A stepwise approach to cardiac risk assessment and stratification in patients undergoing noncardiac surgery is illustrated in Fig. 9-1. Assessment of exercise tolerance in the prediction of in-hospital perioperative risk is most helpful in patients who self-report worsening exercise-induced cardiopulmonary symptoms; those who may benefit from noninvasive or invasive cardiac testing regardless of a scheduled surgical procedure; and those with known coronary artery disease (CAD) or with multiple risk factors who are able to exercise. For predicting perioperative events, poor exercise tolerance has been defined as the inability to walk four blocks or climb two flights of stairs at a normal pace or to meet a metabolic equivalent (MET) level of 4 (e.g., carrying objects of 15–20 lb or playing golf or doubles tennis) because of the development of dyspnea, angina, or excessive fatigue (Table 9-2).
Composite algorithm for cardiac risk assessment and stratification in patients undergoing noncardiac surgery. Stepwise clinical evaluation:  emergency surgery;  prior coronary revascularization;  prior coronary evaluation;  clinical assessment;  RCRI;  risk modification strategies. Preventive medical therapy = beta blocker and statin therapy. RCRI, revised cardiac risk index. (Adapted from LA Fleisher et al: Circulation 116:1971, 2007, with permission.)
TABLE 9-2Assessment of Cardiac Risk by Functional Status
Previous studies have compared several cardiac risk indices. The American College of Surgeons’ National Surgical Quality Improvement Program prospective database has identified five predictors of perioperative myocardial infarction (MI) and cardiac arrest based on increasing age, American Society of Anesthesiologists class, type of surgery, dependent functional status, and abnormal serum creatinine level. However, given its accuracy and simplicity, the revised cardiac risk index (RCRI) (Table 9-3) is favored. The RCRI relies on the presence or absence of six identifiable predictive factors: high-risk surgery, ischemic heart disease, congestive heart failure, cerebrovascular disease, diabetes mellitus, and renal dysfunction. Each of these predictors is assigned one point. The risk of major cardiac events—defined as myocardial infarction, pulmonary edema, ventricular fibrillation or primary cardiac arrest, and complete heart block—can then be predicted. Based on the presence of none, one, two, three, or more of these clinical predictors, the rate of development of one of these four major cardiac events is estimated to be 0.4, 0.9, 7, and 11%, respectively (Fig. 9-2). An RCRI score of 0 signifies a 0.4–0.5% risk of cardiac events; RCRI 1, 0.9–1.3%; RCRI 2, 4–7%; and RCRI ≥3, 9–11%. The clinical utility of the RCRI is to identify patients with three or more predictors who are at very high risk (≥11%) for cardiac complications and who may benefit from further risk stratification with noninvasive cardiac testing or initiation of preoperative preventive medical management.
Risk stratification based on the RCRI: derivation and prospective validation of a simple index for prediction of cardiac risk in patients undergoing major noncardiac surgery. Cardiac events include myocardial infarction, pulmonary edema, ventricular fibrillation, cardiac asystole, and complete heart block. (Adapted from TH Lee et al: Circulation 100:1043, 1999.)
TABLE 9-3Clinical Markers Included in the Revised Cardiac Risk Index ||Download (.pdf) TABLE 9-3Clinical Markers Included in the Revised Cardiac Risk Index
|High-Risk Surgical Procedures |
|Vascular surgery |
|Major intraperitoneal or intrathoracic procedures |
|Ischemic Heart Disease |
|History of myocardial infarction |
|Current angina considered to be ischemic |
|Requirement for sublingual nitroglycerin |
|Positive exercise test |
|Pathological Q-waves on ECG |
|History of PCI and/or CABG with current angina considered to be ischemic |
|Congestive Heart Failure |
|Left ventricular failure by physical examination |
|History of paroxysmal nocturnal dyspnea |
|History of pulmonary edema |
|S3 gallop on cardiac auscultation |
|Bilateral rales on pulmonary auscultation |
|Pulmonary edema on chest x-ray |
|Cerebrovascular Disease |
|History of transient ischemic attack |
|History of cerebrovascular accident |
|Diabetes Mellitus |
|Treatment with insulin |
|Chronic Renal Insufficiency |
|Serum creatinine >2 mg/dL |
PREOPERATIVE NONINVASIVE CARDIAC TESTING FOR RISK STRATIFICATION
There is little evidence to support widespread application of preoperative noninvasive cardiac testing for all patients undergoing major surgery. Rather, a discriminative approach based on clinical risk categorization appears to be both clinically useful and cost-effective. There is potential benefit in identifying asymptomatic but high-risk patients, such as those with left main or left main–equivalent CAD or those with three-vessel CAD and poor left ventricular function, who may benefit from coronary revascularization (Chap. 293). However, evidence does not support aggressive attempts to identify patients at intermediate risk who have asymptomatic but advanced coronary artery disease, in whom coronary revascularization appears to offer little advantage over medical therapy.
