Do You Continue to Take Baby Aspirin Before Carotid Surgery
Original Article
Aspirin in Patients Undergoing Noncardiac Surgery
List of authors.Abstract
Background
There is substantial variability in the perioperative assistants of aspirin in patients undergoing noncardiac surgery, both amidst patients who are already on an aspirin regimen and amid those who are non.
Methods
Using a 2-by-2 factorial trial design, we randomly assigned 10,010 patients who were preparing to undergo noncardiac surgery and were at risk for vascular complications to receive aspirin or placebo and clonidine or placebo. The results of the aspirin trial are reported hither. The patients were stratified according to whether they had non been taking aspirin earlier the study (initiation stratum, with 5628 patients) or they were already on an aspirin regimen (continuation stratum, with 4382 patients). Patients started taking aspirin (at a dose of 200 mg) or placebo only before surgery and connected it daily (at a dose of 100 mg) for xxx days in the initiation stratum and for 7 days in the continuation stratum, afterward which patients resumed their regular aspirin regimen. The primary event was a composite of death or nonfatal myocardial infarction at 30 days.
Results
The primary outcome occurred in 351 of 4998 patients (vii.0%) in the aspirin group and in 355 of 5012 patients (vii.i%) in the placebo group (hazard ratio in the aspirin grouping, 0.99; 95% confidence interval [CI], 0.86 to 1.15; P=0.92). Major bleeding was more common in the aspirin group than in the placebo group (230 patients [four.half dozen%] vs. 188 patients [3.8%]; risk ratio, 1.23; 95% CI, 1.01, to i.49; P=0.04). The primary and secondary outcome results were like in the two aspirin strata.
Conclusions
Administration of aspirin earlier surgery and throughout the early postsurgical period had no meaning event on the rate of a blended of death or nonfatal myocardial infarction but increased the risk of major haemorrhage. (Funded by the Canadian Institutes of Health Research and others; POISE-ii ClinicalTrials.gov number, NCT01082874.)
Methods
Report Design
POISE-2 was an international, randomized, controlled trial with a 2-by-2 factorial pattern to separately evaluate the effects of aspirin versus placebo (reported hither) and clonidine versus placebo (reported elsewhere in the Journal)twenty in patients undergoing noncardiac surgery. Details of the trial objectives, design, and methods have been reported previously.21 All centers obtained ethics approval earlier starting recruitment.
Written report Oversight
The study was funded by the Canadian Institutes of Health Research and others. The Population Health Enquiry Institute was the study coordinating heart and was responsible for the randomization pattern, maintenance of the database, data validation, analyses, and report-middle coordination. Bayer Pharma provided the aspirin used in the study, and Boehringer Ingelheim provided the clonidine and some research funding; both companies were provided with the first typhoon of the manuscript. However, no donor or funder had a role in the design or bear of the study, the collection or analyses of the information, or the preparation of the manuscript. The operations committee designed the trial, prespecified the statistical analysis plan, and vouches for the completeness and accuracy of the data and analyses and the adherence of the study to the protocol (bachelor with the full text of this article at NEJM.org). The first writer wrote the start typhoon of the manuscript, and the writing commission fabricated revisions and made the determination to submit the manuscript for publication.
Patients
We recruited patients from July 2010 through December 2013 at 135 hospitals in 23 countries. Eligibility criteria are reported in Section i in the Supplementary Appendix, available at NEJM.org. Patients were and then stratified according to whether they were not taking aspirin before study enrollment (initiation stratum) or they were already on an aspirin regimen (which was defined as daily employ for at to the lowest degree 1 calendar month within vi weeks earlier surgery) (continuation stratum). Patients in the continuation stratum were required to stop taking aspirin at least 3 days before surgery to participate in the trial.
