Preoperative Evaluation: Assessment of Preoperative Risk

Age(see Chapter 38 )

Geriatric patients are a major growing segment of the surgical population. Age has repeatedly been shown to be an independent predictor of operative risk and postoperative complications, resulting in increased morbidity and mortality. In addition, age is one of the more prominent risk factors for the development of atrial fibrillation in the postoperative period. Pulmonary complications following surgery increase after the fifth decade of life. Lung cancer is predominately a disease of the elderly. In the United States, up to two-thirds of new diagnoses are made in patientsage 65 years and above, with a median age of 71 years. Aging patients with pulmonary malignancies are disproportionately at increased risk because of inherent unmodifiable risk factors. Although there is no upper age limit that precludes a patient from surgery, physiologic age is likely a better predictor of outcome than chronologic age. Elderly patients with adequate cardiopulmonary reserve and without additional significant risk factors may still have an acceptable level of risk for surgery.

Cardiovascular Disease

Cardiac complications are the second most common cause of perioperative morbidity and mortality after pulmonary morbidity in patients undergoing thoracic surgery. The reported incidence of an adverse cardiac event following major pulmonary surgery is approximately 10% to 15%. Because smoking both increases the incidences of cardiac disease by over 60% and causes lung cancer, this is not surprising. Because intrathoracic surgery itself is associated with increased risk of cardiac complications, an electrocardiogram before surgery is appropriate even in otherwise asymptomatic individuals, and is recommended in all patients above the age of 65 years. Anginal symptoms, suspected valvular disease, arrhythmias, shortness of breath, or a history of cardiac disease warrant an appropriate evaluation and noninvasive cardiac testing.

The RCRI predicts major cardiac complications, such as cardiac arrest, complete heart block, acute myocardial infarction, pulmonary edema, and cardiac-related death following noncardiac surgery. It is useful in assessing patients for the following preoperative risk factors: ischemic heart disease, congestive heart failure, cerebrovascular disease, insulin dependence, and renal dysfunction, as well as the nature of the surgery ( Tables 8.2 and 8.3 ). ^, It remains widely used to assess patients for thoracic surgery. Originally validated in a cohort with a limited number of thoracic surgery patients, the RCRI was subsequently demonstrated as able to stratify risk in this population. However, the ThRCRI, a modified and validated version of this tool, which uses only a four-point system that includes the presence of cerebrovascular disease, coronary ischemia, renal disease, and a pneumonectomy as the planned procedure, more effectively stratifies the cardiac risks of thoracic surgery ( Tables 8.4 and 8.5 ). ^, Patients planned for lung resection with a ThRCRI score of 2 to 2.5 (class C risk) or more than 2.5 (class D risk) are at significantly higher risk with cardiac complications rates up to 23%. ^, Besides its use in stratifying risk, more recently, the ThRCRI has been used to select which thoracic surgery patients warrant formal cardiac evaluation preoperatively.

Assessment for Risk of Atrial Fibrillation(see Chapter 22 )

Postoperative atrial fibrillation (POAF) is a very frequent complication following thoracic surgery, occurring most commonly 2 to 4 days postoperatively. ^{, ,} In the 2014 American Association for Thoracic Surgery Guidelines for the Prevention and Management of Perioperative Atrial Fibrillation and Flutter for Thoracic Surgical Procedures, the take home message was that “POAF is triggered by: age, ischemia, atrial dilation, volume overload, and history of heart failure. Standard rate and rhythm control approaches were listed to treat POAF. Hemodynamically unstable patients may require electrical cardioversion. Prevention of POAF included drugs, such as amiodarone, diltiazem, statins (for antiinflammatory actions), and magnesium supplementation. Digoxin prophylaxis is not helpful.” More recently, an improved brain natriuretic peptide-based prediction model, which incorporates the extent of surgery, a baseline elevation of brain natriuretic peptide, age, body mass index (BMI), and a history of atrial fibrillation to predict POAF has become available. Either the brain natriuretic peptide or something similar may soon become a standard part of preoperative assessment for thoracic surgery to more clearly guide decisions on active prevention of POAF with medications, such as amiodarone, diltiazem, and beta blockers.

Asthma

Severe asthma is predictive of an increase in postoperative pulmonary complications during the perioperative period, although no recent study specifically assesses its relative risk in thoracic surgery. Thus a history that documents the frequency of exacerbation and bronchodilator administration, the need for inhaled or oral steroids, the number and frequency of emergency room visits, hospitalizations, and the need for intensive care and endotracheal intubation during exacerbations will help categorize the severity of the asthmatic’s disease process and the likelihood of perioperative exacerbation and probability of postoperative pulmonary complications. Active wheezing at the time of preoperative evaluation in a patient whose symptoms are typically reversible, is a relative indication for deferring surgery because even an excellent acute response to bronchodilator therapy does not also reverse the inflammatory changes in the bronchial tree, which may persist for weeks. The risk of exacerbation of asthma during the perioperative period can be reduced by continuing an effective regimen of inhaled bronchodilators and steroids leading up to the day of surgery and continued throughout the perioperative period.

Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is the most common comorbid condition in the thoracic surgical population, and is the third leading cause of death in the United States. It is estimated that 3.8 million adults in the United States are currently diagnosed with COPD, and it is widespread in both the general and smoking population. It is associated with abnormal and permanent enlargement of the airspaces in the lung, with destruction of the alveolar walls resulting in loss of gas exchange surface area, air-trapping, and hyperinflation of the airspaces distal to the terminal bronchioles. This leads to compromised lung mechanics, hypercapnia, dyspnea, and hypoxia that often require oxygen therapy. It is a progressive and debilitating disease, which in its final stages, greatly impacts the patient’s quality of life and increases healthcare utilization.

COPD is an overarching term that refers to two major lung disease states: (1) chronic bronchitis, and (2) emphysema, both of which are characterized by mucus hypersecretion and airway inflammation. COPD is most commonly caused by cigarette smoking, and more rarely by airborne pollutants or irritants. Although these two conditions may display similar symptoms, such as dyspnea, cough, increased sputum production, and rhonchorous breath sounds, they are distinctly different from one another. Chronic bronchitis results from the repeated inflammation of the airways and narrowing of the bronchial tree resulting in difficulty moving air. Emphysema primarily affects the alveolar sacs, where chronic inflammation leads to the alveolar membrane breakdown, impaired gas exchange, and increased air trapping. Unlike asthma, these conditions are not fully reversible by bronchodilators, and lung function does not return to normal between exacerbations because the alveolar destruction is permanent. In addition to patient history and physical examination findings, the severity of COPD can be categorized on the basis of the results of PFT predicted values by using the criteria established in the Global Initiative for Obstructive Lung Disease. COPD is a major patient-related risk factor that is predictive of postoperative pulmonary complications, including postoperative pneumonia, prolonged mechanical ventilation, and respiratory failure requiring reintubation. Severe COPD may also result in right ventricular dysfunction or cor pulmonale, complicating intraoperative management. Nonpulmonary adverse outcomes, such as myocardial infarction or cardiac arrest are also more likely in patients with COPD.