Preoperative Assessment: Overview
The specialty of anesthesia is continually expanding in scope, particularly in the area of perioperative medicine. The role of an anesthesiologist today encompasses not only the intraoperative period but also preoperative risk assessment and implementation of perioperative risk reduction strategies for improving surgical outcomes. The preoperative evaluation is the cornerstone of safe and effective anesthesia care. Whether performed in a specific preoperative medicine clinic or immediately before anesthesia, the goal of the medical history and physical examination is the same: to formulate an anesthetic plan to minimize risk and maximize the quality of recovery. Testing or consultation with other physicians may be indicated in advance of surgery to diagnose disease based on identified risk factors or to optimize treatment. Medical records and previous anesthetic records often reveal details about past diagnoses or complications and are always reviewed during assessment. The American Society of Anesthesiologists (ASA) Practice Advisory for Preanesthesia Evaluation provides guidance for the preanesthesia history and physical examination and for the selection and timing of preoperative tests.
History and Physical Examination
A preanesthesia history includes the planned procedure, presenting illness, comorbid conditions, detailed review of systems, past anesthetic history with review of complications, assessment of allergies and medications, documentation of substance use or abuse, and the last oral intake if done on the day of surgery. Severity of disease, efficacy of treatment, and impact on daily function is explored to determine if an alteration in anesthesia plan is appropriate. The preanesthesia history is a comprehensive assessment of the patient’s current state of health and ability to perform daily functions, aspects of which are combined to assign an ASA Physical Status (ASA PS) score ( Table 13.1 ). Assessment of functional capacity, or cardiorespiratory fitness, directs further investigations. The ability to achieve a moderate level of activity without symptoms, denoted by a metabolic equivalent of task score (METS) of 4 or more predicts a low risk of perioperative complications ( Box 13.1 ). An inability to exercise indicates either lack of cardiorespiratory reserve or may result from neuromuscular or pulmonary disease, anemia, or general deconditioning, all of which indicate elevated risk.
|ASA PS Classification a||Definition||Examples, including, but not limited to|
|ASA I||A normal healthy patient||Healthy, nonsmoking, no or minimal alcohol use|
|ASA II||A patient with mild systemic disease||Mild diseases only without substantive functional |
limitations. Examples include (but are not limited to)
current smoker, social alcohol drinker, pregnancy, obesity (30 < BMI < 40), well-controlled DM/HTN, mild lung disease
|ASA III||A patient with severe systemic disease||Substantive functional limitations; One or more moderate to severe diseases. Examples include (but are not limited to) poorly controlled DM or HTN, COPD, morbid obesity (BMI ≥ 40), active hepatitis, alcohol dependence or abuse, implanted pacemaker, moderate reduction of ejection fraction, ESRD undergoing regularly scheduled dialysis, premature infant PCA < 60 weeks, history (>3 months) of MI, CVA, TIA, or CAD/stents.|
|ASA IV||A patient with severe systemic disease that is a constant threat to life||Examples include (but are not limited to) recent (<3 months) MI, CVA, TIA, or CAD/stents, ongoing cardiac ischemia or severe valve dysfunction, severe reduction of ejection fraction, sepsis, DIC, ARDS, or ESRD not undergoing regularly scheduled dialysis|
|ASA V||A moribund patient who is not expected to survive without the operation||Examples include (but are not limited to) ruptured abdominal/thoracic aneurysm, massive trauma, intracranial bleed with mass effect, ischemic bowel in the face of significant cardiac pathology or multiple organ/system dysfunction|
|ASA VI||A declared brain-dead patient whose organs are being removed for donor purposes|
METs—Levels of Exercise
Eating, working at computer, dressing
Walking downstairs or in your house, cooking
Walking 1-2 blocks
Raking leaves, gardening
Climbing 1-2 flights of stairs, dancing, bicycling
Playing golf, carrying clubs
Playing singles tennis
Rapidly climbing stairs, jogging slowly
Jumping rope slowly, moderate cycling
Swimming quickly, running or jogging briskly
Skiing cross country, playing full-court basketball
Running rapidly for moderate to long distances
MET, Metabolic equivalent. 1 MET = consumption of 3.5 mL O 2 /min/kg of body weight.
