Chapter 2 – The Preoperative Evaluation
Preoperative evaluation of surgical patients is, in its broadest sense, an extension of the diagnostic process. The surgeon should strive to determine the extent of disease; prove the necessity of surgery or clearly demonstrate its benefit to the patient; optimize the choice of surgical procedure; and minimize the risk to the patient by defining concomitant health problems and instituting appropriate therapy or precautionary measures. Integral to each of these goals is an appreciation of the ideal set forth in the Hippocratic Oath—Above all else, do no harm. It is the surgeon’s responsibility to ensure that an appropriate patient assessment has been completed prior to entering the surgical suite. Surgical complications can often be avoided by recognizing the physiologic limitations of the patient preoperatively. Documentation of findings, decision making, and discussion between surgeon and patient regarding surgical risks and benefits have become medicolegal imperatives.
The patient presenting with an otolaryngologic disease process that requires surgical management must be evaluated by both general and specialty-specific criteria. As with the initial patient evaluation, preoperative assessment relies heavily on a careful history and physical examination. Special attention should be given to the patient’s past medical and surgical history. A thorough review of systems helps to identify the conditions and risk factors that may complicate the perioperative course. Information should be elicited regarding the cardiovascular, pulmonary, renal, gastrointestinal, endocrine, hematologic, neurologic, immune, musculoskeletal, integumentary, and psychiatric systems. Additional testing, prophylactic measures, and behavioral modification prior to surgery can then be implemented to maximize the surgical outcome. In addition, the patient’s prior anesthetic record provides invaluable insight into issues such as airway management and overall tolerance of general, regional, local, or neuroleptic anesthesia. A social history can often be extremely beneficial as well, providing a means of anticipating postoperative needs and circumventing some prolonged admissions. Any significant issues should be raised with the departmental or hospital social worker, preferably prior to surgery. Lastly, it is important to elicit a detailed list of current medications and allergies.
In uncomplicated cases, the history and physical examination are followed by routine screening tests. Blood is drawn for a complete blood count (CBC), serum electrolytes, blood urea nitrogen (BUN), creatinine, glucose, and a clotting profile to rule out a wide range of possible occult abnormalities. In patients over 40 years of age or in those with pertinent past medical histories, chest radiography and electrocardiography (ECG) are performed. Additionally, women of childbearing age should undergo pregnancy testing.
When the need arises, consultation with appropriate specialties should be sought quickly. The consultant should be clearly informed about the nature of the proposed procedure and should be asked to comment specifically on the relative safety of performing the procedure with respect to concomitant disease processes. In cases complicated by many medical problems or in those in which the establishment of a safe airway is an issue, the authors advise close consultation with the anesthesia team to avoid undue delay, cancellation of the procedure, or an undesirable outcome.
Increasingly, the primary care physician conducts the preoperative evaluation. This phenomenon has become particularly prevalent in the managed care environment. Although a good internist can often facilitate the preoperative process,
it is imperative to have copies of all laboratory results, radiographs, and pertinent tests available for review prior to surgery. Additional studies should be ordered by the surgeon as deemed necessary.
Although a detailed discussion of the legal ramifications of informed consent is beyond the scope of this chapter, the ethical ideal deserves consideration. A thorough and candid explanation of the procedure, its risks, and the probable outcomes has become an integral part of the preoperative process. More and more patients now come to their physician prepared to ask in-depth questions and expecting to receive detailed answers. The relationship that develops between the surgeon and patient at this time often does more to prevent litigation in the unfortunate circumstance of maloccurrence than any legal document detailing the “risks and benefits.”
The surgeon must guard against anaphylactic reactions in all patients. The crux of this process is to have the patient identify any untoward reactions to medications, foods, or other materials. In most instances, many of the drug “reactions” quoted by patients do not represent true allergic phenomena. Instead, they are simply medicinal side effects. Nonetheless, these reactions require thorough documentation and avoidance in the perioperative period.
Anaphylaxis is triggered by antigen-specific immunoglobulin E (IgE) antibody crosslinking at the mast cell surface. Subsequent mast cell degranulation releases potent inflammatory agents, vasoactive substances, and proteases, all of which mediate the shock reaction. The patient may develop urticaria, profound hypotension, tachycardia, bronchoconstriction, and airway-compromising edema of the mucosal surfaces of the upper aerodigestive tract. Even in intubated patients, rapid oxygen desaturation is often a prominent feature. As the reaction progresses, cardiac arrest can ensue despite maximal resuscitative efforts. Given the potential morbidity and mortality of anaphylactic reactions, the otolaryngologist must identify all allergens in the preoperative phase.
The incidence of serious adverse reactions to penicillin is about 1%. It is widely believed that there is a 10% to 15% chance that patients who manifest these reactions also react adversely to cephalosporins. The authors frequently administer intravenous cephalosporins intraoperatively, and the safety of their use in patients allergic to penicillin often comes into question. Based on empiric observations at the authors’ institution, it is believed that unless these patients have had a history of significant atopy or penicillin-induced urticaria, mucosal edema, or anaphylaxis, they can be given cephalosporins with relative impunity. Anaphylactic reactions to cephalosporins in true penicillin-allergic patients are probably less than 2%. Moreover, cephalosporins cause their own independent hypersensitivity reactions; the notion of cross-reactivity with penicillin on skin testing seems to stem from data obtained in the 1970s, in which contamination of cephalosporins with penicillin was subsequently proven. Finally, if a serious penicillin allergy is evident, alternative antibiotics such as clindamycin may be substituted for the cephalosporins.