An RCRI score ≥3 in patients with severe myocardial ischemia on stress testing should lead to consideration of coronary revascularization prior to noncardiac surgery. Noninvasive cardiac testing is most appropriate if it is anticipated that, in the event of a strongly positive test, a patient will meet guidelines for coronary angiography and coronary revascularization. Pharmacologic stress tests are more useful than exercise testing in patients with functional limitations. Dobutamine echocardiography and persantine, adenosine, or dobutamine nuclear perfusion testing (Chap. 270e) have excellent negative predictive values (near 100%) but poor positive predictive values (<20%) in the identification of patients at risk for perioperative MI or death. Thus, a negative study is reassuring, but a positive study is a relatively weak predictor of a “hard” perioperative cardiac event.
RISK MODIFICATION: PREVENTIVE STRATEGIES TO REDUCE CARDIAC RISK
Perioperative Coronary Revascularization
Currently, potential options for reducing perioperative cardiovascular risk include coronary artery revascularization and/or perioperative preventive medical therapies (Chap. 293). Prophylactic coronary revascularization with either coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) provides no short- or midterm survival benefit for patients without left main CAD or three-vessel CAD in the presence of poor left ventricular systolic function and is not recommended for patients with stable CAD before noncardiac surgery. Although PCI is associated with lower procedural risk than is CABG in the perioperative setting, the placement of a coronary artery stent soon before noncardiac surgery may increase the risk of bleeding during surgery if dual antiplatelet therapy (aspirin and thienopyridine) is administered; moreover, stent placement shortly before noncardiac surgery increases the perioperative risk of MI and cardiac death due to stent thrombosis if such therapy is withdrawn prematurely (Chap. 296e). It is recommended that, if possible, noncardiac surgery be delayed 30–45 days after placement of a bare metal coronary stent and for 365 days after a drug-eluting stent. For patients who must undergo noncardiac surgery early (>14 days) after PCI, balloon angioplasty without stent placement appears to be a reasonable alternative because dual antiplatelet therapy is not necessary in such patients. One recent clinical trial further suggests that after 6 months, bare metal and drug eluting stents may not pose a threat.
Perioperative preventive medical therapies
The goal of perioperative preventive medical therapies with β-adrenergic antagonists, HMG-CoA reductase inhibitors (statins), antiplatelet agents, and α2 agonists is to reduce perioperative adrenergic stimulation, ischemia, and inflammation, which are triggered during the perioperative period.
The use of perioperative beta blockade should be based on a thorough assessment of a patient’s perioperative clinical and surgery-specific cardiac risk (RCRI ≥2). For patients with or without mild to moderate reactive airway disease, the cardioselective beta blocker of choice should be used and titrated to maintain a target heart rate of 60–80 beats/min in the absence of hypotension in the operative and perioperative period. In RCRI ≥2 patients without a long-term indication for beta blockers, the medications can be administered IV as a preoperative medication on the day of surgery, with a targeted heart rate of 60–80 beats/min without hypotension, and continued for >7 days (preferably 30 days) postoperatively. Abrupt perioperative beta blocker withdrawal should be avoided unless necessary because of the associated increase in risk of MI and angina. IV preparations should be substituted for oral medications if patients are unable to swallow or absorb pills in the perioperative period. The results from the Perioperative Ischemic Evaluation (POISE) trial showed that, although cardiac death, nonfatal myocardial infarction, or cardiac arrest was reduced among patients who received metoprolol rather than placebo, there was an increased incidence of death and stroke among metoprolol recipients because of a high and rapidly loading dose of this drug. The POISE trial highlights the importance of a clear risk-and-benefit assessment, with careful initiation and titration to therapeutic efficacy of preoperative beta blockers in patients undergoing noncardiac surgery. A recent meta-analysis which included the POISE study further supports that excessive beta blocker dosing is, in fact, harmful.
