Preop evaluations: which risk-reduction strategies work? Here are the tests you do (and don't) need by Deborah Gesensway
Published in the August 2011 issue of Today's Hospitalist
Over the last few decades, American doctors have gone from rarely conducting extensive preoperative evaluations to doing them all the time. While that's largely good news, there's a downside: Many of those evaluations aren't done very well.
Research indicates that up to 60% of preop lab tests are unnecessary, while many test results—especially those that are unanticipated—are ignored. Still other tests needlessly delay essential operations.
That leaves hospitalists, who increasingly find themselves performing those evaluations and deciding which tests to order, wondering how to assess and reduce patients' perioperative risks.
A full-day precourse on perioperative
"We do not 'clear' anybody for surgery. We can't give any guarantees with our risk assessment."
–Steven L. Cohn, MD Kings County Hospital Center/SUNY Downstate
medicine at this year's Society of Hospital Medicine annual meeting offered advice on how to do just that, with pearls on choosing appropriate preop testing and risk-reduction strategies.
What to order
One speaker defined the problem with routine preop testing in simple terms. While the testing "rarely detects real abnormalities or changes management," explained hospitalist Paul Grant, MD, it chews up an estimated $30 billion a year.
Dr. Grant, who is the director of perioperative and consultative medicine at the University of Michigan Health System in Ann Arbor and the precourse co-director, said that studies published in the last two years have found that up to 90% of patients receive at least one unnecessary preop test. Research has also found that almost all preop urine, liver function and coagulation tests ordered are not indicated by clinical practice guidelines.
While Dr. Grant conceded that medicolegal concerns may drive much of this over-testing, he added that unnecessary tests bring their own liability, particularly when they lead to more tests and delays in surgery. And when you consider that physicians ignore 30% to 60% of unanticipated abnormalities, he added, unnecessary tests present an even greater risk from a liability standpoint. Another factor that may drive over-testing, he added, is physician distrust of guidelines, many of which are based only on expert opinion.
In general, Dr. Grant said, "labs obtained within the last four months do not require repeating." And taking a good history and physical can go a long way to helping physicians predict whether patients can withstand the stress of surgery and avoid ordering tests they really don't need.
Dr. Grant reviewed some of the most commonly ordered preop tests:
Prothrombin and partial thromboplastin times. Several studies have found that "routine preop coagulation screening tests on all patients will not predict bleeding," Dr. Grant said, even when results are abnormal. In fact, lab error is the most common reason for an abnormal PT or PTT.
The best way to assess bleeding risk, he explained, is to "ask the right questions." He suggested targeting personal and family histories of abnormal bleeding, history of liver disease, malnutrition, anemia, purpura, chemotherapy, radiation therapy and anticoagulant exposure.
Pregnancy testing. This is one preop test that doctors do need to order in the appropriate patient population, Dr. Grant said, because "a positive finding will always affect your management." Preop evaluations for female patients should also include a menstrual bleeding history.
Electrocardiograms. ECGs tend not to be good predictors of cardiovascular risk during surgery, said Dr. Grant; taking a good history is better. Nonetheless, ECGs can be useful both to help stratify risk—by showing evidence of a prior myocardial infarction, for instance—and to establish baseline for patients should postop symptoms develop.
According to the 2007 American College of Cardiology/American Heart Association (ACC/ AHA) guidelines, preop ECGs are reasonable for patients having major vascular surgery. They also may be indicated for patients undergoing intermediate risk surgeries who have at least one clinical risk factor or known coronary heart disease, peripheral arterial disease or cerebrovascular disease.
However, Dr. Grant pointed out, ECGs are not indicated for asymptomatic patients about to undergo low-risk surgery.
Chest X-rays. While chest X-rays are one of the most expensive regularly ordered preop tests, there is "limited evidence that abnormal chest X-rays predict postop pulmonary complications," Dr. Grant explained. "Yes, it is a predictor, but it doesn't change management." For most patients, he added, "you can learn what you need to know from the history and the physical exam."