Mucosal absorption of latex protein allergens from the surgeon’s gloves can rapidly incite anaphylactic shock in patients who are highly sensitive to latex. In fact, the authors have recently witnessed this dramatic reaction in the operating room. In preparation for surgery, a healthy, young patient was intubated, arterial and central venous catheters were placed, and a Foley catheter was inserted. All procedures were performed by physicians and technicians wearing standard latex gloves. Shortly thereafter, the patient became profoundly hypotensive and hypoxic. Resuscitation was initiated and, after ruling out all other likely etiologies, the diagnosis of latex allergy was entertained. The patient was subsequently managed with latex-free products and, fortunately, survived a near catastrophe. The patient later recalled developing orofacial edema when he inflated balloons, and that rubber gloves would cause pruritus of his hands. Subsequent serum testing confirmed his latex allergy. It should be noted that about 7% to 10% of healthcare workers regularly exposed to latex and 28% to 67% of children with spina bifida demonstrate positive skin tests to latex proteins. Preoperatively, if a patient gives a history suspicious for latex allergy, it should be investigated prior to surgery; if the allergy is documented, perioperative precautions to avoid latex exposure must be instituted at all costs.
Similarly, patients with allergic or adverse reactions to soybean or eggs may react to propofol, a ubiquitous induction agent. Protamine and intravenous contrast agents can potentially provoke hypersensitivity responses in patients with known shellfish or other fish allergies. Although rare, some patients may have allergic reactions to ester types of local anesthetics such as cocaine, procaine, and tetracaine.
Finally, if the suspicion of allergy or adverse reaction exists, the best course of action is to avoid use of the potential offending agent altogether during surgery. If this is not feasible for some reason, then the surgeon and anesthesiologist should plan on premedicating the patient with systemic steroids, histamine antagonists, and even bronchodilators and should be prepared to deal with the potential worst-case scenario of anaphylactic shock.
Cardiovascular complications are the most common cause of perioperative mortality. Specifically, there is an almost 50% mortality rate associated with perioperative myocardial infarction. Meticulous review of the cardiovascular system is of utmost importance in determining a patient’s surgical candidacy, especially for those who will require
a general anesthetic. Risk factors for a perioperative cardiovascular complication include jugular venous distention, third heart sounds, recent myocardial infarction (MI) (within 6 months), nonsinus heart rhythm, frequent premature ventricular contractions (>5 per minute), over 70 years of age, valvular aortic stenosis, previous vascular or thoracic surgery, and poor overall medical status. Emergency surgery poses an additional risk for cardiovascular complications. In the head and neck oncology patient population, the high incidence of tobacco and alcohol abuse leads to a relatively high incidence of coronary artery disease, cardiomyopathy, and peripheral vascular disease.
The otolaryngologist should obtain a history of previous MIs, angina, angioplasty or bypass surgery, congestive heart failure (CHF) or dyspnea on exertion, hypertension, general exercise tolerance, paroxysmal nocturnal dyspnea, claudication, stroke or transient ischemic attack (TIA), syncope, palpitations or other arrhythmias, as well as known anatomic or auscultative cardiac anomalies. The presence or suspicion of coronary artery disease, heart failure, untreated hypertension, or significant peripheral vascular disease should prompt a specific anesthesiology or cardiology consultation before surgery. This evaluation would include an assessment of the electrocardiogram as well as possible exercise or chemical stress testing, echocardiography, and cardiac catheterization as indicated. The result of this consultation should determine the surgical and anesthetic risk and should optimize the patient’s preoperative cardiovascular status. Furthermore, specific intraoperative and postoperative physiologic (e.g., invasive monitors) and pharmacologic precautionary measures should be delineated, as should the level of postoperative observation.
In general, patients are maintained on their antihypertensive, antianginal, and antiarrhythmic regimens up to the time of surgery. Certain medications such as diuretics and digoxin may be withheld at the discretion of the anesthesiologist or cardiologist. Preoperatively, serum electrolytes and antiarrhythmic levels should be checked and adjusted as necessary. Coagulation studies (prothrombin time [PT]/partial thromboplastin time [PTT]) and platelet quantification are routinely obtained in patients with the above-mentioned risk factors because significant bleeding can lead to major perioperative cardiovascular complications. A relatively current chest radiograph is considered essential in this high-risk group.
Preoperatively, the otolaryngologist must be aware of the types of procedures that may have specific cardiovascular ramifications. For instance, the intravascular volume loading that occurs during and after free flap surgery, through use of agents such as dextran and Hespan (Hetastarch, Dupont Pharma, Wilmington, Delaware), can have a significant impact on patients with a history of congestive heart failure, poor ventricular function, or atrial fibrillation. Furthermore, the fall in hematocrit often seen with the use of these agents can potentially induce coronary ischemia. Patients with prosthetic valves and those with a history of rheumatic fever, endocarditis, congenital heart defects, mitral valve prolapse with regurgitation, or hypertrophic cardiomyopathy should receive prophylactic antibiotics at the time of surgery. Such prophylaxis is especially important during procedures performed on the oral cavity and upper aerodigestive tract as well as dealing with surgical drainage of head and neck infections, in which the risk of hematogenous bacterial seeding is high. For low-risk procedures, intravenous ampicillin, 2 g given 30 minutes prior to surgery followed by 1 g 6 hours later, is sufficient prophylaxis. In high-risk procedures, intravenous gentamicin, 1.5 mg/kg, and intravenous ampicillin, 2 g, are administered 30 minutes before surgery, followed by the same doses of each 8 hours later. Patients with pacemakers or implanted defibrillators and those with mitral valve prolapse without regurgitation do not require endocarditis prophylaxis.
Airway, carotid, and vagus nerve manipulation can induce bradycardia and hypotension. Agents such as lidocaine, epinephrine, and cocaine, which are frequently used in sinonasal surgery, can trigger undesirable cardiovascular events. Injury to the cervical sympathetic chain may precipitate postural hypotension postoperatively. Finally, the surgeon must also be cognizant of the fact that a unipolar electrocautery device can reprogram a pacemaker during surgery.
