Introduction
Pulmonary complications remain common after many surgical procedures, particularly those involving the upper abdomen or thorax. Procedures that involve resection of lung tissue carry an even higher risk of pulmonary complications. Research concerning the diagnosis and prevention of perioperative cardiac complications after anesthesia and surgery has led to evidence-based interventions such as widespread implementation of perioperative beta-blocker administration. The situation regarding pulmonary complications is different. Many of the preoperative factors that make pulmonary complications more likely are known. A recent comprehensive review breaks down risk factors into those associated with the patient and those associated with the surgical procedure. Patient-associated risk factors include advanced age, American Society of Anesthesiologists (ASA) class 2 or higher, functional dependence, chronic obstructive pulmonary disease (COPD), smoking, and congestive heart failure. More recently, obstructive sleep apnea (OSA) and pulmonary hypertension have also been recognized as risk factors. Surgical procedures associated with increased risk of pulmonary complications include procedures in which the incision sites are close to the diaphragm such as aortic aneurysm repair, nonresective thoracic surgery, and upper abdominal surgery. Neurosurgery, emergency surgery, head and neck surgery, vascular surgery, prolonged surgery, and use of general anesthesia are also associated with increased risk. Unfortunately, most of these risk factors are not modifiable in the preoperative period. Smoking cessation can safely be encouraged, but short-term benefits from cessation are small. Preoperative screening for patients with OSA and asymptomatic pulmonary hypertension may have modest benefits. Appropriate management of OSA before elective surgery must be encouraged.
Perioperative care has changed significantly in the past 10 years, in that the time between preoperative evaluation and surgery is now often very brief. Surgical interventions themselves have changed significantly, often in ways that presumably reduce the likelihood of postoperative pulmonary complications. For example, the widespread application of laparoscopic techniques for many abdominal procedures may improve postoperative pulmonary function, and the introduction and widespread application of video-assisted thoracic surgery (VATS) and lung-volume reduction surgery has transformed into operative candidates patients who would have been previously told that their pulmonary function was “too bad” for surgery. In one study, impaired diffusion capacity of carbon monoxide (D LCO ) and reduced forced expiratory volume in 1 second (FEV 1 ) was not predictive of postoperative pulmonary complications (PPCs) in patients having lobectomy via VATS. In addition, the move toward very rapid ambulation and discharge from the hospital has ramifications that may positively affect those patients whose pulmonary function is improved by rapid resumption of the upright posture and may have negative implications for those who clear their secretions poorly at home.
Unfortunately, there is no standard definition of what constitutes a PPC. This hinders comparison of historical case series. Reported rates of pulmonary complications vary widely depending on the patient population and the surgical intervention studied. The most important complications are those that cause significant morbidity, such as pneumonia or respiratory failure. Preoperative pulmonary function tests (PFTs) have not proved to be better than clinical findings in predicting patients who go on to develop clinically significant pulmonary complications after surgical procedures that do not involve lung resection.
These issues, coupled with the relative insensitivity of pulmonary function testing in identifying patients who subsequently have PPCs, have resulted in more restrictive indications for preoperative pulmonary function testing than 25 years ago. An economic analysis entitled “Blowing Away Dollars” cast significant doubt on the practice of routine spirometric analysis before abdominal surgery. However, it is clear that the incidence of pulmonary complications is increased in patients with pre-existing pulmonary disease. It is also clear that the physical examination is not very sensitive in detecting mild to moderate pulmonary disease. Likewise, clinicians are not particularly accurate in estimating the severity of an exacerbation of COPD. There has been a significant shift away from ordering spirometry except in very specific circumstances (e.g., thoracic surgery that involves lung resection and severe COPD). It may be that it is too much to expect a single diagnostic test such as spirometry to result in improved outcomes when outcomes are, in reality, such complex endpoints.
Some would argue that the ready availability of therapeutic options for bronchospasm may minimize the benefit of preoperative knowledge of the presence and severity of chronic or episodic pulmonary disease. These developments may be tied to the decline in use of preoperative PFTs, but it is more likely that as the use of spirometry to determine who was eligible or ineligible for surgical intervention went out of vogue (largely because of poor correlation between predicted postoperative FEV 1 and measured postoperative FEV 1 ), the enthusiasm clinicians felt toward ordering and interpreting the tests diminished.
