Anesthesia has always been and will be one of the cornerstones of oral and maxillofacial surgery. Indeed, our success in this area has revolutionized the field of outpatient surgery by providing a safe environment where both the surgical procedure and the anesthesia can be provided uniquely by the same person. Our success has been well documented by multiple studies demonstrating the relatively low incidence of morbidity and mortality associated with our anesthesia services. This has been due to a variety of reasons, including advances made in the field of anesthesia itself and in the management of medically compromised patients, in addition to the development of strict criteria for the evaluation of patients requesting anesthesia and, more importantly, the ability to distinguish between patients who can undergo office anesthesia safely and who should be treated in a hospital setting. Moreover, few specialties are as introspective and self-critical with respect to patient safety as we are as a result of our extensive training in residency, state society office evaluations, and continuing education. This chapter reviews some basic principles and includes some of the recent advances made in office anesthesia, including monitoring, anesthetic agents, and combinations of anesthetics, as well as common complications.
Preoperative Evaluation
The goal of every office procedure is to administer anesthesia and perform surgery safely and successfully. Quite succinctly, this means avoiding or minimizing morbidity and mortality while providing adequate patient comfort. Achievement of this goal starts with the preoperative evaluation. The value of the preoperative evaluation cannot be overstated, with the history and physical examination being its centerpiece. The preoperative evaluation is done in a systematic manner so that no pertinent information is missed and all information needed for planning and administering anesthesia is obtained. In addition, risk factors are identified that may alter the perioperative management of the patient and possibly the type of anesthetic given, if any. Most offices will use a health history questionnaire as an initial screening tool. The purpose of this questionnaire is to help identify abnormalities in the health history that may need further investigation, as well as focus, when the practitioner initiates the formal history and physical examination. The questionnaire should be reviewed by the practitioner in the patient’s presence to allow clarification of any questions that may arise.
A thorough history will not only provide information about any medical problems but also allow the oral and maxillofacial surgeon to assess their severity. In addition, information on the patient’s past surgical history is obtained, including any adverse reactions to anesthetic agents; complications during surgery such as excessive bleeding; medications that the patient is taking, including herbals and other over-the-counter medications; allergies; and social history, including tobacco and alcohol use; as well as a family history, including any adverse reactions to anesthetic agents by a relative. Finally, a review of systems with a focus on the cardiac and respiratory systems is done. Indeed, most perioperative morbidity and mortality emanate from these two systems. A positive response to any of the symptoms in Box 30-1 should alert the practitioner to the possibility of underlying disease, diagnosed or undiagnosed. In addition, all patients should be asked about their exercise tolerance because it has been shown to predict long-term mortality, as well as short-term perioperative risks. Although it is beyond the scope of this chapter to review the significance of these symptoms, the practitioner is urged to know this information.
The physical examination is usually guided by the medical history, and once again special focus should be placed on the cardiac and respiratory systems. The basic principles of inspection, palpation, percussion, and auscultation, are followed. Any abnormality found on examination in either of these systems should alert the practitioner to the need for further studies, such as an electrocardiogram (ECG), echocardiogram, chest radiograph, or pulmonary function tests. For most outpatient anesthesia patients, routine laboratory studies do not add any value to the preoperative assessment. However, in select patients, laboratory data may add valuable information when determining whether the patient is a safe risk to undergo the procedure ( Table 30-1 ). Although chest radiography is a relatively low-cost, low-risk means of screening or evaluating for cardiac and pulmonary disease, its efficacy in routine preoperative screening has been questioned. The practice guidelines of the American College of Radiology state that chest radiographs are indicated for evaluation of the signs and symptoms of the cardiac, respiratory, upper gastrointestinal, and thoracic musculoskeletal systems; follow-up of thoracic disease; monitoring of life support devices; surveillance studies required by public health law (i.e., active tuberculosis, occupational exposure); and preoperative assessment of patients with cardiorespiratory disease that may increase perioperative morbidity or mortality.