Procedures
After providing written informed consent before surgery, patients underwent randomization by means of a 24-60 minutes computerized Net system that used block randomization stratified co-ordinate to study center and aspirin stratum. Patients were assigned in a i:one:1:1 ratio to receive aspirin and clonidine, aspirin placebo and clonidine, aspirin and clonidine placebo, or aspirin placebo and clonidine placebo. Patients, clinicians, data collectors, and consequence adjudicators were all unaware of report-group assignments.
Patients started taking aspirin or placebo (at a dose of 200 mg) just before surgery and connected information technology (at a dose of 100 mg per day) for xxx days in the initiation stratum and for 7 days in the continuation stratum, subsequently which patients resumed their regular aspirin regimen. Patients also started clonidine (0.2 mg per day) or placebo but earlier surgery and continued it for 72 hours. If a patient had life-threatening or major bleeding, the aspirin written report drug was to be stopped. (Details regarding the follow-upward procedure are provided in Department 2 in the Supplementary Appendix.)
Study Outcomes
The chief outcome was a composite of decease or nonfatal myocardial infarction 30 days after randomization. Details regarding the two secondary composite outcomes, the 3rd outcomes, and the condom outcomes at 30 days are provided in Section three in the Supplementary Appendix, outcome definitions are provided in Section iv in the Supplementary Appendix, and events evaluated past issue adjudicators, which were used in the analyses, are provided in Department 5 in the Supplementary Appendix.
Statistical Assay
We determined that enrollment of 10,000 patients would give the written report a power of 84% to discover a run a risk ratio of 0.75 in the aspirin grouping, at a two-sided alpha level of 0.05, on the assumption that the rate of the principal outcome in the placebo group would be 6.one%.16 An external data and prophylactic monitoring committee reviewed the data when 25%, 50%, and 75% of the 30-day data were available.
We evaluated patients co-ordinate to the group to which they were assigned, censoring the data for patients who were lost to follow-up on the final twenty-four hours that their condition was known. Outcomes were analyzed with the employ of Cox proportional-hazards models, stratified according to the aspirin stratum and status with respect to receipt of clonidine, except for the event of acute kidney injury with receipt of dialysis, for which we used logistic-regression assay, and outcomes with respect to the length of the hospital stay, for which we used the log-rank test.
For the primary consequence, we performed subgroup analyses that were based on the aspirin stratum, type of surgery (vascular vs. nonvascular), and the number of criteria of the Revised Cardiac Risk Index that the patient met.22 We also performed subgroup analyses, according to the aspirin stratum, for ane of the secondary composite outcomes and for the tertiary outcomes. In a prespecified analysis, nosotros predicted the direction of potential subgroup furnishings. For the subgroup analyses, nosotros used Cox proportional-hazards models that incorporated tests of interaction, with a P value of less than 0.05 indicating statistical significance. All analyses were performed with the use of SAS software, version 9.one.
Results
Patients
A total of 10,010 patients were enrolled (5628 in the initiation stratum and 4382 in the continuation stratum). Of these patients, 4998 were assigned to receive aspirin and 5012 to receive placebo. The 30-mean solar day follow-up was complete for 99.nine% of the patients (Effigy S1 in the Supplementary Appendix).
Table 1.
Table 1. Characteristics of the Patients at Baseline. The baseline characteristics were like in the aspirin and placebo groups (Table 1). The mean historic period was 68.6 years; 52.8% of the patients were men, 32.seven% had a history of vascular disease, and 4.three% had undergone previous coronary stenting. Amidst patients in the continuation stratum, aspirin was stopped a median of seven days (interquartile range, 4 to viii) before surgery. In the first 3 days after surgery, 65.0% of the patients received prophylactic anticoagulation. Overall, 80.4% of the patients in the aspirin group and 82.4% of those in the placebo group took at least eighty% of the doses of the study drug (Table S1 in the Supplementary Appendix).
Study Outcomes
Tabular array 2.
Table 2. Effects of Aspirin on 30-Day Outcomes. Effigy ane. 
