Questions
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An 85-year-old woman presented for left hip arthroplasty after a fall sustained 2 days previously. She has osteoarthritis with severe hip pain and had planned to have a total hip replacement in the future. She has coronary artery disease for which she required two drug-eluting stents 6 months ago. Current medications are metoprolol, 50 mg, simvastatin, 20 mg, aspirin, 325 mg, and clopidogrel, 75 mg.
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What are the preoperative anesthetic considerations for a patient with coronary artery drug-eluting stents currently taking antiplatelet medications?
Elderly patients presenting for orthopedic procedures have a high prevalence of cardiopulmonary comorbidities. These patients are at considerable risk for adverse perioperative events including myocardial infarction (MI), acute stent thrombosis, and death. The evaluation and optimization of all cardiac risks are paramount to patient survival.
Percutaneous coronary intervention with balloon angioplasty and placement of stents within obstructed coronary vessels has emerged as an effective and widespread treatment for symptomatic coronary artery disease. After initial implantation, the foreign body nature of stent struts can serve as a nidus for thrombi formation. Dual antiplatelet therapy with aspirin and a thienopyridine derivative (e.g., clopidogrel) is administered to decrease the risk of stent thrombosis. After a period of time, stent struts are incorporated into coronary artery endothelium, and the risk of thrombosis is significantly reduced. Nevertheless, patients at risk for stent thrombosis requiring elective, urgent, or lifesaving surgery can present at any time.
In 2009, the American Society of Anesthesiologists (ASA) published a practice alert to address perioperative management of patients with coronary artery stents (See Chapter 2 for further details). The most critical preoperative evaluation of these patients involves the type, timing, number, and location of the stents. A cardiology consultation and echocardiography may be considered to assess myocardial perfusion and ventricular function and to plan for perioperative coronary stent management. Current recommendations from this practice alert are summarized as follows:
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Delay elective noncardiac procedures for which there is a significant bleeding risk for the following time frames:
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Bare metal stents—minimum of 1 month (usually chosen over drug-eluting stents if urgent surgery is imminent or planned ahead of time)
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Drug-eluting stents—12 months
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For all procedures (including urgent or emergent), continue aspirin therapy throughout perioperative period.
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Beyond this time frame, discontinue clopidogrel for 7 days or ticlopidine for 14 days before surgery and restart therapy as soon as postsurgical hemostasis is adequate.
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Is there evidence for bridging therapy to decrease the risk of stent thrombosis resulting from premature discontinuation of thienopyridine therapy?
In 2007, several organizations including the American Heart Association (AHA) and American College of Cardiology (ACC) convened and authored two publications on premature discontinuation of antiplatelet therapy. The AHA/ACC guidelines emphasized the increased risk of life-threatening stent thrombosis and acute MI in the perioperative period as a result of premature discontinuation of thienopyridine therapy. The AHA/ACC concluded that there are no clear benefits to using any anticoagulants, including warfarin or heparin, or any antithrombotics as bridging therapy to decrease the incidence of stent thrombosis.
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What are the risks and benefits of early hip surgery in this patient; is this considered elective surgery; would you proceed with this case?
As with many difficult clinical decisions, informed dialogue between the patient and the perioperative care team regarding risks and benefits of surgery is essential to ensure optimal management. In this scenario, the major risks of proceeding with surgery are adverse perioperative cardiac events from premature discontinuation of clopidogrel and increased surgical hemorrhage from prolonged platelet inhibition. This clinical dilemma is a double-edged sword. According to the 2007 AHA/ACC advisory, early discontinuation of antiplatelet therapy in patients with drug-eluting stents is associated with a 25%–29% incidence of stent thrombosis. These data come from two large cohort observational studies on medical patients presenting for percutaneous coronary intervention after acute MI. The reasons for early cessation of therapy in these studies were primarily related to poor patient adherence. Although it may be unfair to extrapolate these findings for the perioperative population, clear evidence for guidance is lacking. Two frequently quoted studies in the surgical population, with only 40 patients and 47 patients in each group, established the incidence of stent thrombosis as 15%–17% (approximately 7 patients in each study). Both retrospective studies involved withholding aspirin, ticlopidine, or both agents prematurely within 2 weeks after bare metal stent placement in patients proceeding with noncardiac surgery. The antiplatelet agents were stopped at least 5 days before surgery in one study, whereas the other study continued these agents up to 2 days and even on the day of surgery. In both studies, six of the seven patients with stent thrombosis died, resulting in an 86% case-fatality rate in patients who developed stent thrombosis. Of the 20 patients who continued antiplatelet therapy throughout the perioperative period, only 1 died after surgery. The authors explain that the stressful, procoagulant, and proinflammatory nature of surgery may exacerbate stent thrombosis further in this setting. No randomized trials have studied bleeding risk in this surgical population. The increased risk of hemorrhage is inferred from studies involving patients with drug-eluting stents taking clopidogrel undergoing cardiac surgery.
