Perioperative antiplatelet therapy: the case for continuing therapy in patients at risk of myocardial infarction

Coagulation concepts update

OBJECTIVE

Since the previous comprehensive radiology review on coagulation concepts that was done in 1990, many studies have been published in the medical and surgical literature that can guide the approach of a radiology practice. The purpose of this article is to provide an analysis of these works, updating the radiologist on proper use and interpretation of coagulation assessment tools, medications that modify the hemostatic system, and the use of transfusions prior to interventions.

CONCLUSION

The basic tools for coagulation assessment have not changed; however, results from subspecialty research have suggested ways in which the use of these tools can be modified and streamlined to safely reduce time and expense for the patient and the health care system.

Nordic guidelines for neuraxial blocks in disturbed haemostasis from the Scandinavian Society of Anaesthesiology and Intensive Care Medicine

BACKGROUND

Central neuraxial blocks (CNBs) for surgery and analgesia are an important part of anaesthesia practice in the Nordic countries. More active thromboprophylaxis with potent antihaemostatic drugs has increased the risk of bleeding into the spinal canal. National guidelines for minimizing this risk in patients who benefit from such blocks vary in their recommendations for safe practice.

METHODS

The Scandinavian Society of Anaesthesiology and Intensive Care Medicine (SSAI) appointed a task force of experts to establish a Nordic consensus on recommendations for best clinical practice in providing effective and safe CNBs in patients with an increased risk of bleeding. We performed a literature search and expert evaluation of evidence for (1) the possible benefits of CNBs on the outcome of anaesthesia and surgery, for (2) risks of spinal bleeding from hereditary and acquired bleeding disorders and antihaemostatic drugs used in surgical patients for thromboprophylaxis, for (3) risk evaluation in published case reports, and for (4) recommendations in published national guidelines. Proposals from the taskforce were available for feedback on the SSAI web-page during the summer of 2008.

RESULTS

Neuraxial blocks can improve comfort and reduce morbidity (strong evidence) and mortality (moderate evidence) after surgical procedures. Haemostatic disorders, antihaemostatic drugs, anatomical abnormalities of the spine and spinal blood vessels, elderly patients, and renal and hepatic impairment are risk factors for spinal bleeding (strong evidence). Published national guidelines are mainly based on experts' opinions (weak evidence). The task force reached a consensus on Nordic guidelines, mainly based on our experts' opinions, but we acknowledge different practices in heparinization during vascular surgery and peri-operative administration of non-steroidal anti-inflammatory drugs during neuraxial blocks.

CONCLUSIONS

Experts from the five Nordic countries offer consensus recommendations for safe clinical practice of neuraxial blocks and how to minimize the risks of serious complications from spinal bleeding. A brief version of the recommendations is available on http://www.ssai.info.

[Antiplatelet agents and anticoagulants: management of the anticoagulated surgical patient]

Among the drugs most widely consumed by patients are both antiplatelet agents (aspirin, clopidogrel, ticlopidine) and anticoagulants (acenocoumarol, warfarin, low molecular weight heparin, fondaparinux). The use of these drugs in the perioperative period is an essential concern in patient care due to the need to balance the risk of bleeding against thrombotic risk (arterial or venous), which is increased in surgical patients. The present review highlights three main aspects. Firstly, withdrawal of antiplatelet agents is recommended between 1 week and 10 days before surgery to minimize perioperative bleeding. However, this practice has been questioned because patients without the required antiplatelet coverage may be at greater risk of developing cardiac, cerebral or peripheral vascular complications. Therefore, the recommendation of systematic antiplatelet withdrawal for a specific period should be rejected. Currently, risks should be evaluated on an individual basis to minimize the time during which the patient remains without adequate antiplatelet protection. Secondly, thromboprophylaxis is required in most surgical patients due to the high prevalence of venous thromboembolic disease. This implies the use of anticoagulants and the practice of regional anesthesia has been questioned in these patients. However, with the safety recommendations established by the various scientific societies, this practice has been demonstrated to be safe. Finally, "bridge therapy" in patients anticoagulated with acenocoumarol should be performed on an individual basis rather than systematically without taking into account the thrombotic risks of each patient. The perioperative period involves high arterial and venous thrombotic risk and the optimal use of antiplatelet agents and anticoagulants should be a priority to minimize this risk without increasing hemorrhagic risk. Multidisciplinary consensus is essential on this matter.