Effigy 1. Kaplan–Meier Estimates of the Primary Composite Outcome of Death or Nonfatal Myocardial Infarction at 30 Days. The inset shows the aforementioned information on an enlarged y axis.
The primary issue (death or nonfatal myocardial infarction) occurred in 351 of 4998 patients (vii.0%) in the aspirin group and in 355 of 5012 patients (vii.ane%) in the placebo group (hazard ratio in the aspirin group, 0.99; 95% confidence interval [CI], 0.86 to 1.15; P=0.92) (Table ii and Effigy ane). The use of aspirin did not significantly affect the secondary composite or tertiary outcomes. Myocardial infarction occurred in 309 patients (6.2%) in the aspirin grouping and in 315 patients (6.3%) in the placebo grouping (hazard ratio, 0.98; 95% CI, 0.84 to ane.fifteen; P=0.85). Aspirin increased the risk of major bleeding, as compared with placebo, with major bleeding occurring in 230 patients (4.vi%) versus 188 patients (3.viii%) (chance ratio, 1.23; 95% CI, ane.01 to i.49; P=0.04) (Table 2, and Figure S2 in the Supplementary Appendix). The most mutual sites of bleeding were the surgical site (78.3%) and gastrointestinal tract (9.3%). Stroke occurred in xvi patients (0.3%) in the aspirin group and in nineteen patients (0.four%) in the placebo group (hazard ratio, 0.84; 95% CI, 0.43 to 1.64; P=0.62). The median length of infirmary stay was 4 days (interquartile range, three to vii) in both the aspirin and placebo groups (P=0.79). There was no meaning difference between the report groups in the length of stay in the intensive care unit or cardiac care unit (P=0.23). There was no significant issue of clonidine on the results comparing aspirin with placebo (P≥0.12 for all interactions).
Figure 2.
Figure 2. Subgroup Analyses of the Chief Issue. The primary composite outcome was death or nonfatal myocardial infarction at 30 days. The area of each square is proportional to the size of the corresponding subgroup. The Revised Cardiac Risk Index ranges from 0 to 6, with higher scores indicating greater risk.
The upshot of aspirin was consistent across subgroups (P≥0.sixteen for all interactions) (Figure 2). The subgroup assay of the secondary composite outcome also showed no pregnant heterogeneity (P=0.72 for interaction).
Differences between Strata
Aspirin use significantly increased the take a chance of major haemorrhage and decreased the chance of stroke in the initiation stratum (P=0.03 for both comparisons) and significantly increased the charge per unit of astute kidney injury requiring dialysis in the continuation stratum (P=0.04) (Tables S2 and S3 in the Supplementary Appendix). Nevertheless, the P value for strata interaction was significant only for stroke (P=0.01) (Table S4 in the Supplementary Appendix). In the initiation stratum, there were iii strokes in the aspirin group and 12 in the placebo grouping (hazard ratio, 0.25; 95% CI, 0.07 to 0.89), whereas in the continuation stratum there were xiii strokes in the aspirin group and 7 in the placebo grouping (hazard ratio, 1.86; 95% CI, 0.74 to iv.66; P=0.19).
The furnishings of aspirin on myocardial infarction were similar in the initiation stratum and the continuation stratum (hazard ratio, 0.98; 95% CI, 0.79 to 1.22 in the initiation stratum; hazard ratio, 0.99; 95% CI, 0.79 to 1.24 in the continuation stratum; P=0.96 for interaction). In addition, the effects of aspirin on the composite of life-threatening or major bleeding were like in the initiation stratum and the continuation stratum (hazard ratio, 1.24; 95% CI, 0.99 to 1.55 in the initiation stratum; hazard ratio, 1.xx; 95% CI, 0.94 to 1.55 in the continuation stratum; P=0.87 for interaction).
Bleeding Chance
Table 3.
