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Acute Aspirin Therapy

5th Edition
June 2015

The Canadian Stroke Best Practice Recommendations for Hyperacute Stroke Care, 5th Edition (2015) is published in the International Journal of Stroke (IJS) and available freely online. To access the specific recommendations for Acute Aspirin Therapy and all other sections of the Hyperacute Stroke Care recommendations, please click on this URL which will take you to the recommendations online in the IJS: http://onlinelibrary.wiley.com/doi/10.1111/ijs.12551/full

For the French version of these recommendations, open the appendix at this link :  http://onlinelibrary.wiley.com/store/10.1111/ijs.12551/asset/supinfo/ijs12551-sup-0001-si.zip?v=1&s=cdf3d494242426450aaa522f104ace17857f037a

All other supporting information, including performance measures, implementation resources, evidence summaries and references, remain available through www.strokebestpractices.ca, and not through the IJS.  Please click on the appropriate sections on our website below for this additional content.


Acute-phase aspirin therapy reduces the risk of early recurrent ischemic stroke. Long-term aspirin therapy reduces the risk of ischemic stroke, myocardial infarction, and vascular death. There is a paucity of data from randomized controlled trials to support the use of other antiplatelet regimes in acute stroke patients. In clinical trials for tPA, antithrombotic drugs (including aspirin) were avoided until after the 24-hour post-thrombolysis scan had excluded intracranial hemorrhage.

System Implications

  • Development and dissemination of protocols and standing order sets should be developed to guide initial management of ischemic stroke and transient ischemic attack patients
  • Pediatric awareness campaigns and education to healthcare professionals to optimize recognition of stroke and management.

Performance Measures

  1. Proportion of ischemic stroke or TIA patients who receive acute aspirin therapy within the first 48 hours following symptom onset (core).
  2. Median time from stroke patient arrival to hospital to administration of first dose of aspirin in hospital.

Measurement Notes

  • Time interval measurements should be taken from the time the patient is triaged or registered at the hospital (whichever time comes first) until the time the first dose is administered.
  • This indicator focuses on aspirin. Some centres may include other antiplatelet medications, such as clopidogrel or ASA combined with extended release dipyridamole. In cases where another agent is used instead of aspirin in the first 48 hours, this should be noted in the indicator definition.
  • Possible data sources include history and physical, physician’s admission notes, nurses’ admission notes, medication record.

Implementation Resources and Knowledge Transfer Tools

Health Care Provider Information

Patient Information

Summary of the Evidence, Evidence Tables and References

Evidence Table 5 Acute Aspirin Therapy

Aspirin therapy, provided acutely following ischemic stroke, is known to reduce the risk of recurrent (ischemic) stroke. In an updated Cochrane review, Sandercock et al. (2014) identified 8 RCTs (n=41,483 patients) that compared a single oral antiplatelet agent (aspirin, n=3 or ticlopidine, n=2) or a combination of antiplatelet agents (aspirin + dipyridamole and/or heparin, n=2) with control (placebo or no treatment). In 8/10 trials, therapy was initiated within one week following stroke. The dose of aspirin ranged from 160-325 mg/day and treatment duration ranged from 5 days to 3 months following stroke. Two large trials testing aspirin, started within 48 hours of stroke onset, contributed 98% of the data (CAST 1997, IST 1997). Antiplatelet therapy was associated with a significant reduction in the odds of being dead or dependent at final follow-up (OR= 0.95, 95% CI 0.91 to 0.99, p= 0.01). Treatment was also associated with a marginally significant reduction in death during treatment (OR= 0.92, 95% CI 0.85 to 1.00, p=0.05) and a significant reduction in the odds of death at a final follow-up (OR=0.92, 95% CI 0.87 to 0.99, p=0.01). Although antiplatelet therapy was associated with a significant increase in the odds of intercerebral hemorrhage (OR=1.23, 95% CI 1.00 to 1.50, p=0.04), a net reduction was reported in terms of the odds of any stroke recurrence (i.e., ischemic or hemorrhagic; OR=0.88, 95% CI 0.80 to 0.97).

In another Cochrane review, Sudlow et al. (2009) examined the use of thienopyridine derivatives vs. aspirin in patients at high risk of vascular events, provided over an average of two years. The majority of trials compared 500 mg ticlopidine with aspirin doses ranging from 80 mg-1,500 mg daily. Data from 10 RCTs (n=26,865) were included. Compared with aspirin, treatment with thienopyridine was associated with a significant reduction in the odds of a serious vascular event (OR=0.92, 95% CI 0.85 to 0.99, p=0.023) and a reduction in the odds of ischemic (or unknown etiology) stroke (OR=0.85, 95% CI 0.75 to 0.97, p= 0.013), but not hemorrhagic stroke (OR=0.96, 95% CI 0.60 to 1.55, p=0.80).

Current evidence suggests that patients who are treated with t-PA should not also receive antiplatelet therapy within 24-hours due to the increased risk of symptomatic intercrainial hemorrhage (sICH). The Antiplatelet Therapy in Combination with Rt-PA Thrombolysis in Ischemic Stroke (ARTIS) Trial randomized 640 patients to receive 300 mg of aspirin within 90 minutes of alteplase treatment or standard treatment (no aspirin).(Zinkstok & Roos, 2012). At the three month follow-up, although there was no difference between groups in the odds of a good outcome, defined as mRS score of 0-2 (54% vs. 57.2%, OR=0.91, 95% CI 0.66 to 1.26), the risk of sICH was significantly higher among patients in the early aspirin group ((RR=2.78, 95% CI 1.01 to 7.63, p=0.04).

Controversy exists regarding the use of antiplatelets in the hyperacute management of pediatric patients following stroke. The Royal College of Physicians and the American Heart Association pediatric stroke guidelines both recommend the use of aspirin unless there is a known dissection or cardiac clot, in which case low molecular weight heparin is recommend (Paediatric Stroke Working Group, 2004; Roach et al. 2008). Conversely, the American College of Chest Physicians guidelines (Monagle et al. 2012) suggests supportive care over anticoagulation or aspirin therapy in the absence of a documented, ongoing cardioembolic source. For neonates with a first ischemic stroke with a documented cardioembolic source, anticoagulation with UFH or LMWH is recommended.