Perioperative handling of patients on antiplatelet therapy with need for surgery

The widespread use of metal stents and drug-eluting stents has shown the extent to which patients with unstable coronary perfusion depend on antiplatelet drugs, and how their risk of late thrombosis depends on the long-term use of agents such as clopidogrel. It has also been shown that the risk of surgical bleeding, if antiplatelet drugs are continued, is lower than that of coronary thrombosis if they are withdrawn. Thus, except for low-risk settings, the practice of withdrawing antiplatelet drugs 5-10 days prior to surgical procedures should be changed. The following suggestions are meant to provide a guideline in this respect. Most of the current surgical procedures may be performed while on low-dose aspirin treatment. Except when bleeding may occur in closed spaces (e.g. intracranial surgery, spinal surgery in the medullary canal, surgery of the posterior chamber of the eye) or where excessive blood loss is expected, where only clopidogrel should be discontinued; in all other cases the surgical procedures should be carried out in the presence of dual antiplatelet agents (if prescribed). Aspirin may be discontinued only in subjects at low risk of thrombosis, and at high risk of intraoperative bleeding. Operations associated with an expected excessive blood loss should be postponed unless vital. When prescribed for acute coronary syndrome or during stent re-endothelialization, clopidogrel should not be discontinued before a noncardiac procedure. For elective procedures, surgery should be postponed until the end of the indication for clopidogrel. After the operation, clopidogrel should be resumed within the 12-24 h. Cardiac procedures should be postponed for at least 4 days after clopidogrel withdrawal. The thrombotic risk of preoperative withdrawal of antiplatelet drugs overwhelms the benefit of regional or neuraxial blockade. Antiplatelet treatment replacement by heparin or low-molecular weight heparin does not provide protection against the risk of coronary artery or stent thrombosis. Haemostasis requires that at least 20% of circulating platelets have a normal function. As the effects of antiplatelet agents are not reversible by other drugs, fresh platelets are the only manner to rapidly restore normal haemostasis. Aprotinin decreases postoperative bleeding and transfusion rates in patients undergoing CABG and on clopidogrel during the days preceding surgery.

Medication reconciliation performed by pharmacy technicians at the time of preoperative screening

BACKGROUND

Medication errors occur regularly in surgical patients, especially due to transfer problems at the time of hospital admission. A method for decreasing the error rate is medication reconciliation by hospital pharmacists as part of a preoperative clinic. The role of pharmacy technicians in this process has not been studied.

OBJECTIVE

To study the use of pharmacy technicians in medication reconciliation by measuring the effect of early reconciliation in the preoperative clinic on medication and allergy discrepancies and on inadvertent continuation of antithrombotics. A secondary objective was to study the effect of community pharmacist follow-up on recommendations to discontinue antithrombotic therapy.

METHODS

During the preintervention measurement period, patients received usual care by anesthesiologists, who recorded the medication and documented allergies of the patient. The intervention consisted of the addition of a pharmacy technician to the preoperative screening clinic to perform the same tasks as anesthesiologists as related to medication reconciliation. If necessary, the patient was advised on stopping the antithrombotic. On the day that the patient was supposed to stop the antithrombotic, that person's community pharmacist contacted the patient to determine whether this had been done. The main outcome measures were the proportions of patients with one or more medication discrepancy, one or more allergy discrepancy, and one or more antithrombotic error.

RESULTS

In the preintervention period, 204 patients were evaluated; 93 were included in the postintervention analysis. The proportion of patients with one or more medication discrepancy (RR 0.29; 95% CI 0.12 to 0.71) was statistically significantly reduced in the postintervention group. The proportions of patients with one or more allergy discrepancy (RR 0.76; 95% CI 0.35 to 1.64) and one or more antithrombotic errors (RR 0.18; 95% CI 0.02 to 1.33) were reduced, but not significantly. Follow-up by the community pharmacist did not identify any patients who had not followed the preoperative clinic's advice on temporarily withholding their antithrombotics.

CONCLUSIONS

The results of this study show that pharmacy technicians can be successfully assigned to a preoperative clinic, resulting in a statistically significant decrease in medication discrepancies.