Table three. Absolute Increase in the Risk of a Blended of Life-Threatening or Major Bleeding with Aspirin Therapy, Starting on Each of the First ten Postoperative Days until 30 Days later on Surgery. To better understand the take chances of bleeding on the basis of the timing of administration of aspirin, nosotros undertook postal service hoc analyses. Among patients who were alive and did not take life-threatening or major haemorrhage, we determined the subsequent chance of a composite of life-threatening or major bleeding until mean solar day 30, starting on the twenty-four hours of surgery and and so starting on each 24-hour interval thereafter (Table 3). The absolute increase in the risk of a composite bleeding outcome associated with aspirin was ane.2% from the day of surgery up to xxx days and 0.9% from mean solar day 4 after surgery upward to 30 days. If a patient survived without the composite haemorrhage outcome until 24-hour interval eight after surgery, the increase in run a risk from day viii to day 30 was 0.3% (3 in 1000 patients).
Tabular array S5 in the Supplementary Appendix shows the results of the post hoc multivariable analysis investigating potential factors associated with perioperative myocardial infarction. The blended of life-threatening or major bleeding was an independent predictor of myocardial infarction (hazard ratio, one.82; 95% CI, 1.forty to 2.36; P<0.001).
Give-and-take
In this trial, the employ of low-dose perioperative aspirin, equally compared with placebo, did non reduce the rate of a composite of expiry or nonfatal myocardial infarction (the primary outcome) or the rates of the two secondary composite outcomes. The utilize of perioperative aspirin increased the run a risk of major haemorrhage (hazard ratio, ane.23; 95% CI, one.01 to 1.49). The results with respect to the chief and secondary outcomes were consistent in the initiation stratum and the continuation stratum.
In a meta-analysis of information from trials involving more than 110,000 patients who were not undergoing surgery, the use of aspirin, for primary and for secondary prevention, reduced the relative take chances of myocardial infarction past 20% and 25%, respectively.nine In contrast, the Pulmonary Embolism Prevention (PEP) trial included xiii,356 patients undergoing surgery for a hip fracture.xiii Patients received 160 mg of aspirin or placebo before surgery and daily for 35 days. Aspirin was associated with an increased run a risk of myocardial infarction (hazard ratio, 1.33; 95% CI, 1.00 to 1.78), although the number of myocardial infarctions (184) was much lower than that in our study (624; hazard ratio with aspirin, 0.98; 95% CI, 0.84 to ane.15).
Consistent with our findings, the PEP trial and other perioperative trials have shown that aspirin significantly increases the risk of haemorrhage requiring a transfusion.13,fourteen In previous surgical trials with hundreds of venous thromboembolism events, the use of aspirin decreased the risk of deep-vein thrombosis and pulmonary embolism by ane third.xiii,xiv In our study, relatively few patients had deep-vein thrombosis (60 patients) or pulmonary embolism (64 patients), and more than patients in our report than in the PEP trial received concomitant anticoagulant prophylaxis (65.0% vs. 44.4%).
Observational data advise that the discontinuation of aspirin before surgery results in an increased thrombotic risk.19,23 In our written report, among the 4382 patients in the continuation stratum, we found no increase in thrombotic events owing to preoperative withholding of aspirin.
In the nonoperative setting, aspirin prevents myocardial infarction in patients with or at risk for atherosclerotic illness. However, in our study, aspirin did not prevent perioperative myocardial infarction. Nosotros offer three potential explanations for this finding. Beginning, previous studies and our post hoc multivariable analysis showed that major bleeding was associated with perioperative myocardial infarction.3,24 The absolute increase in bleeding risk with aspirin is greater in the perioperative setting than the nonoperative setting. It is possible that aspirin prevented some perioperative myocardial infarctions through thrombus inhibition and acquired some myocardial infarctions through haemorrhage and subsequent mismatch between the supply of and demand for myocardial oxygen, thus resulting in the overall neutral outcome in our written report. Second, the lower purlieus of the run a risk ratio for myocardial infarction was 0.84, and we cannot exclude the possibility of a missed moderate effect that would be consistent with results of other aspirin trials.9 Third, coronary-artery thrombus may non exist the dominant mechanism of perioperative myocardial infarction.five,6
The results with respect to the chief and secondary outcomes were similar beyond the two aspirin strata. In that location were significant between-grouping differences in 1 3rd outcome (acute kidney injury with receipt of dialysis) and two safety outcomes (major bleeding and stroke) in one aspirin stratum but not the other (Tabular array S4 in the Supplementary Appendix). The interaction P value for the aspirin stratum was not significant for two of these outcomes (i.east., acute kidney injury with receipt of dialysis and major bleeding), suggesting that there is no significant divergence in effect across the aspirin strata for these ii outcomes and that the results in the overall population provide the nearly reliable effect estimates.
