Coronary Artery Stents: II. Perioperative Considerations and Management

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.

Cardiovascular problems in noncardiac surgery

PURPOSE OF REVIEW

Perioperative cardiac complications remain a major area of concern as our surgical population increases in volume, age and frequency of comorbidity. A variety of strategies can be used to optimize patients and potentially reduce the incidence of these serious complications.

RECENT FINDINGS

Recent literature suggests a trend towards less invasive testing for detection and quantification of coronary artery disease and greater interest in pharmacologic 'cardioprotection' using beta-blockers, statins and other agents targeting heart rate control and other mechanisms (e.g. reducing inflammatory responses). The recent Perioperative Ischemic Evaluation study has substantially altered this approach at least towards widespread application to lower/intermediate risk cohorts. Considerable attention has been focused on ensuring optimal standardized perioperative management of patients with a recent percutaneous coronary intervention, particularly those with an intracoronary stent. Widespread surveillance of postoperative troponin release and increasing recognition of the prognostic potential of elevated preoperative brain natriuretic peptides point towards changing strategies for long-term risk stratification.

SUMMARY

The complexity of a particular patient's physiologic responses to a wide variety of surgical procedures, which are undergoing constant technological refinement generally associated with lesser degrees of invasivity and stress make calculation of patients' perioperative risk very challenging. At the present time, adequate information is available for the clinician to screen patients with high-risk preoperative predictors, delay elective surgery for patients with recent intracoronary stents and continue chronic beta-blockade in appropriate patients. New large-scale database and subanalyses of major trials (e.g. Perioperative Ischemic Evaluation and Coronary Artery Revascularization Prophylaxis) should provide additional information to minimize perioperative cardiac risk.

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.

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).