Evaluating cardiac risk
Steven L. Cohn, MD, director of the medical consultation service at Kings County Hospital Center/SUNY Downstate in Brooklyn and a precourse presenter, agreed that the overriding principle in the ACC/AHA guidelines is this: "No test should be done unless it is going to affect patient management."
"We can't be doing things to patients just because we want more information," said Dr. Cohn, who is one of the nation's top experts on perioperative medicine. "If that information doesn't translate to something useful, we shouldn't ask for it."
When trying to assess cardiac risk during noncardiac surgery, Dr. Cohn said, hospitalists should add up six clinical risk factors to determine a patient's revised cardiac risk index (RCRI) score. Those factors are:
history of ischemic heart disease;
congestive heart failure;
diabetes being treated with insulin; and
preoperative creatinine greater than 2.0.
Patients with three or more of these predictors are considered high risk. But Dr. Cohn pointed out that physicians must weigh several other pieces of information before they can really determine cardiac risk. Here are questions he said doctors should ask:
Do patients have major clinical predictors of increased perioperative risk or only intermediate predictors? Major risk factors, Dr. Cohn said, include active cardiac conditions such as a myocardial infarction within the last month, severe angina, decompensated heart failure, significant arrhythmias or severe valvular disease. For patients with these risk factors, he noted, elective surgery should be delayed for further evaluation or treatment.
Intermediate clinical risk factors include other types of coronary artery disease that don't fall into that first category, as well as compensated or past history of heart failure, stroke or TIA, diabetes mellitus, and renal insufficiency (creatinine >2).
What type of surgery is the patient having? Highest risk is aortic and major vascular surgery. Carotid endarterectomy, endovascular AAA procedures, and intraperitoneal, intrathoracic, orthopedic, prostate and head and neck surgeries make up the intermediate category. Low-risk operations are those that don't invade the body cavity, like endoscopic, cataract and breast surgery.
What is the patient's self-reported exercise capability? Is his functional capacity at least four METs without symptoms? "I am looking for patients who can walk two to four blocks at a good pace," said Dr. Cohn, "and climb at least one flight of stairs carrying packages without any symptoms."
Who can go straight to surgery
Armed with this information, Dr. Cohn said, hospitalists can begin to interpret the 2007 ACC/AHA algorithm to figure out if the patient needs further tests, drugs or procedures before surgery.
The guidelines make it clear, for instance, that many patients should go to surgery without further testing. For instance, patients who need emergent or urgent surgery—which includes common operations like an appendectomy or fixing a hip fracture—should go straight to surgery without further testing or cardiac intervention. "Just try to optimize their clinical condition and adjust medications in the little time you have before surgery," Dr. Cohn said.
Likewise, patients should go straight to the operating room with no further testing if the surgery falls into the low-risk category, if they have adequate exercise capacity (four or more METs), or if they have either no or only one clinical risk factor.
According to the ACC/AHA guidelines, Dr. Cohn pointed out, the only evidence to support further testing applies to "people with clinical risk factors going for intermediate or high-risk procedures and who can't do four METs. And 90% of these patients can still go to the OR with no further tests."
If you do order a stress test, he said, an exercise test is better than a pharmacologic test.
However, "in the preoperative setting, the patients we would consider for stress testing would be those unable to exercise, so pharmacologic testing is used," Dr. Cohn said. If you need a pharmacologic test, the dobutamine stress echo is probably somewhat better than dipyridamole or adenosine nuclear testing, he added, "because it is more physiological and there are fewer false positives." A resting 2D echo should not be requested to predict ischemic complications and should be done only for patients with valvular disease or heart failure.
Dr. Cohn also noted that there is currently no indication for ordering BNPs. Although an elevated value may be associated with postop complications, it is unclear what to do with the test results. But given the most recent POISE study results, he said, it is reasonable to order postoperative troponins in high-risk patients because many patients with perioperative MIs do not have symptoms.
What about tuning up patients for surgery by performing PCI preoperatively? As Dr. Cohn noted, "You can't take low-risk patients and make them any better."