Our data suggest that amidst patients on a long-term aspirin regimen, stopping aspirin 3 or more days before surgery may decrease the adventure of major haemorrhage. Because we did not randomly assign patients according to the timing of aspirin cessation before surgery, nosotros cannot determine the most effective timing to minimize bleeding take a chance. Studies accept suggested that hemostasis is unimpaired if at to the lowest degree 20% of the platelets have normal COX-1 activity25,26 and 12% of circulating platelets are replaced every 24 hours.27,28 Therefore, stopping aspirin 72 or more hours before surgery may be acceptable to minimize the run a risk of perioperative bleeding.
We observed one significant interaction: aspirin appeared to reduce the incidence of stroke in the initiation stratum simply not in the continuation stratum (P=0.01 for interaction). Several considerations suggest that this is a spurious subgroup effect.29 First, at that place were only 15 strokes in the initiation stratum, so the power to detect a change is pocket-sized. Second, the effect of aspirin on reducing the take chances of stroke in the initiation stratum was large (hazard ratio, 0.25), an effect that was inconsistent with the upshot in the nonoperative setting on the basis of analyses of more than g strokes and the perioperative data from the PEP trial with 103 strokes (hazard ratio for aspirin, ane.10; 95% CI, 0.75 to 1.62).9,13 Tertiary, since this analysis was 1 of xix tertiary or safety subgroup analyses that we performed, the results may be a chance finding. Finally, our hypothesized direction was opposite to that observed (i.eastward., nosotros expected more than benefit in the continuation stratum because of an aspirin-withdrawal effect). Therefore, the all-time approximate of the effect of aspirin on stroke is probably reflected in the overall population (hazard ratio, 0.84; 95% CI, 0.43 to ane.64).
If clinicians program to use an anticoagulant agent for perioperative prevention of venous thromboembolism, our results suggest that starting or continuing aspirin throughout the perioperative flow volition provide no additional do good but volition increment the risk of major bleeding. However, our findings do non resolve the issue of the relative merits of aspirin versus other anticoagulant agents for perioperative thromboprophylaxis.30 Although the POISE-2 trial is a large study by perioperative standards, the lower boundary (0.86) and upper purlieus (1.15) of the hazard ratio for the main outcome evidence that we have not excluded the possibility of observable benefit or impairment.
It should be noted that nosotros excluded patients who received a blank-metallic coronary stent less than 6 weeks before surgery or a drug-eluting coronary stent less than 1 year before surgery. Observational data accept suggested that perioperative aspirin prevents myocardial infarction and stent thrombosis in these ii groups of patients.31
For patients on a long-term aspirin regimen, the most constructive fourth dimension to restart aspirin would exist eight to x days after surgery, when the bleeding take chances has macerated considerably. If physicians consider starting aspirin after surgery to treat a thrombotic event (e.g., stroke or myocardial infarction), they can expect an absolute increase of 1.0 to 1.3 per centum points in the gamble of life-threatening or major bleeding if aspirin is administered within the first 2 days after surgery. Physicians and their patients will have to weigh this chance against the loftier risk of expiry from the thrombotic event and the potential benefits of aspirin.3,12,16
In conclusion, the administration of aspirin earlier noncardiac surgery and throughout the early on postsurgical period had no significant issue on the rate of death or nonfatal myocardial infarction but increased the risk of major haemorrhage. These findings employ both to patients who were not already receiving aspirin and to those who were on a long-term aspirin regimen.
