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Can we predict pulmonary complications after thoracic surgery?

Lung cancer is the primary cause of cancer-related death in the United States and many other countries, with 5-year survival rates of approximately 15%. Despite the grim overall prognosis, there are better outcomes among patients with stage I or II non–small cell lung cancer who undergo a complete anatomic resection. Unfortunately, approximately 90% of patients with lung cancer are smokers, and a substantial percentage will have chronic obstructive pulmonary disease. Moreover, many of these patients will also have significant cardiovascular disease and other medical conditions that increase overall perioperative risk. Despite improvements in pre-, intra-, and postoperative care, the mortality and morbidity associated with pulmonary resection remain high. The American College of Chest Physicians (ACCP) guidelines recommend surgical mortality risk to be 4% for lobectomy and 9% for a pneumonectomy; the British Thoracic Society guidelines offer similar expectations. A review of a large European lung cancer registry revealed 30-day postoperative mortality to be 3.1% after lung resection. Among the elderly (age 70 years), mortality rates are reported to be even higher: 14% for pneumonectomy and 4% to 7% for lobectomy. These rates, however, seem to have more to do with comorbid conditions than age alone as a risk factor. The risk of pulmonary complications, including pneumonia, acute respiratory distress syndrome, prolonged ventilator support, atelectasis requiring bronchoscopy, and reintubation, is also a serious concern. A recent review of almost 7900 patients in The Society of Thoracic Surgeons’ General Thoracic Surgery Database revealed an overall pulmonary complication rate of 13%. The challenge confronting the multidisciplinary teams of pulmonologists, oncologists, thoracic surgeons, anesthesiologists, and critical care intensivists caring for these patients is to identify those patients at greatest risk for perioperative cardiopulmonary complications. Fortunately, there are several guidelines for preoperative evaluation, each with a helpful algorithm describing a step-wise investigation of a patient’s suitability for lung resection. The algorithms usually begin with a thorough cardiac assessment, followed by basic spirometry. Depending on these initial results, the guidelines make a variety of recommendations with regard to additional testing of the diffusing capacity of the lung for carbon monoxide (DLCO) and different methods of cardiopulmonary exercise testing. Yet, despite the presence of these guidelines, questions remain about the strength of the evidence backing them. Without question, there is still controversy regarding the specific steps in the proposed algorithms. What matters most in predicting bad outcomes: spirometry or DLCO, or a combination of the two? Should patients be stratified according to spirometric results reported as absolute volumes or percent predicted? What is the best method of determining predicted postoperative lung function: perfusion or anatomic methods? Do the guidelines place too little emphasis on exercise testing? Should we encourage more use of cardiopulmonary exercise testing, as some authors have suggested? A recent review expressed concern that there was not better “harmonization” among the guidelines. Perhaps we can attribute the lack of consensus as an indication that we need further examination of the specific tests and their ability to predict postoperative complications. To that end, in this issue of Anesthesia & Analgesia, Amar et al. investigated whether predicted postoperative DLCO (DLCOppo) or forced expired volume in 1 second (FEV1) is better able to predict pulmonary complications after thoracic surgery. Their study was a retrospective review of 956 patients from a prospective database undergoing resection for primary lung cancer between 1992 and 2003 at a single institution. Approximately 20% underwent preoperative chemotherapy. Pulmonary complications, defined as respiratory failure requiring intensive care unit admission or intubation, pneumonia, atelectasis requiring bronchoscopy, pulmonary embolism, and need for supplemental oxygen at hospital discharge, occurred in approximately 13% of patients. The authors found significant univariate associations between pulmonary complications and preoperative serum albumin, preoperative chemotherapy, and both DLCO and DLCOppo. Only DLCOppo From the Department of Anesthesia and Perioperative Care, University of California San Francisco, San Francisco, California.