Dr. Gregory Weiss, a cardiovascular anesthesiologist, breaks down and provides real-world perspective on the application of a recent scientific statement from the AHA and ASA on perioperative management to lower stroke risk in patients undergoing noncardiac and nonneurological procedures.
Complications can, and do, occur in the peri-operative period. While much of the research devoted to peri-operative safety focuses on preventing mortality, stroke remains a potentially devastating complication that deserves its own attention.
While stroke is known to be a greater possibility when patients undergo either cardiac or neurological surgery the risk, management, and prevention of stroke when undertaking other types of surgery is less well-publicized. Recently, the American Heart Association and the American Stroke Association issued a joint statement published in Circulation addressing this disparity.
As a cardiothoracic anesthesiologist, recognizing risk factors and designing an anesthetic plan that minimizes the risk for perioperative stroke are a part of my daily routine. However, it is important for all anesthesiologists and surgeons alike to take this problem seriously and plan accordingly. This timely statement by the AHA and ASA focuses on three main points in an effort to disseminate the information about stroke and surgery and improve patient outcomes.
The three areas of focus are: Preoperative optimization, intraoperative strategies to reduce the risk of stroke, and strategies for the evaluation and treatment of patients with suspected postoperative strokes.
The risk for stroke after non-cardiac and non-neurological surgery ranges from 0.1% to 1.0%.1 While these numbers are small the devastating implications of even one stroke make prevention strategies of great importance. As expected, strategies for preventing perioperative stroke focus on the recognition of factors that put patients at risk. Key risk factors for perioperative stroke include advanced age, renal disease, prior transient ischemic stroke, heart attack within six months, atrial fibrillation, hypertension, chronic obstructive pulmonary disease, smoking, female sex, and diabetes mellitus.
Evidence clearly shows that following a stroke, waiting to perform non-cardiac/non-neurological surgery for as long as prudent is the best way to prevent subsequent perioperative stroke. As an anesthesiologist, I am very comfortable suggesting that a surgeon wait to perform an elective procedure if the patient has had a stroke within the last six months to a year. For the most part, there are no reasons to rush a purely elective surgery in such a patient.
Carotid stenosis represents another common cause of stroke. Currently, it is not completely clear whether people with moderate or asymptomatic carotid stenosis should undergo carotid endarterectomy (CEA) or carotid stenting (CAS) before elective surgery. I do agree with current guidelines that strongly suggest carotid revascularization prior to elective surgery when the carotid stenosis is greater than 70% and is accompanied by same-sided symptoms. Ultimately, the decision to perform a CEA or CSA should be based on the risk versus benefit for the individual patient.
Present in nearly one-third of patients, a patent foramen ovale (PFO) also increases the risk for stroke. While weak links between cryptogenic stroke and PFO have been found, I agree with the authors of this statement that if PFO closure is already planned it is reasonable to proceed prior to elective surgery.
While perioperative beta-blockers have been linked to reductions in cardiac events, some evidence suggests that they may increase the risk for stroke and death.1 Current recommendations support continuing beta-blockers in the perioperative period if the patient has been on them long-term and starting them prior to surgery if the patient is at higher risk for cardiac complications. This decision should be based on the unique characteristics of the patient and the planned surgery.
Statin therapy has become ubiquitous for preventing cardiovascular events. Good evidence suggests continuing statin therapy in the perioperative period even though no significant reductions in stroke have been found through their use. Studies lacking significance should be taken with a grain of salt. The safety profile of statin medications makes the choice to continue them an easy one.
While extensive guidelines on managing anticoagulants in the perioperative period exist, the take-home message with regards to stroke prevention and perioperative bleeding should be to weigh the risks with the benefits of the surgery. I strongly suggest reviewing the recommendations prior to proceeding with elective procedures.
Intraoperative blood pressure management has been a hot topic in recent years. We know that low blood pressures during anesthesia put patients at higher risk for cardiac events, kidney injury, and death. As a general rule, we try to keep blood pressure within 20% of baseline during surgery and mean arterial pressures (MAP) over 60 mmHg. Recognizing that there is insufficient data to make concrete blood pressure targets, the AHA/ASA workgroup recommends keeping MAP over 70mmHg. Anesthesiologists recognize that arbitrary numbers are of little use as all patients respond differently to anesthetics. However, we generally support the idea of providing a margin of safety in the operating room.
Both goal-directed blood pressure management and transfusion thresholds are mentioned in these recommendations. The role of global perfusion directed fluid and blood pressure management is unclear and the need for continuous measures of cardiac output make its utility for routine surgery uncertain. As for transfusion thresholds, I believe it is reasonable to set a goal slightly higher than the traditional Hgb level of 7g/dL as the paper suggests 8g/dL may be more appropriate in patients with cerebrovascular disease or prior strokes. I believe that this issue is not clear-cut. The choice to maximize oxygen delivery must be weighed against increasing viscosity and preventing volume overload.
While the AHA/ASA workgroup does address the choice of anesthetic best suited to prevent perioperative stroke, no clear recommendations were made. This is owing to the fact that, despite exhaustive study, no currently used anesthetic agent has been found to be either neurotoxic or neuroprotective. The best practice is to tailor every anesthetic to the individual patient based on their unique characteristics. I do, however, agree with the recommendation to avoid hyperventilation and to provide lung-protective ventilation to the majority of surgical patients.
Studies show that more than 60% of in-hospital strokes are likely perioperative or periprocedural. It is of vital importance to recognize postoperative strokes quickly so that treatment can be initiated before permanent damage occurs. It is suggested that regular neurological assessments should be made in the post-anesthesia care unit to include an established stroke scale when assessments are abnormal.
Most hospitals have an emergency alert for strokes. Once identified a “stroke alert” should be called and the stroke or rapid response team activated. An immediate non-contrast head CT should be performed plus or minus angiography if the situation warrants it. If a large vessel occlusion is identified mechanical thrombectomy should be primarily considered with intravenous alteplase thrombolytic therapy in small vessel ischemic stroke being weighed against the risk of bleeding after surgery. If thrombolytic therapy is to be considered, it must be administered within 4.5 hours of symptom onset.
In conclusion, perioperative stroke is a devastating surgical complication. While thankfully rare, the incidence of stroke during or after surgery should not be discounted. Advanced planning, a thoughtful anesthetic that avoids prolonged hypotension, and a plan ready to go if a stroke is discovered are the keystones of preventing a devastating outcome. This effort relies on the entire care team rather than any single clinician. Together, armed with guidance from the American Heart Association and American Stroke Association, we can reduce the occurrence of perioperative strokes and rapidly treat them if they do occur, improving outcomes and the lives of our patients.
This statement, "Perioperative Neurological Evaluation and Management to Lower the Risk of Acute Stroke in Patients Undergoing Noncardiac, Nonneurological Surgery: A Scientific Statement From the American Heart Association/American Stroke Association," was published in Circulation.