Point-of-care assessment of antiplatelet agents in the perioperative period: a review

The aim of this paper was to review the strengths and limitations of current 'point-of-care' techniques for the detection of antiplatelet drug effects. The review was based on a Medline search for articles with key words related to "platelet function tests", "point-of-care", and "anaesthesia", published in English between January 1996 and September 2008. It was found that global assessments of 'haemostasis', such as the standard thrombelastograph, Sonoclot, Clot Signature Analyser and Hemodyne, are not specific for platelet function and are essentially insensitive to cyclooxygenase inhibitors (aspirin, non-steroidal anti-inflammatory drugs) and P2Y12 antagonists (ticlopidine, clopidogrel). Global assessments of 'platelet function', such as the PFA-100 and PlateletWorks, are more specific for platelet function, but also have limited sensitivity for cyclooxygenase inhibitors and P2Y12 antagonists. The newer devices developed specifically for the assessment of antiplatelet drugs, such as Platelet Mapping, the Impact Cone and Platelet Analyser and the VerifyNow, are more promising, but are not as sensitive as laboratory platelet aggregometry. All three categories of devices detect G(p)II(b)/III(a) antagonists (abciximab, tirofiban, eptifibatide) activity, but not all provide quantitative assessments for monitoring therapy. The limitations appeared to be related to the complexity of platelet function, the multiple pathways of platelet activation, the wide interpatient variability in platelet responses and the interdependence between platelets and other aspects of coagulation. The strengths and limitations of point-of-care devices should be appreciated before they are used to assist clinical decision-making in the perioperative period.

[Patients with coronary artery stents: when and how should operations be carried out?]

Nowadays stents are implanted in over 90% of percutaneous coronary interventions. Depending on the type of stent implanted, dual antiplatelet therapy combining a cyclooxygenase inhibitor such as acetylsalicylic acid and an adenosine diphosphate receptor antagonist (thienopyridine) such as clopidogrel is required for 1-12 months. Premature termination of antiplatelet therapy during non-cardiac surgery significantly increases the risk of stent thrombosis and consequently myocardial infarction, whereas continuation of dual antiplatelet therapy during surgery increases the risk of severe bleeding. Accordingly, treatment recommendations have to be based on the individual relative risk. In cases with a high risk for major bleeding during surgery, interruption of antiplatelet therapy may be required, whereas in cases of a high risk of stent thrombosis, both antiplatelet drugs should be continued throughout surgery. Patients on dual antiplatelet therapy should be counseled by a team of anesthesiologists, surgeons and cardiologists, to devise the right point in time for the operation, the best perioperative antiplatelet therapy and the appropriate perioperative monitoring.

Perioperative management of antiplatelet agents in noncardiac surgery

It is common that patients who are scheduled for surgery are treated with antiplatelet agents (APAs) due to their wide indications. The management of these APAs in the perioperative period (acetylsalicylic acid alone, a thienopyridine alone or, in most cases, a combination of them) has a dual perspective: the risk of bleeding when the patient is operated under the effect of the APA against the risk of thrombosis if it has been withdrawn. The main challenges for the anaesthesiologist and the surgeon include patients with a coronary stent (mainly, new drug-eluting coronary stents), those undergoing urgent surgery and those undergoing high bleeding risk surgery. We review current protocols and discuss the most recent proposals for the management of APAs in patients undergoing noncardiac surgery. Current recommendations include the maintenance of aspirin if possible throughout the perioperative period, in order to limit the risks of cardiological, vascular or neurological postoperative events, although this makes it necessary to assume a small risk for haemorrhagic complications in some patients. Nevertheless, there are many circumstances that are not clear yet and, in this situation, it is crucial that patients are treated with a multidisciplinary approach (anaesthesiologists, surgeons, cardiologists and haematologists).

Perioperative cardiac evaluation: assessment, risk reduction, and complication management

Perioperative cardiac complications are among the most feared outcomes after surgery. Using evidence-based guidelines and expert opinion, physicians can perform a risk assessment and decide whether further cardiac testing, medical therapy, or coronary intervention is necessary to optimize the patient's medical condition prior to surgery. This article reviews the major concepts and recommendations from the ACC guidelines for preoperative cardiac evaluation and perioperative management to reduce risk. Medical management of the major postoperative cardiac complications is also discussed.

