Preoperative Evaluation: Assessment of Preoperative Risk




Preoperative Evaluation: Assessment of Preoperative Risk



Allen Ninh, David Bronheim



Introduction


The main purposes of a comprehensive preoperative evaluation before thoracic surgery are to assess the risk associated with anesthesia and surgery throughout the perioperative period; to identify, modify, and optimize the treatment of comorbidities that may affect perioperative outcome; and to provide the basis for the design of an appropriate, individually tailored, anesthetic plan. Additional advantages include patient education and consent, providing advanced knowledge to clinicians when preparation needs vary from the usual routine, and avoiding delay or cancellation on the day of surgery. All patients undergoing thoracic surgery, regardless of age, type of planned surgery, or extent of underlying disease, should be thoroughly evaluated for comorbid risk factors. These include but are not limited to the severity of their underlying pulmonary disease, the presence of cardiovascular disease, nutritional status, and any or all medical conditions whose modification could potentially improve outcome.


For the anesthesiologist, the preoperative evaluation should include the patient’s American Society of Anesthesiologists (ASA) classification, a primary anesthetic plan and potential adjunctive measures, considerations for special monitoring (i.e., arterial catheter, central line, pulmonary artery catheter, intraoperative esophageal echocardiography, neuromonitoring), and likelihood of requiring continued postoperative mechanical ventilation or additional critical care monitoring.1 The use of the Revised Cardiac Risk Index (RCRI) and a frailty index may further aid in risk stratification. This chapter will serve to highlight the preoperative assessment and independent risk factors of patients planned for thoracic surgery, and the tools used to evaluate surgical risk. The preoperative rehabilitation of these patients will be discussed in a following chapter (seeChapter 9).



Preoperative Medical Assessment


A focused medical history that includes past surgical and anesthetic experiences is the foundation of the preoperative medical assessment. Patients should be evaluated for the history of the present illness resulting in the need for surgery, significant past medical history, with an emphasis on all the past and current medical problems. Specific attention should be paid to exercise tolerance, surgical and anesthetic history, current medications, drug allergies, and social history, including tobacco, alcohol, and drug use. This must be followed by a thorough physical examination, which includes meticulous airway assessment in particular in anticipation of the need to provide lung separation. Relevant preoperative testing (i.e., electrocardiogram, echocardiography, myocardial stress testing, pulmonary function testing [PFT], exercise testing) should be based on the history and physical, and reviewed before surgery. An impression of the patient’s overall medical condition can then be summarized and be applied to various patient preoperative risk assessment tools to stratify a patient’s overall surgical risk, such as the ASA physical status classification system (Table 8.1), the RCRI, and in patients undergoing thoracic surgery, the ThRCRI.



Table 8.1


























American Society of Anesthesiology Physical Classification System
American Society of Anesthesiology Physical Status Classification Definition
ASA I Normal healthy patient
ASA II Patient with mild systemic disease
ASA III Patient with severe systematic disease
ASA IV Patient with severe systemic disease that is a constant threat to life
ASA V Moribund patient who is not expected to survive without the operation
ASA VI Declared brain-dead patient whose organs are being removed for donor purposes

Addition of “E” to the ASA physical classification denotes emergency surgery where delay in treatment would be a significant threat to life or body part. (From ASA Physical Status Classification System. | American Society of Anesthesiologists (ASA) at www.asahq.org/standards-and-guidelines/asa-physical-status-classification-system. With permission.)



Age(see Chapter 38)


Geriatric patients are a major growing segment of the surgical population.2 Age has repeatedly been shown to be an independent predictor of operative risk and postoperative complications, resulting in increased morbidity and mortality.3–5 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.6 Lung cancer is predominately a disease of the elderly. In the United States, up to two-thirds of new diagnoses are made in patients age 65 years and above, with a median age of 71 years.7 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.8 The reported incidence of an adverse cardiac event following major pulmonary surgery is approximately 10% to 15%.9 Because smoking both increases the incidences of cardiac disease by over 60% and causes lung cancer, this is not surprising.10 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).11,12 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).13,14 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%.13,15 Besides its use in stratifying risk, more recently, the ThRCRI has been used to select which thoracic surgery patients warrant formal cardiac evaluation preoperatively.