Postoperative pulmonary complications are considered the second most common cause of perioperative mortality. This is not surprising when considering the effects of general anesthesia and surgery on pulmonary performance. Atelectasis and ventilation/perfusion mismatch occur secondary to a number of factors, including the use of anesthetic agents and positive pressure ventilation as well as supine positioning. Anesthetic agents, barbiturates, and opioids tend to diminish the ventilatory response to hypercarbia and hypoxia. Endotracheal intubation bypasses the warming and humidifying effects of the upper airway, leading to impaired ciliary function, thickened secretions, and subsequent decreased resistance to infection. Furthermore, postoperative pain substantially affects a patient’s ability to cough, especially following thoracic or abdominal procedures (e.g., chest myocutaneous flap, gastric pull up, percutaneous endoscopic gastrostomy (PEG), rectus free-flap, iliac crest bone graft). Because of their attenuated respiratory reserve, patients with chronic pulmonary disease are much more likely to suffer postoperative pulmonary complications than are healthy patients. For instance, heavy smokers have a threefold increase in the risk of postoperative pulmonary complications when compared with nonsmokers. Hence it is imperative to identify these patients during the preoperative evaluation.
Specifically, a positive history of asthma, chronic obstructive pulmonary disease (COPD), emphysema, tobacco abuse, pneumonia, pulmonary edema, pulmonary fibrosis, or adult respiratory distress syndrome (ARDS) requires
heightened attention prior to surgery. The prior treatment of these lung problems, including the number of hospitalizations and emergency room visits; the use of medications like steroids, antibiotics, and bronchodilators; and the need for intubation or chronic oxygen therapy should be addressed. The otolaryngologist should obtain an estimate of the patient’s dyspnea, exercise limitation, cough, hemoptysis, and sputum production. Factors that exacerbate chronic lung disease must be identified. Once again, it is of paramount importance to investigate the tolerance of previous anesthetics in this high-risk group. Coexisting cardiac and renal disease such as CHF and chronic renal failure also impact heavily on pulmonary function. Pulmonary hypertension and cor pulmonale secondary to obstructive sleep apnea, cystic fibrosis, muscular dystrophy, emphysema, or kyphoscoliosis further complicate anesthetic management. Congenital diseases affecting the lungs such as cystic fibrosis and Kartagener’s syndrome (rare) present the challenge of perioperative clearance of secretions.
On physical examination, the clinician should be attuned to the patient’s body habitus and general appearance. Obesity, kyphoscoliosis, and pregnancy can all predispose to poor ventilation, atelectasis, and hypoxemia. Cachectic patients are more likely to develop postoperative pneumonia. It should be noted that clubbing and cyanosis, although suggestive, are not reliable indicators of chronic pulmonary disease. The patient’s respiratory rate is determined, and the presence of accessory muscle use, nasal flaring, diaphoresis, or stridor should be documented. Auscultation that reveals wheezing, rhonchi, diminished breath sounds, crackles,rales, and altered inspiratory:expiratory time ratios should raise the suspicion of pulmonary compromise.
In patients with pulmonary disease, preoperative posteroanterior and lateral chest radiography is mandatory, because findings will often direct modification of the anesthetic technique used during surgery. Arterial blood gas (ABG) testing on room air is also indicated. Patients with an arterial oxygen tension less than 60 mm Hg or an arterial carbon dioxide tension greater than 50 mm Hg are more likely to have postoperative pulmonary complications. Serial ABG determinations can also assess the overall efficacy of preoperative medical and respiratory therapy. As with chest radiography, preoperative ABG levels also provide a baseline for postoperative comparison. Preoperative pulmonary function tests such as spirometry and flow-volume loops are quite helpful. A quantitative measure of ventilatory function can also be used to assess the efficacy of both preoperative and surgical interventions. Spirometry can be used to differentiate restrictive from obstructive lung disease as well as to predict perioperative morbidity from pulmonary complications. Generally, a forced expiratory volume in 1 second: forced vital capacity ratio of less than 75% is considered abnormal, whereas a ratio of less than 50% carries a significant risk of perioperative pulmonary complications. Preoperative flow-volume loops can distinguish among fixed (e.g., goiter), variable extrathoracic (e.g., unilateral vocal cord paralysis), and variable intrathoracic (e.g., tracheal mass) airway obstructions.
The preoperative management of otolaryngology patients with significant pulmonary disease is vital and should follow the recommendations of a pulmonologist. Smokers are advised to cease smoking for at least a week prior to surgery. Known airway irritants and triggers of bronchospasm should be avoided as much as possible. The patient should be well hydrated and should breathe warm, humidified air or oxygen. Chest physiotherapy aimed at increasing lung volumes and clearing secretions is instituted. This includes coughing and deep breathing exercises, incentive spirometry, and chest percussion with postural drainage. It is not advisable to operate on a patient with an acute exacerbation of pulmonary disease or with an acute pulmonary infection. Acute infections should be cleared with antibiotics and chest physiotherapy prior to elective surgery. Prophylactic antibiotics in noninfected patients are not recommended for fear of selecting out resistant organisms. Finally, the medical regimen, including the use of inhaled ß-adrenergic agonists, cromolyn, and steroids (inhaled or systemic), must be optimized. Serum levels of theophylline, if used, should be therapeutic.
