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The preoperative cardiac risk evaluation
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Earn Category I CME credit by reading this article and the associated article and successfully completing the post-test. Successful completion is defined as a cumulative score of at least 70% correct. This material has been reviewed and is approved for 1 hour of clinical Category I (Preapproved) CME credit by the AAPA. The term of approval is for 1 year from the publication date of May 2004. |
Learning objectives
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Of the more than 27 million people who undergo noncardiac surgery each year, 8 million have either known coronary artery disease or one or more risk factors for it, and approximately 1 million develop perioperative cardiac complications.1 Screening patients for cardiac risk factors before surgery is an important step in optimizing the surgical outcome, but preoperative stress testing for all surgical patients would be prohibitively expensive. Tailoring the preoperative evaluation to the patient is therefore essential.
Although PAs often perform preoperative cardiac risk assessments for patients undergoing elective noncardiac surgery, few PA programs include preoperative evaluation skills in the curriculum. In addition, although past studies on preoperative risk stratification have focused on patients undergoing vascular surgery, most surgical procedures performed today are noncardiac. Recognizing a need for current guidelines that take into account the range of noncardiac surgeries and the increasingly elderly patients who undergo many of them, in 2002 the American College of Cardiology/American Heart Association (ACC/AHA) Task Force updated its 1996 guidelines for perioperative cardiovascular evaluation for noncardiac surgery.2 The guidelines are the result of searches of various databases of literature published between 1995 and 2000, journal reviews, and expert opinions by the task force committee members, who represent multiple disciplines in cardiovascular care.
The most common major cardiovascular complications from noncardiac surgery are acute myocardial infarction (MI), heart failure, angina, and arrhythmia.3,4
The hemodynamic and adrenergic stresses placed on the cardiovascular system from anesthesia and surgery are well known.3 Both IV and inhaled anesthesia decrease systemic arterial BP by depressing sympathetic tone and myocardial contractility. Arterial and venous dilatation may occur, and systemic BP may drop by as much as 20% to 30% in normotensive patients and by even more in those with hypertension. BP drops that last longer than 10 minutes may reduce myocardial blood flow enough to precipitate myocardial ischemia in patients with underlying cardiac disease. Some anesthetic agents, such as ketamine (Ketalar), stimulate the sympathetic nervous system; although BP is maintained, oxygen demand on the myocardium is increased. Tachyarrhythmias and bradyarrhythmias may occur as a result of vasodilation, reduced ventricular preload (from anesthesia or from positive-pressure ventilation), or stimulation by circulating catecholamines; these arrhythmias may be poorly tolerated in patients with underlying cardiac disease.
Anesthesia delivered by spinal and epidural routes reduces sympathetic tone, resulting in peripheral arterial and venous dilation. There appears to be no difference in perioperative cardiovascular risk among general, spinal, and epidural routes of administration.5 Local and regional forms of anesthesia do not have significant cardiovascular effects, unless systemic absorption occurs, which is uncommon, but the effects of inadequate analgesia on the cardiovascular system may be significant. While the PA may find it helpful to know which type of anesthesia is planned, the choice of type is the anesthesiologist's.
The primary goal of preoperative risk assessment is to minimize morbidity and mortality resulting from surgery. By reducing perioperative complications and avoiding unnecessary preoperative testing (stress testing, blood work, pulmonary testing, etc.), a careful preoperative evaluation has the additional benefit of minimizing health care costs. In addition, performing the preoperative evaluation allows the provider to participate in the patient's perioperative management.
Frequently, the referring surgeon asks the primary care clinician to "clear" a patient for surgery. The term clear should be avoided, as it implies that the planned procedure carries no risk, when, in fact, anesthesia and surgery pose a potential risk for all patients. The provider's goals, therefore, are to evaluate the patient's current medical condition, to make recommendations regarding the management of medical conditions during the perioperative period, and to provide a clinical risk profile that will assist the patient and the surgical team in weighing the risks and benefits of the surgery.
The evaluation described in the ACC/AHA guidelines encompasses clinical risk predictors, prior coronary evaluation or intervention, functional capacity, and surgery-specific risk.
The evaluation begins with a thorough history and physical examination (see Table 1). A listing of the patient's known medical conditions may assist the surgical and anesthesia teams in making management decisions. Signs or symptoms that suggest cardiac disease should be elicited, and they should be documented along with the severity and status of known cardiac disease. Documentation should be provided on the following: prior surgeries and perioperative complications; the presence of existing cardiovascular disease or previous MI; previous cardiac testing or interventions; type of surgery planned; type of anesthesia planned; exercise tolerance; and tobacco, alcohol, and drug use. All medications should be listed, including OTC medications and dietary or herbal supplements. In addition, a complete physical exam that emphasizes cardiopulmonary function should be performed.