Table 8.2


























Revised Cardiac Risk Index
Risk Factors Points
High-risk surgery (intrathoracic, intraperitoneal, suprainguinal vascular) 1
History of ischemic heart disease 1
History of congestive heart failure 1
History of cerebrovascular disease 1
Insulin-dependent diabetes mellitus 1
Renal dysfunction (creatinine > 2 mg/dL) 1

(From Lee TH, Marcantonio ER, Mangione CM, Thomas EJ, Polanczyk CA, Cook EF, et al. Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery. Circulation. 1999;100:1043–1049. With permission.)



Table 8.3




















Revised Cardiac Risk Index Scoring System and Interpretation
RCRI Score Risk of Major Adverse Cardiac Event
0 3.9%
1 6.0%
2 10.1%
≥3 15%

(From Duceppe E, Parlow J, MacDonald P, Lyons K, McMullen M, Srinathan S, et al. Canadian Cardiovascular Society Guidelines on perioperative cardiac risk assessment and management for patients who undergo noncardiac surgery. Can J Cardiol. 2017;33:17–32. With permission.)



Table 8.4




















Thoracic-Revised Cardiac Risk Index
Risk Factors Points
Pneumonectomy 1.5
History of ischemic heart disease 1.5
History of cerebrovascular disease 1.5
Renal dysfunction (creatinine > 2 mg/dL) 1

(From Brunelli A, Varela G, Salati M, et al. Recalibration of the Revised Cardiac Risk Index in lung resection candidates. Ann Thorac Surg. 2010;90:199–203. With permission.)



Table 8.5

























Thoracic-Revised Cardiac Risk Index Risk Classes
Thoracic-Revised Cardiac Risk Index Score Risk Class Risk of Major Adverse Cardiac Event
0 A 1.5%
1–1.5 B 5.8%
2–2.5 C 19%
≥2.5 D 23%

(From Brunelli A, Varela G, Salati M, et al. Recalibration of the Revised Cardiac Risk Index in lung resection candidates. Ann Thorac Surg. 2010;90:199–203. With permission.)




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.7,8,16 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.”17 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.18 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.19 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.20



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.21 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.22



Obstructive Sleep Apnea


Obstructive sleep apnea (OSA) is characterized by episodes of hypopnea (slow shallow breathing) or apnea (cessation of breathing) during sleep as a direct result of collapsing upper airway tissues. This results in intermittent periods of hypoxia and hypercarbia. Factors that increase the likelihood of OSA include obesity (BMI > 35 kg/m2), large neck circumference (>40 cm), age (>50 years), and male gender. Symptoms include loud snoring, daytime somnolence, episodes of apnea observed by a partner, and hypertension.23 Patients with three or more of these features are at high risk for OSA as described by the STOP-BANG (Tired, Observed, Pressure, Body Mass Index, Age, Neck size, Gender) score for OSA. The STOP-BANG questionnaire for OSA consists of eight dichotomous (yes/no) items related to the clinical features of sleep apnea as described earlier and was specifically developed to meet the need for a reliable, concise, and easy-to-use screening tool described in Table 8.6.24 Patients with abnormal craniofacial features, such as an enlarged uvula, macroglossia, or mandibular micrognathia are also predisposed to pharyngeal airway collapse. The formal diagnosis of OSA is made by nocturnal polysomnography in a sleep laboratory, and patients are often prescribed a positive pressure airway device (bilevel positive airway pressure or continuous positive airway pressure) to be worn at home while asleep. The preoperative assessment visit is the ideal time to establish and record the usual settings on these devices, as their continuation postoperatively is usually indicated.



Table 8.6
































STOP-BANG Questionnaire for Obstructive Sleep Apnea Screening
Three or More Features = High-Risk for Obstructive Sleep Apnea  
Do you snore loudly? Yes / No
Do you often feel tired, fatigued, or sleepy during the daytime? Yes / No
Has anyone observed you stop breathing while asleep? Yes / No
Do you have (or are being treated for) high blood pressure? Yes / No
BMI > 35 kg/m2 Yes / No
Age ≥ 50 years Yes / No
Neck circumference > 40 cm Yes / No
Male gender Yes / No

(From Chung F, Yegneswaran B, Liao P, Chung SA, Vairavanathan S, Islam S, et al. STOP questionnaire: a tool to screen patients for obstructive sleep apnea. Anesthesiology. 2008;108:812–821; Chung F, Subramanyam R, Liao P, Sasaki E, Shapiro C, Sun Y. High STOP-BANG score indicates a high probability of obstructive sleep apnoea. Br J Anaesth. 2012;108:768–775. With permission.)

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