Clinical predictors of difficult airway management identified through screening questions may prompt alterations in care ( Table 13.2 ; also see Chapter 16 ). A personal or family history of malignant hyperthermia or pseudocholinesterase deficiency (also see Chapter 11 ) is noted so appropriate precautions are taken.
|Difficult Mask Ventilation a||Difficult Direct Laryngoscopy|
|Age > 55 years||Reported history of difficult intubation, aspiration pneumonia after intubation, dental or oral trauma following intubation|
|Obstructive sleep apnea (OSA) or snoring||OSA or snoring|
|Previous head/neck radiation, surgery, or trauma||Previous head/neck radiation, surgery, or trauma|
|Lack of teeth||Congenital disease: Down syndrome, Treacher-Collins syndrome, Pierre Robin syndrome|
|A beard||Inflammatory/arthritic disease: rheumatoid arthritis, ankylosing spondylitis, scleroderma|
|Body mass index (BMI) > 26 kg/m 2||ObesityCervical spine disease or previous surgery|
A preanesthesia physical examination begins with general inspection of the patient, such as dependent functional status (e.g., walker or wheelchair aids) or altered respiratory status (e.g., oxygen or accessory muscle use, cyanosis). Altered mental status is important to identify. Examination includes assessment of the airway ( Table 13.3 ) including Mallampati classification ( Fig. 13.1 ); vital signs including oxygen saturation; and measurement of height and weight. Inspection of the pulse for rate and rhythm, auscultation for murmurs, and examination for peripheral edema are done. Auscultation for abnormal breath sounds is important. Findings divergent from a patient’s baseline may indicate new or evolving disease.
|Airway Examination Component||Nonreassuring Findings|
|Length of upper incisors||Relatively long|
|Relationship of maxillary and mandibular incisors during normal jaw closure||Prominent “overbite” (maxillary incisors anterior to mandibular incisors)|
|Relationship of maxillary and mandibular incisors during voluntary protrusion of mandible (ability to prognath; upper lip bite test)||Inability to bring mandibular incisors anterior to (in front of) maxillary incisors; unable to bite the upper lip|
|Interincisor distance||Less than 3 cm|
|Visibility of uvula||Not visible when tongue is protruded with patient in sitting position (e.g., Mallampati class II)|
|Compliance of the mandibular/oral space||Highly arched or very narrow; radiation or surgical changes; stiff, indurated, occupied by mass or nonresilient|
|Thyromental distance||<3 fingerbreadths or <6 cm|
|Length of neck||Short|
|Thickness of neck||Thick|
|Range of motion of head and neck||Cannot touch tip of chin to chest or extend neck|
Investigations and Testing
Preoperative investigations are indicated for evaluating existing medical conditions or disease diagnosis when an abnormal result will have an impact on management of the patient or direct further testing ( Box 13.2 ). Performing a battery of screening or routine preoperative tests is seldom helpful, yet this unnecessary practice persists among some physicians based on “practice tradition, belief that other physicians want tests done, medicolegal worries, concerns about surgical delays or cancellation, and lack of awareness of evidence or guidelines.” Yet routine (not disease-indicated) preoperative testing rarely results in changes in management or benefit to the patient. Mandatory preoperative testing is not cost-conscious medical care, as testing is expensive and follow-up of results is time-consuming for limited clinical utility. Preoperative tests may be indicated based on disease-based criteria, as summarized in Table 13.4 , provided that abnormal results will have an impact on patient management. Also, testing for selected patients may be indicated based on the planned procedure or patient status ( Table 13.5 ).
