Don't forget the lungs

Hospitalists familiar with preop cardiovascular evaluation may be less comfortable with pulmonary evaluations, which can also be crucial to reducing risk for surgical patients.

“You're probably comfortable with the notion of preoperative cardiac evaluation,” Gerald W. Smetana, FACP, told attendees at Internal Medicine 2010, held in Toronto in April.

Hospitalists may be less comfortable and familiar with pulmonary evaluations, which can also be crucial to reducing risk for surgical patients, he noted. Indeed, pneumonia, respiratory failure and atelectasis should be on the perioperative radar just like cardiac problems are, according to Dr. Smetana, an associate professor of medicine at Harvard Medical School, and other experts.

Photo by Thinkstock
Photo by Thinkstock.

“Most of the research and press goes to perioperative cardiac complications, but perioperative pulmonary complications are actually more frequent and receive very little attention in research journals, at least until the recent past,” said Nick Fitterman, FACP, director of the hospitalist program at Huntington Hospital in New York City.

In addition to pulmonary complications' frequency (2.7% in one study of surgical patients, published in the November 2003 American Journal of Medicine, compared to 2.5% for cardiac complications), they can also be more dangerous and costly, resulting in longer stays and more intensive care admissions, experts said.

“In the modern era, post-op MIs can be treated and aborted fairly early; infectious complications can usually be treated early when they're recognized as well,” said Dr. Smetana. “When a pulmonary complication occurs, it's quite morbid.”

The pulmonary risks of surgery may get less attention than other dangers because there's historically been less research on them, particularly on how to reduce them. “There are really still limited-quality data on interventions to reduce perioperative pulmonary complications,” said Dr. Fitterman. Still, he and the other experts think there's enough data on certain interventions that hospitalists should be incorporating screening, and preventive tactics, into their practice.

How to screen

The first step is to figure out who might be at risk. “The simple things, like a careful history and physical exam, we must do on everyone. The details of that would be asking for symptoms—cough, shortness of breath, exercise intolerance,” said Sat Sharma, FACP, head of the division of pulmonary medicine at the University of Manitoba in Canada.

Some additional risk factors for perioperative pulmonary complications were identified in ACP's 2006 guidelines on the topic, written by a group of experts that included Dr. Smetana and Dr. Fitterman. The guidelines gave letter grades (ranging from A to D) to risk factors, based on the level of evidence that supported their relationship to adverse pulmonary outcomes.

The most predictive risk factors were not necessarily those most closely related to the lungs. As one might expect, chronic obstructive pulmonary disease (COPD) scored an A, but it can also take a backseat to other concerns, especially when well controlled. “It's actually a weaker risk factor than a number of other patient-related risk factors, such as heart failure, for example,” said Dr. Smetana.

Age, which is not a factor in cardiac operative risk, also got an A. “Even your healthy older patients who are going to major noncardiac surgery are going to be at higher risk for pulmonary complications,” said Dr. Smetana. Being over 80 increases the risk of complications fivefold, while COPD only doubles the risk, he noted.

Functional dependence and general ill health (an American Society of Anesthesiologists score of 2 or greater) are also likely predictors. And although there's not as much evidence in support, it's worth asking patients about their exercise capacity. “If someone is short of breath walking for two to three blocks or cannot climb one flight of stairs, obviously that's a red flag right there,” said Dr. Sharma.

A patient who reports such inability to exercise may require further testing, specifically spirometry. The guideline experts found insufficient evidence (and gave a grade of I) for routine spirometry before surgery (except for lung resections, in which it should be standard). But it may be helpful to identify the cause of poor effort tolerance “if you can't figure out after taking the history and doing the physical whether it's cardiac, pulmonary or deconditioning,” said Dr. Smetana.

The cause could turn out to be COPD or another lung disease. “You can make a diagnosis of that and then treat it before surgery,” said Dr. Sharma. Optimizing control of existing lung diseases is another recommended way to avoid complications. As long as it's well controlled (a peak flow greater than 80% of personal best and no wheezing), asthma does not increase risk.

Treatment for these lung diseases should be the same as it would be in a non-surgical situation. “You don't need to do anything differently. In particular, if they need corticosteroids, go ahead and give them and don't be concerned about the impact on wound healing and infection rates,” said Dr. Smetana.

Another issue you don't need to be too concerned about is obesity. “This is the one that people have the most difficulty believing: Obesity is not a risk factor for pulmonary complications after surgery,” said Dr. Smetana.

