GTN Infusion Dosing and Titration
Start intravenous nitroglycerin at 10 mcg/min and increase by 10 mcg/min every 3-5 minutes until symptoms resolve or blood pressure responds, with a commonly used ceiling of 200 mcg/min. 1
Initial Dosing Strategy
- Begin at 10 mcg/min through an infusion pump using non-absorbing tubing (polyethylene preferred, though standard PVC tubing is clinically effective) 2, 1
- The European Society of Cardiology recommends an alternative starting range of 10-20 mcg/min for acute heart failure patients 2
- Ensure the infusion pump is capable of exact delivery to avoid dosing errors 1
Titration Protocol
- Increase by 10 mcg/min every 3-5 minutes for the first 20 minutes until symptom relief or blood pressure response occurs 2, 1
- If no response at 20 mcg/min, use larger increments of 10 mcg/min, then advance to 20 mcg/min increments 2, 1
- Once partial response is achieved, reduce the increment size and lengthen the interval between increases 1
- Stop titrating when symptoms resolve—there is no need to continue increasing the dose solely for blood pressure effect 2, 1
Maximum Dose Considerations
- The commonly recommended ceiling is 200 mcg/min, though this is not an absolute limit 2, 1
- Prolonged infusions at 300-400 mcg/min have been safely administered for 2-4 weeks without increasing methemoglobin levels 2, 1
- If doses exceed 200 mcg/min without adequate response, consider switching to alternative vasodilators 1
Critical Safety Parameters
Blood Pressure Thresholds
- **Do not initiate if systolic BP <90 mmHg** or >30 mmHg below baseline 2, 1
- In acute heart failure, GTN is recommended for patients with systolic BP >110 mmHg and may be used cautiously between 90-110 mmHg 2
- Target systolic BP should not fall below 110 mmHg in normotensive patients 1
- In hypertensive patients, do not reduce mean arterial pressure by more than 25% 1
- Frequent blood pressure monitoring is mandatory during titration to avoid large drops in systolic BP 2
Absolute Contraindications
- Phosphodiesterase-5 inhibitor use within 24 hours (sildenafil) or 48 hours (tadalafil) due to risk of profound hypotension, MI, and death 2, 1
- Right ventricular infarction—these patients depend critically on preload and may experience cardiovascular collapse 1
- Marked bradycardia or tachycardia 1
High-Risk Populations
- Patients with aortic stenosis may demonstrate marked hypotension following initiation 2
- An arterial line is not routinely required but facilitates titration in patients with borderline pressures 2
Tolerance Management
- Tolerance develops after 24 hours of continuous infusion and is dose and duration dependent 1
- Tachyphylaxis is common after 24-48 hours, necessitating incremental dosing 2
- Increase infusion rate periodically if therapy extends beyond 24 hours 1
- Transition to oral/topical nitrates within 24 hours once the patient is stable and symptom-free for 12-24 hours 1
- When transitioning from prolonged GTN infusion (>24 hours), use oral isosorbide dinitrate 10 mg three times daily to prevent rebound vasoconstriction 3
Practical Considerations
Cannula Size and Flow Rate
- With large-bore cannulas (e.g., 16-gauge), starting at 1 mL/h results in a >6-minute delay before drug enters the body due to dead space 4
- Smaller cannulas (e.g., 20-gauge) reduce this delay to approximately 1.5 minutes at the same rate 4
- If using a large-diameter cannula, choose a faster initial infusion rate to ensure GTN begins acting quickly, then adjust based on clinical response 4
Tubing Type
- While GTN is absorbed into PVC tubing in vitro, clinical studies demonstrate that beneficial hemodynamic effects occur at 80 mcg/min regardless of tubing type (PVC vs. polyethylene) 5
- Non-absorbing polyethylene tubing is preferred but not essential for clinical effectiveness 1, 5