How do I dilute a vial of nitroglycerin and what is the recommended rate of infusion?

Nitroglycerin IV Dilution and Infusion Protocol

To administer intravenous nitroglycerin, dilute the vial in D5W or 0.9% saline to a concentration of 100 mcg/mL, and initiate infusion at 5 mcg/min, titrating by 5 mcg/min every 3-5 minutes until desired response is achieved, using non-absorbing tubing with an infusion pump.

Dilution Instructions

Initial Dilution

1. Use only glass bottles of D5W or 0.9% Normal Saline for dilution
2. Standard concentration:
   • Add 50 mg nitroglycerin to 500 mL of solution = 100 mcg/mL
   • Alternative: Add 5 mg nitroglycerin to 100 mL = 50 mcg/mL

Important Preparation Notes

• NEVER administer undiluted nitroglycerin directly
• Use only non-absorbing (non-PVC) tubing for administration 1
• Do not mix nitroglycerin with other medications
• Invert glass bottle several times to ensure uniform dilution
• Higher concentrations (up to 400 mcg/mL) may be used to limit fluid administration 1

Administration Protocol

Initial Dosing

• Start at 5 mcg/min using an infusion pump capable of exact delivery 1
• For acute coronary syndromes or pulmonary edema: Begin with 5-10 mcg/min 2
• For hypertensive emergencies: Begin with 5 mcg/min 2

Titration

• Increase by 5 mcg/min every 3-5 minutes until clinical response 2, 1
• If no response at 20 mcg/min, increase by 10 mcg/min increments
• Once partial response is observed, reduce increment size and increase interval between adjustments 1

Target Endpoints

1. Relief of symptoms (chest pain, pulmonary edema)
2. Blood pressure response:
   • Decrease mean arterial pressure by 10% in normotensive patients
   • Decrease by up to 30% in hypertensive patients
   • Never reduce systolic BP below 90 mmHg 2
3. Heart rate increase <10 beats/min (not exceeding 110 beats/min)
4. Decrease in pulmonary artery end-diastolic pressure by 10-30% 2

Clinical Considerations

Dosing Cautions

• Doses >200 mcg/min increase risk of hypotension; consider alternative therapy 2
• Some patients (especially those with normal LV filling pressures) may be hypersensitive to nitroglycerin and respond to doses as low as 5 mcg/min 1
• Prolonged infusion (>24 hours) may lead to tolerance 2, 3

Monitoring Requirements

• Continuous blood pressure monitoring
• ECG monitoring for heart rate changes
• Monitor for headache (common side effect)
• For high doses or prolonged use, consider arterial line placement 2

Special Situations

• Avoid in patients with:
  • Systolic BP <90 mmHg
  • Severe bradycardia (<50 bpm)
  • Right ventricular infarction
  • Concurrent phosphodiesterase inhibitor use (sildenafil, tadalafil, vardenafil) 2

Infusion Rate Calculation

For a 100 mcg/mL concentration:

• 5 mcg/min = 3 mL/hr
• 10 mcg/min = 6 mL/hr
• 50 mcg/min = 30 mL/hr
• 100 mcg/min = 60 mL/hr

Remember that the actual delivered dose may vary based on tubing type. Non-absorbing tubing delivers more medication to the patient than PVC tubing, requiring lower doses 1.