Home Analysis New guidelines dispel old myths about pulmonary complications after surgery

New guidelines dispel old myths about pulmonary complications after surgery

June 2006

Published in the June 2006 issue of Today’s Hospitalist

Your patient is about to undergo abdominal surgery, but you’re concerned about pulmonary complications because he is a smoker with COPD. Should you order a pre-operative chest Xray to get more information?

According to new guidelines on assessing and preventing pulmonary complications after noncardiac surgery, the answer is yes, but with a caveat: The strategy should not be routinely used for predicting risk. If you’re ordering a chest radiograph ” or spirometry, for that matter “to estimate the patient’s risk of developing pulmonary problems during surgery, you can probably get just as much information from a good history and physical examination.

The guidelines, which were released by the American College of Physicians (ACP) and published in the April 18 Annals of Internal Medicine, make a number of recommendations that may turn other conventional wisdom on its head. And far from identifying strategies that don’t work, the recommendations point to techniques that physicians may be underusing, such as checking serum albumin levels.

The guidelines also make recommendations on how to treat patients at high risk of pulmonary complications, giving a thumbs-up to strategies like deep breathing exercises or incentive spirometry and nasogastric tubes for patients who are experiencing postoperative problems like nausea or vomiting.

The big picture

While parts of the guidelines are likely to generate some controversy, their goal is to help physicians focus on the big picture when it comes to the pulmonary risks that patients face during surgery. According to Amir Qaseem, MD, PhD, lead author of the guidelines and the Annals article, those risks all too often take a back seat to concerns about cardiac complications.

That’s a problem, Dr. Qaseem explains, because studies have consistently shown that pulmonary complications include atelectasis, pneumonia, respiratory failure and exacerbations of underlying chronic lung disease. And while those complications often better predict long-term mortality after surgery, particularly among older patients, many physicians nonetheless believe that cardiac problems are the bigger threat.

By citing data in the medical literature, the new recommendations hope to dispel that and other myths about pulmonary risks. So while the guidelines acknowledge that COPD is the most commonly identified risk factor of pulmonary problems, they also point out that there is no evidence that other pulmonary problems like chronic restrictive lung disease increase the risk of pulmonary complications.

And while the guidelines note that smoking increases the risk of pulmonary problems after surgery, they point out that the effect is relatively modest, with an odds ratio of 1.26. Many physicians view obesity and asthma as important predictors of pulmonary complications, but the guidelines point out that a review of the data found that’s simply not the case.

Chest X-rays and spirometry

One recommendation that is likely to generate some controversy focuses on the use of chest X-rays and spirometry before surgery solely to assess the risk of pulmonary complications.

The guidelines explain that the data show that spirometry has little value as a screening tool for risk prediction before noncardiac surgery. Because the test provides no threshold below which physicians should cancel the procedure, it may not add much to the decision-making process.

The recommendations paint a similar picture of pre-operative chest X-rays, noting that few studies have really examined their effectiveness when screening patients for pulmonary risk. One study cited by the guidelines, for example, found that 23.1 percent of chest X-rays before surgery were abnormal, but only 3 percent of those findings were important enough to change the patient’s management.

As a result, the guidelines conclude that chest X-rays only rarely provide information that changes treatment, and they urge physicians to rely on a history and physical examination. “Although chest radiographs are used routinely as part of preoperative evaluation,” Dr. Qaseem says, “that doesn’t mean they’re an effective risk predictor for individual patients.”

(The guidelines do note, however, that both modalities may be appropriate in patients with a history of COPD.)

Serum albium levels

While the guidelines dispel much of the conventional wisdom about lab testing for pulmonary complications, they suggest that physicians look to another measure: serum albium levels. Data show that a low serum albumin level “less than 35 g/L “is associated with increased pulmonary risk. The recommendations cite one study that found that a low serum albumin level was the most important predictor of 30-day perioperative morbidity and mortality.

As a result, the guidelines urge physicians to measure serum albumin levels in all patients who are clinically suspected of hypoalbuminemia, or in patients with one or more risk factors for pulmonary complications.

Dr. Qaseem acknowledges that the importance of serum albium levels in predicting pulmonary problems may not be earth-shattering news, but he says that it’s important to highlight the evidence. “It’s true that some physicians may be aware of albumin levels,” he says, “but they might not understand that there’s strong evidence behind it.”

Preventive and therapeutic strategies

Suppose that you find that your patient does face a high risk of pulmonary complications? What can you do to reduce the risk that patients will develop a pulmonary complication both before and after surgery?

The guidelines make the following recommendations:

“¢ Smoking cessation. While urging patients to quit smoking before surgery may sound like an obvious place to start, the guidelines found that the medical literature does not support such a recommendation.

“The medical literature suggests a moderate increase in the risk of post-op complications among current smokers,” Dr. Qaseem explains, “but most of the research evaluating this is done related to cardiopulmonary surgeries, and our guidelines address noncardiothoracic surgery. A lot of physicians, however, do talk to their patients about the importance of quitting smoking six to eight weeks before surgery.”

“¢ Lung expansion. When it comes to preventing pulmonary complications before surgery in high-risk patients, data show that lung expansion techniques such as incentive spirometry and deep breathing exercises appear to provide some benefit. The guidelines, however, fall short of endorsing any individual strategy because the data are not clear. While studies have shown that any type of lung expansion intervention is better than nothing, there are no data to indicate that one strategy works any better than another.

“¢ Total parenteral nutrition. The guidelines conclude that giving patients total parenteral nutrition after surgery offers no benefit when compared to no supplementation. They note that more research is needed on immunonutrition.

“¢ Nasogastric tubes. The guidelines recommend selective use of nasogastric tubes after abdominal surgery in patients with postoperative nausea or vomiting, inability to tolerate oral intake or abdominal distension. While the strategy has been associated with lower rates of pneumonia and atelectasis, the guidelines note that nasogastric tubes should not be used routinely in all patients.

Edward Doyle is Editor of Today’s Hospitalist.