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Anticoagulation in the Perioperative Period
Millions of people in the United States are on antithrombotic therapy—either antiplatelet therapy or anticoagulants—for treatment and prevention of venous and arterial thromboembolism. During a given year, as many as 10% of these patients will need an invasive procedure. How to manage antithrombotic therapy during a procedure depends on multiple factors—the indication for therapy, the nature of the intervention, and the patient's risk for either bleeding and thrombosis. While in the past recommendations were based on conjecture, there are increasing data—including randomized trial data—to guide therapy. In this chapter, we outline an approach to the patient on antithrombotic therapy who needs a procedure.
General Approach
When consulting on a patient on antithrombotic therapy who needs a procedure, several facts need to be ascertained. The first is to review the reason for antithrombotic therapy. In some cases, it may be that the patient no longer requires therapy (e.g., a remote history of a provoked venous thrombosis). Second, the consultant should clearly understand the nature of the planned procedure, including the inherent risk of bleeding. For complex procedures, it is often helpful to communicate directly with the surgeon to fully understand both the risk of bleeding and the potential benefit of the intervention. Finally, knowledge of the patient's antithrombotic agent(s) will permit the consultant to craft specific perioperative recommendations that will minimize but never eliminate both the risk of thrombosis and the risk of bleeding.
Thrombosis Risk by Reason for Antithrombotic Therapy
Venous Disease
The risk of venous thrombosis recurrence with short-term cessation of anticoagulation is most dependent on the timing of the thrombotic event(s) for which anticoagulation is being prescribed ( Table 35.1 ). Patients with recent (within the previous 90 days) thrombosis appear at the highest risk of new thrombosis, with annualized rates as high a 40%. During this active treatment, it is wisest to postpone elective procedures for at least 3 to 6 months after the last thrombotic event; the longer the surgery can be postponed, the lower the risk for recurrence of venous thromboembolism (VTE). With the possible exception of selected patients with highly prothrombotic conditions—for example, triple positive antiphospholipid syndrome, myeloproliferative neoplasm, and paroxysmal nocturnal hemoglobinuria—many patients with a more remote history of VTE can briefly interrupt anticoagulation with a low risk of periprocedural venous thromboembolism. There is no evidence that the presence of an inherited thrombophilia should influence decisions about periprocedural antithrombotic therapy.
TABLE 35.1
Risk Stratification for Perioperative Thromboembolism
| High Risk of Thromboembolism |
| Mechanical Heart Valve |
|
| Atrial Fibrillation |
|
| VTE |
|
| Not High Risk of Thromboembolism |
| Mechanical Heart Valve |
|
| Atrial Fibrillation |
|
| Venous Thromboembolism |
|
FVL, Factor V Leiden; TIA, transient ischemic attack.
Arterial Disease
Myocardial Infarction and Stroke
The risk of arterial thrombosis after aspirin (ASA) interruption is not well studied. There are rare situations (e.g., a recently deployed coronary artery stent) in which ASA interruption would be clearly contraindicated. For most other scenarios, awareness of the impact of aspirin on thrombotic risk can help clinicians weigh the risks and benefits of interrupting versus continuing aspirin treatment. For primary prevention of myocardial infarction, ASA provides a small benefit over the long term—absolute risk reduction of 0.06%—but no effect on mortality. The effect of aspirin is stronger for secondary prevention of acute coronary syndromes, with reduction in both the risk of new vascular events and mortality. For secondary prevention of stroke, aspirin effects a risk reduction of 17%.
Atrial Fibrillation
For most patients with atrial fibrillation (AF), anticoagulation provides powerful protection against stroke; the early warfarin trials showed the risk of first stroke decreased from 5% per year to 1% per year with warfarin therapy. Several tools exist to stratify patients with AF by annual stroke risk; the CHADS2 and CHADS2-VASc are the most studied ( Box 35.1 ). Although these scoring systems were developed to define the long-term (annual) chance of stroke according to individual patient characteristics, there is some evidence that they also correlate with perioperative stroke or systemic embolism in AF patients who interrupt anticoagulation for a procedure. The risk of AF patients having a stroke off anticoagulation varies. In the CHADS2 system, one point each is assessed for the presence of congestive heart failure, hypertension, age over 75, and diabetes, respectively, and two points for a history of stroke. The CHA2D2—VASc includes additional risk factors of female gender, other vascular disease and age older than 75. Both of these prediction rules have predictive value for stroke, but the CHA2D2—VASc is superior in defining a subgroup of patients at very low risk of stroke, under 0.5%. However, studies have shown that even in higher risk groups of AF patients, the periprocedural risk of stroke is low, approximately 0.3%.
Box 35.1
Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ. Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation. JAMA . 2001;285(22):2864–2870.
CHADS 2 and CHA2DS 2 -VASc Scoring System a
CHADS 2 : One point each for recent heart failure, hypertension, age >75, and diabetes. Two points assigned for history of stroke.
| CHADS2 Score | Yearly Risk of Stroke |
|---|---|
| 0 | 1.9 |
| 1 | 2.8 |
| 2 | 4.0 |
| 3 | 5.9 |
| 4 | 8.5 |
| 5 | 12.5 |
| 6 | 18.2 |
CHA 2 DS 2 -VASc: one point each for congestive heart failure, hypertension, diabetes, vascular disease, age 65–74, and female gender. Two points for stroke or age ≥75.
| Score | Yearly Risk of Stroke |
|---|---|
| 0 | 0 |
| 1 | 0.7 |
| 2 | 1.9 |
| 3 | 4.7 |
| 4 | 2.3 |
| 5 | 3.9 |
| 6 | 4.5 |
| 7 | 10.1 |
| 8 | 14.2 |
a Estimates annual risk of stroke without anticoagulation in patients with atrial fibrillation; there is limited evidence that these scores may correlate with the risk of thrombosis associated with perioperative warfarin interruption.
