Pre-op evaluations: emerging evidence for four areas
By Deborah Gesensway
When the Agency for Healthcare Research and Quality (AHRQ) released a massive report last year on ways to make health care "safer," particularly for hospitalized patients, it put two items at the top of the list: prophylaxis to prevent venous thromboembolism, and perioperative beta-blockers to prevent cardiac complications in high-risk patients.
To reach those conclusions, the report's authors reviewed a growing body of evidence about how to treat hospitalized patients, particularly about ways to avoid postoperative problems. One result of the report is that internists who care for hospitalized surgical patients now have some scientific evidence to help guide their practices. Good perioperative medicine no longer needs to be guided only by the time-honored principles of logic, tradition and judgment.
Or, as Andrew D. Auerbach, ACP-ASIM Member, an assistant professor of medicine at the University of California, San Francisco, and co-author of the AHRQ report, described the dilemma of practicing perioperative medicine: "There is a lot of style, but not as much evidence as there should be."
As the AHRQ evidence report makes clear, however, in the last decade, clinical evidence has made significant inroads into the field of perioperative medicine. The growing body of data has addressed everything from how to evaluate cardiac risk for patients undergoing noncardiac surgery and what to do about it, to how to analyze pulmonary risk and predict and prevent postoperative delirium.
Interestingly, not all research into perioperative care has produced positive results. There is mounting evidence, for example, that some of the tests ordered routinely during presurgical medical consults (such as complete blood counts) may be unnecessary, incapable of predicting and reducing postoperative complications.
There is even evidence that preoperative evaluations of patients scheduled for low-risk surgery may be a waste of time and money. A study in the Jan. 20, 2000, issue of the New England Journal of Medicine, for instance, concluded that routine laboratory testing before cataract surgery did not improve patient safety.
Emerging areas of research also promise to do even more to transform perioperative care. The AHRQ report, for example, put "improved perioperative glucose control to decrease perioperative infections" at the top of its list of patient safety practices most in need of further research because of its potential to make an enormous difference in patient morbidity and mortality.
Here is a look at four areas of perioperative care where the most evidence exists—and where you can help your patients about to undergo inpatient surgery:
Perioperative beta-blockers. Because myocardial events are the most common medical complication of surgery—experienced by 2% to 5% of all patients undergoing noncardiac surgery, and 30% of patients undergoing vascular surgery—researchers have focused much of their attention on how to predict and prevent cardiac events.
Both ACP-ASIM and the American College of Cardiology/American Heart Association have published guidelines in the last five years telling physicians how to assess and manage cardiac complications of noncardiac surgery. Both come down in favor of beta-blockade.
Research, however, has shown that most physicians have not yet put the evidence-based guidelines into practice. Peter K. Lindenauer, FACP, for example, studied noncardiac surgeries at Baystate Medical Center in Springfield, Mass. His goal was to determine whether patients who appeared to be "ideal candidates" for perioperative beta-blockade got a drug like atenolol at any point during their treatment.
The results were less than encouraging: Only one-third of eligible patients received the drug. (His paper was published in the February 2002 Archives of Internal Medicine.) Other studies cited in the AHRQ report had similar findings.
In addition, Dr. Lindenauer said, few Baystate patients received optimal courses of the drug. According to practice guidelines, physicians should start to administer the drug days or weeks before elective surgery and continue the drug therapy for a week or even a month after surgery.
"We found that it was very rare for someone to start beta-blockers while they were in the hospital," Dr. Lindenauer said. "That's important, because when people come into the hospital, this is the time to intervene at low cost and with low risk to reduce their complications."
Baystate recently was scheduled to begin a program that will work with primary care physicians to make sure patients receive proper drug therapy before surgery. If physicians and nurses working at the preoperative anesthesia clinic determine that a patient should be put on beta-blockers, a fax will notify the patient's primary care physician that the patient would benefit from the drug. The goal is to ensure beta-blockers are considered during all preoperative evaluations.
"Most internists know the literature, but there are systems problems," Dr. Lindenauer said. "This is true even with perioperative beta-blockade, which is really easy to do."
DVT prophylaxis. Deep venous thrombosis (DVT) prophylaxis is another area where the evidence is strong, but adoption has been weak.
According to the AHRQ report, DVT occurs after 20% of all major surgical procedures when prophylaxis is not given. Pulmonary embolisms develop in 1% to 2% of patients who do not receive prophylaxis.
While the American College of Chest Physicians has released several sets of guidelines on the topic—most recently in the January 2001 issue of Chest—the AHRQ report found that "prophylaxis is often underused or used inappropriately."
Hugo Quinny Cheng, ACP-ASIM Member, assistant clinical professor at UCSF and co-director of a new continuing medical education course on medical consultation, said that while DVT prophylaxis is extremely effective, it can easily fall through the cracks. Because internists can take a few simple steps to make sure their patients receive the therapy, he said, it represents an easy way to make a big difference.
Dr. Cheng also explained that an internal medicine preoperative consultation is important for patients who are already receiving antithrombotic therapy such as warfarin. Because there is uncertainty about exactly when the risks of thrombosis outweigh the chances of bleeding, internists need to use their judgment about how aggressively to anticoagulate such patients perioperatively.
Glycemic control. When it comes to diabetes, perioperative medicine is grappling with two issues: a new understanding about the importance of tightly controlling blood sugar levels, and a growing awareness that diabetes is as important a predictor of postoperative myocardial infarction as angina.
Dr. Cheng said that while the literature is still unclear, he starts his diabetic patients about to undergo inpatient surgery on beta-blockers. "It is consistent with what we are finding out in nonperioperative medicine," he said. "Diabetes is being treated more and more as an equivalent of coronary artery disease."