TABLE 1
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History |
The ACC/AHA guidelines categorize clinical predictors for increased perioperative cardiovascular risk as major, intermediate, and minor (see Table 2). Major risk predictors generally require immediate attention and management, which may necessitate delay or cancellation of the surgical procedure. Major risk predictors include acute MI or MI within 1 month before planned surgery, unstable or severe angina, decompensated heart failure, significant arrhythmias, and severe valvular disease.
TABLE 2
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| Major Decompensated heart failure Severe valvular disease Significant arrhythmias High-grade atrioventricular block Supraventricular arrhythmias with uncontrolled ventricular rate Symptomatic ventricular arrhythmias in the presence of underlying cardiac disease Unstable coronary syndromes MI within 30 d Unstable or severe angina Intermediate Compensated or prior heart failure Diabetes mellitus (particularly insulin-dependent) Mild angina MI >1 mo previously or abnormal Q waves Renal insufficiency Minor Abnormal ECG (left ventricular hypertrophy, left bundle branch block, ST-T abnormalities) Advanced age History of stroke Low functional capacity Abnormal heart rhythm Uncontrolled hypertension |
| MI = myocardial infarction. |
| Adapted from Eagle et al.2 Copyright 2002, with permission from the American College of Cardiology Foundation. |
Intermediate risk predictors are those that are proven to increase the risk of perioperative cardiac complications and that may justify further assessment of the patient's cardiac status. Intermediate risk predictors include mild angina, MI more than 1 month prior to surgery or pathologic Q waves, compensated heart failure, diabetes, and renal insufficiency.
Minor risk predictors include age older than 70 years, abnormal findings on ECG, abnormal heart rhythm (anything other than sinus rhythm), poor functional capacity, and history of stroke or uncontrolled hypertension. Although considered markers of cardiovascular disease, minor risk predictors have not been proven to independently increase perioperative risk.
Patients who have undergone either a cardiac stress test within 2 years or a coronary artery bypass graft (CABG) within 5 years and who have no recurrent symptoms or change in their clinical status may proceed to surgery without further cardiac testing. Similarly, angioplasty appears to be protective for at least 2 years, assuming there has been no recurrence of symptoms or change in clinical status.
Poor exercise tolerance is associated with a significantly increased risk for perioperative cardiac complications.6,7 Exercise tolerance is expressed in metabolic equivalent tasks (METs). For example, activities such as eating, dressing, and washing dishes range from 1 to 4 METs; climbing stairs, walking on level ground at 4 mph, running a short distance, and scrubbing a floor range from 4 to 10 METs. More strenuous activities and sports can exceed 10 METs. Patients who are unable to perform activities that require 4 METs have a significantly increased risk for perioperative cardiac complications (see Table 3). The Duke Activity Status Index and other activity scales can be used to assess functional capacity.7-9 Each scale measures exercise tolerance through a set of questions tied to typical activities, which are weighted according to the known metabolic cost of each activity.
TABLE 3
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| Performing calisthenics Doing heavy housework: scrubbing floors, lifting or moving heavy furniture Gardening (no lifting) Golfing (without cart), bowling, dancing, playing doubles tennis Swimming Walking 4 miles per hour on level ground Playing badminton Chopping wood Climbing one flight of stairs or walking up a hill Cycling (moderate speed) Jogging (10-min mile) Doing karate or judo Skipping rope Skating (ice, roller) Skiing Surfing |
| METs = metabolic equivalent tasks. |
| Data from Eagle et al2 and Hlatky et al.8 |
The two factors that determine the specific risk of each surgical procedure are the magnitude of the procedure and the degree of hemodynamic stress involved. Although the duration of surgery appears to correlate with increased cardiovascular risk, that may be because high-risk procedures are generally of long duration. Cardiac complications are two to five times more likely to occur in emergent surgery than in elective procedures, particularly in elderly patients. This may be explained, in part, by the presence of uncontrolled or undiagnosed medical conditions. Major vascular procedures and procedures with prolonged duration, large fluid shifts, or blood loss have the highest risk. These high-risk procedures are associated with a 5% or greater risk of cardiac complications.
Carotid endarterectomy; prostate surgery; and abdominal, thoracic, head, neck, and orthopedic surgeries have an intermediate risk of cardiac complications, generally 1% to 5%. Surgeries that have less than a 1% risk of cardiac complications include breast, cataract, and superficial surgeries and endoscopic procedures.
Generally, tests should be ordered only when the history or physical examination suggests specific disease.2 For example, if there is reason to suspect renal disease (because the patient is aged 60 years or older and has hypertension, ischemic heart disease, or heart failure), a blood test to evaluate renal function should be obtained, since the type or dosing of perioperative medications may require adjustment. A recent glycosylated hemoglobin (A1C) level is helpful for recommending perioperative management of patients who have diabetes. A hemoglobin level is useful for patients who have a history of ischemic heart disease or renal disease or whose surgery may cause significant blood loss. Coagulation studies should be obtained in patients with known bleeding disorders or hepatic disease.
