Perioperative medicine: Combining the science and the art
STRESS TESTING
Significant background knowledge is required to answer the important question in the ACC/AHA algorithm, ie, whether further testing will have an impact on decision-making or perioperative care.2 Dr. Cohn provides some of this information by noting the abysmal positive predictive value of preoperative noninvasive cardiac testing (with studies ranging from 0% to 37%) and by correctly stating that no benefit has been observed with preoperative cardiac revascularization.
If this is not widely known, I share Dr. Cohn’s fear that the new guidelines may stimulate increased ordering of preoperative stress tests. We observed this trend with the highly scripted 2002 ACC/AHA perioperative guidelines7 and subsequently learned that stress testing before surgery very seldom changes patient management.
A preoperative stress test should be reserved for patients with symptoms suggestive of ischemic heart disease. As a diagnostic study, the value of stress testing is excellent. This is not true when it is used as a screening test for asymptomatic patients, where its ability to predict perioperative cardiovascular events is extremely poor. The only other indication for preoperative stress testing is the rare occasion when further risk stratification is desired for exceptionally high-risk patients. In this scenario, test results may influence the decision to proceed with surgery vs seeking nonoperative approaches or palliative care.
MANAGING MEDICATIONS
Dr. Cohn discusses pertinent issues in the perioperative management of patients’ medications, an important component of the preoperative evaluation.
Despite the inconsistent clinical trial results on perioperative beta-blockers, his assessment of their risks and benefits is clinically accurate and practical. Furthermore, I fully agree with Dr. Cohn’s thoughtful approach regarding perioperative statins, despite the limited data available from randomized controlled trials.
With respect to perioperative aspirin use, I have concerns with Dr. Cohn’s statement that it may be reasonable to continue aspirin perioperatively if the risk of potential cardiac events outweighs the risk of bleeding. Given the result of the recently published second Perioperative Ischemic Evaluation (POISE-2) trial8 that showed a significantly higher risk of major perioperative bleeding in patients randomized to low-dose aspirin, it is difficult to advocate continuing aspirin when no cardiovascular protection was found in this very large trial. I agree with Dr. Cohn that this applies only to patients with no history of coronary artery stent placement, as patients with a stent should remain on low-dose aspirin throughout the entire perioperative period.
Controversy also surrounds angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. Dr. Cohn agrees with the ACC/AHA guidelines to continue these agents before surgery; however, I favor holding them on the day of surgery. Although the risk of hypotension-induced cardiac events has not been clearly demonstrated, a recent retrospective study involving more than 1,100 patients showed significantly more acute kidney injury (even after adjusting for hypotension) as well as an increased length of hospital stay in the patients exposed to these agents before surgery.9 Given these findings, in addition to the postinduction hypotension (which can be profound) commonly observed by our anesthesiology colleagues, I recommend holding angiotensin-converting enzyme inhibitors and angiotensin receptor blockers on the day of surgery, with very few exceptions.
THE SCIENCE AND ART OF MEDICINE
Dr. Cohn acknowledges that we lack scientific data to answer many questions that arise when caring for the perioperative patient and thus we rely on the ACC/AHA guidelines to provide a framework. These scientific knowledge gaps emphasize the importance of the art of medicine in the perioperative arena. Although we may desire “cookbook” guidelines, the significant gaps in the perioperative medicine evidence base reinforce the necessity to provide individual patient-level care in a multidisciplinary environment with our surgery and anesthesiology colleagues. Without the proper balance of science and art in perioperative medicine, we sacrifice our ability to deliver optimal care for this high-risk patient population.