However, if your obese patient has obstructive sleep apnea, as many do, he or she may be at risk. Sleep apnea has been definitely linked to postoperative airway complications, and there's some evidence also that it leads to traditional pulmonary complications.

And if sleep apnea (or any other cause) has led to the development of pulmonary hypertension, the patient is particularly at risk. A study published in the British Journal of Anesthesia in August 2007 found that respiratory failure occurs in about a quarter of patients with pulmonary hypertension. “At this point, I'm not recommending screening for it, but if you have a patient with the benefit of an echo done for some clinical reason, and they're found to have pulmonary hypertension, then you need to be careful,” said Dr. Smetana.

The role of tests

Tests generally are not a major component of the preoperative pulmonary evaluation. Like spirometry, cardiopulmonary exercise testing may be most useful for patients whose exercise intolerance is unexplained, according to Dr. Smetana. Chest x-rays also should be conducted as needed, rather than routinely.

“If people have any respiratory symptoms or have previous lung pathology, then definitely a chest radiograph needs to be done,” said Dr. Sharma.

Some lab tests may be helpful. An arterial blood gas can identify hypoxemia or hypercapnia. “There's some controversy over whether that definitely helps in assessing risk,” said Dr. Sharma. Complications have been shown convincingly to be associated with low serum albumin (below 3) and high blood urea nitrogen (over 30), so those lab tests may be useful, at least to find high-risk patients.

“The albumin level identifies a risk, but there are no proven interventions to mitigate that risk,” said Dr. Fitterman.

Helpful interventions

A couple of interventions have been proven to reduce patients' overall chance of pulmonary complications.

Although smoking increases the risk of complications only mildly for otherwise healthy patients its worth suggesting that patients quit before surgery Photo by Thinkstock
Although smoking increases the risk of complications only mildly for otherwise healthy patients, it's worth suggesting that patients quit before surgery. Photo by Thinkstock.

Smoking increases risk only mildly for otherwise healthy patients, but it's worth suggesting that they quit. The effect is greater if one quits at least two months before surgery, but new research indicates that there's a benefit even closer in. “If you have the teachable moment and are seeing the patient a week or two before surgery, it's still worth trying to get them to stop smoking,” said Dr. Smetana. Or, in some cases, it may be possible to delay an elective surgery, Dr. Sharma noted.

The specifics of surgery—location, length, type of incision—are a major determinant of pulmonary risk. “The closer the incision is to the diaphragm, the higher the risk of complications,” said Dr. Smetana. Shorter surgeries with smaller incisions and neuraxial anesthesia pose less pulmonary danger.

“By and large, hospitalists are not going to be in the position of making recommendations on surgical or anesthetic techniques,” acknowledged Dr. Smetana. But it's still helpful for hospitalists to be aware of these issues and perhaps offer advice, according to Dr. Sharma. “Hospitalists, anesthesiologists, surgeons, bedside nurses and physiotherapists—they all need to play a role and contribute to a patient's benefit,” he said.

Hospitalists can take the lead role in the implementation of lung-expansion strategies, which the authors of the ACP guideline found to be one of the most effective strategies for reducing pulmonary risk. A study published in the Journal of the American Medical Association in April 2006 found that two weeks of preoperative inspiratory muscle training lowered complication rates.

Training in deep breathing techniques, whether by a physician or a respiratory therapist, can also help. The techniques need to be used after surgery, but the education should take place before. “In the postoperative state, they're on pain medicines, they're in pain, they might not be able to comply as well,” said Dr. Fitterman.

Appropriate pain management is also necessary to make breathing exercises effective. “The pain control should be adequate, not under, not over. If you're over, they may be sedated or groggy and not do the breathing exercises. If the pain control is less [than adequate], they're still not going to do breathing exercises,” said Dr. Sharma. An epidural analgesia can control pain while allowing patients to be alert and breathing deeply, he said.

There are also methods for helping patients who aren't functioning as well after surgery. “Postoperative CPAP [continuous positive airway pressure] is another lung-expansion strategy that can be used after surgery in patients who can't cooperate with incentive spirometry or deep breathing,” said Dr. Smetana.

Selective use of nasogastric tubes is the final risk reduction strategy recommended by the ACP guidelines, earning a B. “We'll probably upgrade this in the next version based on more recent data,” said Dr. Smetana. “I would move [it] up to a letter A.”