The ACC/AHA guidelines recommend the following: (1) Beta blockers should be continued in patients with active cardiac conditions who are undergoing surgery and are receiving beta blockers. (2) Beta blockers titrated to heart rate and blood pressure are probably recommended for patients undergoing vascular surgery who are at high cardiac risk defined by CAD or cardiac ischemia on preoperative testing. (3) Beta blockers are reasonable for high-risk patients (RCRI ≥2) who undergo vascular surgery. (4) Beta blockers are reasonable for patients with known CAD or high risk (RCRI ≥2) who undergo intermediate-risk surgery. (5) Nondiscriminant administration of high-dose beta blockers without dose titration to effectiveness is contraindicated for patients who have never been treated with a beta blocker.
HMG-CoA reductase inhibitors (statins)
A number of prospective and retrospective studies support the perioperative prophylactic use of statins for reduction of cardiac complications in patients with established atherosclerosis. The ACC/AHA Guidelines support the protective efficacy of perioperative statins on cardiac complications in intermediate risk patients undergoing major noncardiac surgery. For patients undergoing noncardiac surgery and currently taking statins, statin therapy should be continued to reduce perioperative cardiac risk. Statins are reasonable for patients undergoing vascular surgery with or without clinical risk factors (RCRI ≥1).
Angiotensin-converting enzyme (ACE) inhibitors
Evidence supports the discontinuation of ACE inhibitors and angiotensin receptor blockers for 24 h prior to noncardiac surgery due to adverse circulatory effects after induction of anesthesia.
Evidence-based recommendations regarding perioperative use of aspirin and/or thienopyridine to reduce cardiac risk currently lack clarity. A substantial increase in perioperative bleeding and in the need for transfusion in patients receiving dual antiplatelet therapy has been observed. The discontinuation of thienopyridine and aspirin for 5–7 days prior to major surgery to minimize the risk of perioperative bleeding and transfusion must be balanced with the potential increased risk of an acute coronary syndrome and of subacute stent thrombosis in patients with recent coronary stent implantation. If clinicians elect to withhold antiplatelet agents prior to surgery, these agents should be restarted as soon as possible postoperatively.
Several prospective and retrospective meta-analyses of perioperative α2 agonists (clonidine and mivazerol) demonstrated a reduction of cardiac death rates among patients with known coronary artery disease who underwent noncardiac surgery. α2 agonists thus may be considered for perioperative control of hypertension in patients with known coronary artery disease or an RCRI score ≥2.
Evidence is lacking to support the use of calcium channel blockers as a prophylactic strategy to decrease perioperative risk in major noncardiac surgery.
Mortality risk is low with safe delivery of modern anesthesia, especially among low-risk patients undergoing low-risk surgery (Table 9-4). Inhaled anesthetics have predictable circulatory and respiratory effects: all decrease arterial pressure in a dose-dependent manner by reducing sympathetic tone and causing systemic vasodilation, myocardial depression, and decreased cardiac output. Inhaled anesthetics also cause respiratory depression, with diminished responses to both hypercapnia and hypoxemia, in a dose-dependent manner; in addition, these agents have a variable effect on heart rate. Prolonged residual neuromuscular blockade also increases the risk of postoperative pulmonary complications due to reduction in functional residual lung capacity, loss of diaphragmatic and intercostal muscle function, atelectasis, and arterial hypoxemia from ventilation-perfusion mismatch.
TABLE 9-4Gradation of Mortality Risk of Common Noncardiac Surgical Procedures ||Download (.pdf) TABLE 9-4Gradation of Mortality Risk of Common Noncardiac Surgical Procedures
|Higher ||• Emergent major operations, especially in the elderly |
| ||• Aortic and other noncarotid major vascular surgery (endovascular and nonendovascular) |
| ||• Prolonged surgery associated with large fluid shift and/or blood loss |
|Intermediate ||• Major thoracic surgery |
| ||• Major abdominal surgery |
| ||• Carotid endarterectomy surgery |
| ||• Head/neck surgery |
| ||• Orthopedic surgery |
| ||• Prostate surgery |
|Lower ||• Eye, skin, and superficial surgery |
| ||• Endoscopic procedures |
Several meta-analyses have shown that rates of pneumonia and respiratory failure are lower among patients receiving neuroaxial anesthesia (epidural or spinal) rather than general anesthesia (inhaled). However, there were no significant differences in cardiac events between the two approaches. Evidence from a meta-analysis of randomized controlled trials supports postoperative epidural analgesia for >24 h for the purpose of pain relief. However, the risk of epidural hematoma in the setting of systemic anticoagulation for venous thromboembolism prophylaxis (see below) and postoperative epidural catheterization must be considered.