Preoperative testing is recommended when an abnormal result is suspected based on clinical risk factors and this result will:
Establish a new diagnosis
Direct further preoperative testing or consultation
Inform preoperative medication use
Alter intraoperative monitoring or management
Influence choice of surgical approach or anesthetic technique
Influence decision to postpone or cancel surgery
Change postoperative disposition
Establish perioperative risk profile for communication with other physicians and patient
|Albumin||Anasarca; liver disease; malnutrition; malabsorption|
|CBC||Alcohol abuse; anemia; dyspnea; hepatic or renal disease; malignancy; malnutrition; personal history of bleeding; poor exercise tolerance; recent chemotherapy or radiation therapy|
|Creatinine||Renal disease; poorly controlled diabetes|
|Chest radiograph||Active, acute or chronic significant pulmonary symptoms such as cough or dyspnea; abnormal unexplained physical findings on chest examination; decompensated heart failure; malignancy within the thorax; radiation therapy b|
|Electrocardiogram||Alcohol abuse; active cardiac condition (new or worsening chest pain or dyspnea, palpitations, tachycardia, irregular rhythm, unexplained bradycardia, undiagnosed murmur, S 3 , decompensated heart failure); implanted cardioverter-defibrillator (ICD); obstructive sleep apnea; pacemaker; pulmonary hypertension; radiation therapy b ; severe obesity; syncope; use of amiodarone or digoxin|
|Electrolytes||Alcohol abuse; cardiovascular, hepatic, renal, or thyroid disease; diabetes; malnutrition; use of digoxin or diuretics|
|Glucose and/or HbA 1c||Diabetes; severe obesity; use of steroids|
|LFTs||Alcohol abuse; hepatic disease; recent hepatitis exposure; undiagnosed bleeding disorder|
|Platelet count||Alcohol abuse; hepatic disease; bleeding disorder (personal or family history); hematologic malignancy; recent chemotherapy or radiation therapy; thrombocytopenia|
|PT||Alcohol abuse; hepatic disease; malnutrition; bleeding disorder (personal or family history); use of warfarin|
|PTT||Bleeding disorder (personal or family history); undiagnosed hypercoagulable state; use of unfractionated heparin|
|TSH, T 3 , T 4||Goiter; thyroid disease; unexplained dyspnea, fatigue, palpitations, tachycardia|
|Urinalysis||Urinary tract infection (suspected)|
a These tests are only indicated to either establish a diagnosis, predict risk, or alter treatments in situations when it will impact perioperative management. This is less likely to be useful for low-risk procedures or in patients with chronic, stable conditions.
|Injection of contrast dye||Creatinine b|
|Potential for significant blood loss||Hemoglobin/hematocrit b|
|Likelihood of transfusion requirement||Type and screen|
|Possibility of pregnancy||Pregnancy test c|
|End-stage renal disease||Potassium level d|
|Diabetes||Glucose level determination on day of surgery d|
d No absolute level of either potassium or glucose has been determined to preclude surgery and anesthesia. The benefits of the procedure must be balanced against the risk of proceeding in a patient with abnormal results.
For most patients undergoing ambulatory or low-risk surgery, no preoperative testing is required (also see Chapter 37 ). For patients having ambulatory surgery with stable or nonsevere disease, there is no increase in adverse perioperative events or differences in outcome in those who have no preoperative tests. Additionally, for cataract surgery (also see Chapter 31 ), eliminating preoperative medical testing does not change outcomes and provides a significant cost savings. Investigations are indicated only when clinical evaluation of the patient reveals new or worsening symptoms that warrant testing even in the absence of an upcoming procedure. Eliciting a history of increased dyspnea on exertion, new-onset chest pain, or syncope is of greater benefit than routinely ordering electrocardiogram (ECG) or chest radiographs. In choosing preoperative investigations, both the disease-based indications and risk profile of the proposed surgical procedure are considered to ensure only indicated tests are ordered and unnecessary testing avoided.
Although commonly ordered, routine preoperative ECG does not add value to the care of surgical patients, particularly if ordered for those of advanced age (also see Chapter 35 ). Recommendations for age-based testing were derived from the frequent incidence of abnormalities found on ECGs of elderly patients. The specificity of an ECG abnormality in predicting postoperative cardiac adverse events is only 26%, and a normal ECG does not exclude cardiac disease. The ASA Practice Advisory for Preanesthesia Evaluation advises that age alone, in the absence of other clinical risk factors, may not be an indication for an ECG ( Box 13.3 ). ECG may be useful for suspected electrolyte abnormalities, active cardiac symptoms, suspected or known pulmonary hypertension, and arrhythmias (see Table 13.4 for more details). See Table 13.5 for recommendations from the American College of Cardiology/American Heart Association (ACC/AHA) regarding preoperative ECG.