Because there are no meta-analyses or modern randomized, placebo-controlled therapeutic trials to review concerning preoperative PFTs, the evidence that does exist will be reviewed, and a rational strategy will be suggested for the use of preoperative PFTs. The fact that a noninvasive diagnostic test such as spirometry has not been shown to improve clinical outcome does not mean that it should never be ordered.
Options/Therapies
Pulmonary Function Testing and Therapeutic Options
The term pulmonary function test is very broad. Examples of PFTs include measures of anatomic volumes, resistance to airflow, reversibility of increased airway resistance, and assessment of pulmonary reserve. Available tests include spirometry, flow volume loops, assessment of membrane surface area available for gas transport via D LCO , assessment of cardiopulmonary reserve by exercise testing, ventilation-perfusion scintigraphy, and split-function lung studies. For most clinical situations an anesthesiologist encounters, the pertinent tests will be spirometry and exercise testing. Patients about to undergo pulmonary resection may require more extensive evaluation, depending on the severity of their lung disease and on the magnitude of the planned pulmonary resection. Reviews of individual tests are readily available for additional detail.
Spirometry is a very low-risk, effort-dependent test that can be performed in a physician’s office. Spirometric measurements such as the FEV 1 , vital capacity (VC), and forced vital capacity (FVC) are well-known to many clinicians. Spirometry is sensitive and specific for the accurate diagnosis of obstructive respiratory disease, and it may allow estimation of the effectiveness of bronchodilators in an individual patient. Diagnosis of restrictive lung disease requires measurement of lung volumes.
The second set of options that must be discussed are the therapeutic options. PFTs allow accurate categorization of a patient’s pulmonary disease. Accurate diagnosis should allow for effectively targeted preoperative therapy. The therapeutic options available for pulmonary disease are well described. Antibiotics can effectively treat pulmonary infection, bronchodilators (both beta-agonists and anticholinergics) can effectively treat bronchoconstriction, and steroid therapy may be helpful for subgroups of patients with asthma and COPD. Aggressive treatment with mechanical measures such as incentive spirometry can help minimize the frequency of PPCs after abdominal surgery but perhaps not after coronary artery bypass grafting. A recent review of strategies to reduce PPCs finds good evidence to support the postoperative use of lung expansion interventions (e.g., incentive spirometry, deep-breathing exercises, and continuous positive airway pressure), fair evidence to support the selective use of nasogastric tubes after abdominal surgery and the use of short-acting neuromuscular blockers intraoperatively, and conflicting evidence concerning smoking cessation, epidural analgesia or anesthesia, and the use of laparoscopic surgical techniques. PPCs have, however, been shown to occur less frequently in laparoscopic than in open bariatric surgery. Specific pulmonary rehabilitation programs have proved beneficial in improving cardiopulmonary capacity and may be useful in preparing patients for surgical intervention.
Evidence
There is no evidence of a beneficial effect from preoperative pulmonary function testing in asymptomatic patients having nonthoracic surgery. There is evidence that abnormal results on PFTs identify a group of patients who have a higher incidence of PPCs. Although historically pulmonary function testing was used to identify patients who were thought to be at excessive risk, recent experience shows that some patients with chronic hypercapnia (often used as a marker signifying inoperability) can safely undergo lung-volume reduction surgery. As surgical practice has become more aggressive in patients with emphysema, it has become clear that removing a nonfunctional segment of pulmonary parenchyma can be, surprisingly, well tolerated. However, there is also evidence that low FEV 1 , in combination with knowledge of the homogeneity of emphysema or an estimate of D LCO , identifies patients at prohibitive risk of lung-volume reduction surgery. Evidence has also shown that a surprisingly high percentage of patients, 37% in one series, may still be denied potentially curative lung cancer resection for non–small cell lung cancer on the basis of poor preoperative PFTs.