Given these catastrophic cardiac and possible bleeding risks, it seems reasonable to postpone surgery. However, the decision to delay hip surgery in an elderly patient is not always straightforward. First, the 30-day and 1-year mortality rates in the elderly population with hip fractures are 5%–10% and 12%–37%, respectively. In two separate large meta-analyses, ) and ) demonstrated 19%–40% risk reduction in mortality if hip surgery was performed <72 hours after fracture. These meta-analyses were based on numerous clinical trials with a cumulative number of patients up to 250,000. Risk reduction in mortality is calculated after adjusting for a myriad of perioperative confounding factors. Other benefits of early hip surgery include decreased incidences of pneumonia and pressure ulcers and improved quality of life for patients who would otherwise be bed bound. Overall, these benefits make a strong and convincing argument that early surgical intervention reduces mortality, and hip fracture surgery should not be classified as a purely elective procedure.
As mentioned, the best approach to explain the risks and benefits is to have an informed dialogue with the patient. On one hand, performing surgery after acute discontinuation of clopidogrel puts the patient at risk for the opposing problems of stent thrombosis (incidence and mortality approximately 15%) and increased risk of bleeding. As mentioned, the dearth of large prospective clinical studies makes it nearly impossible to quantify these individual risks. On the other hand, deferring surgery puts the patient at significant risk for mortality (37%), developing pneumonia and pressure ulcers while bed bound, and an overall decrease in quality of life. The urgent and complex nature of this clinical dilemma calls for a critical perioperative evaluation on an individual basis with an interdisciplinary approach that uses all pertinent medical information.
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Summarize the current guidelines on neuraxial anesthesia for an anticoagulated patient in terms of commonly used agents, herbal agents, and new agents.
Table 51-1 summarizes evidenced-based guidelines published by the American Society of Regional Anesthesia and Pain Medicine (ASRA) in 2010. The authors note that “variances from recommendations contained in this document may be acceptable based on the judgment of the responsible anesthesiologist.”
| Drug | Key ASRA Guidelines | Wait Time between Anticoagulant and Needle Insertion | Wait Time between Last Needle Puncture or Catheter Removal to Initiating Anticoagulation |
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| Thienopyridine derivatives | Actual risk unknown due to lack of clinical trials | Clopidogrel—7 days Ticlopidine—14 daysPrasugrel—5–7 days | Restart as soon as adequate surgical hemostasis is achieved |
| Warfarin * | Check INR if first dose given >24 hours or more than one dose given preoperatively | Initiating therapy: INR <1.5 or first dose given within 48 hours Discontinuation of long-term therapy: 5 days with normal INR | No wait time necessary because warfarin takes >24 hours to reach peak effect |
| Heparin | Safe with 5000 units SQ BID >10,000 units daily or TID dosing: Proceed but MONITOR † On heparin for > 4 days obtain platelet count owing to risk of heparin-induced thrombocytopenia | 2–4 hours after heparin is stopped For IV or TID dosing, consider MONITOR † after needle insertion | 1–2 hours |
| LMWH (i.e., enoxaparin, dalteparin, tinzaparin) | No evidence for routine checking of anti-Xa level Female, elderly, renal impairment, and concomitant anticoagulants associated with increased risks of spinal hematoma | 12 hours for prophylactic dose 24 hours for higher doses (e.g., bridging therapy, DVT treatment, postoperative prophylaxis) | 24 hours after bloody or difficult placement BID: first dose 24 hours; remove catheters at 22 hours after surgery Daily dosing: >8 hours after surgery and then second dose 24 hours afterward Remove catheter >12 hours after last dose but 2 hours before next dose |
| NSAIDs | Single agent: no added risk | No contraindication | No contraindication |
| Glycoprotein IIb/IIIa antagonists | Contraindicated within 4 weeks of surgery | Abciximab—24–48 hours | Unclear |
| Risk with neuraxial anesthesia unknown | Eptifibatide and tirofiban—4–8 hours | ||
| Thrombin inhibitors: argatroban, desirudin, lepirudin, bivalirudin; dabigatran (oral) ‡ | No antidote or reversal Avoid neuraxial techniques | Unknown timing from published guidelines Most recent ASRA expert recommendation: dabigatran—5–7 days European experience: 8–10 hours | Insufficient evidence about safety European experience: 2–4 hours |
| Factor Xa inhibitor: fondaparinux; Rivaroxaban (oral) § | Unknown risk; proceed if atraumatic, first-pass needle insertion § | Unknown | 2 hours in the trial |
| European experience: fondaparinux—36–42 hours | Fondaparinux in Germany: 6–12 hours | ||
| Fibrinolytics/thrombolytics | Never proceed “except highly unusual circumstances” | No data; avoid needle if possible Wait at least 10 days if neuraxial blockade must proceed | No data on safety and timing Avoid agents after needle if possible |
| Herbal medications | Garlic, ginkgo biloba, and ginseng all increase bleeding, but clinical studies are lacking | No interference as single agent | No interference as single agent |
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