The preoperative identification and evaluation of renal problems is also imperative. Any significant electrolyte abnormalities uncovered during the routine screening of healthy patients should be corrected preoperatively, and surgery should be delayed if additional medical evaluation is warranted. Preexisting renal disease is a major risk factor for the development of acute tubular necrosis both during and after surgery. Renal failure, whether acute or chronic, influences the types, dosages, and intervals of perioperative drugs and anesthetics. An oliguric or anuric condition requires judicious fluid management, especially in patients with cardiorespiratory compromise. Furthermore, chronic renal failure (CRF) is often associated with anemia, platelet dysfunction, and coagulopathy. Electrolyte abnormalities, particularly hyperkalemia, can lead to arrhythmias, especially in the setting of the chronic metabolic acidosis that often accompanies CRF. Hypertension and accelerated atherosclerosis resulting from CRF are risk factors for developing myocardial ischemia intraoperatively. Blunted sympathetic responses may predispose to hypotensive episodes during administration of anesthesia. The otolaryngologist must also be wary of the potential for injury to demineralized bones during patient positioning. An impaired immune system can contribute to poor wound healing and postoperative infection. Finally, because patients with CRF have often received blood transfusions, they are at increased risk of carrying blood-borne pathogens such as hepatitis B and C.
The possible causes of renal disease, including hypertension, diabetes, nephrolithiasis, glomerulonephritis, polycystic disease, lupus, polyarteritis nodosa, Goodpasture’s or
Wegener’s syndromes, trauma, or previous surgical or anesthetic insults, should be elicited. The symptoms of polyuria, polydipsia, fatigue, dyspnea, dysuria, hematuria, oliguria or anuria, and peripheral edema are recorded, as is a complete listing of all medications taken by the patient.
In dialyzed patients, it is important to document the dialysis schedule. A nephrologist should assist with the preoperative evaluation and should optimize the patient’s fluid status and electrolytes prior to surgery. A nephrologist should also be available to help manage these issues postoperatively, especially when major head and neck, skull-base, or neurotologic surgery, which may require large volumes of fluids or blood transfusions intraoperatively, is planned.
Preoperative testing on patients with significant renal disease routinely includes ECG, chest radiography, electrolytes and chemistry panel, CBC, PT/PTT, platelet counts, and bleeding times. In addition to a nephrologic consultation, patients with significant renal disease should also receive a preoperative anesthesiology consultation, and, if indicated, further evaluation by a cardiologist.
A history of benign prostatic hypertrophy or prostate cancer, with or without surgery, may predict a difficult urinary tract catheterization intraoperatively. Finally, elective surgery should not be performed on patients with acute genitourinary tract infections because the potential for urosepsis can be increased by the transient immunosuppression associated with general anesthesia.
Preoperative evaluation of patients with suspected or clinically evident liver failure should begin with a history eliciting the details of hepatotoxic drug therapy, jaundice, blood transfusion, upper gastrointestinal bleeding, and previous surgery and anesthesia. The physical should include examination for hepatomegaly, splenomegaly, ascites, jaundice, asterixis, and encephalopathy. The list of blood tests is fairly extensive and includes hematocrit, platelet count, bilirubin, electrolytes, creatinine, BUN, serum protein, PT/PTT, serum aminotransferases, alkaline phosphatase, and lactate dehydrogenase. A viral hepatitis screen can be obtained as well. Of note, patients with moderate to severe chronic alcoholic hepatitis may present with relatively normal-appearing liver function tests and coagulation parameters; these patients are at risk for perioperative liver failure. In the last few years, at least four patients under the authors’ care ultimately succumbed to complications of liver failure following surgery.
Cirrhosis and portal hypertension have wide-ranging systemic manifestations. Arterial vasodilation and collateralization leads to decreased peripheral vascular resistance and an increased cardiac output. This hyperdynamic state can occur even in the face of alcoholic cardiomyopathy. The responsiveness of the cardiovascular system to sympathetic discharge and administration of catechols is also reduced, likely secondary to increased serum glucagon levels. Cardiac output can be reduced by the use of propranolol, which has been advocated by some as a treatment for esophageal varices. By decreasing cardiac output, flow through the portal system and the esophageal variceal collaterals is diminished. Additionally, there is likely a selective splanchnic vasoconstriction. Once initiated, ß-blockade cannot be stopped easily because of a significant rebound effect.
Renal sequelae vary with the severity of liver disease from mild sodium retention to acute failure associated with the hepatorenal syndrome. Diuretics given to decrease ascites can often lead to intravascular hypovolemia, azotemia, hyponatremia, and encephalopathy. Fluid management in the perioperative period should be followed closely and dialysis instituted as needed for acute renal failure.
From a hematologic standpoint, patients with cirrhosis often have an increased 2,3-diphosphoglycerate level in their erythrocytes causing a shift to the right of the oxyhemoglobin dissociation curve. Clinically, this results in a lower oxygen saturation. This situation is further compounded by the frequent finding of anemia. Additionally, significant thrombocytopenia and coagulopathy may be encountered. The preoperative use of appropriate blood products can lead to short-term correction of hematologic abnormalities, but the prognosis in these patients remains poor.
Encephalopathy stems from insufficient hepatic elimination of nitrogenous compounds. Although measurements of BUN and serum ammonia levels are useful, they do not always correlate with the degree of encephalopathy. Treatment includes hemostasis, antibiotics, meticulous fluid management, low-protein diet, and lactulose.
Symptoms of hyperthyroidism include weight loss, diarrhea, skeletal muscle weakness, warm, moist skin, heat intolerance, and nervousness. Laboratory test results may demonstrate hypercalcemia, thrombocytopenia, and mild anemia. Elderly patients also can present with heart failure, atrial fibrillation, or other dysrhythmias. The term thyroid storm refers to a life-threatening exacerbation of hyperthyroidism that results in severe tachycardia and hypertension.
