From the Guidelines
Nitroglycerin infusion should be initiated at 10 mcg/min and titrated upward by 10 mcg/min every 3-5 minutes until the desired clinical response is achieved, typically a reduction in blood pressure or relief of angina symptoms, as recommended by the most recent guidelines 1. The maximum dose is generally 200 mcg/min, though higher doses may be used in specific situations. Prior to initiation, establish reliable IV access, preferably with a dedicated line, and ensure continuous blood pressure and heart rate monitoring. Use a glass bottle and non-PVC tubing for administration as nitroglycerin can bind to plastic. The solution should be prepared as 50-100 mg in 250-500 mL of D5W or normal saline (concentration 100-400 mcg/mL). Some key points to consider when using nitroglycerin infusion include:
- Contraindications: severe hypotension (systolic BP <90 mmHg), right ventricular infarction, severe aortic stenosis, hypertrophic cardiomyopathy, and concurrent phosphodiesterase inhibitor use 1.
- Monitoring: hypotension, reflex tachycardia, and headache during administration 1.
- Mechanism of action: nitroglycerin works by releasing nitric oxide, causing vascular smooth muscle relaxation and venodilation at lower doses, with arterial dilation at higher doses, reducing preload, afterload, and myocardial oxygen demand while improving coronary blood flow 1.
- Indications: acute coronary syndromes, hypertensive emergencies, and acute heart failure 1. It is essential to note that tolerance to the hemodynamic effects of nitrates is dose and duration dependent and typically becomes important after 24 h of continuous therapy with any formulation 1. Patients who require continued intravenous NTG beyond 24 h may require periodic increases in infusion rate to maintain efficacy. An effort must be made to use non–tolerance-producing nitrate regimens (lower doses and intermittent dosing) 1.
From the FDA Drug Label
Although the usual starting adult dose range reported in clinical studies was 25 mcg/min or more, these studies used PVC administration sets. THE USE OF NON-ABSORBING TUBING WILL RESULT IN THE NEED FOR REDUCED DOSES. When using a non-absorbing infusion set, the initial dosage should be 5 mcg/min delivered through an infusion pump capable of exact and constant delivery of the drug. Subsequent titration must be adjusted to the clinical situation, with dose increments becoming more cautious as partial response is seen Initial titration should be in 5 mcg/min increments, with increases every 3-5 minutes until some response is noted. If no response is seen at 20 mcg/min, increments of 10 and later 20 mcg/min can be used. Once a partial blood pressure response is observed, the dose increase should be reduced and the interval between increases should be lengthened Some patients with normal or low left ventricular filling pressures or pulmonary capillary wedge pressure (e.g., angina patients without other complications) may be hypersensitive to the effects of nitroglycerin and may respond fully to doses as small as 5 mcg/min. These patients require especially careful titration and monitoring. There is no fixed optimum dose of nitroglycerin Due to variations in the responsiveness of individual patients to the drug, each patient must be titrated to the desired level of hemodynamic function. Therefore, continuous monitoring of physiologic parameters (i.e., blood pressure and heart rate in all patients, other measurements such as pulmonary capillary wedge pressure, as appropriate) MUST be performed to achieve the correct dose. Adequate systemic blood pressure and coronary perfusion pressure must be maintained.
The nitroglycerin infusion is used to manage hemodynamic instability by:
- Dilating blood vessels and reducing blood pressure
- Improving coronary perfusion
- Reducing cardiac workload Key considerations for initiating and managing a nitroglycerin infusion include:
- Starting dose: 5 mcg/min with a non-absorbing infusion set
- Titration: incremental increases of 5 mcg/min every 3-5 minutes until a response is seen
- Monitoring: continuous monitoring of blood pressure, heart rate, and other relevant physiologic parameters
- Dose adjustment: cautious increases in dose, with reductions in dose increments and longer intervals between increases as a partial response is observed
- Individualization: each patient must be titrated to their desired level of hemodynamic function 2 2 2
From the Research
Hemodynamic Effects of Nitroglycerin Infusion
- Nitroglycerin infusion has been shown to decrease systolic blood pressure, mean blood pressure, mean pulmonary artery pressure, and mean pulmonary capillary wedge pressure in patients with heart failure 3.
- The infusion also decreases systemic vascular resistance and has a slight effect on pulmonary vascular resistance 3.
- The hemodynamic effects of nitroglycerin infusion depend on the initial hemodynamic condition of the patient, with decreases in systemic vascular resistance and increases in cardiac output only occurring when these parameters are initially elevated 4.
Guidelines for Initiating and Managing Nitroglycerin Infusion
- Nitroglycerin infusion can be initiated at a rate of 10-20 micrograms per minute and titrated to achieve the desired hemodynamic effects 3.
- The infusion rate can be increased to 80 micrograms per minute to achieve beneficial hemodynamic effects in heart failure patients 3.
- The type of infusion tubing system used does not affect the hemodynamic response to nitroglycerin infusion 3.
Comparison with Other Vasodilators
- Nitroglycerin infusion has been compared to other vasodilators, such as milrinone, in patients with advanced heart failure 5.
- Milrinone was found to be more effective in achieving and maintaining hemodynamic goals, including decreases in systemic vascular resistance and increases in cardiac index 5.
- Nicorandil, another vasodilator, has been shown to result in significantly less hemodynamic tolerance over a 24-hour period compared to nitroglycerin 6.