How to adjust dose of NTG infusion. Equation for titration
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nitroglycerin IV infusion titration equation dose adjustment mcg/min
Here is a complete, practical guide to NTG (nitroglycerin) infusion titration:
NTG IV Infusion - Dose Titration
Standard Preparation
| Concentration | Calculation |
|---|---|
| 50 mg in 250 mL D5W | = 200 mcg/mL |
| 25 mg in 250 mL D5W | = 100 mcg/mL |
Titration Protocol (Adults)
Starting dose: 5-10 mcg/min
| Phase | Action | Interval |
|---|---|---|
| Initial | Increase by 5 mcg/min | Every 3-5 minutes |
| If no response at 20 mcg/min | Increase by 10 mcg/min | Every 3-5 minutes |
| If still no response | Increase by 20 mcg/min | Every 3-5 minutes |
| Partial response seen | Reduce increment size + lengthen interval | - |
Maximum dose: 200-400 mcg/min (rarely more than 100 mcg/min needed in AHF per Goldman-Cecil)
Rate Calculation Equation (Pump Rate in mL/hr)
For 50 mg in 250 mL (200 mcg/mL):
mL/hr = (Desired dose in mcg/min × 60) ÷ Concentration (mcg/mL)
mL/hr = (mcg/min × 60) ÷ 200
This simplifies to a conversion factor of 0.3:
mL/hr = mcg/min × 0.3
Quick reference table (50 mg/250 mL):
| Dose (mcg/min) | Pump Rate (mL/hr) |
|---|---|
| 5 | 1.5 |
| 10 | 3 |
| 15 | 4.5 |
| 20 | 6 |
| 30 | 9 |
| 40 | 12 |
| 50 | 15 |
| 100 | 30 |
General Formula (any concentration)
mL/hr = (Dose in mcg/min × 60 min/hr) ÷ Concentration in mcg/mL
Or if weight-based:
mL/hr = (Dose in mcg/kg/min × Weight in kg × 60) ÷ Concentration in mcg/mL
Clinical Endpoints (When to Stop Titrating Up)
- SBP drop >10% (or SBP <90-100 mmHg - hold/reduce)
- Relief of chest pain (ischemia/ACS)
- Adequate reduction in filling pressures / PCWP
- Relief of dyspnea in acute decompensated heart failure
- Symptomatic headache or hypotension
Indication-Specific Starting Points
| Indication | Start | Usual Range |
|---|---|---|
| ACS / Angina | 5-10 mcg/min | 50-200 mcg/min |
| Acute heart failure (SBP >100) | 10 mcg/min, double q10min | Up to 100 mcg/min |
| Hypertensive emergency | 10-20 mcg/min | Up to 100-200 mcg/min |
| Variceal bleeding (+ vasopressin) | 40 mcg/min | Up to 400 mcg/min |
Children (not FDA-approved)
- Start: 0.25-0.5 mcg/kg/min
- Titrate: increase by 0.5-1 mcg/kg/min every 3-5 min
- Maximum: 5-10 mcg/kg/min
Key Precautions
- Use non-PVC tubing (NTG is absorbed by PVC) - when using non-absorbing tubing, doses are lower than older PVC-based studies suggest
- Monitor BP continuously - hypotension is the main dose-limiting side effect
- Tolerance develops within 24 hours of continuous use
- Contraindicated with phosphodiesterase-5 inhibitors (sildenafil, etc.)
- Use with caution if SBP <100 mmHg, severe aortic stenosis, or hypertrophic cardiomyopathy
Sources: Braunwald's Heart Disease (Table 49.7) - Initial dose 20 mcg/min, effective range 40-400 mcg/min; Goldman-Cecil Medicine - Start 10 mcg/min, double every 10 min (AHF protocol); FDA prescribing information via DailyMed - start 5 mcg/min, titrate q3-5 min.
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