Why Aspirin is Given to Patients with Chest Pain in the Emergency Room
Aspirin (162-325 mg) is administered to patients with chest pain in the emergency room because early aspirin administration significantly improves survival in acute myocardial infarction by inhibiting platelet aggregation and reducing thrombosis, with the greatest mortality benefit achieved when given within the first few hours of symptom onset. 1
Mechanism and Mortality Benefit
Aspirin reduces mortality in acute coronary syndromes through its antiplatelet effects, preventing further thrombus formation in coronary arteries. 1
Two observational studies with 2,122 patients demonstrated higher survival with early aspirin administration (median 1.6 hours from pain onset) compared to late administration (median 3.5 hours), with this survival benefit persisting at 1 year. 1
A 2020 systematic review confirmed that early or first aid administration of aspirin to adults with non-traumatic chest pain was associated with reduced mortality at 7 days, 30 days, and one year compared to late or in-hospital administration. 1, 2
Recommended Dosing and Administration
The dose is 162-325 mg of non-enteric aspirin, which should be chewed and swallowed rather than swallowed whole to achieve rapid buccal absorption and faster antiplatelet effect. 1, 3, 4
Chewing the aspirin is critical because it allows for immediate absorption through the oral mucosa, providing faster onset of antiplatelet action during the critical early phase of myocardial infarction. 4
Enteric-coated formulations should not be used in acute presentations as they significantly delay absorption when rapid action is most needed. 4
Timing is Critical
The benefit of aspirin is greatest when administered within the first 4 hours after symptom onset, making early administration in the emergency room or even pre-hospital setting crucial. 1
Studies show that early prehospital administration of aspirin is associated with decreased in-hospital complications and reduced 7-day and 30-day mortality in STEMI patients. 1
Even patients already on chronic daily aspirin therapy benefit from an additional loading dose, as many display platelet hyperfunction during acute coronary syndrome that requires additional aspirin to adequately suppress platelet activity. 5
Safety Profile
The risk of major complications from a single dose of aspirin in patients with chest pain is low, with studies showing no significant difference in complication rates between early and late aspirin administration. 1
However, aspirin should be withheld if the patient has a known aspirin allergy, active gastrointestinal bleeding, or recent intracranial hemorrhage. 1, 4
Clinical Implementation
EMS providers and emergency department staff should administer aspirin immediately upon encountering patients with suspected acute coronary syndrome, unless contraindications exist. 3, 4
First aid providers and 9-1-1 dispatchers may encourage patients to chew aspirin (162-325 mg) while awaiting EMS arrival, provided there is no aspirin allergy or signs of active bleeding. 1, 4
If there is any uncertainty about contraindications, it is reasonable to wait for EMS arrival rather than risk administration in an inappropriate patient. 1
Common Pitfalls to Avoid
Do not delay aspirin administration to obtain physician consultation if the patient meets criteria and has no contraindications, as time to treatment directly correlates with mortality reduction. 4
Do not give aspirin to patients with recent bleeding, even if cardiac symptoms are severe, as mortality from rebleeding can equal or exceed cardiac mortality in this population. 4
Be aware that prehospital providers sometimes fail to administer aspirin because they incorrectly judge chest pain as non-cardiac in origin, or because the patient already took aspirin that day—however, additional loading doses are beneficial even in patients on chronic aspirin therapy. 5, 6