A resting 12-lead ECG has not been found to be a reliable predictor of increased perioperative risk in patients undergoing low-risk procedures, leading the ACC/AHA guidelines to recommend against performing a routine ECG in an asymptomatic patient undergoing a low-risk procedure. A resting ECG may be useful in patients undergoing intermediate- and high-risk procedures. Although resting left ventricular function is not recommended as a routine test in patients with no history of heart failure, it may be indicated in patients with known heart failure or in those with a history of dyspnea of unknown etiology.
The most common perioperative pulmonary complications are pneumonia, bronchitis, and atelectasis. Pulmonary function testing has not been shown to be predictive of postoperative pulmonary complications, and few data support pulmonary function testing during the preoperative evaluation, except in patients undergoing lung resection surgery.10,11
The need for further preoperative cardiac testing is determined by a careful assessment and integration of clinical risk predictors, prior coronary evaluation or treatment, functional capacity, and surgery-specific risk. Cardiac stress testing is indicated if at least two of the following conditions are met: the patient has intermediate clinical predictors, has poor functional capacity (inability to perform activities that require at least 4 METs), or is undergoing a high-risk procedure. In addition, cardiac stress testing can provide an objective evaluation of exercise capacity when a subjective assessment by history is unreliable or when the patient is unable to exercise because of noncardiac problems (such as osteoarthritis).
The exercise treadmill test is the most cost-effective and least invasive cardiac stress test. Patients unable to exercise may undergo pharmacologic stress testing. The guidelines recommend that preoperative cardiac testing be limited to those situations where the results would affect patient treatment and outcomes. Cardiac interventions such as angioplasty or CABG are recommended only for patients who would require them irrespective of the planned noncardiac surgery. The algorithm from the ACC/AHA guidelines (see "Stepwise approach to preoperative cardiac assessment") can help PAs to determine when further cardiac testing is indicated.
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Click here to view full-size graphic
A preoperative risk evaluation requested by a referring surgeon should be performed promptly and coded as a consultation. The provider's recommendations for perioperative management of chronic medical conditions should be clear, concise, specific, and preferably limited to five items and should emphasize therapeutic rather than diagnostic issues.
The patient's chart should document that a copy of the preoperative risk evaluation was sent directly or communicated verbally to the referring surgeon and that the results were communicated to the patient. While the primary care provider may communicate the cardiac risk profile to the patient, the decision as to whether the patient should undergo the planned procedure is best left to the patient and the surgeon.
Improved treatments and outcomes for cardiac disease have resulted in longer lives for many patients, who are now living into their 80s and beyond. The primary care PA's ability to perform preoperative evaluations is critical to decreasing the risk of morbidity and mortality from perioperative cardiac complications. The ACC/AHA algorithm gives the provider a stepwise, evidence-based approach that is easy to apply in the primary care setting.
REFERENCES
1. Mangano DT, Goldman L. Preoperative assessment of patients with known or suspected coronary disease. N Engl J Med. 1995;333:1750-1756.
2. Eagle KA, Berger PB, Calkins H, et al. ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery: a report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). J Amer Coll Cardiol. 2002;39:542-553.
3. Goldman L, Adler J. General anesthesia and noncardiac surgery in patients with heart disease. In: Braunwald E, Zipes DP, Libby P, eds. Heart Disease: A Textbook of Cardiovascular Medicine. 6th ed. Philadelphia, Pa: WB Saunders; 2001:2084-2096.
4. Auerbach AD, Goldman L. Beta-blockers and reduction of cardiac events in non-cardiac surgery. JAMA. 2002;287:1435-1444.
5. Go AS, Browner WS. Cardiac outcomes after regional or general anesthesia. Do we have the answer? Anesthesiology. January 1996;84:1,2.
6. Reilly DF, McNeely MJ, Doerner D, et al. Self-reported exercise tolerance and the risk of serious perioperative complications. Arch Intern Med. 1999;159:2185-2192.
7. Older P, Hall A, Hader R. Cardiopulmonary exercise testing as a screening test for perioperative management of major surgery in the elderly. Chest. August 1999;116:355-362.
8. Hlatky MA, Boineau RE, Higginbotham MB, et al. A brief self-administered questionnaire to determine functional capacity (the Duke Activity Status Index). Am J Cardiol. 1989;64:651-654.
9. Fletcher GF, Balady G, Froelicher VF, et al. Exercise standards: A statement for healthcare professionals from the American Heart Association Writing Group. Circulation. 1995;91:580-615.
10. American College of Physicians. Preoperative pulmonary function testing. Ann Intern Med. 1990;112:793-794.
11. Lawrence VA, Dhanda R, Hilsenbeck SG, Page CP. Risk of pulmonary complications after elective abdominal surgery. Chest. 1996;110:744-750.
Tina Kaufman. Preop cardiac risk evaluation in primary care--putting guidelines into practice. JAAPA May 2004;17:25-34.
Copyright © 2004, Advanstar Medical Economics Healthcare Communications at Montvale, NJ 07645-1742. All rights reserved.