Treatment of hyperthyroidism attempts to establish a euthyroid state and to ameliorate systemic symptoms. Propylthiouracil inhibits both thyroid hormone synthesis and the peripheral conversion of T4 to T3. Complete clinical response may take up to 8 weeks, during which the dosage may need to be tailored to prevent hypothyroidism. Potassium iodide (Lugol’s solution), which works by inhibiting iodide organification, can be added to the medical regimen. In patients with sympathetic hyperactivity, ß-blockers have been used effectively. Propranolol has the added benefit of decreasing T4-to-T3 conversion. It should not be used in patients with CHF secondary to poor left ventricular function or bronchospasm because it will exacerbate both of these conditions. Ideally, medical therapy should prepare a mildly
thyrotoxic patient for surgery within 7 to 14 days. If the need for emergency surgery arises, intravenous propranolol or esmolol can be administered and titrated to keep the heart rate below 90 bpm. Other medications that can be used include reserpine and guanethidine, which deplete catechol stores, and glucocorticoids, which decrease both thyroid hormone secretion and T4-to-T3 conversion. Radioactive iodine also can be used effectively to obliterate thyroid function but should not be given to women of childbearing years.
The symptoms of hypothyroidism result from inadequate circulating levels of T4 and T3 and include lethargy, cognitive impairment, and cold intolerance. Clinical findings may include bradycardia, hypotension, hypothermia, hypoventilation, and hyponatremia. There is no evidence to suggest that patients with mild to moderate hypothyroidism are at increased risk for anesthetic complications, but all elective surgery patients should be treated with thyroid hormone replacement prior to surgery. Severe hypothyroidism resulting in myxedema coma is a medical emergency and is associated with a high mortality rate. Intravenous infusion of T3 or T4 and glucocorticoids should be combined with ventilatory support and temperature control as needed.
The prevalence of primary hyperparathyroidism increases with age. Sixty percent to 70% of patients with primary hyperparathyroidism present initially with nephrolithiasis secondary to hypercalcemia, and 90% are found to have benign parathyroid adenomas. Hyperparathyroidism secondary to hyperplasia occurs in association with medullary thyroid cancer and pheochromocytoma in multiple endocrine neoplasia (MEN) type IIA and, more rarely, with malignancy. In humoral hypercalcemia of malignancy, nonendocrine tumors have been demonstrated to secrete a parathyroid hormone-like protein. Secondary hyperparathyroidism usually results from chronic renal disease. The hypocalcemia and hyperphosphatemia associated with this condition lead to increased parathyroid hormone production and, over time, to parathyroid hyperplasia. Tertiary hyperparathyroidism occurs when the CRF is rapidly corrected as in renal transplantation.
In addition to nephrolithiasis, signs and symptoms of hypercalcemia include polyuria, polydipsia, skeletal muscle weakness, epigastric discomfort, peptic ulceration, and constipation. Radiographs may show significant bone resorption in 10% to 15% of patients. Depression, confusion, and psychosis also may be associated with marked elevations in serum calcium levels.
Immediate treatment of hypercalcemia usually combines sodium diuresis with a loop diuretic and rehydration with normal saline as needed. This becomes urgent once the serum calcium levels rise above 15 g/dl. Several medications can be used to decrease serum calcium levels. Etidronate inhibits abnormal bone resorption. The cytotoxic agent mithramycin inhibits parathyroid hormone-induced osteocytoclastic activity but is associated with significant side effects, and calcitonin works transiently again by direct inhibition of osteoclast activity. Hemodialysis can also be used in the appropriate patient population.
The most common cause of hypoparathyroidism is iatrogenic. Thyroid and parathyroid surgery occasionally results in the inadvertant removal of all parathyroid tissue. Ablation of parathyroid tissue can also occur after major head and neck surgery and postoperative radiation therapy. Symptoms include tetany, perioral and digital paresthesias, muscle spasm, and seizures. Chvostek’s sign (facial nerve hyperactivity elicited by tapping over the common trunk of the nerve as it passes through the parotid gland) and Trousseau’s sign (finger and wrist spasm after inflation of a blood pressure cuff for several minutes) are clinically important indicators of latent hypercalcemia. Treatment is with calcium supplementation and vitamin D analogs.
Adrenal gland hyperactivity can result from a pituitary adenoma, a corticotropin hormone (ACTH)-producing nonendocrine tumor, or a primary adrenal neoplasm. Symptoms include truncal obesity, proximal muscle wasting, “moon” facies, and changes in behavior that vary from emotional lability to frank psychosis. Diagnosis is made through the dexamethasone suppression test, and treatment is adrenalectomy or hypophysectomy. It is important to regulate blood pressure and serum glucose levels and to normalize intravascular volume and electrolytes. Primary aldosteronism (Conn’s syndrome) results in increased renal tubular exchange of sodium for potassium and hydrogen ions. This leads to hypokalemia, skeletal muscle weakness, fatigue, and acidosis. The aldosterone antagonist spironolactone should be used if the patient requires diuresis.
Idiopathic primary adrenal insufficiency (Addison’s disease) results in both glucocorticoid and mineralocorticoid deficiencies. Symptoms include asthenia, weight loss, anorexia, abdominal pain, nausea, vomiting, diarrhea, constipation, hypotension, and hyperpigmentation. Hyperpigmentation is caused by overproduction of ACTH and ß-lipotropin, which leads to melanocyte proliferation. Measurement of plasma cortisol levels 30 and 60 minutes after intravenous administration of ACTH, 250 mg, aids in diagnosis. Patients with primary adrenal insufficiency demonstrate no response. Glucocorticoid replacement is required on a twice-daily basis and should be increased with stress. Mineralocorticoid therapy can be given once daily. Of note, patients treated for more than 3 weeks with exogenous glucocorticoids for any medical condition should be assumed to have suppression of their adrenal–pituitary axis and should be treated with stress-dose steroids perioperatively.
