Can we give nitroglycerin (NTG) to a patient with hypotension?

Nitroglycerin Administration with Systolic Blood Pressure of 90 mmHg

No, nitroglycerin should NOT be administered to patients with a systolic blood pressure of 90 mmHg or less. This is an absolute contraindication based on established ACC/AHA guidelines. 1

Clear Contraindications

The ACC/AHA guidelines explicitly state that nitrates should not be administered to patients with:

• Systolic blood pressure less than 90 mm Hg 1
• Systolic blood pressure ≥30 mm Hg below baseline 1
• Severe bradycardia (<50 bpm) 1
• Tachycardia (>100 bpm) 1
• Suspected right ventricular infarction 1
• Recent phosphodiesterase inhibitor use (24 hours for sildenafil/vardenafil, 48 hours for tadalafil) 1

Why This Matters: The Risk of Severe Hypotension

Inadvertent systemic hypotension with resulting worsening of myocardial ischemia is the most serious potential complication of nitroglycerin therapy in patients with acute myocardial infarction. 1

The mechanism of harm includes:

• Nitroglycerin causes venous and arterial vasodilation, reducing preload and afterload 2
• In patients already hypotensive (SBP ≤90 mmHg), further vasodilation can precipitate profound hypotension 1
• This may trigger reflex tachycardia and paradoxically worsen myocardial ischemia 1
• Patients become dependent on adequate preload to maintain cardiac output, which nitroglycerin directly compromises 1

Special Caution: Right Ventricular Infarction

Even if blood pressure appears marginally acceptable, nitroglycerin should be used with extreme caution or avoided entirely in patients with suspected right ventricular infarction, as these patients are especially dependent on adequate right ventricular preload to maintain cardiac output and can experience profound hypotension. 1

• This is particularly relevant in inferior wall myocardial infarction, which is frequently associated with RV involvement 1
• A right-sided ECG should be performed to evaluate for RV infarction before administering nitrates in inferior STEMI 1

The One Narrow Exception

The 1990 ACC/AHA guidelines note that even if systolic blood pressure is <90 mm Hg, a single sublingual nitroglycerin tablet may be tried in the hospital provided there is evidence of ongoing ischemic pain and an intravenous line has been inserted. 1

However, this exception requires:

• Hospital setting with immediate monitoring capability 1
• Established IV access for rapid fluid resuscitation 1
• Careful and frequent observation of vital signs for several minutes after the initial dose 1
• Readiness to manage hypotension with leg elevation, rapid fluid administration, and atropine if needed 1

Evidence from Clinical Practice

Recent large-scale studies support the guideline recommendations:

• In a nationwide registry of 80,760 encounters, adverse events occurred in 7% of patients receiving prehospital nitroglycerin, with lower baseline systolic blood pressure being inversely associated with adverse events (OR = 0.99 per mmHg) 3
• Adverse events were rare in patients with SBP >110 mmHg and HR <100 bpm 3
• A study of 10,308 patients found that pre-nitroglycerin blood pressure was the strongest predictor of post-nitroglycerin hypotension (AOR for units of 10mmHg: 0.64) 4

Practical Algorithm

For patients with chest pain and SBP = 90 mmHg:

1. Do NOT administer nitroglycerin 1
2. Establish IV access immediately 1
3. Consider fluid resuscitation if appropriate for the clinical scenario 1
4. Obtain 12-lead ECG to assess for inferior STEMI or signs of RV involvement 1
5. Administer aspirin 162-325 mg (chewed) if no contraindications 1
6. Consider morphine sulfate (2-4 mg IV) for pain relief instead 1
7. Monitor blood pressure continuously 2
8. Only after blood pressure rises above 90 mmHg (and ideally above 110 mmHg) should nitroglycerin be considered 1, 2

FDA Labeling Reinforcement

The FDA drug label for nitroglycerin emphasizes that severe hypotension, particularly with upright posture, may occur with small doses of nitroglycerin. This drug should therefore be used with caution in patients who may be volume-depleted or who, for whatever reason, are already hypotensive. 5