Expanding the recognition and assessment of bleeding events associated with antiplatelet therapy in primary care

Antiplatelet therapy is an evidence-based, guideline-recommended, worldwide standard of care for treatment of patients with atherothrombosis. However, clinical implementation of the guidelines is suboptimal, in part because of physician and patient nonadherence. The increased risk of bleeding associated with antiplatelet therapy is often the reason for nonadherence, and several programs have been created to increase adherence to guideline treatment recommendations. Despite the relative success of such initiatives, including Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes With Early Implementation of the ACC/AHA Guidelines, Guidelines Applied in Practice, and the American Heart Association's Get With the Guidelines and a Science Advisory, a current estimate is that less than 50% of atherothrombotic patients are taking antiplatelet therapies as recommended by national guidelines. A PubMed and MEDLINE search of the literature (January 1, 1983-May 15, 2008) was performed to examine the bleeding risks associated with various antiplatelet therapies. Relevant clinical trials, observational registry data, and other studies relevant to treatment and guideline recommendations were selected from articles generated through specific search terms. This comprehensive review contributes to the understanding of the benefit-to-risk ratio of antiplatelet therapy for patients with atherothrombosis.

Expanding the recognition and assessment of bleeding events associated with antiplatelet therapy in primary care

Antiplatelet therapy is an evidence-based, guideline-recommended, worldwide standard of care for treatment of patients with atherothrombosis. However, clinical implementation of the guidelines is suboptimal, in part because of physician and patient nonadherence. The increased risk of bleeding associated with antiplatelet therapy is often the reason for nonadherence, and several programs have been created to increase adherence to guideline treatment recommendations. Despite the relative success of such initiatives, including Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes With Early Implementation of the ACC/AHA Guidelines, Guidelines Applied in Practice, and the American Heart Association's Get With the Guidelines and a Science Advisory, a current estimate is that less than 50% of atherothrombotic patients are taking antiplatelet therapies as recommended by national guidelines. A PubMed and MEDLINE search of the literature (January 1, 1983-May 15, 2008) was performed to examine the bleeding risks associated with various antiplatelet therapies. Relevant clinical trials, observational registry data, and other studies relevant to treatment and guideline recommendations were selected from articles generated through specific search terms. This comprehensive review contributes to the understanding of the benefit-to-risk ratio of antiplatelet therapy for patients with atherothrombosis.

Preoperative screening, evaluation, and optimization of the patient's medical status before outpatient surgery

PURPOSE OF THE REVIEW

Preoperative evaluation and optimization of a patient's medical condition are important components of anesthesia practice. With ever increasing numbers of patients with serious comorbidities having complex procedures as outpatients, the task of gathering information and properly preparing for their care is challenging. Improvements in assessment and management can potentially reduce adverse events, improve patient and caregiver satisfaction, and reduce costs.

RECENT FINDINGS

A growing body of literature and evidence-based practices and guidelines can assist clinicians who work in the expanding field of preoperative medicine. Care providers from various specialties in medicine are developing innovative methods, tools, and knowledge to advance science and processes. Data-driven practices are beginning to close the information gap that has plagued this field of medical practice.

SUMMARY

Preparation of patients before surgery is a necessary and vital component of perioperative medicine. Practices are developing to guide effective interventions that benefit patients and healthcare systems. Outpatients present special challenges to preoperative assessment.

[Perioperative discontinuation of antiplatelet therapy of patients with coronary stents. Reevaluating the risks]

According to the present guidelines, patients with coronary stents are to be treated with dual antiplatelet therapy. In case surgery is needed, the risk of a fatal stent thrombosis by withdrawing antithrombotics needs to be balanced in each individual case against the risk of haemorrhagic complications on continued antiplatelet medication. We present a case of fatal stent thrombosis and discuss the current evidence regarding perioperative continuation and interruption of antiplatelet therapy for this patient population. In summary the haemorrhagic risk with acetylsalicylic acid for secondary prevention seems very low, and it should be discontinued only in selected cases. Continued dual anticoagulation concepts are also discussed.

Perioperative management of systemic oral anticoagulants in patients having outpatient hand surgery

Long-term oral anticoagulant therapy is frequently initiated in patients with elevated risk of venous or arterial thromboembolism. The most common indications for anticoagulation are chronic atrial fibrillation, mechanical heart valves, a history of venous thromboembolism, and hypercoagulable states. In the perioperative setting, these patients pose considerable challenges to physicians, who must weigh the thrombotic risks of therapy interruption against the bleeding risks of continuation. Development of uniform recommendations for management of anticoagulated patients undergoing elective hand surgery has proven problematic. Difficulties intrinsic to study design include a short duration of risk exposure, lack of patient uniformity, and rarity of baseline adverse events. Given the paucity of substantive evidence on which to base management decisions, physicians have long relied on clinical judgment to guide their choices. This review summarizes the available data specific to elective hand surgery and provide a general context in which evidence-based treatment decisions can be made.