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Original Articles: Adult Cardiac

Clopidogrel Increases Blood Transfusion and Hemorrhagic Complications in Patients Undergoing Cardiac Surgery

^a Division of Cardiac Surgery, Queen Elizabeth II Health Sciences Center, Halifax, Nova Scotia, Canada
^b Department of Anesthesia, Queen Elizabeth II Health Sciences Center, Halifax, Nova Scotia, Canada

Accepted for publication October 21, 2009.

^_* Address correspondence to Dr Hirsch, Division of Cardiac Surgery, Queen Elizabeth II Health Sciences Center, 1796 Summer St, Room 2006, Halifax, Nova Scotia, B3H 3A7, Canada (Email: ghirsch{at}dal.ca).

CARDIOTHORACIC ANESTHESIOLOGY: The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.

 

	Abstract

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Background: Utilization of the irreversible antiplatelet agent clopidogrel is increasing in the treatment acute coronary syndrome patients. Consequently, more patients are presenting for urgent cardiac surgery with an irreversible defect in platelet function. The objective of this study was to determine whether recent clopidogrel administration predicts transfusion and hemorrhagic complication in cardiac surgery patients.

Methods: This retrospective study included all patients undergoing isolated coronary artery bypass graft surgery (CABG), isolated valve, or CABG plus valve at a single center between 2004 and 2008. The outcomes of interest were transfusion and hemorrhagic complication. Clopidogrel stop interval was defined as the time between last dose and presentation to the operating room, and was examined in daily increments from 0 to 5 days, more than 5 days, and not receiving clopidogrel preoperatively. By logistic regression, the association of clopidogrel stop interval with transfusion and with hemorrhagic complication was examined after adjusting for other risk factors.

Results: Of 3,779 patients included in this study, 26.4% (999) received clopidogrel preoperatively. The overall rates of transfusion and hemorrhagic complication were 34.1% and 4.1%, respectively. Clopidogrel use within 24 hours was an independent predictor of transfusion (odds ratio 2.4; 95% confidence interval: 1.8 to 3.3) and of hemorrhagic complication (odds ratio 2.1; 95% confidence interval: 1.3 to 3.6).

Conclusions: Patients receiving clopidogrel within 24 hours of surgery are at increased risk for transfusion and hemorrhagic complication. Timing of surgery for patients receiving clopidogrel should take into account the interval from the last dose.

The effectiveness of clopidogrel in acute coronary syndrome is well established, with level 1 evidence indicating reduction in death and major morbidity in ST-segment elevation myocardial infarction, non–ST-segment elevation MI, as well as a reduction in in-stent thrombosis after percutaneous coronary intervention (PCI) [1–6]. American Heart Association/American College of Surgery guidelines support the administration of clopidogrel in STEMI, NSTEMI, and before PCI [7–9]. As a consequence of these developments, more patients are presenting for urgent cardiac surgery having received clopidogrel.

Several studies suggest cardiac surgical patients are at increased risk of adverse outcomes, transfusion, and hemorrhagic complications when receiving clopidogrel preoperatively [10, 11], although these results are inconsistent. Karabulut and colleagues demonstrated no increased risk for transfusions or hemorrhagic complications in cardiac surgical patients receiving clopidogrel [12], whereas others have shown an increase in transfusion of two to four units on average [10, 13], and still others, including Ley and coworkers [14] have shown a tenfold increase in reexploration for tamponade. The potential for increased bleeding complications with clopidogrel extends to off-pump surgery as well [15].

Cardiac surgery patients who experience significant postoperative bleeding or receive blood transfusions are at increased risk for other adverse outcomes. Blood transfusions have been associated with increased rates of clinically significant infections, ischemic, and 30-day mortality [16]. Return to the operating room for bleeding complications has been identified as an independent risk factor for operative mortality, and nonfatal adverse outcomes [17].

Given the adverse outcomes associated with blood transfusion and hemorrhagic complication after cardiac surgery we believed that further study of clopidogrel use in cardiac surgery patients was warranted. Additionally, the relationship between the interval from the last dose of clopidogrel to cardiac surgical intervention and hemorrhagic complications has not been well delineated. The purpose of this study was to study the relationship between clopidogrel use and the risk of blood transfusion and hemorrhagic complication.

	Material and Methods

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Approval for conducting this study was obtained by the Instituitonal Review Board of the Capital District Health Authority. We note that the need for individual patient consent for this study was waived by the Review Board.

Data Sources and Study Population
This retrospective study includes all consecutive patients undergoing isolated CABG, isolated valve, or CABG plus valve at the Queen Elizabeth II Health Sciences Center (QEII HSC) in Halifax, Nova Scotia, between June 2004 and August 2008. Data were obtained from the Maritime Heart Center (MHC) registry, a detailed clinical database containing preoperative, intraoperative, and postoperative data collected prospectively on all cardiac surgical cases performed at the QEII HSC from 1995 to the present.