Lip GY, Nieuwlaat R, Pisters R, Lane DA, Crijns HJ. Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach: the euro heart survey on atrial fibrillation. Chest . 2010;137(2):263–272.
Mechanical Prosthetic Valves
The thrombotic risk of mechanical prosthetic valves depends on both valve type and position ( Table 35.2 ). Older Starr-Edwards cage ball valves have the highest risk of thrombosis, with an estimated annual risk of 12% to 30% without anticoagulation, while currently used bileaflet valves have an annual risk of less than 10%. Location of the prosthetic valve is also important in determining risk; aortic valves have a lower incidence of thrombosis than mitral valves. Multiple prosthetic valves also increase the thrombosis risk. With the possible exception of a modern valve in the aortic position in a patient who has normal left ventricular function, no prior history of stroke and in normal sinus rhythm, most current guidelines suggest that the thrombotic risk of patients with mechanical heart valves warrant bridging during any elective interruption of anticoagulant therapy. Bioprosthetic valves including transcatheter aortic valves have low risk of thrombosis, and unless there are other indications for anticoagulation, antiplatelet agents are used.
TABLE 35.2
Thrombotic Risk Associated With Valve Prosthesis in the Absence of Antithrombotic Therapy
Modified from Ansell J, Hirsh J, Poller L, et al. The pharmacology and management of the vitamin K antagonists: The Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest . 2004;126:204S–233S.
| Prosthesis Type | Rate of Thrombosis (% Per Year) |
|---|---|
| Multiple St. Jude prosthetic valves | 91 |
| Dual-leaflet (St. Jude) mitral valve | 22 |
| Single-leaflet (Björk-Shiley) aortic valve | 23 |
| Dual-leaflet (St. Jude) aortic valve | 10–12 |
Bleeding Risk
The risk of bleeding is based on several factors. One is the inherent risk of bleeding with the procedure ( Table 35.3 ). Patient-specific factors (e.g., chronic kidney or liver disease) may also impact bleeding risk. Surgeries on avascular structures or simple procedures have low rates of bleeding compared with procedures on highly vascular structures. The consequences of excess bleeding must also be considered. For example, even a small amount of excess bleeding into a confined space—especially brain or spinal cord—can be devastating. Ultimately, the surgeon or proceduralist may be able to provide the most accurate assessment of the bleeding risk associated with any particular procedure.
TABLE 35.3
Risk Stratification for Perioperative Hemorrhage
Modified from Douketis JD. Perioperative anticoagulation management in patients who are receiving oral anticoagulant therapy: a practical guide for clinicians. Thromb Res . 2002;108:3–13; and Spyropoulos AC. To bridge or not to bridge: that is the question. The argument for bridging therapy in patients on oral anticoagulants requiring temporary interruption for elective procedures. J Thromb Thrombolysis . 2010;29:192–198.
| High Risk |
|
| Moderate Risk |
|
| Low Risk |
|
Recommended Approaches Listed by Antithrombotic Agents
Antiplatelet Agents
Aspirin
Aspirin acts by permanently inhibiting cyclooxygenase; this then abolishes the production of the key platelet agonist, thromboxane A2. Platelet function returns 5 days after stopping aspirin (see Chapter 21 ).
The most robust data on the effects of aspirin on surgical bleeding are from the POISE-2 trial, in which 10,010 patients were randomized to receive either aspirin or no treatment before noncardiac surgery. This study showed no difference in deaths or nonfatal myocardial infarction (HR = 0.99) with or without aspirin, but it did show a mildly increased risk of major bleeding with aspirin (HR = 1.23). No difference in outcomes was seen in patients newly started on aspirin versus those who were continuing previously prescribed aspirin. Of note, the risk of bleeding was increased with postoperative aspirin resumption until postoperative day 8. Therefore in noncardiac surgery, aspirin can be stopped 3 to 5 days before surgery and restarted 8 to 10 days after surgery in patients whose risk of thrombosis is low. For most patients at higher risk of thrombosis (e.g., those with acute coronary syndrome in the last year, stroke in past month, or a cardiac stent), the risks of continuing aspirin will be outweighed by the benefits.
The perioperative use of aspirin in patients undergoing cardiac surgery has been controversial. A 2015 study of 4143 patients at the Cleveland Clinic who stopped aspirin therapy 6 days or more before surgery showed no difference in thrombotic outcomes yet a lower rate of bleeding. A 2016 meta-analysis that included patients undergoing both cardiac and noncardiac procedures showed no difference in cardiovascular outcomes with aspirin cessation and a decreased risk of bleeding. A randomized trial of 5784 patients showed that the use of aspirin before coronary artery surgery neither improved the primary outcome of death/thrombotic events nor increased rates of bleeding. In this trial there was a trend for increased risk of cardiac tamponade associated with ASA use (1.1% vs. 0.4%, P = .08). Taken together, the available evidence suggests it would be prudent to stop aspirin several days before cardiac surgery in most patients.
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