Applying best evidence to perioperative assessment
Knowing what to look for is one key to determining risk
From the October ACP Hospitalist, copyright © 2007 by the American College of Physicians
By Karen Lusky
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Sidebars: Breathe easier with these recommendations The Revised Cardiac Risk Index |
An 85-year-old diabetic woman was being evaluated for an aortal-femoral versus a femoral-popliteal bypass to treat a slowly healing ulcer on her right heel. She had one complete leg and a below-the-knee amputation. Her Revised Cardiac Risk Index (RCRI) was 2 (see sidebar), and she was facing potentially high-risk vascular surgery.
The American Hospital Association/American College of Cardiology guidelines suggest considering noninvasive cardiac preoperative testing in a patient with these characteristics. But Darrell W. Harrington, ACP Member, chose instead to order a beta-blocker, and the woman underwent an uneventful revascularization procedure for her leg.
Darrell W. Harrington, ACP Member
This scenario illustrates the potential complexity of preoperative cardiovascular risk assessment, said Dr. Harrington, who spoke about evidence-based approaches at Internal Medicine 2007 in San Diego in April. A good assessment uses best evidence and knowledge of the patient's condition to help minimize and manage risk, or at least to prevent an outcome that blindsides everyone.
In the case of Dr. Harrington's patient, the potential risk of invasive cardiac interventions was unacceptable. When he explained the procedures to her, she said adamantly, "No one is cracking my chest open," Dr. Harrington recalled. It was clear that the woman, who enjoyed sewing clothes for her grandchildren, wanted to save her foot at all costs and thus undergo revascularization rather than a lower-extremity amputation.
Functional status also played a role in Dr. Harrington's decision. The patient's family told him that the patient ambulated by hopping around on one foot. Dr. Harrington might not have believed this, he said, if he hadn't seen her swing from the bed "almost like a gymnast would" and hop down the ward. For Dr. Harrington, the case reinforced the importance of considering the patient's wishes and functional status as part of the preoperative evaluation and decision making.
Defining risk
Laying a patient's risk of cardiac perioperative complications on the table at the outset not only helps manage risks but also helps the patient decide whether to forgo an elective procedure.
"The patient may decide to live with that inguinal hernia or arthritic joint because the risk of perioperative complications is too high," said Dr. Harrington, chief of the division of general internal medicine and director of inpatient medical consultation at Harbor-UCLA Medical Center in Los Angeles.
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"The patient may decide to live with that inguinal hernia or arthritic joint because the risk of perioperative complications is too high." —Darrell W. Harrington, ACP Member |
For patients with an RCRI of 3 or more, physicians might strongly consider ordering diagnostic cardiac stress testing and beta-blockers before a noncardiac surgery. Test results might lead them to reconsider the type of procedure or delay it, Dr. Harrington said.
But if physicians order noninvasive preoperative cardiac testing for asymptomatic patients, they need to have a plan for what to do with the subsequent results, Dr. Harrington said. Otherwise, the testing simply "opens a can of worms," he warned. Very little data support performing aggressive interventions in asymptomatic individuals simply to get them through noncardiac surgery, Dr. Harrington said. And physicians may do more harm than good in this group by intervening for that purpose alone.
Treading knowledgeably with testing
Preoperative cardiac diagnostic testing can provide false reassurance or raise unnecessary concerns if the physician doesn't know what the results really predict.
For example, Dr. Harrington noted, some physicians believe a preoperative test showing that a patient will do well in surgery protects the patient and the physician. But nuclear medicine scans, for example, have an almost equal negative and positive predictive value, so the risk for a perioperative event is the same with a negative or a positive test, Dr. Harrington said.
The dobutamine echo test, which has been studied mostly in patients undergoing vascular procedures, is a slightly better noninvasive method for predicting a good surgical outcome, according to Dr. Harrington. If the patient has a negative test result, the negative predictive value is 99%. However, 80% of patients who receive a positive result on the test still do "just fine" when undergoing surgery, Dr. Harrington said.
Although certain dramatic findings on both of these diagnostic tests have a much higher positive predictive value, Dr. Harrington noted, they're uncommon in an asymptomatic person.
For patients with multiple cardiac risk factors who are considering an elective procedure, however, a cardiac stress test can provide helpful additional information.
"Data show that people with high RCRI scores of 3 or more who had beta-blockers on board and a negative stress test did pretty well in vascular surgery," Dr. Harrington said, with 2% to 3% experiencing adverse cardiac events.