Pheochromocytoma is a tumor of the adrenal medulla that secretes both epinephrine and norepinephrine. Five percent of these tumors are inherited in an autosomal dominant fashion as part of a multiple endocrine neoplasia syndrome.
Symptoms include hypertension (which is often episodic), headache, palpitations, tremor, and profuse sweating. Preoperative treatment begins with phenoxybenzamine, a long-acting a-blocker, or prazosin at least 10 days prior to surgery. A ß-blocker is added only after the establishment of a-blockade to avoid unopposed ß-mediated vasoconstriction. Acute hypertensive crises can be managed with nitroprusside or phentolamine.
Diabetes is a disorder of carbohydrate metabolism that results in a wide range of systemic manifestations. It is the most common endocrine abnormality found in surgical patients and can be characterized as either insulin-dependent (type I or juvenile onset) or non-insulin-dependent (type II). Hyperglycemia may result from a variety of etiologies that affect insulin production and function. Management techniques seek to avoid hypoglycemia and maintain high normal serum glucose levels throughout the perioperative period. These goals are often difficult to maintain, however, because infection, stress, exogenous steroids, and variations in carbohydrate intake can all cause wide fluctuations in serum glucose levels. Close monitoring is mandatory, with correction of hyperglycemia using a sliding scale for insulin dosage or continuous intravenous infusion in more severe cases. Fluid management should focus on maintaining hydration and electrolyte balance.
A history of easy bruising or excessive bleeding with prior surgery should raise suspicion of a possible hematologic diathesis. A significant number of patients will also present on anticoagulative therapy for coexisting medical conditions. It is therefore important for the surgeon to recognize and treat the diagnosis and therapy of the more common hematologic disorders, both congenital and acquired.
After a careful history, the physician should obtain laboratory studies. PT, PTT, and platelet count are included in the routine preoperative screen. PT evaluates both the extrinsic and the final common pathways. Included in the extrinsic pathway are the vitamin K-dependent factors II, VII, IX, and X, which are inhibited by warfarin. Conversely, heparin inhibits thrombin and factors IXa, Xa, and XIa, elements of the intrinsic clotting pathway. PTT measures the effectiveness of the intrinsic and final common pathways. Relative to the normal population, some patients may demonstrate significant variation in the quantitative levels of certain factors in the absence of clinically relevant clotting abnormalities. Thrombocytopenia or platelet dysfunction can also lead to derangements in coagulation. A standard CBC includes a platelet count, which should be greater than 50,000 to 70,000 before surgery. The ivy bleeding time, a clinical test of platelet function, should be between 3 and 8 minutes. Fibrin split products may also be measured to help determine the diagnosis of disseminated intravascular coagulation.
Congenital deficiencies of hemostasis affect up to 1% of the population. Fortunately, the majority of these deficiencies are clinically mild. Two of the more serious deficiencies involve factor VIII, which is a complex of two subunits, factor VIII:C and factor VIII:von Willebrand’s factor. Sex-linked recessive transmission of defects in the quantity and quality of factor VIII:C leads to hemophilia A. Because of its short half-life, perioperative management of factor VIII:C requires infusion of cryoprecipitate every 8 hours. Historically, these patients have had a high incidence of hepatitis and HIV due to the administration of pooled blood products. Improved screening of blood products and recombinant deoxyribonucleic acid (DNA) technology have markedly diminished this problem.
von Willebrand’s disease has a milder presentation than hemophilia A; bleeding tends to be mucosal rather than visceral. There are three subtypes. Types I and II represent quantitative and qualitative deficiencies, respectively, and are passed by autosomal dominant transmission. Type I also is characterized by low levels of factor VIII:C. Much rarer and transmitted as an autosomal recessive gene, type III von Willebrand’s disease presents with symptoms similar to those of hemophilia A. Because of the longer half-life of factor VIII:von Willebrand’s factor, patients with type II von Willebrand’s disease can be transfused with cryoprecipitate up to 24 hours before surgery, with repeat infusions every 24 to 48 hours. Patients with type I von Willebrand’s disease require additional transfusion just prior to surgery in order to boost factor VIII:C levels and normalize bleeding time.
Patients with hemophilia, von Willebrand’s disease, and other less common congenital hemostatic anomalies should be followed perioperatively by a hematologist. Correction of factor deficiencies should be instituted in a timely fashion, and patients should be monitored closely for any evidence of bleeding.
Warfarin, heparin, and aspirin have become commonly used medications in the medical arsenal. Conditions such as atrial fibrillation, deep vein thrombosis, pulmonary embolism, and heart valve replacement are routinely treated initially with heparin, followed by warfarin on an outpatient basis. This therapy markedly decreases the incidence of thromboembolic events and, when appropriately monitored, only slightly increases the risk of hemorrhagic complications. Aspirin is widely used both as an analgesic and as prophylaxis for coronary artery disease. Patients taking any of these medications need careful evaluation to assess the severity of the condition necessitating anticoagulation. The benefit of surgery relative to the risk of normalizing coagulation should be clearly established with both the patient and the physician prescribing the anticoagulant.
Warfarin should be stopped at least 3 days prior to surgery
depending on liver function. Patients who have been determined to be at high risk for thromboembolism should be admitted for heparinization prior to surgery. The infusion rate can then be adjusted to maintain the PTT in a therapeutic range. Discontinuation of heparin approximately 6 hours before surgery should provide adequate time for reversal of anticoagulation. In emergency situations, warfarin can be reversed with vitamin K in approximately 6 hours and more quickly with the infusion of fresh frozen plasma (FFP). Heparin can be reversed with protamine or FFP. Of note, a heparin rebound phenomenon in which anticoagulative effects are reestablished can occur up to 24 hours after the use of protamine. Anticoagulative therapy can be reinstituted soon after surgery if necessary. Most surgeons, however, prefer to wait several days unless contraindicated. It is often helpful to discuss the timing of postoperative therapy with the hematologist prior to surgery.
