4. Discussion:
Bleeding is the main concern when operating on patients on anticoagulants with possibly requiring blood transfusion and re-exploration, both identified as independent risk factors for postoperative morbidity and mortality.1,2,5,6 In a study of over 18,000 patients at Cleveland
Clinic over 10-years, it was noted that transfusions and reoperations for bleeding were independently associated with increased risk of morbidity and mortality (8.5% vs 1.8%).5 Similarly, others showed a higher mortality (14.2% vs 3.4%) in patients requiring re-exploration compared to the rest, and the amount of packed red blood cells (pRBC) was associated with an incremental increased risk (0.25% for each unit transfused).41 In one study of almost 5,400 patients, those who required re-exploration for bleeding had a twofold mortality increase in early postoperative period, as well as an overall mortality increase beyond 90 days.8
A review of 528,686 CABG patients, from the Society of Thoracic Surgery (STS) database, revealed that patients requiring emergent surgery or were on antiplatelet medications within 24-hours before the operation had a significantly higher rate of re-exploration for bleeding, with an increased risk-adjusted mortality of 5.9% compared to 2.0% for others.9 In addition, a meta-analysis review of observational studies showed that preoperative exposure to clopidogrel was associated with increased risk of death, blood loss, transfusions and reoperations.42 Likewise, in a meta-analysis of 557,923 patients, emergency surgery and preoperative aspirin use were among the risk factors resulting in higher rate of re-exploration with an increased risk of mortality and major morbidity.6
The risk of bleeding complications in emergency settings in patients on anticoagulants has not been studied in large patient cohorts.40 Nevertheless, an international prospective study of patients undergoing urgent CABG on antithrombotic agents (ACUITY trial) noted that transfusions of ≥ 4 units pRBC was an independent mortality risk factor for up to 1-year post surgery.7 Similarly, Kapetanakis showed a higher rate of blood transfusions and re-exploration in patients who received clopidogrel prior to urgent CABG.43 An individualized strategy for clopidogrel suspension was suggested in patients undergoing CABG following ACS, guided by platelet function testing, which significantly reduced postoperative bleeding and blood use.44
Cardiac surgery, compared to other surgical specialties, presents a unique challenge. While a normal coagulation profile is initially desirable to ensure a dry entry and minimize blood loss, the patient will paradoxically require full anticoagulation shortly thereafter for CPB. Therefore, it is paramount that any treatment modalities instituted preoperatively in an attempt to correct the coagulopathy do not interfere with the ability to fully and rapidly anticoagulate with heparin in preparation for CPB. It is also important to avoid the potential of a hypercoagulable state that may increase the thromboembolic risk and overall morbidity.45
The decision process is easier in patient where surgery can be done semi-electively or at least delayed for adequate anticoagulant washout, as per the guidelines set forth by the STS.46 Patients with high risk for thromboembolism can be bridged on short half-life medications such as heparin that surgeons are most comfortable dealing with and can be quickly reversed. Patients on anticoagulants presenting with an ACS may persuade surgeons to push for alternatives to surgical intervention such as PCI rather than dealing with a bleeding patient, even if the patient’s anatomy and long-term outcome favor surgical revascularization.
It is inevitable that surgeons will be confronted where emergency surgery is needed for patients on anticoagulants. Examples would be a patient with ACS where PCI in not possible due to coronary anatomy or lack of expertise, or a patient with an aortic dissection where the risk of bleeding is further aggravated by coagulopathy induced by hypothermia and circulatory arrest, resulting in platelet dysfunction and reduced activity of clotting factors.47 Other examples include endocarditis and sepsis, where underlying issues such as DIC, dilution and hemolytic anemia worsens coagulopathy. In addition, CPB creates its own insults of endothelial activation, fibrinolysis, coagulopathy and consumption of platelets and coagulation factors, all aggravating an already attenuated hematological profile.48
Proposals in the literature on management of the cardiac surgical patient on anticoagulants in the acute setting are mainly based on expert opinion and extrapolation from non-emergent cardiac or emergent non-cardiac guidelines, rather from controlled trials. Proper knowledge of mechanism of action of the anticoagulants on coagulation cascade and the effectiveness of available antidotes is essential. Decision is typically made on a case-by-case basis considering product availability, local hospital policies and overall patient’s clinical condition. The development of hospital and system wide strategies that promote a multidisciplinary approach utilizing evidence-based clinical practice ensures appropriate and judicious use of these reversal agents.