Reducing perioperative lung complications
Any surgery raises concern about complications, some of which affect the lungs. New guidelines tell you how to minimize pulmonary risk.
Most clinicians are fully aware of the risk of cardiac complications after noncardiothoracic surgery. But not all appreciate that pulmonary complications—primarily atelectasis, pneumonia, and exacerbation of existing lung disease—are as common and contribute similarly to postoperative morbidity, mortality, and increased length of hospital stay. Among older patients at least, perioperative pulmonary complications are more predictive of long-term mortality than cardiac complications.
“This is a topic that we felt needed to be addressed,” says Amir Qaseem, MD, senior medical associate at the American College of Physicians (ACP) and an author of that organization's recent Guideline on risk assessment for and strategies to reduce such complications. The perioperative period, defined as from two to three months before surgery to up to three months after, represents a critical window of opportunity to forestall adverse consequences, Dr. Qaseem says. “Clinicians should take steps [at this time] if they predict that the patient is more likely to have lung problems.”
Patients at risk
Factors that may increase the risk of pulmonary complications (Table 1) should be evaluated in all patients undergoing noncardiothoracic surgery, according to the Guideline. Among the most important:Age: While it had been widely believed that the increase in pulmonary complications observed in older patients was due to greater comorbidity, the ACP's review of evidence identified advancing age as an important independent risk factor. The adjusted odds ratio for complications was 2.09 in the 60- to 69-year-old group and 3.04 in those aged 70-79.
Chronic lung disease: Thirteen of the 15 studies that included chronic obstructive pulmonary disease (COPD) in multivariate analyses found it a significant predictor of postoperative complications. The corrected odds ratio for COPD, compiled from those studies that provided usable data, was 1.79.
No study examined additional risk associated with chronic restrictive lung disease or restrictive physiology associated with chest-wall deformity or neuromuscular disease. The absence of data does not mean these patients are not at risk, the authors point out, and clinicians may still want to consider the possibility.
Perhaps surprisingly, there was good evidence to suggest that mild-to-moderate asthma is not a risk factor for postoperative pulmonary complications.
Other conditions: Another unanticipated conclusion from a reasonable body of data was that obesity—even morbid obesity—confers no increased risk.
In addition, there was some evidence, albeit weaker, that diabetes does not contribute to risk and insufficient data to determine possible connections with HIV infection or reduced exercise capacity.
The contribution of obstructive sleep apnea is unclear, although airway-management difficulties are known to be more common in the immediate postoperative period. A single study did find a significant increase in all serious complications, unplanned ICU transfers, and length of stay, suggesting that the risk of pulmonary complications per se may rise as well.
The rate of complications associated with congestive heart failure (CHF) is substantial: Data from three high-quality studies associated CHF with an adjusted risk ratio of 2.93.
Global measures: American Society of Anesthesiologists (ASA) classifications represent an integrated index of comorbidity; the system was designed to predict perioperative mortality overall. As ASA rankings go up (indicating increasing severity of systemic disease), pulmonary risk rises significantly and substantially. Partial functional dependence (the need for assistance in activities of daily living) is associated with increased risk of complications. Total dependence confers an even greater in-crease in risk.
Laboratory studies: Spirometry does not, in general, augment the predictive power of history and physical examination and is indicated only when undiagnosed COPD is suspected. The utility of chest x-ray is likewise limited: It appears to add useful information only in patients with known cardiopulmonary disease and those older than 50 who face upper abdominal or thoracic surgery.
Low levels (<35 g/L) of serum albumin are “one of the most powerful patient-related risk factors,” according to the Guideline authors. This parameter should be measured in all patients who have one or more risk factors, as well as those suspected of having hypoalbuminemia.
The specific surgical procedure should be taken into account in assessing a patient's risk of postoperative pulmonary complications. Abdominal surgery, thoracic surgery, head and neck surgery, neurosurgery, and vascular surgery are associated with an increased risk of pulmonary complications. Emergency and prolonged, i.e., lasting three to four hours, surgeries have a comparable effect. General anesthesia raises the risk as well.
Both before and after surgery, appropriate interventions should be implemented in patients found to be at elevated risk of pulmonary complications (Table 2).
Encourage smoking cessation: Patients who smoke should be assisted in quitting, as far in advance of surgery as possible. There is actually little evidence on this score: The only study found was negative, but it involved patients undergoing hip or knee replacement, procedures that carry relatively little pulmonary risk.
Timing appears important: Another trial found no reduction in pulmonary complications in patients who quit smoking within two months of surgery. “Cessation should be done early to have an impact,” Dr. Qaseem advises. The effect of smoking on lung function may linger for weeks after smoking cessation. Paradoxically, transient increases in production of mucus and reduced coughing in patients who quit smoking may actually lead to an increase in complication risk.
Manage conditions that raise risk: Certain conditions, notably COPD and CHF, should be optimized during the preoperative period, and the condition of patients with hypoalbuminemia or other indications of poor nutrition improved, e.g., with enriched diet or supplements. Total parenteral nutrition, however, appears to offer no advantage and is not recommended.
Lung expansion: After surgery, patients at risk of complications should be prescribed incentive spirometry, deep breathing exercises, chest physical therapy, or continuous positive airway pressure (CPAP). Although there is good evidence of the efficacy of these interventions as a whole, none has proven clearly superior. Combining methods does not appear to improve outcome. CPAP may have particular merit for patients who are not capable of more active modalities like deep breathing.
Nasogastric decompression: Placement of a nasogastric tube should be selective, i.e., reserved for patients who, after abdominal surgery, experience nausea, vomiting, or symptomatic abdominal distension or are incapable of oral intake. A recent meta-analysis pooling data from 28 trials found that selective nasogastric decompression reduced pulmonary complications (as well as promoting earlier bowel recovery) but that routine use of the modality conferred no additional benefit.
Risk Assessment for and Strategies to Reduce Perioperative Pulmonary Complications for Patients Undergoing Noncardiothoracic Surgery: a Guideline from the American College of Physicans appeared in Annals of Internal Medicine (2006;144:575-580). It is available online at: www.annals.org/cgi/reprint/144/8/575.pdf. Accessed March 10, 2008.
The systematic reviews on which the Guideline is based appeared in the same issue of Annals of Internal Medicine and are available online at: www.annals.org/cgi /reprint/144/8/581.pdf and www.annals.org/cgi/reprint/144 /8/596.pdf" target="_blank">www.annals.org/cgi /reprint/144/8/596.pdf. Both accessed March 10, 2008.