| Medical Condition | Required Labs |
|---|---|
| Type 1 and 2 diabetes | Serum glucose, hemoglobin A 1c , serum electrolytes |
| Liver disease, coagulopathic disorders | Platelets, INR, PT, PTT |
| Kidney disease | Serum electrolytes |
| Blood disorders (e.g., anemia) | CBC |
Although oral and maxillofacial surgeons are adequately trained in assessing a patient’s risk related to anesthesia, in some instances a medical consultation may also be required to further clarify the extent and severity of any underlying conditions and anesthesia risk. Much has been written about assessing the risk for perioperative morbidity and mortality. In 1977, Goldman and co-authors published a landmark article that identified certain factors associated with perioperative morbidity. The usefulness of the Goldman criteria was that each factor was assigned a certain number of points based on its relative contribution to cardiac risk, thus allowing risk to be quantified. Therefore, the more points accumulated by the patient, the higher the risk for perioperative morbidity. Since Goldman and colleagues’ article, others have modified the criteria or devised their own system of risk stratification. Regardless of the system used, there are known risk factors—because of their association with increased perioperative morbidity—that should make the practitioner reconsider administering office anesthesia. Such risk factors include decompensated heart failure, recent myocardial infarction (<6 months), unstable angina, presence of significant arrhythmias, severe valvular disease, and renal insufficiency. Advanced age, usually older than 70 years, has been reported as a risk factor in the literature. However, there does not seem to be uniform consensus on which age should be considered advanced. The simplest and arguably the most common classification used for assessing risk is the American Society of Anesthesiologists (ASA) Physical Status Classification System ( Table 30-2 ). Patients who are ASA I and II are good candidates for office anesthesia, whereas those considered ASA III and IV are better suited for a hospital setting.
| ASA I | A normal healthy patient |
| ASA II | A patient with mild systemic disease |
| ASA III | A patient with severe systemic disease |
| ASA IV | A patient with severe systemic disease that is a constant threat to life |
| ASA V | A moribund patient who is not expected to survive with or without surgery |
| ASA VI | A patient declared brain-dead whose organs are being removed for donor purposes |
Oral and maxillofacial surgeons know all too well the potential pitfalls that exist when the area that we work in, mainly the mouth, is not only the surgical site but also the entrance to the airway. Factors that will make establishing an airway difficult, including adequate ventilation or a potentially difficult intubation, need to be noted. Such factors include limited mouth opening, large tongue size, retrognathic mandible, thyromental distance of less than 6 cm, and limited cervical spine mobility. In addition, the Mallampati classification should be used to assess the airway. For this classification the patient sits upright with the head in a neutral position, mouth open as wide as possible, and the tongue extended to the maximum. The practitioner then tries to visualize the hard palate, soft palate, uvula, and tonsillar pillars. In class I patients the hard palate, soft palate, uvula, and tonsillar pillars are all visible. In class II patients the hard palate, soft palate, and uvula are visible. In class III patients the hard palate and soft palate are visible. Finally, in class IV patients only the hard palate is visible. Needless to say, a patient who is Mallampati class I is relatively easy to intubate, whereas Mallampati class IV poses a difficult intubation. The presence of any of the aforementioned limiting factors, as well as a Mallampati classification of III or IV, should make the practitioner consider the comfort of a hospital operating room rather than office anesthesia.
The remainder of the preoperative evaluation should consist of discussing the anesthetic options; surgical options; the risks, benefits, and complications associated with the anesthesia and surgery; requirements for when to cease intake of food and drink ( Table 30-3 ); escort requirements; and furthering the doctor-patient bond. This may be reinforced by allowing the patient time to express concerns and ask additional questions. The American Association of Oral and Maxillofacial Surgeons (AAOMS) has established standards for evaluating patients preoperatively before administration of an anesthetic.
| Clear liquids | 2 hours |
| Nonhuman milk | 6 hours |
| Light solid meal * | 6 hours |
* Large, fatty meals prolong gastric emptying and may require an increase in NPO time. Medical conditions such as obesity, diabetes, pregnancy, hiatal hernia, and gastroesophageal reflux disease may also prolong gastric emptying.
PeriOperative Management of Common Medical Problems
The majority of patients undergoing oral and maxillofacial surgery in the office setting have few risk factors, if any, and good functional status. In addition, the oral and maxillofacial surgeon can take some comfort from the fact that the surgery usually performed is of low or intermediate risk, thus further diminishing the overall risk for an adverse perioperative event. For patients with advanced disease, however, it is imperative for the oral and maxillofacial surgeon to be able to identify those who are not candidates for office anesthesia, which is achieved by adequate history taking and physical examination.