Surgical Technique
For CABG surgery conducted with cardiopulmonary bypass (CPB), we utilized upper aortic cannulation and two-stage venous cannulation of the right atrium/inferior vena cava. During CPB, the target mean perfusion pressure was 60 mm Hg. Body temperature was allowed to drift to a minimum of 32°C. Intermittent cold blood cardioplegia (1:4 blood to crystalloid/max K⁺ concentration 22 mEq/L) was delivered antegrade through the aortic root unless otherwise indicated. A small proportion of patients were operated upon with non–CPB-based beating-heart techniques utilizing a commercially available tissue stabilizer (Octopus III system; Medtronic Inc, Minneapolis, MN). Distal anastomoses were carried out with continuous polypropylene suture (7-0 venous grafts, 8-0 arterial grafts). Choice of conduit (arterial versus venous), construction of grafts (sequential, composite, and so forth), choice of valve (tissue versus mechanical), surgical approach for valve replacement (Sondergaard's groove, transseptal, and so forth) were surgeon dependent. Heparin was given at a dose of 300 IU /kg to achieve a target activated clotting time of greater than 450 s (in the beating-heart group, a dose of 100 IU/kg was utilized). On completion of the procedure, heparin was reversed with protamine sulphate with a goal of normalizing the activated clotting time. No special blood conservation techniques were employed other that nonhemic prime, retransfusion of all contents of the oxygenator/circuit at the end of CPB, and acceptance of normovolemic anemia. Postoperatively, nonhemic volume expnaders were used routinely.

Variable Selection
The interval between the last dose of clopidogrel and cardiac surgical intervention (clopidogrel stop interval) was examined in daily increments from 0 to 5 days and greater than 5 days, and was compared with patients not receiving clopidogrel preoperatively. Preoperative patient characteristics of interest included age (less than 60 years old, 60 to 69, 70 to 79, and 80 years or more), sex, diabetes mellitus, renal failure (serum creatinine greater than 176 µmol/L), procedure (isolated CABG, isolated valve, CABG plus valve), low hemoglobin (less than 120 g/L), peripheral vascular or cerebrovascular disease, left ventricular dysfunction defined as ejection fraction (EF) less than 40%, prior cardiac surgery, and urgency status: elective cases (waiting at home), in-house cases (requiring hospitalization but able to wait more than 24 hours before surgery); and urgent (requiring a procedure within 24 hours to prevent further clinical deterioration), and emergent (requiring immediate surgery).

Primary postoperative outcomes were transfusion of any blood product, including packed red blood cells, platelets, fresh frozen plasma, or cryoprecipitate, received during the intraoperative or postoperative period; and hemorrhagic complication (tamponade or reexploration for bleeding). Other outcomes included mortality, sepsis, and deep sternal wound infection, and prolonged mechanical ventilation (longer than 24 hours).

Statistical Analysis
Preoperative, intraoperative, and postoperative characteristics were examined among the various clopidogrel stop intervals. The association of clinical characteristics with blood transfusion and with hemorrhagic complication was evaluated univariately. Continuous variables were compared using a two-tailed t test or Wilcoxon rank sum test, and categorical variables were analyzed by ² or Fisher's exact test, as appropriate. Fully-adjusted logistic regression models were generated to examine the association of clopidogrel stop interval with blood transfusion and with hemorrhagic complication after adjusting for relevant prognostic variables. A receiver operating characteristic curve was calculated as a measure of sensitivity and specificity for each logistic regression model. A bootstrap procedure was performed on 200 subsamples to confirm the independent predictors of each outcome; furthermore, the 95% confidence interval (CI) of the receiver operating characteristic curve was obtained from the 2.5 and 97.5 percentiles of the bootstrap distribution. Statistical analysis was performed using SAS software version 9.1 (SAS, Cary, NC).

The authors had full access to the data and take full responsibility for its integrity. All authors have read and agree to the manuscript as written.

	Results

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Patient Population
This study included 3,779 consecutive patients undergoing isolated CABG, isolated valve surgery, or CABG plus valve surgery. In the study, 26.4% of patients (999) received clopidogrel preoperatively and of those, 74.3% (742) presented to the operating room within 5 days of receiving clopidogrel. Compared with patients not prescribed clopidogrel, preoperative clopidogrel use was associated with higher transfusion (43.6% [436] versus 30.7% [854], p = 0.0001) and hemorrhagic complication (4.9% [49] versus 3.8% [105], p = 0.12). Examined by stop interval, 8.6% of patients (324) underwent surgery within 24 hours of receiving clopidogrel, 3.2% (120) discontinued clopidogrel 2 days before surgery, and 2.4% (90) discontinued 3 days before surgery, 2.6% (98) discontinued 4 days before surgery, and 2.9% (110) discontinued 5 days before surgery; 6.8% of patients (257) discontinued clopidogrel more than 5 days before surgery and 73.6% (2,780) were not taking clopidogrel. Preoperative clinical characteristics among the clopidogrel stop intervals are shown in Table 1. Patients receiving clopidogrel within 24 hours of surgery were more likely to be urgent or emergent, and have ejection fraction less than 40% and hemoglobin less than 120 g/L. Overall bilateral internal mammary artery use was 5.3% (163). Although bilateral internal mammary artery use had lower rates of blood product transfusion (21.5% [35] versus 34.7% [1,020], p = 0.0005), rates with its use did not differ in relation to whether the patient received preoperative clopidogrel (4.7% [45] versus 5.5% [118]; p = 0.36). Overall, 1.2% of patients (32) underwent isolated CABG with a beating-heart approach. Of the clopidogrel group, this represents 0.8% of patients (7), and in the nonclopidogrel group, this represents 1.4% (25), a nonsignificant difference (p = 0.17).

