Obtain an early 12-lead, check medication exclusions, and coordinate a cardiac destination.
OCEMS source summary · Updated 2026-09-16
Key cautions & base contact
Hold aspirin for allergy, anticoagulant/antiplatelet use, or direct midline mid-back pain raising concern for dissection.
Do not give nitroglycerin after sildenafil, vardenafil, or tadalafil within 24 hours. Avoid IO in potential CVRC patients because of possible thrombolysis-related bleeding.
Recognize & assess
Suspect an anginal equivalent with unexplained diaphoresis, sudden weakness, dyspnea, anxiety, or atypical chest discomfort. Heartburn-like, pleuritic, or musculoskeletal-sounding pain does not exclude cardiac disease.
Monitor rhythm and obtain a 12-lead as soon as practical before leaving the scene. A normal/non-STEMI tracing does not rule out acute MI.
Initial treatment
If no source contraindication applies, give four 81 mg aspirin tablets (324 mg) or one 325 mg tablet to chew.
When room-air SpO₂ is below 95%, provide mask oxygen or nasal cannula at 6 L/min as tolerated.
For discomfort, give nitroglycerin 0.4 mg SL if systolic BP is above 100; repeat about every 3 minutes, up to 3 EMS doses while BP stays above 100. Prior self-doses are not included in that EMS count.
Persistent pain or nausea
If 3 nitroglycerin doses fail or nitroglycerin cannot be given, the source permits morphine 5 mg (or 4 mg carpuject) IV, or fentanyl 50 mcg IV. Either may repeat once after about 3 minutes; hold if systolic BP is below 90.
For nausea/vomiting without known or suspected pregnancy: ondansetron 8 mg ODT or 4 mg IV, with one IV repeat after about 3 minutes if needed.
Destination & reassessment
Suspected/identified acute MI requires base contact for a CVRC with an available catheterization lab. Otherwise provide ALS escort to an appropriate ERC.
Reassess pain, BP, breathing, rhythm, and treatment response. If a patient with a performed 12-lead requests AMA, contact base before leaving the scene.