Cardiac Disease
According to the American Heart Association, in 2005 the overall death rate from cardiovascular disease was 278.9 per 100,000 in the United States. Although death rates declined by 26.4% in the preceding 10-year period, cardiovascular disease remains a significant problem for most developed nations, including the United States. Therefore, it is not uncommon for the oral and maxillofacial surgeon to encounter patients with cardiac disease who desire office anesthesia for their procedure. Concern is minimal for a patient with stable cardiac disease but not for one with a recent myocardial infarction, unstable angina, decompensated heart failure, severe valvular disease, uncontrolled hypertension, or arrhythmias. Given the fact that approximately 46 million Americans do not have health insurance, it will be more likely that the oral and maxillofacial surgeon will encounter patients with unstable disease. In the hospital setting the anesthesiologist plays the central role in preoperative assessment. In the office setting, that role belongs to the oral and maxillofacial surgeon.
Several studies have demonstrated an increased incidence of reinfarction within 6 months of a myocardial infarction. It is for this reason and the potential for the development of arrhythmias that a history of myocardial infarction within the last 6 months has generally been regarded as a reason to postpone elective surgery. Some have made the case for postponement of elective surgery within the first 6 weeks after a myocardial infarction and that the risk after this period is based on the clinical manifestations of the disease. Regardless of whether one chooses to follow the 6-week or 6-month mantra, it is important to make sure that the patient is being managed in such a way that the risk for morbidity and mortality is being minimized. Rather than risk stratification, some authors argue for risk modification, which includes having the patient take beta blockers and statins. However, the role of coronary revascularization specifically to reduce perioperative cardiac morbidity in non-cardiac surgery is unproven.
Similarly, the same risk modification is undertaken in patients who have stable angina, and office anesthesia is avoided in patients with unstable angina. Stable angina is characterized by chest pain precipitated by physical exertion or emotional stress. It is predictable with regard to precipitating factors, frequency, intensity, duration, and relieving factors. Stable angina is successfully relieved by rest or nitroglycerin given in 0.4-mg tablets or by sublingual spray repeated every 5 minutes if there is no relief of pain (provided that systolic blood pressure is >90 mm Hg). Lack of relief after three doses may indicate infarction and should lead to immediate activation of emergency medical services. In addition, any change in any of the aforementioned factors represents unstable angina or pre-infarction angina. Anyone suspected of having acute myocardial infarction should receive morphine, oxygen, and non-enteric aspirin (MONA), in addition to nitroglycerin.
A patient with decompensated congestive heart failure will be found to have any or all of the symptoms in Box 30-1 on physical examination: elevated jugular venous pressure on inspection, hepatomegaly on palpation and percussion, pitting edema in the extremities, and the presence of a third heart sound (S 3 ) and pulmonary crackles on auscultation. Patients with these signs and symptoms are not candidates for office anesthesia, let alone any elective surgery, and should be referred for cardiac evaluation to determine the cause of the decompensation and to optimize their condition.
When a patient interview elicits a history of valvular disease, the two main concerns are the extent of cardiac disease and the possible need for antibiotic prophylaxis. Fortunately, in the United States it is uncommon for valvular disease to go unrepaired well into adulthood. When there is a history of valve repair, the possible presence of residual cardiac disease needs to be investigated. A recent echocardiogram may be helpful because it provides information on valvular function and the ejection fraction if the patient has concurrent heart failure. In 2007, the American Heart Association revised the recommendations for antibiotic prophylaxis. Patients with the following cardiac conditions require antibiotic prophylaxis for oral surgical procedures:
- •
Prosthetic cardiac valves
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Previous infective endocarditis
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Unrepaired cyanotic congenital heart disease
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Completely repaired congenital heart disease with prosthetic material or a device during the first 6 months after the procedure
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Repaired congenital heart disease with residual defects
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Cardiac transplant recipients with cardiac valvular disease
Patients with a history of hypertension should be encouraged to not cease taking their antihypertensive medications and continue taking them until and including the day of surgery. According to a 2002 report of the American College of Cardiology/American Heart Association, surgery should be delayed for patients whose blood pressure is higher than 180/110 mm Hg because the likelihood of myocardial ischemia is increased. Clinical judgment is clearly exercised in evaluating the patient regardless of blood pressure. Patients whose blood pressure is well controlled are less likely to have labile readings during the procedure. Certainly, factors such as anxiety, the effects of epinephrine in local anesthetics, pain, and hypercapnia can increase blood pressure intraoperatively. When blood pressure is unacceptably elevated, beta blockers such as esmolol and labetalol should be considered. Esmolol is a selective beta-1 blocker with a rapid onset (60 seconds) and short duration (10 to 20 minutes). The dosage is 0.5 to 1.0 mg/kg intravenously administered over a 30-second period for immediate control of tachycardia and hypertension, followed by an infusion of 150 µg/kg/min to a maximum of 300 µg/kg/min. Labetalol is a selective alpha-1 blocker and nonselective beta blocker. Therefore, it is contraindicated in patients with asthma. It is administered in a loading dose of 5 to 20 mg intravenously over a 2-minute period, followed by a 20- to 80-mg dose at 10-minute intervals or an infusion of 1 to 2 mg/min. The onset of action of labetalol is 5 minutes and its duration of action is 3 to 6 hours. For patients in whom beta blockers are contraindicated (i.e., asthmatics), hydralazine should be considered. The dosage of hydralazine is 5 to 25 mg intravenously. It takes effect in 5 minutes and its duration of action is 2 hours.
