Aspirin in the Prehospital Setting

A yellow bottle of Bayer aspirin sits on a green counter
Photo by the author.

Use this article to learn what aspirin is and when it should — and should not — be used in the prehospital setting.

You and your partner are dispatched to a 65-year-old male complaining of mid-sternal chest pain. The pain is non-reproducible and does not radiate. On a scale of one to 10, the patient rates this as an eight and it feels like a crushing pain. He goes on to report he has felt this same discomfort in the past. The last time he felt this he went to the emergency department and received a cardiac stent. As you continue to evaluate this patient you find that they have a heart rate of 96, a blood pressure of 146/75, respiratory rate of 22, and SpO2 of 97%. They are ashen in color and diaphoretic.

During the response, the dispatcher advised the patient to take four low-dose 81mg aspirins. The patient advised the dispatcher that he did not think he had any in the house, so he was unable to take them. When the EMS crew arrived on the scene, they were advised that the patient has no known drug allergies and no current bleeding. They immediately administered four 81mg chewable aspirin. This patient was later transported to the emergency department. On arrival at the emergency department, the cardiac team took the report from the EMS agency and asked if the patient had received aspirin.

What Is Aspirin?

Acetylsalicylic Acid (ASA), otherwise known as aspirin, is a nonsteroidal anti-inflammatory drug (NSAID) that was the first of its kind to be developed approximately 4,000 years ago.1 ASA has a variety of uses such as pain relief, fever reduction and reduction of inflammation. Additionally, ASA has been used and is recommended in treatment for acute cardiac symptoms such as chest discomfort. The immediate administration of aspirin is not to treat or improve the patient’s pain level. ASA is administered because of its anti-platelet aggregation properties.


Many people believe ASA to be classified as a blood thinner. However, ASA is not at all a blood thinner but a platelet aggregation inhibitor. Simply stated, aspirin coats the blood platelets and makes them less sticky. The overall intent of administering ASA during a possible myocardial infarction is to keep platelets from sticking together thus reducing the possibility of a growing blood clot.2 Many physicians are directing patients to begin a daily aspirin regimen as it has been proven to help reduce the risk of heart attacks. The overall intention is to have patients consume the ASA every day. This will allow the platelets to be coated reducing the likelihood of them forming clots which can ultimately lead to myocardial infarction.2

Why Is It Important This Patient Received Aspirin?

In the case above, a 65-year-old male is experiencing chest pain and diaphoresis. He had a myocardial infarction (MI) in the past and is ashen in color. Being that chest pain, changes in color and diaphoresis are all signs of infarction, all of these symptoms are pointing to the possibility that this patient is having another MI.3 ASA needs to be administered as soon as possible to allow the aspirin to begin to coat the platelets. For this reason, when 911 is called, the emergency medical dispatcher (EMD) will question the patient to see if they are a candidate to take ASA. If the dispatcher’s questions lead them to believe it is safe to administer the aspirin, the dispatcher will advise the patient to chew and swallow the medication.4

In the event that the patient does not have access to the medication, or they do not take it when advised by the dispatcher, it becomes the responsibility of the EMS team to perform the treatment. Just like with any other medication it is essential to ensure that the patient does not have an allergy to the medication. The EMS provider must also ensure the patient is at least 19 years old, does not have any active bleeding and is not pregnant.

The ASA should be chewed and swallowed by the patient. If the patient insists, they can have a sip of water to wash the sour taste of the ASA out of their mouth. EMS will not advise the patient to have any more than a mouthful of water. The purpose of chewing the aspirin as opposed to swallowing it will have to do with its rate of absorption. By chewing and crushing the medication it will be absorbed into the body quicker than if it is swallowed whole and is forced to dissolve.5

When Aspirin Should be Withheld

While there are many uses of aspirin, there are also a number of contraindications that must be noted when preparing to administer the medication. First and foremost, aspirin should be withheld when there is a known hypersensitivity to the drug.6 There is no need to add the potential of an anaphylactic reaction to the patients already existing emergency. As Nancy Caroline said many times, our main purpose is to “Do No Harm.”7

Furthermore, patients who have a history of or have current bleeding disorders not to exclude ulcers, gastrointestinal bleeding and a possible aortic aneurysm should not be administered the medication.6

The Cambridge Studies

In 2012, Cambridge University did a study of 52 patients over an 8-week period of time who had a chief complaint of chest pain. Of those 52 patients, the study discovered only 13 had received aspirin – which is 25% of the total patient population. The primary reason the aspirin was not administered to the remaining patients was that the crew did not believe the pain was cardiac-related.6

Another common reason that the aspirin was withheld was because of the fear of adverse effects. Cambridge University did another study regarding the potential negative effects of EMS-administered aspirin. A total of 1,478 patients were evaluated after receiving ASA prior to hospital arrival. Of those patients, 585 received the medication before the EMS response, and 893 were administered ASA by EMS providers. The study yielded that there were zero negative effects on patients who received the medication.7


The administration of ASA to potential cardiac patients is an essential part of the care provided by EMS. Patients who are experiencing chest discomfort, have no known allergy to aspirin, and do not have current bleeding, should be administered the medication if protocol allows. Furthermore, the providers must inform the receiving hospital of the administered medication and the intervention needs to be appropriately documented in the patient care report. By administering aspirin to these patients as soon as possible, EMS has the ability to impact the patient’s overall outcome. Not only will early administration help the patient receive the benefits of ASA sooner, but it will also help to reduce the time the patient spends in the ED. Just like the saying time is brain, the same goes for the heart. Administering ASA prior to ED arrival will leave one less step for the doctors and nurses to have to take and reduce the door to balloon time in the cardiac catheterization lab.


1. Brazier. (2020). Aspirin: Health benefits, uses, risks, and side effects. Medical News Today.

2. Pai, R. (2019). Aspirin to Prevent Heart Attack and Stroke. Health Link British Columbia. 

3. Ornato, & Hand (2001). Cardiology patient page: Warning signs of a heart attack. Circulation103(25), e124-e125.

4. Barron, T., Clawson, J., Scott, G., Patterson, B., Shiner, R., Robinson, D., & Olola, CH. (2013). Aspirin administration by emergency medical dispatchers using a protocol-driven aspirin diagnostic and instruction tool. Emergency Medicine Journal30(7), 572-578.

5. Hendrick. (2009). Chewable Aspirin Is Best for the Heart. WebMD. 

6. EMSTAR. (2021). Aspirin administration. EMSTAR. Retrieved from /aspirinadmin. 

7. Pilbery, R., & Caroline, N. L. (2016). Nancy Caroline’s emergency care in the streets. Jones & Bartlett Learning. 

8. Hooker, Benoit, & Price. (2012). Reasons Prehospital Personnel Do Not Administer Aspirin to All Patients Complaining of Chest Pain: Prehospital and Disaster Medicine. Cambridge Core. 

9. Quan, D., LoVecchio, F., Clark, B., & Gallagher, J. V. (2004). Prehospital use of aspirin rarely is associated with adverse events. Prehospital and disaster medicine19(4), 362-365.


  • Peter DeNicola, BS, MICP, NRP, is a mobile intensive care paramedic and communications supervisor for JFK EMS in Edison, New Jersey. He has been an EMT for 15 years and a paramedic for eight years. In addition to his duties on the ambulance and in the communication center, he has a passion education and assists in teaching a variety of courses.

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