Starting Nitroglycerin Infusion: Practical Dosing Guide
Start nitroglycerin at 5-10 mcg/min (0.3-0.6 mL/hour for a 50 mL infusion at 100 mcg/mL concentration) when using non-absorbing tubing, and titrate upward by 5-10 mcg/min every 3-5 minutes based on blood pressure and symptom response. 1
Concentration Preparation
- Standard concentration: Mix 50 mg nitroglycerin in 500 mL D5W or normal saline to yield 100 mcg/mL 1
- Alternative concentration: Mix 5 mg in 100 mL to yield 50 mcg/mL 1
- For your 50 mL pump: Use 5 mg nitroglycerin in 50 mL = 100 mcg/mL concentration 1
- Maximum concentration should not exceed 400 mcg/mL 1
Initial Dosing Algorithm
Starting dose depends on clinical indication and blood pressure:
For Acute Coronary Syndrome or Pulmonary Edema (SBP >110 mmHg):
- Start at 5 mcg/min (3 mL/hour at 100 mcg/mL) using non-absorbing tubing 2, 1
- If using older PVC tubing, start at 10-20 mcg/min due to drug absorption 2, 1
For Hypertensive Emergency:
- Start at 5 mcg/min (3 mL/hour) 2
- Increase by 5 mcg/min every 3-5 minutes 2
- Maximum dose typically 20 mcg/min for this indication 2
For Unstable Angina or Heart Failure:
Titration Strategy
Increase dose systematically based on response:
- At doses <20 mcg/min: Increase by 5 mcg/min every 3-5 minutes 2, 1
- At doses 20-100 mcg/min: Increase by 10 mcg/min increments 2, 1
- At doses >100 mcg/min: Increase by 20 mcg/min increments 2, 1
- Slow titration once partial blood pressure response achieved 2, 1
Maximum Dosing
- Standard maximum: 200 mcg/min (120 mL/hour at 100 mcg/mL) 2, 3
- Extended maximum: Up to 400 mcg/min may be used with careful monitoring in refractory cases 3, 1
- Most patients respond adequately at doses <100 mcg/min 1
Blood Pressure Targets and Safety
Critical blood pressure parameters:
- **Avoid if SBP <90 mmHg** or >30 mmHg below baseline 2, 3
- Target SBP >110 mmHg in previously normotensive patients 2, 3
- In hypertensive patients: Do not reduce mean arterial pressure by >25% in first hour 2, 3
- Consider arterial line for doses >100 mcg/min or borderline blood pressure 2, 3
Conversion Table for 50 mL Pump (100 mcg/mL concentration)
| Dose (mcg/min) | mL/hour |
|---|---|
| 5 mcg/min | 3 mL/hour |
| 10 mcg/min | 6 mL/hour |
| 20 mcg/min | 12 mL/hour |
| 40 mcg/min | 24 mL/hour |
| 60 mcg/min | 36 mL/hour |
| 100 mcg/min | 60 mL/hour (requires new bag) |
| 200 mcg/min | 120 mL/hour (requires new bag) |
Critical Clinical Considerations
Absolute contraindications:
- Phosphodiesterase inhibitor use within 24 hours (sildenafil, tadalafil, vardenafil) 2
- Volume depletion 2
- Right ventricular infarction 3
- Severe aortic stenosis 2, 3
Common pitfalls:
- Tachyphylaxis develops after 24-48 hours of continuous infusion, requiring dose increases 2, 3
- Hypersensitive patients may respond fully to 5 mcg/min; monitor closely 1
- Headache is common but usually manageable 2, 3
- Flush infusion set when changing concentrations to avoid delayed effect 1
Monitoring Requirements
- Continuous blood pressure monitoring (non-invasive acceptable initially) 2, 3
- Heart rate and rhythm 2
- Oxygen saturation 2
- Urine output 2
- Symptoms (dyspnea, chest pain) 2
- Consider arterial line if SBP 90-110 mmHg or doses >100 mcg/min 2, 3