Treatment of blood pressure intraoperatively needs to be tempered by the fact that some of these patients require relatively high pressure to perfuse vital organs. Consequently, lowering blood pressure excessively may produce the same unwanted effects as excessive blood pressure does, an ischemic event. Treatment of hypotension is directed at the underlying cause. Therefore, if the patient is hypovolemic, a fluid bolus is given. If the cause is hypoxemia or hypercapnia (or both), the airway is secured while making sure that the patient is adequately oxygenated and ventilated. Sympathomimetic agents used in the management of hypotensive emergencies include ephedrine and phenylephrine. Ephedrine is both an alpha and beta receptor agonist. The dosage is 2.5 to 5 mg intravenously, which can be repeated until the blood pressure stabilizes. Its onset of action is 10 minutes, with a peak in 20 minutes and duration of action of 4 hours. Phenylephrine is an alpha agonist administered in 0.1-mg increments until the blood pressure is stabilized. Its effects are seen within 2 to 3 minutes and last for approximately 15 minutes. Epinephrine is used for hypotension secondary to anaphylaxis, bronchospasm, or cardiac arrest.
Patients with disturbances in cardiac rhythm may or may not be symptomatic. Indeed, the surgery and anesthesia itself may unmask an underlying arrhythmia and even exacerbate it by release of catecholamines from stress and hypoxia as a result of inadequate ventilation and lead to a decrease in cardiac output and an ischemic event. Arrhythmias may also be exaggerated by the epinephrine present in local anesthetics and by the use of inhalational anesthetics. All patients with serious arrhythmias should have a 12-lead ECG performed and a cardiology consultation before any elective surgery. The most common arrhythmia in the oral surgical office is bradycardia secondary to a vasovagal reaction. Vasovagal reactions are triggered by anxiety and characterized by an initial rapid increase in heart rate, decrease in systolic pressure, and increase in diastolic pressure, followed by a decrease in the pulse rate. Patients are managed by placement in a reclined position with the legs elevated, administration of 100% oxygen, monitoring of vital signs, and administration of spirits of ammonia if needed.
In summary, the goal for patients with a history of cardiac disease should be to provide adequate oxygenation, maintain sufficient intravascular volume and control of blood pressure, and minimize pain and anxiety via proper sedation techniques. In addition, cardiac medications should not be discontinued. If patients are regularly scheduled to take their cardiac medication the morning of the procedure, they should be encouraged to continue to take it with a small sip of water.
Diabetes
Diabetes is the most commonly encountered endocrine disorder. Patients with diabetes are best scheduled for morning procedures. Management depends on the patient’s metabolic control, the length of the procedure, and the likelihood of the patient having oral intake after the procedure. Traditionally, patients with type 1 diabetes who were to undergo relatively short procedures with office anesthesia were managed by administering a third to two thirds of their usual intermediate-acting insulin in the morning and withholding their regular insulin. Once intravenous access was established, glucose was given intravenously and the patients were monitored for hypoglycemia and hyperglycemia. During surgery, regular insulin was given subcutaneously to treat hyperglycemia while keeping blood glucose between 120 and 200 mg/dL. Patients were also encouraged to begin oral intake soon after surgery, usually within 3 hours. If oral intake was going to be restricted, the morning intermediate-acting insulin dose was decreased accordingly. For patients who use continuous subcutaneous insulin infusion, the basal rate is continued during surgery, with insulin boluses given as needed for hyperglycemia. Patients with type 2 diabetes who are to undergo office anesthesia should have their oral hypoglycemic agents discontinued the morning of surgery and restarted when adequate oral intake resumes. Metformin is an exception; it is discontinued 48 hours before surgery to protect against metformin-induced lactic acidosis. Perioperative blood glucose levels may be controlled with subcutaneous administration of regular insulin via a sliding scale.