Exercise testing is useful for examining cardiopulmonary integration and reserve, and it may allow identification of patients who are more likely to survive major thoracic surgical procedures. Although formal exercise testing remains the gold standard for assessment of the maximal rate of total body oxygen consumption ( 
) and cardiopulmonary function, it is expensive and labor intensive, and it is not necessary in patients who can give a clear history of adequate exercise tolerance. If a patient cannot walk more than 2000 feet in 6 minutes, the patient’s 
is likely to be less than 15 mL/kg/min. Exercise oximetry also shows promise in identifying patients who are at high risk of adverse outcomes. A predicted postoperative 
of less than 10 mL/kg/min may be one of the few remaining contraindications to pulmonary resection because the reported mortality rate in this group of patients was 100% in one study.
Additional research is necessary to refine recommendations for preoperative estimation of cardiopulmonary reserve, but it appears that physiologic testing may offer advantages over simple spirometry in identifying patients at very high risk. A recent study suggests that poor performance on exercise testing predicts patients who will experience extended stays after thoracic surgery. The overall strength of the respiratory musculature is doubtless important as well, and efforts to increase the strength of the respiratory musculature may be helpful. There is now evidence that a rigorous preoperative pulmonary rehabilitation program directed at increasing exercise ability and diaphragmatic strength can improve patient well-being before surgery, may increase the number of frail patients with pulmonary disease who can reasonably undergo potentially curative thoracic surgery, and may decrease PPCs after cardiac surgery.
Areas of Uncertainty
There are many areas of uncertainty regarding when PFTs should be ordered preoperatively. In the absence of controlled clinical trials that demonstrate that pulmonary function testing is associated with improved outcomes, it is difficult to recommend PFTs as a necessary prerequisite for any patient or surgical procedure. However, spirometry is inexpensive to obtain, very low risk, and accurate in diagnosing what may be clinically occult pulmonary disease. Although an abnormal result on spirometry allows identification of a group of patients at elevated risk of pulmonary complications, it is poor at attempting to stratify risk among the patients at elevated risk.
Guidelines
The American College of Chest Physicians recommended guidelines using PFTs for physiologic evaluation of patients with suspected lung cancer being evaluated for surgery in 2007. As FEV 1 and D LCO progressively worsen, additional testing is recommended for prediction of postoperative pulmonary function. Very poor predicted postoperative pulmonary function is associated with an increased risk of perioperative death and cardiopulmonary complications with standard lung resection. Preoperative exercise testing is recommended for these patients, and if these test results are poor, nonstandard surgery or nonoperative treatment options for lung cancer are recommended. These guidelines are not based on prospective randomized studies that demonstrate improved outcomes; however, there is overall agreement for the use of PFTs in predicting the risk of surviving lung resection in patients with lung cancer.
In 2009, the European Respiratory Society and the European Society of Thoracic Surgeons also recommended a set of guidelines using PFTs for evaluation of the fitness of patients for radical therapy for lung cancer, including surgical resection. Their guidelines also used FEV 1 , D LCO , prediction of postoperative pulmonary function, and exercise testing.
With regard to cardiac and upper abdominal surgery, it may be prudent to do preoperative arterial blood gas analysis and spirometry in patients with a history of tobacco use and dyspnea. However, the recent evidence-based guidelines published by the American College of Physicians (ACP) do not recommend arterial blood gas analysis. For lower abdominal surgery, preoperative spirometry may be indicated for patients with uncharacterized pulmonary disease, particularly if the surgical procedure will be prolonged or extensive. For other types of surgery, PFTs might be useful for patients in whom uncharacterized pulmonary disease is present, particularly in those who might require strenuous postoperative rehabilitation programs.
A set of guidelines aimed at reducing perioperative pulmonary complications in patients undergoing noncardiothoracic surgery was published by the ACP in 2006. The recommendations include screening for the patient-specific and procedure-specific risk factors listed in the introduction section of this chapter, screening for low serum albumin levels (an albumin concentration less than 35 g/L predicts an increased risk of PPCs), and the use of postoperative lung expansion maneuvers and indicated postoperative nasogastric tubes. The fifth recommendation states clearly that preoperative spirometry and chest radiography should not be used routinely for predicting postoperative pulmonary risk. The last recommendation is that right-sided heart catheterization and total parenteral nutrition should not be used solely to attempt to reduce pulmonary complications from noncardiothoracic surgery.
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Optimal Postoperative Analgesia
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