Appendix
The authors' affiliations are as follows: the Population Health Research Found, Hamilton Health Sciences and McMaster Academy (P.J.D., Thousand.1000., A.R., F.B., G.L.B., J.E., Y.L.Thou., P.G., J.P., R.Westward., A.L., S.P., S.C., S.Y.), the Departments of Clinical Epidemiology and Biostatistics (P.J.D., One thousand.G., D.C., J.E., Y.50.1000., J.P., C.Chiliad., S.Y.), Medicine (P.J.D., G.Yard., M.T., D.C., J.E., R.Grand., C.One thousand., S.Y.), Anesthesia (T.V., Y.L.M.), Surgery (R.W., A.L.), and Disquisitional Care (R.Due west.), McMaster University, Hamilton, ON, the Section of Medicine, London Health Sciences Centre, London, ON (G.M.), the Department of Anesthesiology and Perioperative Medicine, Kingston General Hospital and Queen'due south University, Kingston, ON (J.L.P.), the Section of Medicine, Sectionalization of Nephrology, University of Western Ontario, London, ON (A.X.G.), the Department of Surgery, Academy of Manitoba, Winnipeg (South.South.), and the Section of Medicine, University of Alberta, Edmonton (M.G.) — all in Canada; the Section of Outcomes Research, Anesthesiology Establish, Cleveland Dispensary, Cleveland (D.I.Due south., A.G.); the Section of Anaesthesia and Pain Management, Imperial Melbourne Hospital, Melbourne, VIC, Australia (K.L.); Iberoamerican Cochrane Eye (P.A.-C.) and the Anesthesiology Department (P.P.), Biomedical Inquiry Institute, Barcelona; Universidad Autónoma de Bucaramanga and Fundación Cardioinfantil, Bogota, Colombia (J.C.V.); the Department of Pharmacology, Division of Clinical Research and Grooming, St. John'southward National Academy of Health Sciences, Bangalore, India (A.Due south., D.X.); the Section of Anaesthetics, Perioperative Research Group, Nelson R Mandela School of Medicine, University of KwaZulu-Natal, Durban, South Africa (B.M.B., R.North.R.); the Department of Anesthesiology, Herlev Hospital, Academy of Copenhagen, Herlev, Denmark (C.S.M.); Estudios Clínicos Latino América, Instituto Cardiovascular de Buenos Aires, Buenos Aires (F.B.); the Department of Anesthesia, Academy Hospital Basel, Basel, Switzerland (G.L.B.); the Department of Anaesthesia and Intensive Care, Chinese Academy of Hong Kong, Hong Kong (G.T.V.C.); the Department of Anesthesiology, University of North Carolina, Chapel Hill (P.A.Chiliad.); Anesthesiology, Cliniques universitaires Saint-Luc, Brussels (P.F.); Universidad Peruana Cayetano Heredia, Lima, Republic of peru (One thousand.1000.); the Section of Anesthesia and Intensive Care, Medical Academy of Vienna, Vienna (E.F.); the Department of Surgery, Shifa International Hospital, Islamabad, Pakistan (M.A.); the Department of Anesthesiology, Clinica Santa Maria, Santiago, Chile (D.T.); the Department of Anesthesiology, Academy of Malaya, Kuala Lumpur, Malaysia (C.Y.W.); Research Found HCor (Hospital do Coracão), São Paulo (O.B.); Anesthesia and Intensive Intendance, San Raffaele Scientific Found, Milan (50.P.); Clinical Trial Service Unit and Epidemiological Studies Unit, University of Oxford, Oxford, United Kingdom (C.B.); and the George Institute for Global Health and the University of Sydney, Sydney (C.C.).
Supplementary Cloth
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