And because diabetes has been shown to be an independent risk factor for surgical site infections, the traditional practice of erring on the side of high blood sugar levels in hospitalized patients is now being rethought. Many experts now recommend that diabetic surgical patients regularly receive an intravenous infusion of insulin to keep glucose levels between 125 and 175 mg/dL.
Dr. Chang pointed out that this recommendation is controversial, however, because it has not been clearly proven that high postoperative glucose levels are directly responsible for more wound infections. High wound infection rates in diabetic patients may be caused by other factors, he said, and a strategy of tight control may needlessly increase risks of hypoglycemia.
'Over the last few years, there has been a growing recognition of the importance of tighter glycemic control of patients undergoing surgery.' —Peter K. Lindenauer, FACP
Despite the controversy, Baystate's Dr. Lindenauer said that the debate gets at a relatively new development. "What is considered to be a tolerable level of hyperglycemia has been lowered," he said. "Over the last couple of years, there has been a growing recognition of the importance of tighter glycemic control of patients undergoing surgery."
The bottom line? Internists need to keep on top of their diabetic patients undergoing surgery. Noting the preoperative status and recommending postoperative care are important parts of a preoperative evaluation, experts said.
Postoperative delirium. Ask Edward R. Marcantonio, MD, assistant professor of medicine at Harvard Medical School, what should be on every internist's preoperative evaluation checklist, and he points to preventing delirium.
"Many pre-op clearance consults are very cardiac-focused, to the exclusion of many other problems," he said. "It often turns out that the cardiac issues are not the primary ones in terms of causing morbidity or even mortality in the surgical setting."
While you can expect 10% of patients over 50 to experience postoperative delirium, that number jumps to 15% for patients over 70. In addition, nearly half of older hip fracture patients experience some form of postoperative delirium.
Making matters worse, patients with delirium tend to develop other postoperative complications. While 2% of nondelirious patients develop pneumonia, for example, 15% of patients suffering from postoperative delirium develop the condition. Four percent of delirious patients are likely to die after surgery, compared to 0.2% of other patients, according to Dr. Marcantonio.
Internists can cut the odds that patients will develop complications by adding 10 minutes to preoperative visits.
The good news is that internists can cut the odds that patients will develop complications by adding 10 minutes to preoperative visits. In that time, he said, internists can administer the Mini-Mental State Examination and a functional status test, such as one that asks about activities of daily living.
A study Dr. Marcantonio published in the Jan. 12, 1994, Journal of the American Medical Association demonstrated that the results of these two tests, coupled with information such as the patient's age, results of serum chemistry tests, history of alcohol abuse and the type of surgery the patient was undergoing, could predict which patients had a high (50% or more) chance of developing postoperative delirium.
In addition, his group has found that a few interventions can reduce delirium by a third, from 50% to 32%. In the study, which was published in the May 2001 Journal of the American Geriatric Society, researchers gave hip fracture patients at high risk of developing delirium a multifaceted intervention. Physicians avoided benzodiazipines and some opiod analgesics, used prophylactic blood transfusions to keep patients' hematocrits up, and provided proactive and scheduled pain management regimens.
"If, as the internist, you bring the issue of delirium up on the radar screen, then often the other treating doctors will be able to manage things," Dr. Marcantonio said.
Deborah Gesensway is a freelance writer in Glenside, Pa.
The information included herein should never be used as a substitute for clinical judgment and does not represent an official position of ACP-ASIM.
Given how medically complex hospitalized surgical patients tend to be these days, combined with the number of physicians and therapists involved in one patient's care, there has never been a greater need for one person to coordinate all that is going on. Experts say that the preoperative evaluation is often the golden opportunity to get everyone on the same page and organize a plan to minimize avoidable complications.
There is a growing debate, however, about exactly who should take on this role. Should it be the patient's primary care physician, who knows the patient well and is best situated to oversee therapies that begin before and continue after hospitalization, such as perioperative beta-blockers? Or is it the hospitalist, who in a growing number of communities is the only internist a hospitalized patient will ever see?
Some hospitalist groups are making it a priority to set up preoperative clinics and establish contracts with surgery groups—particularly orthopedic surgeons, urologists and neurosurgeons—for exclusive rights to co-manage their hospitalized patients. This work includes preoperative evaluations.
A study of a hospitalist-orthopedic surgery co-management program at Mayo Clinic in Rochester, Minn., found that patients randomized to hospitalist co-management, as opposed to traditional care, had shorter hospitalizations and fewer complications. Hospitalists are also, in many cases, leading the effort to develop an evidence base for perioperative medicine.
In other communities, however, primary care physicians have been unwilling to turn this job over to either medical consultants or hospitalists. Geno J. Merli, FACP, professor and director of the division of internal medicine at Thomas Jefferson University Hospital in Philadelphia, said some insurers also refuse to pay for medical preoperative consultations unless the patient's primary care physician specifically requests such a consultation from another generalist.
Dr. Merli added that the physician who does a preoperative evaluation should be prepared to follow the patient through the entire hospitalization, adding that preoperative screening should not be conducted only to "clear" a patient as ready for surgery. Most of the care flagged or begun preoperatively needs to be managed throughout the hospitalization.
Physicians, he said, should not order beta-blockers for inpatients and walk away. Doctors also need to keep a close eye on glucose levels, on pain levels and on all the medications—outpatient to inpatient and back again—to make sure they are appropriately stopped and restarted with nothing getting lost in the many handoffs. This is one of the most common causes of avoidable patient harm.
"Co-management is really what intenists are being asked to do," said Andrew D. Auerbach, MD, an assistant professor of medicine at the University of California, San Francisco. "The thing that is changing is that people are realizing that they aren't taught this very well in residency."
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