Aspirin, an irreversible inhibitor of platelet function, leads to prolonged bleeding time. There is no strong evidence to link aspirin therapy with excessive intraoperative bleeding. However, the theoretical risk that aspirin and other nonsteroidal antiinflammatory medications present leads most surgeons to request that their patients stop taking these medications up to 2 weeks prior to surgery to allow the platelet population to turn over.
Patients with liver failure can present with several hematologic abnormalities. Bleeding from esophageal varices secondary to portal hypertension can lead to anemia. Hypersplenism and alcoholic bone marrow suppression can result in serious thrombocytopenia. An elevated PT may indicate a deficiency in the vitamin K-dependent factors of the extrinsic clotting pathway as well as factors I, V, and XI, which are also produced in the liver. Lastly, as liver failure progresses, excessive fibrinolysis may occur. All of these hematologic sequelae of hepatic failure increase the risk of operative morbidity and mortality. Preoperative management should attempt to correct anemia and thrombocytopenia as indicated and replenish deficient clotting factors with FFP. Fluid management may prove to be a difficult issue.
Another less common cause of PT elevation is the intestinal sterilization syndrome in which intestinal flora, a major source of vitamin K, are eradicated by prolonged doses of antibiotics in patients unable to obtain vitamin K from other sources. Reversal occurs rapidly with vitamin K therapy.
A decrease in platelet count can occur as a result of a variety of medical conditions, including massive transfusion, liver failure, disseminated intravascular coagulation, aplastic anemia, hematologic malignancy, and idiopathic thrombocytopenic purpura. With the increasing use of chemotherapeutics for a variety of malignancies, the prevalence of iatrogenic thrombocytopenia has risen. Preoperatively, the platelet count should be greater than 50,000; at levels below 20,000, spontaneous bleeding may occur. Additionally, any indication of platelet dysfunction should be evaluated with a bleeding time. Severe azotemia secondary to renal failure may lead to platelet dysfunction (uremic platelet syndrome). Dialysis should be performed as necessary.
Correction of thrombocytopenia with platelet transfusion should preferably come from human leukocyte antigen-matched donors, particularly in patients who have received prior platelet transfusions and may be sensitized. One unit of platelets contains approximately 5.5 × 1011 platelets. One unit per 10 kg of body weight is a good initial dose. The platelets should be infused rapidly just prior to surgery.
Of the more than 300 hemaglobinopathies, sickle cell disease and thalassemia are by far the most common. Approximately 10% of blacks in the United States carry the gene for sickle cell anemia. The heterozygous state imparts no real anesthetic risk. There are significant clinical manifestations to the 1 in 400 blacks who are homozygous for hemoglobin S. The genetic mutation results in the substitution of valine for glutamic acid in the sixth position of the ß-chain of the hemoglobin molecule, leading to alterations in the shape of erythrocytes when the hemoglobin deoxygenates. The propensity for sickling directly relates to the quantity of hemoglobin S. Clinical findings include anemia and chronic hemolysis. Infarction of multiple organ systems can occur secondary to vessel occlusion. Most patients die by 30 years of age as a result of complications of their disease.
Treatment consists of preventive measures. Oxygenation and hydration help maintain tissue perfusion. Transfusion prior to surgical procedures decreases the concentration of erythrocytes carrying hemoglobin S, thereby lowering the chance of sickling.
There are multiple types of thalassemia, each caused by genetic mutations in one of the subunits of the hemoglobin molecule. Symptoms vary on the severity of the mutation. Patients with the most severe form, ß-thalassemia major, are transfusion dependent, which often leads to iron toxicity. Other thalassemias cause only mild hemolytic anemia. If transfusion dependency exists, the patient should be screened carefully for hepatic and cardiac sequelae of iron toxicity.
A solid, working familiarity with the cranial nerves is intrinsic to the specialty of otolaryngology. Numerous pathologic processes, both benign and malignant, as well as traumatic injuries have the potential for cranial nerve and intracranial involvement. In the preoperative setting, therefore, the otolaryngologist is obliged to perform a thorough neurologic examination and review of the neurologic system. A cursory search for symptoms of visual loss, diplopia, anosmia, facial pain and tics, headaches, paresthesias and hypoesthesias,
facial paralysis or paresis, dysequilibrium, hearing loss, dysphagia, hoarseness, and tongue deviation or fasciculations forms a basis of the neurologic history. A more specific review can then be tailored based on the presenting complaint and physical findings. Recognition of constellations of signs and symptoms, as seen in Horner’s syndrome, is useful in establishing a diagnosis.
Confirmation of neurologic deficits can be made using various examinations and tests such as audiometry, electronystagmography, electromyography, cine-esophagography, videostroboscopy, and fiberoptic laryngoscopy. For medicolegal reasons, it is critical to document all neurologic abnormalities. It is important to distinguish peripheral from central lesions, and computed tomography (CT) or magnetic resonance imaging (MRI) is often helpful in this regard. Frequently, neurologic consultation is sought in the setting of subtle findings or confusing or paradoxic findings and for evaluation of possible nonotolaryngologic etiologies of certain complaints such as headache and dysequilibrium. During preoperative counseling of the patient, the surgeon must be aware of the potential for nerve injury or sacrifice and must communicate the possible sequelae of these actions to the patient.
