thromboplastin time (PTT) and the prothrombin time (PT) would be indicated in the presence of a bleeding disorder, anticoagulant use, liver disease, or poor nutritional status. Preoperative urinalysis has not been shown to be useful as a screening test and is no longer required in a routine anesthetic evaluation.

Abnormalities in the chest x-ray in asymptomatic patients are rare, and the risks to the patient probably exceed the benefits. A preoperative chest x-ray is indicated only for patients with a history or clinical findings of active pulmonary disease. Extremes of age, smoking, stable chronic obstructive pulmonary disease, stable cardiac disease, or resolved recent upper respiratory infection should not be considered absolute indications for chest x-ray.

It has not been established that information obtained from the preoperative ECG affects clinical care. Indeed, the American College of Cardiology/American Heart Association (ACC/AHA) guidelines published in 2007 were silent on the need for a preoperative ECG based on age alone. According to the updated 2014 ACC/AHA guideline, a preoperative ECG is “reasonable for patients with known coronary artery disease, significant arrhythmia, peripheral arterial disease, cerebrovascular disease, or other significant structural heart disease, except for those undergoing low-risk surgery.” The 2014 guideline specifically states that a preoperative ECG is “not useful for asymptomatic patients undergoing low-risk surgical procedures.” The 2007 ACC/AHA guidelines considered ambulatory surgery as one entity, classifying all ambulatory procedures as low-risk, with reported cardiac mortality <1%. The 2014 version, however, defines a low-risk procedure as one in which the combined surgical and patient characteristics predict a risk of major adverse cardiac event (MACE) of death or myocardial infarction to be <1% and cites as examples cataract and plastic surgery. A further refinement in the 2014 guideline was to eliminate the separate categories of intermediate risk and high risk, substituting the category of elevated risk, reflecting procedures with a risk of MACE of ≥1%. These guidelines reflect the belief that in the absence of active cardiac conditions (defined as unstable coronary syndromes, decompensated heart failure, and significant arrhythmias [e.g., high-degree atrioventricular block, symptomatic ventricular arrhythmias,
and supraventricular tachycardia with uncontrolled ventricular rate]), cardiovascular testing in stable patients would rarely result in a change in management and it would be appropriate to proceed with surgery without further testing.

Nonetheless, Correll and colleagues found that age older than 65 years is an independent predictor of preoperative ECG abnormalities. In general, a preoperative ECG should be considered in ambulatory patients in whom there is a reasonably high likelihood of cardiac dysfunction and the results of the ECG would have the potential to influence perioperative management. Clearly, the patient’s history, including a thorough exploration of activity level and exercise tolerance, the physical examination, and the proposed surgical procedure are vital elements in the assessment of whether an ECG is indicated.

Even patients at the extremes of age (e.g., younger than 6 months and older than 80 years) have been managed successfully at ambulatory centers throughout the country. With the exception of the former preterm infant and newborns in the first few weeks of life, age alone should not be considered a deterrent in the selection of patients for outpatient surgery. Premature infants (gestational age at birth <37 weeks) who undergo general anesthesia during the first months of life are at increased risk for postoperative apnea for up to 12 hours. This risk is greatest for infants younger than 46 weeks postconceptional age, but some investigators have reported apnea in infants as old as 60 weeks postconceptional age. Unfortunately, the postconceptional age at which the former premature infant no longer represents an increased risk for postoperative apnea and, therefore, would be considered an acceptable candidate for an ambulatory surgical procedure is not absolutely known. Thus, at the present time, it is safest to admit to a hospital or to a 24-hour recovery unit all former premature infants less than 46 weeks postconceptional age so that they can be monitored for apnea. Many anesthesiologists are more conservative and adhere to cut-offs ranging from 52 to 60 weeks postconceptional age. If anemia, bronchopulmonary dysplasia, or other neonatal problems are present, this period may need to be extended. Likewise, postoperative apneic episodes have been described in otherwise healthy full-term infants who are anesthetized in the first few weeks of life. For this reason, many anesthesiologists are reluctant to proceed with outpatient anesthesia and surgery on a healthy full-term infant of younger than 2 to 4 weeks of age.

For the geriatric patient, recent clinical experience has not demonstrated an age-related effect on the duration of recovery or the incidence of postoperative complications after outpatient surgery. However, in determining the acceptability of a geriatric patient for an ambulatory surgical procedure, one must consider the patient’s physiologic age and physical status, the surgical procedure, the anesthetic technique, and the quality of care that will be provided at home. Chronologic age per se is not a determinant of suitability for ambulatory surgery.

No longer is outpatient surgery restricted to patients of American Society of Anesthesiologists (ASA) physical status I and II. ASA physical status III and IV patients whose diseases are well controlled preoperatively may be considered acceptable candidates for outpatient surgery.

An individual may be classified as an inappropriate ambulatory surgery patient for the following reasons:

The appropriateness of each patient must be evaluated on an individual basis, taking into account a combination of several factors, such as the patient’s circumstances, the nature of the surgical procedure, anesthetic technique, anticipated severity of postoperative pain, and comfort level of the anesthesiologist.