Preoperative resting 12-lead electrocardiogram (ECG) is reasonable for patients with known coronary heart disease, significant arrhythmia, peripheral arterial disease, cerebrovascular disease, or other significant structural heart disease, except for those undergoing low-risk surgery
Preoperative resting 12-lead ECG may be considered for asymptomatic patients without known coronary heart disease, except for those undergoing low-risk surgery
Class III: No Benefit
Routine preoperative resting 12-lead ECG is not useful for asymptomatic patients undergoing low-risk surgical procedures
Routine pregnancy testing, particularly of adolescents, is a controversial issue. Some practices and facilities provide patients with information about the potential risks of anesthesia and surgery on pregnancy but allow them to decline testing. Other practices mandate that all females of childbearing age undergo a urine pregnancy test on the day of surgery (also see Chapter 34 ). The ASA Practice Advisory for Preoperative Evaluation states that “the literature is inadequate to inform patients or physicians on whether anesthesia causes harmful effects on early pregnancy” and recommends that pregnancy testing be offered to women if the test result will alter management. If proceeding with testing, rapid reliable results are obtained from urine screening and the test is best performed on the day of surgery rather than in advance unless the history suggests pregnancy.
Forming a comprehensive preoperative management plan for a patient with complex or undifferentiated comorbid conditions is often best accomplished in collaboration with consultant specialists. The purpose of consultation is to seek specific advice regarding the diagnosis or management of a condition in order to aid safe anesthetic planning, not for preoperative clearance, which is seldom helpful. A summary of the patient’s medical history and relevant diagnostic testing along with a specific question or goal for consultation improves utility. Close coordination and good communication among the preoperative anesthesiologist, surgeon, and consultant are vitally important for improving perioperative outcomes and avoiding adverse events.
Preoperative consultations may be sought for the following:
Diagnosis, evaluation, and improvement of a new or poorly controlled condition, or
Creation of a clinical risk profile that the patient and perioperative team use to make management decisions.
Anesthetic Implications of Common Comorbid Conditions
The severity and duration of hypertension (HTN) correlate with the degree of end-organ damage, morbidity, and mortality risks. Ischemic heart disease, heart failure, renal insufficiency, and cerebrovascular disease are common in hypertensive patients. Severe preinduction of anesthesia hypertension (systolic blood pressure [BP] > 200 mm Hg) is an independent risk factor for postoperative myocardial infarction (MI). Hypertensive patients are more likely to have arrhythmias, labile intraoperative BP, and myocardial ischemia. However, in patients with BP less than 180/110 mm Hg, there is little evidence that delaying surgery improves patient outcome. A true baseline BP is best established by taking several consecutive measurements in a low-stress environment, rather than immediately before induction in the operating room. Maintaining BP within 20% of the patient’s baseline is recommended for adequate organ perfusion. If significant end-organ damage is present, or intraoperative hypotensive techniques are planned, risk is minimized by excellent BP control through titration of medications in advance of surgery. This requires weeks of therapy for slow regression of vascular changes, as sudden decreases in BP may result in myocardial ischemia or cerebrovascular events.
Coronary Artery Disease
Coronary artery disease (CAD) varies from a mild, stable disease with little impact on perioperative outcome to a severe disease accounting for significant complications during anesthesia and surgery. The history and the physical examination, especially a determination of functional status, form the foundation for the cardiac assessment. The goal is to identify those patients likely to benefit from further medical therapy or rarely coronary revascularization before surgery. The ACC/AHA Guideline on Perioperative Cardiovascular Evaluation and Management of Patients Undergoing Noncardiac Surgery guides evaluation for CAD and appropriate testing to identify patients at risk of major adverse cardiovascular events (MACE).