Cardiac stress test results might also help the surgeon and anesthesiologist determine the choice of procedure or treatment and when to schedule it, he added.
It's all about minimizing a patient's cumulative risk, Dr. Harrington said. If physicians don't use that mindset when performing a preoperative evaluation, then what they do with the information from the noninvasive testing is not reproducible, he emphasized. The risk of performing an intervention must always be added into the equation. In teaching and consultation in one large hospital, for example, Dr. Harrington found that physicians were very inconsistent about intervening when patients had stress tests.
"There was no rhyme or reason to why asymptomatic patients were selected for preoperative diagnostic tests and interventions," he said. "Absolutely none."
Karen Lusky is a freelance writer in Brentwood, Tenn.
Breathe easier with these recommendations
Pulmonary risk is another important part of the preoperative assessment. At ACP's Internal Medicine 2007 in San Diego in April, Gerald Smetana, FACP, associate professor of medicine at Harvard Medical School, summarized the College's 2006 clinical guidelines for evaluating risk factors for and preventing perioperative pulmonary complications in noncardiothoracic surgery. Dr. Smetana was one of the guidelines' coauthors.
Gerald W. Smetana, FACP
Pulmonary complications are defined as "pneumonia, respiratory failure requiring mechanical ventilation for more than 48 hours after surgery, atelectasis and exacerbation of preexisting chronic lung disease," Dr. Smetana said.
The following patient-related factors earned a grade of "A," meaning that good evidence supported an association with risk of surgery-related pulmonary complications:
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Older age;
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American Society of Anesthesiologists class II or higher;
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Functional dependence;
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Chronic obstructive pulmonary disease;
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Congestive heart failure; and
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Serum albumin level less than 3.5 mg/dL (<35 g/L).
Older age as a risk factor was a new finding and was not apparent from a casual reading of the literature, Dr. Smetana said. "It's important because it differs from preoperative cardiac assessment where age is not a predictor of complications," he added. Also, he said, it was a relatively new finding that congestive heart failure conferred a risk similar to that of COPD.
Procedure-related risk factors primarily involved surgical site. "There's good evidence that aortic aneurysm repair, thoracic surgery, upper abdominal surgery, vascular surgery and head and neck surgery confer high risk," Dr. Smetana said. Emergency surgery and surgery lasting more than three hours are also risk factors.
One unexpected finding in the guidelines was that spirometry is not useful as a routine test to identify high-risk patients. It may provide some value "in a small select group of patients with COPD whose status is unclear, or in patients with unexplained dyspnea," Dr. Smetana said.
"Patients with abnormal spirometry can generally be identified based on history and physical," he added.
The evidence shows that the most important way to reduce risk is with postoperative lung expansion modalities, such as incentive spirometry and deep breathing exercises. "Teaching people inspiratory muscle training, which is a type of deep breathing, is more effective when begun before surgery than after surgery," Dr. Smetana said.
As for smoking cessation, the literature suggests that quitting smoking at least two months before surgery may reduce risk of pulmonary complications, Dr. Smetana said. But patients who stop smoking briefly may actually increase their risk, he cautioned, because of the resulting increased cough and sputum production.
One key take-away message for hospitalists performing preoperative assessments is that cardiac and pulmonary risk factors differ considerably. A person at high risk for one type of complication isn't necessarily at high risk for the other, Dr. Smetana pointed out. "If [risk factors for these two major types of complications] were similar, it would be easier to learn and remember," he said.
The Revised Cardiac Risk Index
The Revised Cardiac Risk Index (RCRI) can identify patients who have greater odds of suffering a major cardiac complication (myocardial infarction, pulmonary edema, ventricular fibrillation or primary cardiac arrest and complete heart block) when undergoing major noncardiac surgery. Researchers developed the RCRI by studying more than 4,000 patients 50 years or older undergoing elective major noncardiac surgery at a teaching hospital from 1989 to 1994.
The RCRI includes six factors that predict an adverse cardiac event:
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High-risk surgical procedure (thoracic, abdominal, pelvic vascular);
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History of ischemic heart disease;
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History of congestive heart failure;
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History of cerebrovascular disease;
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Preoperative treatment with insulin; and
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Renal impairment (preoperative serum creatinine concentration >2.0 mg/dL)
A patient receives one point for each risk factor, with a corresponding risk as follows:
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No points = 0.4% risk of a major adverse cardiac event
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1 point = 0.9% risk
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2 points = 7% risk
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3 or more points = 11% risk
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