Preoperative Evaluation of Patients Undergoing Thoracic Surgery

Physiologic Effects of Thoracic Surgery

Surgical procedures and the anesthesia administered to allow such procedures have significant effects on respiratory physiology that contribute to the development of postoperative pulmonary complications. Given that the incidence of pulmonary complications is directly related to the proximity of the planned procedure to the diaphragm, patients undergoing pulmonary, esophageal, or other thoracic surgical procedures fall into the category of patients at high risk for postoperative respiratory complication.

The intraoperative use of inhaled volatile agents can affect gas exchange by altering diaphragmatic and chest wall function. These changes occur without corresponding alterations in blood flow, which creates low ventilation-perfusion areas, resulting in widening of the alveolar-arterial oxygen gradient.

In the postoperative period, a variety of factors contribute to the development of complications; these include an alteration in breathing pattern to one of rapid shallow breaths with the absence of periodic deep breaths (sighs) and abnormal diaphragmatic function. These complications result both from pain and from diaphragmatic dysfunction resulting from splanchnic efferent neural impulses arising from the manipulation of abdominal contents. This has the effect of reducing the functional residual capacity (FRC)—the resting volume of the respiratory system. The FRC declines by an average of 35% after thoracotomy and lung resection and by approximately 30% after upper abdominal operations. If the FRC declines sufficiently to approach closing volume, the volume at which small airway closure begins to occur, patients develop atelectasis and are predisposed to infectious complications. Closing volume is elevated in patients with underlying lung disease.

The alterations in lung volumes that occur result in a reduction in both the inspiratory capacity (the maximal inhalation volume attained starting from a given lung volume) and the expiratory reserve volume (the maximal exhalation volume from a given lung volume), contribute to a decline in the effectiveness of cough, and result in increased difficulty in clearing of pulmonary secretions.

Patient Population Undergoing Thoracic Surgery

Many patients undergoing a noncardiac thoracic surgical procedure do so because of known or suspected lung or esophageal cancer. These diseases share the common risk factor of a significant and prolonged exposure to cigarette smoking. The combination of age and prolonged cigarette smoking results in a patient population with a significant incidence of comorbid factors in addition to the primary diagnosis. Several reports use the Charlson Comorbidity Index as an indicator of comorbid conditions and predictor of postoperative complications. This index generates a score based on the presence of comorbid conditions; it has been demonstrated to stratify risk of postoperative complications in thoracic surgery patients.

In one study, the mean age of patients undergoing esophagectomy was 58.1 years; 45% of patients were older than 60 years. In another Japanese study, the median age was 62.3 years; 88% were male. In a study comparing transhiatal esophagectomy with transthoracic esophagectomy, the mean ages of the patients were 69 years and 64 years, with patients up to the age of 79 years being included in the study. In a review, 28% to 32% of patients undergoing esophagectomy in the United States were older than 75 years, and 40% had a Charlson score above 3.

Similarly, patients with lung cancer tend to be older and have comorbid conditions. In a series of 344 patients, 36% were older than 70 years and 95% had a significant smoking history. A review of Medicare patients undergoing thoracic surgery in the United States showed that of patients undergoing lobectomy, 32% to 35% were older than 75 years (44% women), and 32% had a Charlson score greater than 3. In the same series, 21% to 26% of patients undergoing pneumonectomy were older than 75 years (28% women), and 56% had a Charlson score above 3.

A significant source of comorbidity in the population of patients with lung cancer is chronic obstructive pulmonary disease (COPD). The diagnosis of COPD is an independent risk factor, controlling for cigarette smoke exposure, for the development of lung cancer.

Thus, the patient population presenting for major thoracic surgical procedures tends to be older, has a high incidence of comorbid conditions, and contains a disproportionate number of patients with obstructive lung disease. The combination of these factors, plus the magnitude of the surgical procedures, presents a challenge to the clinicians evaluating such patients. The potential for perioperative morbidity and mortality is substantial, but at the same time, the lack of effective alternative therapy for the patient's malignant disease means that the consequence of not being a surgical candidate is almost certain mortality. This quandary has led Gass and Olsen to ask: What is an acceptable surgical mortality in a disease with 100% mortality?

Common Complications after Thoracic Surgery

These are discussed in more detail elsewhere in this book (see Chapter 4 ). In general, the most frequent complications after major thoracic procedures fall into the categories of respiratory and cardiovascular. Although the exact frequency varies by series, pneumonia, atelectasis, arrhythmias (particularly atrial fibrillation), and congestive heart failure are the most common. Myocardial infarction, prolonged air leak, empyema, and bronchopleural fistula also occur at a significant frequency. It follows, therefore, that particular attention to pulmonary and cardiac reserve and risk factors should be a major component of the preoperative evaluation.

Effect of Surgical Approach on Perioperative Complications

Two developments in thoracic surgical practice have had particular impact on the assessment of marginal candidates for thoracic surgical procedures. The first is the rise in the prevalence of “minimally invasive” approaches, including video-assisted thoracoscopic approaches, for both pulmonary parenchymal resections and esophageal surgery. The reported data suggest a lower rate of pulmonary complications after the use of thoracoscopic resection as compared with conventional thoracotomy, likely because of reduction in pain and improved chest wall mechanics. The second is the reemergence of lung volume reduction surgery and the recognition that a subset of patients with COPD have nonhomogeneous distribution of emphysema with an upper-lobe predominance, which is also the most common site of non-small-cell lung cancer, and that upper lobe resection in such individuals produces less deleterious impact on measured pulmonary function and in some instances can result in improvement in measured lung function after resection.

Goals of the Preoperative Evaluation

The clinicians evaluating a patient for a major thoracic surgical procedure have several goals for the evaluation process. The most obvious of these goals is to provide all parties with an assessment of the risks, both short and long term, of morbidity and mortality from the procedure in a given patient and simultaneously to identify factors that can be addressed to reduce the possibility of adverse events. Less obvious is that the comprehensive evaluation of a patient as part of the preoperative assessment allows the identification of risk factors and health issues independent of the planned surgery and facilitates the institution of interventions indicated regardless of plans for surgery.

History and Physical Examination

Although the field of thoracic surgery has been dramatically altered by the development of new technologies in both imaging and therapeutics, the history and physical examination remain the most important components of the preoperative evaluation. There is no substitute for a careful history and examination by an experienced clinician.