Not all patients with suspected CAD require stress testing or angiography. In patients with stable symptoms (e.g., excluding patients with symptomatic heart failure, significant arrhythmias, severe valvular heart disease, new-onset angina, or an acute coronary syndrome), a moderate or greater functional capacity (≥4 METS) excludes the need for further cardiac investigation. Patients at low risk (<1%) of MACE based on combined clinical and surgical risk do not require additional testing. Fig. 13.2 details an algorithm for assessment for CAD. Risk of MACE is easily calculated through online tools established by the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP). These assessment tools were developed through data analysis from over 1.4 million patients at multiple institutions and incorporate patient factors and Current Procedural Terminology (CPT) codes to estimate risk of specific adverse outcomes. Alternatively, the Revised Cardiac Risk Index (RCRI) is a validated tool for assessing risk of MACE and incorporates six criteria: (1) presence of ischemic heart disease, (2) history of heart failure, (3) history of cerebrovascular disease, (4) diabetes mellitus treated with insulin, (5) creatinine level of 2 mg/dL or more, and (6) intrathoracic, intra-abdominal, or suprainguinal vascular procedures. The presence of 0, 1, 2, or 3 of these factors is associated with 0.5%, 1.3%, 4%, and 9% risk of MACE, respectively. Therefore, the presence of 2 or more RCRI criteria constitutes increased risk. Patients with increased risk of MACE (>1%) who cannot function at 4 METs of exertion may benefit from pharmacologic stress testing but only if the results will have an impact on perioperative care.
Contrary to what might be expected, coronary revascularization with percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) before noncardiac surgery does not benefit most patients with CAD. The only randomized prospective study of preoperative revascularization versus medical management failed to show a difference in outcome. Noncardiac surgery soon after revascularization is actually associated with higher rates of morbidity and mortality. Only those patients with unstable or severe disease who would undergo revascularization even in the absence of noncardiac surgery are likely to benefit from preoperative revascularization. The management of antiplatelet agents is complex in patients having preoperative PCI, especially with drug-eluting stents (DES), as they require months, if not a lifetime, of antiplatelet therapy to prevent catastrophic stent restenosis or acute thrombosis. The type of stent, DES or bare metal stent (BMS), must be identified and managed in collaboration with a cardiologist according to published recommendations, which were updated in 2016 by the ACC/AHA ( Box 13.4 ). Prescribed antiplatelet therapy should not be interrupted during the high-risk period without consultation with a cardiologist familiar with coronary stents and an in-depth discussion with the patient regarding the risks of terminating these drugs, especially for elective procedures. If at all possible, aspirin is continued throughout the perioperative period and the thienopyridine (typically clopidogrel) restarted as soon as possible. Evidence supports continuation of aspirin for high-risk patients (secondary prevention or after coronary stenting) during most procedures despite the small risk of bleeding complications. See Fig. 13.3 for details regarding antiplatelet agents in specific situations. In the event of stent thrombosis, PCI can be performed safely even in the immediate postoperative period, so high-risk patients are best managed in facilities with immediate access to interventional cardiology.
Premature discontinuation of thienopyridine (e.g., clopidogrel or ticlopidine) therapy has potentially catastrophic consequences. Health care providers should discuss strategies for periprocedural antiplatelet therapy with the patient’s cardiologist prior to discontinuation.
Elective procedures requiring discontinuation of thienopyridine therapy should be deferred until 1 month after placement of bare metal stents (BMS).
Elective procedures requiring discontinuation of thienopyridine therapy should be deferred until 6 months after placement of a drug-eluting stent (DES) if placed for stable coronary artery disease, or until 12 months after DES if placed for acute coronary syndrome (ACS) or in other high risk situations (e.g., multiple stents, small stents, recent in-stent stenosis).
Proceeding with urgent surgery within 3 to 6 months following DES placement may be considered if the risk with delayed surgery is greater than the stent thrombosis risk.
Patients with either a BMS or DES should continue aspirin if at all possible throughout the procedure. The recommended daily dose is 81 mg (range 75-100 mg) as the bleeding risk is lower and with comparable ischemic protection.