Another anesthetic concern in diabetics is gastroparesis. Delayed gastric emptying as a result of diabetic gastroparesis can increase the risk for aspiration pneumonitis. Other patients at increased risk include those with hiatal hernia, obesity, and gastroesophageal reflux. Administration of prophylactic medications for the prevention of lung injury from aspiration of gastric contents is controversial. Medications used to prevent aspiration pneumonitis include H 2 -receptor antagonists (e.g., ranitidine), metoclopramide, and non-particulate oral antacids (e.g., sodium citrate). H 2 -receptor antagonists are effective in decreasing gastric acid secretion and raising pH. However, they do not affect acid already present in the stomach. Metoclopramide, a dopamine antagonist, reduces gastric volume by increasing gastric emptying and increases lower esophageal tone. It also has anti-emetic properties, which makes it a very useful drug in this patient population. Finally, non-particulate oral antacids raise pH but increase gastric volume. Aspiration pneumonitis is a life-threatening complication. Management includes aggressive suctioning and administration of 100% oxygen. If there is no improvement, activation of emergency medical services, intubation, and ventilation with positive pressure will be required.
Asthma
Asthma is an inflammatory disorder of the airways that causes episodic attacks of wheezing, shortness of breath, chest tightness, and coughing. The hallmark of asthma is airway hyperreactivity in response to a variety of stimuli, including pollen, dust, pollutants, exercise, exposure to cold, and viral infections. This reversible airway obstruction is the result of bronchial smooth muscle constriction or bronchospasm, edema, and increased mucus secretion. The severity of asthma is classified according to symptom frequency, nighttime symptoms, and forced expiratory volume in the first second (FEV 1 ) or the peak expiratory flow (PEF) rate (percentage of predicted and variability). In addition, valuable information regarding severity can be obtained by questioning the patient about the frequency of inhaler use; hospitalizations, including use of steroids and intubation; and visits to the emergency department. Assessment of severity will help determine whether the patient is a viable office anesthesia candidate. Suffice it to say, patients with intermittent (symptoms occurring less than once a week, brief exacerbations, nocturnal symptoms twice per month, FEV 1 or PEF 80% of predicted, PEF or FEV 1 variability less than 20%) and mild persistent (symptoms occurring more than once per week but less than once per day, exacerbations affecting activity and sleep, nocturnal symptoms more than twice per month, FEV 1 or PEF 80% of predicted, PEF or FEV 1 variability 20% to 30%) asthma are generally good candidates. Moderate persistent (symptoms occurring daily, exacerbations affecting activity and sleep, nocturnal symptoms more than once per week, daily use of an inhaled short-acting beta-2 agonist, FEV 1 or PEF 60% to 80% of predicted, PEF or FEV 1 variability greater than 30%) and severe persistent (symptoms occurring daily, frequent exacerbations, frequent nocturnal symptoms, limitations in physical activities, FEV 1 or PEF less than 60% of predicted, PEF or FEV 1 variability greater than 30%) are not good candidates.
All patients should have their lungs auscultated before the procedure. Audible wheezing should be treated with a beta-2 agonist by inhaler before proceeding with the planned procedure. Bronchospasm may occur intraoperatively. If the patient is awake, bronchospasm is managed by administering inhaled beta-2 agonist drugs as first-line treatment. If the patient is unable to cooperate, subcutaneous administration of 0.3 to 0.5 mg of a 1 : 1000 solution of epinephrine is the first choice. In both cases supplemental oxygen is given as well.
Children with a recent or current upper respiratory tract infection are susceptible to bronchospasm. A viral infection within 2 to 4 weeks places the child at an increased risk for perioperative pulmonary complications (laryngospasm, atelectasis, and hypoxemia). Therefore, elective surgery should be deferred until 3 weeks after the symptoms (runny nose with fever, cough, or sore throat) have resolved.
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