If present, a history of seizures should be outlined with respect to the type, pattern, and frequency of epilepsy as well as the current anticonvulsant medications in use and their side effects. Phenytoin therapy can lead to poor dentition and anemia, whereas treatment with carbamazepine can cause hepatic dysfunction, hyponatremia, thrombocytopenia, and leukopenia, all of which represent concerns for the surgeon and anesthesiologist. Preoperative CBC, liver function tests, and coagulation studies are thus advised. Anesthetic agents such as enflurane, propofol, and lidocaine have the potential to precipitate convulsant activity, depending on their doses. In general, antiseizure medications must be at therapeutic serum levels and should be continued up to and including the day of surgery.
Symptomatic autonomic dysfunction can contribute to intraoperative hypotension. It may be necessary to augment intravascular volume preoperatively through increasing dietary salt intake, maximizing hydration, and administering fludrocortisone.
Additional considerations must be taken into account in patients with upper motor neuron diseases, such as amyotrophic lateral sclerosis, or lower motor neuron processes affecting cranial nerve nuclei in the brainstem. In either case,the otolaryngologist may be confronted with bulbar symptoms such as dysphagia, dysphonia, and inefficient mastication. As bulbar impairment progresses, the risk of aspiration increases significantly. When respiratory muscles are affected, the patient is likely to have dyspnea, intolerance to lying flat, and an ineffective cough. Coupled with aspiration, these factors put the patient at considerable surgical risk for pulmonary complications. Hence, if surgery is necessary for these patients, preoperative evaluation should include a pulmonary workup (including chest radiography, pulmonary function tests, ABG analysis) and consultation. A video study of swallowing function may also be indicated. Finally, the patient’s neurologist should be closely involved in the decision making (i.e., whether to proceed with surgery).
Parkinsonism presents the challenges of excessive salivation and bronchial secretions, gastroesophageal reflux, obstructive and central sleep apnea, and autonomic insufficiency, all of which predispose to difficult airway and blood pressure management in the perioperative period. Dopaminergic medications should be administered up to the time of surgery in order to avoid the potentially fatal neuroleptic malignant syndrome. Medications such as phenothiazines, metoclopromide, and other antidopaminergics should be avoided. Preoperatively, the patient’s pulmonary function and autonomic stability should be investigated.
If clinically indicated, patients with multiple sclerosis should also undergo full pulmonary evaluation preoperatively, because these patients can present with poor respiratory and bulbar function. The presence of contractures can limit patient positioning on the operating table. In addition, prior to surgery, the patient must be free of infection because pyrexia can exacerbate the conduction block in demyelinated neurons.
Otolaryngologists often must manage patients with facial trauma and head injury, usually in the acute care setting. Preoperative evaluation should be guided by the ABC’s of resuscitation. Emergency situations predisposing to loss of the airway or cardiovascular collapse must be addressed immediately. Additionally, once stabilized, a thorough neurosurgical or neurologic assessment is required prior to elective fixation of injuries such as facial fractures.
Preoperative management of patients with any of the other remaining neurologic disorders is not discussed here.Evaluation in these patients should be focused primarily on airway, cardiopulmonary, and neurologic issues, as well as any other coexisting medical problems that may compromise anesthetic outcome.
Finally, for medicolegal reasons, an estimation of the mental status of all patients should be documented preoperatively.
THE GERIATRIC PATIENT
The elderly represent the fastest growing segment of the U.S. population. Twenty-five percent to 33% of all surgeries are currently performed on individuals over 65 years of age, and this percentage is likely to increase in the next decade as the “baby boom” generation reaches retirement age. A greater likelihood of comorbid conditions exists with increasing age. In addition, physiologic reserve is often compromised. Preoperative assessment in this population should take these considerations into account and weigh the benefit of the procedure against the often increased risks in this population. Consultation with the anesthesia service facilitates planning for high-risk elderly patients.
Approximately 50% of all postoperative deaths in the elderly occur secondary to cardiovascular events. Severe cardiac disease should be treated prior to any elective procedure and should be weighed against the benefit of any more urgent procedure. If surgery is required, cardiac precautions should be instituted. Patients with physical evidence or a history of peripheral vascular disease should be evaluated for carotid artery stenosis. If a critical stenosis is identified, carotid endarterectomy should be performed to any elective procedure that requires a general anesthetic. The risk of a cerebrovascular accident should be considered when evaluating patients for more urgent procedures. In vasculopathic patients requiring free-flap reconstruction after major head and neck resection, examination of both recipient and donor vessels should be performed prior to surgery to minimize complications and assist in the appropriate choice of reconstructive options.
From a respiratory standpoint, increasing age leads to loss of lung compliance, stiffening of the chest wall, and atrophy of respiratory muscles. In many otolaryngology procedures, the risk of intraoperative or postoperative aspiration and postobstructive pulmonary edema must also be considered. Patients with borderline pulmonary function may not tolerate even mild respiratory complications. The function of all the organ systems diminishes with age, necessitating a thorough preoperative evaluation to maximize patient safety in the elderly population.
This chapter has provided a brief overview of the preoperative evaluation. Disturbances in one organ system often have repercussions for other systems, and so an interdisciplinary approach involving the otolaryngologist, anesthesiologist, internist, and specialized consultants is often warranted. The authors have chosen to emphasize the physiologic aspects of the evaluation. This is not intended to overshadow the importance of gaining insight into a patient’s psychosocial preparedness, which often requires the help of family members, social workers, psychiatrists, and support groups as well as a keen sense of intuition on the part of the surgeon. Furthermore, preoperative teaching provides a means to reinforce postoperative expectations and coping mechanisms. Finally, it must be reiterated that the responsibility of ensuring an appropriate preoperative evaluation lies with the surgeon and that the expediency of this process should be in keeping with the best interest of the patient.