Further medical therapy with β-adrenergic blockade or statin therapy in patients with CAD may reduce MACE. See Box 13.5 for a summary of these recommendations.
β-Adrenergic blockers should be continued in patients undergoing surgery who have been on β-adrenergic blockers chronically.
It is reasonable for the management of β-adrenergic blockers after surgery to be guided by clinical circumstances, independent of when the agent was started.
In patients with intermediate- or high-risk myocardial ischemia noted in preoperative risk stratification tests, it may be reasonable to begin perioperative β-adrenergic blockers.
In patients with three or more Revised Cardiac Risk Index (RCRI) risk factors (e.g., diabetes mellitus, HF, CAD, renal insufficiency, cerebrovascular accident), it may be reasonable to begin β-adrenergic blockers before surgery.
In patients with a compelling long-term indication for β-adrenergic blocker therapy but no other RCRI risk factors, initiating β-adrenergic blockers in the perioperative setting as an approach is of uncertain benefit to reduce perioperative risk.
In patients in whom β-adrenergic blocker therapy is initiated, it may be reasonable to begin perioperative β-adrenergic blockers long enough in advance to assess safety and tolerability, preferably more than 1 day before surgery.
Class III: Harm
β-Adrenergic blocker therapy should not be started on the day of surgery.
Statins should be continued in patients currently taking statins and scheduled for noncardiac surgery.
Perioperative initiation of statin use is reasonable in patients undergoing vascular surgery.
Perioperative initiation of statins may be considered in patients with clinical indications according to guideline-directed medical therapy who are undergoing elevated-risk procedures.
CAD, Coronary artery disease; HF, heart failure.
Heart failure is a significant risk factor for perioperative adverse events. Patients with symptomatic heart failure are at a significantly increased risk of perioperative death than patients with CAD, especially those with left ventricular ejection fraction (LVEF) of less than 30%. Heart failure may be caused by systolic dysfunction (decreased ejection fraction from abnormal contractility), diastolic dysfunction (increased filling pressures with abnormal relaxation but normal contractility and ejection fraction), or a combination of the two. Symptoms and signs of heart failure include complaints of shortness of breath, fatigue, orthopnea, paroxysmal nocturnal dyspnea, rales/crackles, or third heart sound. Assessment of left ventricular function by echocardiography may be indicated in patients with a change in physical status ( Box 13.6 ). Diastolic dysfunction accounts for up to half of all cases of heart failure, but there is little science to guide care in the perioperative period. Advanced age and hypertension are associated with diastolic dysfunction. Because decompensated heart failure is a high-risk cardiac condition, elective surgery should be postponed until it is controlled.
It is reasonable for patients with dyspnea of unknown origin to undergo preoperative evaluation of left ventricular (LV) function.
It is reasonable for patients with heart failure with worsening dyspnea or other change in clinical status to undergo preoperative evaluation of LV function.
Reassessment of LV function in clinically stable patients with previously documented LV dysfunction may be considered if there has been no assessment within a year.
Class III: No benefit
Routine preoperative evaluation of LV function is not recommended.
Based on the New York Heart Association Functional Classification, patients with class IV failure (symptoms at rest) need evaluation by a cardiologist before undergoing anesthesia. Minor procedures with monitored anesthesia care (MAC) may proceed as long as the patient’s condition is stable.
Cardiac murmurs can be clinically unimportant or a sign of valvular abnormalities. Functional murmurs from turbulent flow across the aortic or pulmonary outflow tracts are found with high-output states (hyperthyroidism, pregnancy, anemia). Elderly patients and those with risk factors for CAD, a history of rheumatic fever, excessive intravascular volume, pulmonary disease, cardiomegaly, or an abnormal ECG and a murmur are more likely to have valvular disease. Diastolic murmurs are always pathologic and require evaluation. If significant valvular disease is suspected, evaluation with echocardiography is recommended if general or spinal anesthesia is planned. In patients found to have a severe valvular lesion (regurgitation or stenosis) for which intervention would be indicated, preoperative repair should be considered prior to nonurgent surgery ( Box 13.7 ).