	Comment

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

In light of the adverse outcomes associated with postoperative transfusion and hemorrhagic complication, the AHA/ACC guidelines recommend that clopidogrel be discontinued for at least 5 days and preferably for 7 days before CABG [7]. This is not always possible, however, when patients are presenting acutely for surgical intervention. In this study, 74.3% of patients receiving preoperative clopidogrel presented to the operating room within 5 days of discontinuing the drug. Similarly, Mehta and colleagues [13] found that 87% of patients receiving preoperative clopidogrel presented to the operating room within 5 days of their last dose. Surgeons are now faced with patients presenting with traditional urgent/emergent surgical indications (eg, tight left main disease, acute ischemia with myocardial dysfunction, or severe aortic stenosis with hemodynamic compromise) who have recently received clopidogrel. Some cases are being delayed, at times for several days, to avoid the negative outcomes associated with bleeding complications. Alternatively, surgeons are compelled to take patients with recent clopidogrel treatment to the operating room and deal with potential resultant coagulopathy.

Our study suggests that delaying surgery by at least 24 hours decreases the risk of transfusion and hemorrhagic complication. This is a far more feasible delay interval than 5 to 7 days for patients with relatively urgent indications for surgical intervention, although the safety of such an approach with patients with urgent indications for cardiac surgery remains to be demonstrated. Our findings are in substantial agreement with those of Ascione and associates [18] who found clopidogrel administration within 48 hours was associated with increased transfusion and adverse outcomes.

Alternative approaches include delaying clopidogrel administration until appropriate diagnostic studies or images are obtained, especially for patients with clinical indications of cardiovascular disease that is likely to be best treated by surgical intervention. These could reasonably include patients with systolic murmurs and clinical signs of either significant mitral regurgitation or aortic stenosis, patients with prior noninvasive testing suggestive of left main disease or its equivalent, or patients with advanced diabetes who may have diffuse disease not amenable to PCI. Recent evidence from administrative data indicates that as many as 50% of patients receiving clopidogrel did not have documented indications for its use [19]. A more conservative approach to clopidogrel use in patients with strong potential for emergency cardiac surgery may be beneficial to overall outcomes in light of our results.

It is worth noting that the recent publications of a randomized trial as well as several retrospective studies have effectively removed aprotinin, an effective antifibrinolytic agent in relatively common use in cardiac surgery, from the market. While legitimate concerns were raised about the safety of this agent, aprotinin was demonstrated effective in decreasing the primary end point of massive transfusion set in the randomized trial [20], and its removal from the market reduces the ability of surgeons to offset the hemorrhagic risk of clopidogrel. We were unable to demonstrate a risk-adjusted effect of aprotinin administration on transfusion rates. Whether off-label aprotinin use is safe or effective in the subset of patients with recent clopidogrel use remains an area of potential interest and deserving of further study.

A recent multicenter retrospective study demonstrates a rapidly increasing utilization of recombinant activated factor VII as a rescue therapy in bleeding cardiac surgical patients [21]. This agent promotes systemic activation of the clotting system and is associated with high mortality (32%). Forty-six percent of nonsurvivors in that study had received antiplatelet agents other than aspirin. Indeed, in our own center, the utilization rate of recombinant activated factor VII has increased over time, and the percentage of these cases receiving clopidogrel at the time of surgery has risen from 11% in 2006 to 56% in 2008 (data not shown). Taken together, these data indicate that the use of nonaspirin antiplatelet agents is associated with the requirement for rescue therapy with a systemic procoagulant agent associated with high mortality.

We acknowledge several limitations to this study. Firstly, it is retrospective in nature and, as such, subject to bias by unmeasured confounders, particularly with regard to patient factors that lead to earlier surgical intervention even after clopidogrel administration. Secondly, although this is a relatively large cohort of patients, there may still be limitations in statistical power to detect significant differences in bleeding risk among the various stop intervals.

In conclusion, we recommend that if the clinical situation allows, for patients receiving clopidogrel, undergoing cardiac surgery should be delayed at least 24 hours. Also, for cardiac surgery patients, clopidogrel administration should be restricted to those with clear-cut indications for its use. For patients with a high likelihood of surgical intervention, consideration should be given to delaying clopidogrel loading until relevant diagnostic studies can be obtained that will determine the role for urgent cardiac surgical intervention.

	Acknowledgments

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
This work was funded in part by a CIHR Team Grant through the Canadian Cardiovascular Outcomes Research Team.

	References

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Christine R. Herman Blaine A. Kent Gregory M. Hirsch Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Herman, C. R. Articles by Hirsch, G. M. Search for Related Content PubMed PubMed Citation Articles by Herman, C. R. Articles by Hirsch, G. M. Related Collections Coronary disease