How do you administer an NTG (Nitroglycerin) infusion?

How to Administer an NTG (Nitroglycerin) Infusion

Nitroglycerin infusion must be diluted in Dextrose (5%) or Sodium Chloride (0.9%) solution prior to administration and should be delivered through non-absorbing tubing using an infusion pump capable of exact and constant delivery. 1

Initial Preparation and Dilution

• Standard Dilution:

  • Transfer 50 mg of nitroglycerin into a 500 mL glass bottle of either D5W or NS to yield a concentration of 100 mcg/mL 1
  • Alternative dilution: 5 mg nitroglycerin into 100 mL to yield 50 mcg/mL 1

• Important Considerations:

  • Use glass bottles (not plastic bags) for dilution
  • Use non-absorbing tubing for administration (PVC tubing absorbs nitroglycerin)
  • Do not mix nitroglycerin with other drugs 1
  • Invert the glass bottle several times to ensure uniform dilution 1

Dosing and Titration

• Initial Dose: Start at 5 mcg/min when using non-absorbing tubing 1

• Titration Protocol:

  • Initial titration: Increase by 5 mcg/min every 3-5 minutes until response is noted 1
  • If no response at 20 mcg/min, increase by 10 mcg/min increments
  • Once partial response is observed, reduce dose increments and lengthen intervals between increases 1
  • Titration end points:
    • Control of clinical symptoms
    • Decrease in mean arterial pressure of 10% in normotensive patients or 30% in hypertensive patients (but never below 90 mmHg systolic)
    • Increase in heart rate >10 beats/min (but not usually >110 beats/min) 2

• Maintenance Dosing:

  • Doses >200 mcg/min are associated with increased risk of hypotension; consider alternative therapy 2
  • For prolonged infusions, concentration may be increased up to 400 mcg/mL to limit fluid administration 1

Monitoring and Precautions

• Vital Signs: Monitor blood pressure, heart rate, and clinical symptoms regularly

• Contraindications:

  • Systolic blood pressure <90 mmHg
  • Right ventricular infarction (patients are preload dependent)
  • Use of phosphodiesterase-5 inhibitors within 24-48 hours 3

• Potential Complications:

  • Hypotension: If severe, discontinue drug, elevate legs, administer fluids, and consider atropine 2
  • Tolerance: May develop with prolonged infusion; effectiveness usually returns after 12 hours of removal 2

Special Considerations

• If tolerance develops, the infusion rate can be increased, but if doses >200 mcg/min become necessary, consider substituting with another vasodilator 2
• When adjusting concentration, flush or replace the infusion set before using the new concentration to avoid delayed delivery of the new concentration 1
• For patients with normal or low left ventricular filling pressures, doses as small as 5 mcg/min may be sufficient 1
• The combination of intravenous nitroglycerin with a beta-blocker is well tolerated and may reduce the risk of undesired tachycardia 2

Discontinuation

• Avoid abrupt cessation as it may exacerbate ischemic changes
• Implement a graded reduction in the dose when discontinuing the infusion 2

By following these guidelines for NTG infusion administration, you can effectively manage conditions such as unstable angina, acute myocardial infarction complicated by heart failure, and hypertensive emergencies while minimizing the risk of adverse effects.