And with the risk of complications that comes with prophylactic revascularization before noncardiac surgery, Dr. Cohn said he questions its utility much of the time. "You are talking about 5% to 10% morbidity and mortality for a prophylactic strategy," he pointed out. "Does that make sense?" Studies of both lower-risk patients with stable cardiac disease and high-risk patients undergoing vascular surgery have failed to show any benefit on top of good medical therapy.
"Both extremes were not helped by revascularization," he said.
Because patients who receive a drug-eluting stent need to continue dual antiplatelet therapy for at least 12 months, Dr. Cohn's advice is to avoid those stents in the preoperative setting.
"If a patient is being considered for surgery in the near future, tell the cardiologist not to put in a drug-eluting stent," he said. Patients who receive a bare-metal stent, he added, should wait at least four to six weeks and complete the course of dual antiplatelet therapy before subsequent surgery.
If prophylactic procedures are of limited value to reduce cardiac risk during noncardiac surgery, what about medical therapy?
Dr. Cohn said he does not recommend routine use of prophylactic beta-blockers for low-risk patients (those with RCRI scores of 0-2), the elderly (more than 75 years old), people with prior strokes, those with sepsis and those going to emergency surgery. And for patients for whom beta-blockade is indicated, timing is important. According to Dr. Cohn, patients benefit the most if the drugs are started at least a week—and better yet, up to a month—before surgery.
"You need to have time to titrate the dose," he said. Patients already taking beta-blockers should continue on them. With patients who are new to beta-blockers, he said, use the drugs selectively, start with low doses and titrate until the heart rate is between 55 and 70, watching carefully to avoid hypotension. Patients should continue using them for at least 30 days.
While there are only three randomized controlled trials on the preoperative use of statins in noncardiac surgery, Dr. Cohn said he sees a potential benefit without any downside. Many of the patients you'll consider giving statins to probably should be taking them anyway.
"I would continue them indefinitely," he said.
Finally, hospitalists should keep in mind that "we do not 'clear' anybody for surgery," Dr. Cohn cautioned. "We are not a clearinghouse. We are not an insurance agency. We can't give any guarantees with our risk assessment."
Instead, he said, he recommends saying something to this effect: "Based on our judgment, this patient is in his or her optimal medical condition for the planned low-/intermediate-/high-risk procedure."
Managing pulmonary risk
Postop pulmonary complications—primarily pneumonia, atelectasis, respiratory failure and exacerbation of underlying chronic lung disease—are actually a bigger problem both in terms of frequency and cost than cardiovascular complications, said Christopher Whinney, MD, interim chair of the department of hospital medicine at the Cleveland Clinic and precourse co-director.
According to Dr. Whinney, new studies provide some clues about which patients have the greatest risk of developing postop pulmonary complications.
In addition to the well-known risks of undergoing surgery in sites close to the diaphragm (upper abdominal or thoracic), high-risk operations include procedures that last longer than three hours or involve patients with
"There is now evidence that obstructive sleep apnea, hypoxia, prior respiratory infection and anemia are also important risks," Dr. Whinney added. "Clearly, obstructive sleep apnea has predictive value."
As a result, he now includes the brief STOP questionnaire to screen patients for sleep apnea during preop examinations. Depending on those results, Dr. Whinney may order postoperative CPAP for patients. He also suggests that some patients have a sleep study done after they are discharged.
Dr. Whinney agreed that ordering a chest X-ray preoperatively will "rarely change management." He therefore doesn't recommend one for routine perioperative pulmonary risk assessment.
And on the question of whether preop smoking cessation can reduce perioperative risks, Dr. Whinney noted that "controversial" evidence suggests an increase in postop pulmonary complications with preoperative smoking cessation.
However, a recent meta-analysis found essentially no difference in complication rates between current and former smokers and between early or late quitters. He suggested considering the preop period a "teachable moment" to encourage smoking cessation among patients undergoing elective surgery.
Deborah Gesensway is a freelance writer who covers U.S. health care from Toronto.