What is the appropriate administration of bystander nitroglycerine (sublingual) for a patient with chest pain, likely due to acute coronary syndrome, with a history of angina or myocardial infarction?

Bystander Administration of Sublingual Nitroglycerin for Chest Pain

If a patient with a history of angina or MI experiences chest pain and has previously been prescribed nitroglycerin, a bystander should assist them in taking 1 sublingual nitroglycerin tablet (0.3-0.4 mg) immediately, and if symptoms are unimproved or worsening after 5 minutes, call 9-1-1 immediately to activate emergency medical services. 1

Immediate Administration Protocol

For patients with previously prescribed nitroglycerin:

• Administer 1 sublingual nitroglycerin tablet (0.3-0.4 mg) immediately when chest pain begins 1, 2
• The tablet should be dissolved under the tongue or in the buccal pouch 2
• Patient should be seated or lying down during administration to prevent falls from lightheadedness or dizziness 2

Critical 5-Minute Decision Point

If chest pain is unimproved or worsening 5 minutes after the first dose:

• Call 9-1-1 immediately to activate EMS—do not wait to give additional doses before calling 1
• This represents a significant change from the traditional "3 doses before calling" approach, specifically modified to encourage earlier EMS contact 1

While awaiting ambulance arrival:

• Additional nitroglycerin may be given every 5 minutes for a maximum of 3 total doses if the patient tolerates it 1, 2
• Healthcare providers or 9-1-1 dispatchers can instruct bystanders to give these additional doses 1

Safety Parameters Before Each Dose

Check these vital signs before administering each dose:

• Systolic blood pressure must be ≥90 mmHg (or not ≥30 mmHg below baseline) 3
• Heart rate must be 50-100 bpm (avoid if <50 or >100 bpm without heart failure) 3
• Severe hypotension can occur even with small doses, particularly in upright posture 2

Special Considerations for Chronic Stable Angina

For patients known to have frequent angina with typical response patterns:

• If symptoms are significantly improved after 1 nitroglycerin dose, it is appropriate to repeat every 5 minutes for a maximum of 3 doses 1
• Call 9-1-1 if symptoms have not totally resolved after 3 doses 1
• This tailored approach accounts for patients whose angina typically responds well to nitroglycerin 1

Critical Contraindications and Warnings

Do not administer nitroglycerin if:

• Patient has taken phosphodiesterase inhibitors (Viagra/sildenafil) recently—this can cause catastrophic hypotension 1, 2
• Patient has signs of right ventricular infarction (ST elevation in V4R, inferior wall involvement)—these patients are preload-dependent and can experience life-threatening hypotension 3
• Patient appears to have very low blood pressure or is in shock 2

What NOT to Do

Common pitfalls to avoid:

• Do not seek someone else's nitroglycerin if the patient has not been previously prescribed it—instead call 9-1-1 immediately 1
• Do not delay calling 9-1-1 to give all 3 doses first—self-treatment with nitrates is a documented cause of dangerous delays in patients with acute coronary syndrome 1
• Do not have the patient swallow the tablet—it must be dissolved sublingually or buccally 2
• Do not allow the patient to stand or walk—keep them seated or lying down 2

Additional Bystander Actions While Awaiting EMS

Beyond nitroglycerin administration:

• Keep the patient calm and at rest in a seated or semi-recumbent position 2
• Monitor for worsening symptoms including radiation of pain to arms, back, neck, jaw; shortness of breath; weakness; sweating; nausea; or lightheadedness 4
• If the patient has aspirin available and has not already taken it, EMS personnel will likely administer 162-325 mg (chewed, non-enteric-coated) upon arrival 4
• Do not give aspirin if the patient is elderly (≥65 years) and on anticoagulation therapy due to severe bleeding risk 4, 5

Monitoring Response

Expected effects within 2-5 minutes:

• Relief or improvement of chest pain 3, 2
• Patient may experience a burning or tingling sensation under the tongue (though absence of this does not indicate ineffective medication) 2
• Possible headache, lightheadedness, or flushing 2

If pain persists after 3 tablets in 15 minutes, prompt medical attention is mandatory 2