Aspirin in ACS
Objective: Give chewable aspirin early for suspected ACS when your protocol allows it. Screen for bleeding, true allergy, and possible aortic dissection. It can still harm the wrong patient. Your protocol card sets the amount.
Why this matters
Aspirin is one of the few prehospital drugs with strong outcome evidence in ACS, acute coronary syndrome. It is still easy to give it to the wrong patient. That includes aortic dissection, vomiting blood, or a patient who already took a full dose at home.
Your job is the indication, then the cautions, then the protocol dose and route. The usual route is chewed. Write down what the patient already took. Your protocol card sets the amount. This site does not list milligrams.
- This is suspected ACS, or it is not.
- Screen for a true allergy, active bleeding, or a tearing dissection picture.
- Did they already take aspirin today? What, and when?
- Chew it if that is how your packaging is used. The dose comes from the protocol only.
Clinical sequence
- If ACS is likely, the patient can chew, and there is no major gastrointestinal bleed or true allergy: give aspirin per protocol early. Do not wait for the hospital to start it.
- Say the dose and the route you actually gave. Chewed, not swallowed whole, is the usual teaching. Confirm they have not already taken an adequate dose today. A baby aspirin last week is not today’s dose.
- Stroke, active significant bleeding, or true allergy: leave it in the pouch.
- Aspirin is not a STEMI alert and not a 12-lead. Acquire and transmit the tracing. The tablet does not replace the destination.
When It Fits
- Suspected ACS: pain that sounds ischemic, sweating, radiation, shortness of breath that may be an equivalent, or a concerning 12-lead. Use your protocol’s inclusion list.
- Give it early when the picture fits and the caution screen is clear.
When to Pause
- True aspirin or NSAID anaphylaxis. Stomach upset alone is not that allergy unless your protocol says to hold.
- Active significant bleeding.
- A possible aortic dissection: sudden tearing pain to the back, pulse deficits, or unequal blood pressures. This is not an automatic ACS aspirin. Follow your protocol or medical control.
Practice habits
- Chewed, not swallowed whole, is the usual teaching for a faster effect. Follow your packaging.
- This site does not list milligrams. Your protocol is the authority.
- Document the time, the dose if you know it, who gave it, and the cautions you screened.
Common errors
- Skipping aspirin because the hospital has it.
- Giving it for every chest-wall strain after a workout.
- Not asking what the patient already took.
Practice
One-minute check
For each scene, say aspirin yes, pause, or ask medical control, and give one reason: (1) sweating, pressure-like pain radiating to the arm, and a clear caution screen; (2) coffee-ground vomit and black stool; (3) sudden tearing pain to the back with unequal radial pulses.
Related: 12-lead STEMI.
Sources & Further Study
Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.
- 2025 ACC/AHA/ACEP/NAEMSP/SCAI ACS Guideline — Class 1 initial oral aspirin in ACS.
- NASEMSO National Model EMS Clinical Guidelines (2022) — EMS model language for suspected ACS.
- Give chewable aspirin early in suspected ACS unless allergy, significant bleeding, or a dissection-type picture says otherwise. Your protocol sets the dose.
Education only. Apply learning within your protocols and medical direction. This is not clinical care guidance.
Check Your Understanding
Questions drawn only from this lesson. After you check, the key is highlighted. Education practice — not a certification exam.